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The Potential Hazards of Aspergillus sp in Foods and Feeds, and the Role of Biological Treatment: A Review
Abstract
The contamination of food and feed by Aspergillus has become a global issue with a significant worldwide economic impact. The growth of Aspergillus is unfavourable to the development of food and feed industries, where the problems happen mostly due to the presence of mycotoxins, which is a toxic metabolite secreted by most Aspergillus groups. Moreover, fungi can produce spores that cause diseases, such as allergies and asthma, especially to human beings. High temperature, high moisture, retarded crops, and poor food storage conditions encourage the growth of mold, as well as the development of mycotoxins. A variety of chemical, biological, and physical strategies have been developed to control the production of mycotoxins. A biological approach, using a mixed culture comprised of Saccharomyces cerevisiae and Lactobacillus rhamnosus resulted in the inhibition of the growth of fungi when inoculated into fermented food. The results reveal that the mixed culture has a higher potential (37.08%) to inhibit the growth of Aspergillus flavus (producer of Aflatoxin) compared to either single culture, L. rhamnosus NRRL B-442 and S. cerevisiae, which inhibit the growth by 63.07% and 64.24%, respectively.
... Usually, cyclopiazonic acid occurs as a co–contaminant with aflatoxins (Pitt et al., 2013). Further important mycotoxins produced by Aspergillus include ochratoxins, patulin and fumagillin (Bennett and Klich, 2003;Sheikh-Ali et al., 2014). One of the traditional ways of managing the risks of contaminated food is through the addition of herbs and spices. ...
... Fungi from the genus Aspergillus play an important role as contaminants of food and animal feed (Sheikh-Ali et al., 2014). Many species of this genus produce mycotoxins (Chulze et al., 2015;Pitt et al., 2013;Sacchi et al., 2009), including these used in our study, which can be dangerous for humans (Reddy et al., 2010;Zain, 2011). ...
Traditionally, chemical pesticides have played a central role in food protection, forcing trends towards reduction of using chemicals in agriculture leads to call for the development of new strategies of protection agricultural product. Antimicrobial volatile substances from plants have become known as a suitable alternative to synthetic pesticides and food preservatives. In this study, we explored the potential of six essential oils retrieved from cinnamon (Cinnamomum zeylanicum Nees.), thyme (Thymus vulgaris L.), oregano (Origanum vulgare L.), clove (Syzygium aromaticum L.), lemongrass (Cymbopogon citratus [DC] Stapf.) and ginger (Zingiber officinale Rosc.) essential oils. Inhibitory activity of essential oils were assessed against three strains of postharvest pathogens of the Aspergillus parasiticus, A. flavus and A. clavatus isolated from oats. In continue, the effect of the essential oils treatment on the sensory profile of the product was evaluated. The results indicated that the essential oils of lemongrass, clove, oregano and thyme have strong antifungal activity; however, only treatment with the oil of lemongrass is acceptable by consumers. The new technology of application of the essential oil vapours was highly effective, suggesting it could be used in the control of postharvest fungal pathogens of grains.
... [67]. The contamination of food and feed by Aspergillus has become a global issue with significant worldwide impact [118]. In particular, derived mycotoxins contaminate feed and food chains, being found in dairy products, dried fruits, vegetables and grain products, and representing a serious problem for public health [119,120]. ...
Zerumbone is a multifunctional compound with antimicrobial, antitumor, hyperalgesic, antioxidant and anti-inflammatory applications, and constitutes a point molecule for the future synthesis of derivatives with improved efficiency. This monocyclic sesquiterpenoid is found in high content in wild ginger (Zingiber zerumbet Smith), a perennial herb with economic importance as an ornamental as well as a medicinal plant. The presence of zerumbone is a distinctive feature that allows identification and differentiation from other species, not only in Zingiber, but also in Curcuma, Alpinia, Boesenbergia, Ethlingera and Ammomum spp., as well as related families (Costaceaee). To successfully use zerumbone in areas such as medicine, food and agriculture, further research on improving its low solubility and bioavailability, as well as its preservation, is a major current priority. In addition, despite its promising pharmacological activities, preclinical and clinical studies are required to demonstrate and evaluate the in vivo efficacy of zerumbone.
... Other Aspergillus species identified in this study are Aspergillus flavus and Aspergillus nigar isolated from 11(4.5%) and 2(0.8%) of buildings sampled, respectively. Again, these two species have also been reported by Sheikh-Ali et al. (2014) to be infectious to humans. Furthermore, Trichophyton genera, which were identified as the most common microbial genera in the façade finishes, comprise several species with the most common being Trichophyton schoenleinii, Trichophyton tonsurans, Trichophyton verrucosum, Trichophyton violacieum and others. ...
Purpose
This research examines the association of physical development density, prevalence and types of microbes in colonized façade finishes of buildings in Enugu metropolis, Nigeria.
Design/methodology/approach
Survey and experimental research designs were adopted. A total of 383 buildings were investigated with samples collected from those with colonized façade finishes. The microbes were identified using the standard procedure for genomic sequencing with descriptive statistics, and the chi-square test used to analyse the data.
Findings
The results revealed a 64% prevalence of microbial colonization and a significant association between this and physical development density with 71.0% of the colonized buildings located in high-density neighbourhoods of the metropolis. The sequencing also showed 24 different microbes with Trichophyton tonsurans , Trichophyton mentagrophytes and Trichoderma harzianum species being the most common in the colonized façade finishes.
Practical implications
The research informs building professionals and owners of the specific microbes involved in the colonization of façade finishes of buildings in high-density urban areas. It also provides a clue about the nature of damages and defects associated with microbial colonization of building façades and the type of biocide additives required for the production of microbial-resistant façade finishes in the hot-humid tropical environment of Nigeria and beyond.
Originality/value
The study has shown that there is a significant relationship between the intensity of urban land use and microbial colonization of façade finishes of buildings. It also identified some new or less known microbes responsible for the biodeterioration of façade finishes and the effects this has on the buildings and public health in the hot-humid tropics of Enugu, Southeast Nigeria.
... Efforts made to prevent contamination of agricultural commodities by aflatoxin are often hindered by pre-harvest contamination (Klich, 2007). Aflatoxin contaminated food/feeds when consumed, constitute a menace to animal or human health and could impact negatively on both inter-regional and international trade (Sheikh-Ali et al., 2014). The effect of aflatoxin contamination on the economy includes; drop in value of agricultural commodity, inaccessibility to high value markets, loss of international market trade especially in countries with stricter regulations on food safety and control (Zain, 2011). ...
Aspergillus parasiticus is a pre-harvest and postharvest pathogen that is known to produce aflatoxin; however, it is less studied compared to A. flavus. Inappropriate storage conditions is a cause of food spoilage and growth of mycotoxigenic fungi especially in low moisture foods thus constituting hazards to health. Hence, this study investigated the behaviour of A. parasiticus on aflatoxin production in inoculated wheat flour as influenced by storage conditions using the response surface methodology. Twenty experimental runs consisting of independent variables (incubation temperature (A), time (B) and (C) moisture content) and responses (aflatoxin concentrations, i.e., AFB1, AFB2, AFG1, AFG2 and AFTOT) were developed. A central composite face-centered design was used with lower and upper limits: A (25 - 35 oC), B (7 - 15 days) and C (15 -25%), while the non-inoculated wheat flour served as the negative control. Aflatoxin production was determined using High Performance Liquid Chromatography (HPLC) according to standard procedures. Numerical and graphical process variables were optimised, adequate models were predicted and optimal point prediction for aflatoxin concentration was determined. AFG1 concentrations ranged from 1.10 to 360.06 μg/g, AFG2 (0.91 - 446.94 μg/g), AFB2 (7.95 - 488.77 μg/g), AFB1 (17.21 -20666.6 μg/g) and AFTOT (15.91 -21851.09 μg/g). Aflatoxin concentration increased with increase in ‘B’ and ‘A’ but decreased with prolonged increase in ‘B’. AFB1 concentrations in A. parasiticus inoculated wheat flour increased at prolonged ‘B’ and ‘A’ at constant moisture (12.09%). A reduced cubic model was significantly adequate to describe the relationship between process variables and responses (AFG1 and AFG2), cubic model (AFB1 and AFTOT) and a transformed square root cubic model for AFG2 concentrations (p≤0.05). ‘A’ influenced AFG1 production more than ‘C’ while ‘C’ and ‘A’ had no significant effect on AFG2 production. Process variables ‘AB’ influenced AFB2 concentrations more than ‘C’ while ‘A’ had a more significant effect on the AFTOT production than ‘B’ (p≤0.05). The predicted (R²) and adjusted coefficient of regression (adj R²) were in reasonable agreement. After optimal point prediction and validation, minimum aflatoxin concentration ≤ 0 μg/g could be achieved at the predicted conditions (A = 30.42 oC, B = 10.58 days and C = 14.49%) except in AFG2 (3.33 μg/g).
... Although a detailed discussion about these additional secondary metabolites is beyond the thematic topic of the present paper, some important points are worth mentioning. For example, studies [57,59] suggest that cyclopiazonic acid (PCA) does lead to a variety of human diseases, including muscle necrosis, intestinal hemorrhage, and edema oral lesions, while aflatrem causes neurological disorders. In contrast, kojic acid is sometimes used in the food industry and in some health and cosmetic products as a natural preservative [58]. ...
Aspergillus flavus (A. flavus) is a ubiquitous and opportunistic fungal pathogen that causes invasive and non-invasive aspergillosis in humans and animals. This fungus is also capable of infecting a large number of agriculture crops (e.g., peanuts, maze, cotton seeds, rice, etc.), causing economic losses and posing serious food-safety concerns when these crops are contaminated with aflatoxins, the most potent naturally occurring carcinogens. In particular, A. flavus and aflatoxins are intensely studied, and they continue to receive considerable attention due to their detrimental effects on humans, animals, and crops. Although several studies have been published focusing on the biosynthesis of the aforementioned secondary metabolites, some of the molecular mechanisms (e.g., posttranslational modifications, transcription factors, transcriptome, proteomics, metabolomics and transcriptome, etc.) involved in the fungal development and aflatoxin biosynthesis in A. flavus are still not fully understood. In this study, a review of the recently published studies on the function of the genes and the molecular mechanisms involved in development of A. flavus and the production of its secondary metabolites is presented. It is hoped that the information provided in this review will help readers to develop effective strategies to reduce A. flavus infection and aflatoxin production.
... The presence of Penicillium spp., Aspergillus niger and Aspergillus flavus in the food sample is not surprising as they are dispersed in the form of spores which are abundant in the environment and can be introduced through dust and soil. Mixed culture has a higher potential (37.08%) to inhibit the growth of Aspergillus flavus (producer of Aflatoxin) compared to either single culture, L. rhamnosus NRRL B-442 and S. cerevisiae [41]. ...
This study was undertaken to evaluate the microbial contamination of some locally prepared snacks sold by street vendors in Lagos mainland, Lagos State, Nigeria. A total of (20) twenty snack samples-Meat-pie, Sausage roll, Egg roll, Puff puff and Doughnut were aseptically purchased in a sterilized polythene bags from four different locations in Lagos Mainland Local Government Area. The snacks were analyzed by standard microbiological methods using Bergey's manual to determine the colony-forming units per gram, to isolate and determine the number of microbiological population contaminants. Unilag showed the bacteria count on snacks as follows: Meat-pie 1.50 × 10 6 cfu/ g), Sausage 2.20× 10 6 cfu/ g, Doughnut 3.20× 10 5 cfu/ g, Puffpuff 1.58x 10 6 cfµ/ g and Egg roll 9.80x10 5 cfµ/ g. At Yaba-Meat pie had bacteria count of 1.82x10 2 cfµ / g, Sausage 7.00x10 1 cfµ / g, Doughnut 1.09x 10 2 cfµ /g, Puff puff 3.64x10 4 cfµ/ g and Egg roll Original Research Article Okeke et al.; AJRIZ, 4(2): 37-45, 2021; Article no.AJRIZ.67141 38 5.00x10 1 cfµ/g. Snacks from Oyingbo had no growth on Meat pie, Doughnut and Puff puff but had bacteria cou nts on Sausage (1.00x10 2) and on Egg roll (1.95× 10 5 cfµ/ g).At Abule-Oja-Meat pie had bacteria count of 9.75x10 4 cfµ/ g, Puff puff 1.65x10 5 cfµ/ g and Egg roll 1.95x10 5 cfu/ g.The location with lowest bacteria count was Oyingbo which had no growth on a Meat pie, Doughnut and Puff puff, but had on Sausage 1.00x10 2 cfµ/ g and Egg roll 9.60x10 2 cfµ/ g. There were no coliforms in all the locations. Bacteria percentage range was 10.52% to 36.84%while Fungi percentage range was 0.71%-37.59%. Four bacteria and seven fungi were identified: Bacillus cereus, Bacillus substillis, Staphylococcus aureus, Lactobacillus delbruckii with Aspergillus niger, Penicillium notatum, Trichoderma spp., Aspergillus fumigatus, Saccharomyces cerevisiae, Fusarium spp. and Aspergillus flavus. Bacillus cereus had the highest prevalence of 36.84%, Bacillus substillis 31.58%, Staphylococcus aureus 21.05% and Lactobacillus delbruckii 10.52%. Bacillus species were present at all sampled sites. It is concluded that the quality of these snacks can be improved by following quality control protocol and good manufacturing practices (GMP) in food.
... Aspergillus species usually interact with organisms in an asymptomatic manner and do not cause illness. However, some species have been shown to be responsible for several disorders in organisms with low immunity that have been massively exposed to fungal spores, such as immunocompromised humans [3][4][5][6][7][8], or plants and plant-derived products that have been exposed to mycotoxinproducing molds, leading to food contamination and spoilage [9][10][11]. Invasive aspergillosis can be among the most serious fungal infections [12][13][14][15]. ...
The Aspergillus Metabolome Database is a free online resource to perform metabolite annotation in mass spectrometry studies devoted to the genus Aspergillus. The database was created by retrieving and curating information on 2811 compounds present in 601 different species and subspecies of the genus Aspergillus. A total of 1514 scientific journals where these metabolites are mentioned were added as meta-information linked to their respective compounds in the database. A web service to query the database based on m/z (mass/charge ratio) searches was added to CEU Mass Mediator; these queries can be performed over the Aspergillus database only, or they can also include a user-selectable set of other general metabolomic databases. This functionality is offered via web applications and via RESTful services. Furthermore, the complete content of the database has been made available in .csv files and as a MySQL database to facilitate its integration into third-party tools. To the best of our knowledge, this is the first database and the first service specifically devoted to Aspergillus metabolite annotation based on m/z searches.
... The genus Aspergillus mainly responsible for green mold disease, is also a widespread fungus causing deterioration of several foodstuffs, and also produces several toxins (Akil et al., 2014;Pandey et al., 2016). Among the Aspergillus species, A. flavus and A. parasiticus are extensively involved in the food deterioration, producing mycotoxins such as aflatoxins that are carcinogenic, and cause serious diseases in both humans and animals (Miri & Djenane, 2019). ...
https://authors.elsevier.com/c/1ckpj3I9F4Jdfw
Background
The biodeterioration of food commodities by microbial pathogens remains a major public health concern. Worldwide, investigations have been carried out to develop harmless natural food preservatives based on essential oils (EOs) to protect food commodities, and advances have been made to meet users’ acceptance as a substitute for synthetic preservatives.
Scope and approach
In recent years, antimicrobial and antioxidant potential of the EOs from Thymus species have been documented with increasing demands from legislation changes, adaptation to the consumer trends, search for alternatives to solve rising food microbial pathogen resistance, and substitution of synthetic preservatives associated with adverse health effects. Hence, the present review paper emphasizes on the antimicrobial and antioxidant applications of EOs from different species of the genus Thymus and discloses the gaps where investigations are required. In addition, progress in the using Thymus EOs (TEOs) based nanoemulsions in food preservation, and their challenges in the application in food systems have also been discussed.
Key findings and conclusions
TEOs are rich in pharmacologically active constituents that confirm their industrial and health applications. In addition, TEOs and their nanoemulsions not only provide themselves to exploit in the food industry, but are also put under GRAS (Generally Recognized As Safe) category, and have shown potential inhibitory activity against a broad range of pathogens in food commodities. Thus, TEOs can be a source for the development of natural preservatives that meet the needs of the food industry to satisfy both its requirements and those of the consumers. However, despite the potential for EOs, more studies are required to assess their probable side effects and safety levels before considering their deployment for food purposes.
https://authors.elsevier.com/c/1ckpj3I9F4Jdfw
... However, some fungi species including Penicillium and Aspergillus detected were be able to produce mycotoxins such as ochratoxin A, aflatoxin B1, citrinin, which could affect consumer health because mutagenic, carcinogenic, nephrotoxic and pathogenic (Hsuuw et al., 2013;Klaric et al., Vol.5, No.2, September 2018. Microbiological And Physicochemical Changes … 130 2013; Ostry et al., 2013;Kumar et al., 2014;Sheikh-Ali et al., 2014;Aaraj et al., 2015;Carvajal-Moreno, 2015;Gan et al., 2015;Madrigal-Bujaidar et al., 2015;Park et al., 2015;Bovdisova et al., 2016).Therefore, this matter needs to be considered in coffee production. Fortunately, these were not found in this study. ...
... Aflatoxigenic fungi can result in a reduction in production, a decrease of nutritional value, and a reduction of market value of food products (Ren et al., 2020). One of the most widely distributed mycotoxigenic fungi, which cause risk on human health, is Aspergillus flavus (Sheikh- Ali et al., 2014). A. flavus play a major role in contamination and degradation of both quality and quantity in several agricultural commodities (Mongalo et al., 2018). ...
Pathogenic fungi are the primary infectious cause of plant diseases during pre- and post-harvest. Nuts, although recognized as a food with health benefits, are frequently contaminated by aflatoxins. In this study, we investigated the antifungal and anti-aflatoxigenic effects of our previously isolated phytochemical coumarin derivative, named (5′-hydroxy-aurapten) (5′-HA) from Lotus lalambensis Schweinf on Aspergillus flavus isolated from nuts. 5′-HA showed higher antifungal potential against A. flavus, by inhibiting its growth (MIC and MFC were 62.5 and 125 µg/l, respectively). 5′-HA also inhibited conidial germination of A. flavus by 60% at concentration 40 µg/ml. 5′-HA (40 µg/ml) displayed anti-aflatoxigenic activity against the production of aflatoxins, AFB1 and AFB2 by 50% and 23.3% respectively in association with the down-regulation of gene expression of early (aflA, alfB and alfC), middle (aflL, aflM and aflN) and late (aflP, aflQ and aflW) stages of aflatoxin biosynthesis pathway. 5′-HA (40 µg/ ml) resulted in the leakage of sugars from the mycelia by 235.8 μg/mL. Additionally, the extracellular conductivity in cells exposed to 5′-HA at 20, 40, and 80 µg/ml increased to values of 26.0 4, 43.2, and 55.1 μs/cm, respectively. Interestingly, 5′-HA significantly stimulated the activities of antioxidant enzymes, CAT (Catalase) and SOD (Superoxide dismutase) by 56.25% and 66.66% respectively. The anti-aflatoxigenic mechanism of 5′-HA was found to be mediated via modulating the oxidative stress process by upregulating the mRNA expression of the stress response transcription factors, atfA and atfB, by 2 and 2.5 folds respectively. In conclusion, our data identified 5′-HA as a novel natural antifungal compound against A. flavus that can be potentially applied to protect foodstuffs against aflatoxigenic fungi in agroindustry.
... As heterotrophs, fungi have evolved to utilize various organic matter. As a result, they can cause food spoilage events, contaminate foods and feeds with mycotoxins, and infect animals and plants ( De Lucca, 2007;Filtenborg, Frisvad, & Thrane, 1996;Fisher et al., 2012;Sheikh-Ali et al., 2014). Fungi, however, have been used as both producers and processors in food industries (Campbell-Platt & Cook, 1989;Moore & Chiu, 2001). ...
The filamentous fungal genus Aspergillus consists of over 340 officially recognized species. A handful of these Aspergillus fungi are predominantly used for food fermentation and large-scale production of enzymes, organic acids, and bioactive compounds. These industrially important Aspergilli primarily belong to the two major Aspergillus sections, Nigri and Flavi. Aspergillus oryzae (section Flavi) is the most commonly used mold for the fermentation of soybeans, rice, grains, and potatoes. Aspergillus niger (section Nigri) is used in the industrial production of various enzymes and organic acids, including 99% (1.4 million tons per year) of citric acid produced worldwide. Better understanding of the genomes and the signaling mechanisms of key Aspergillus species can help identify novel approaches to enhance these commercially significant strains. This review summarizes the diversity, current applications, key products, and synthetic biology of Aspergillus fungi commonly used in industry.
... Aspergillus niger causes black mold of foodstuffs. Aspergillus oryzae is used to ferment sake, and Aspergillus wentii to process soybeans [8]. Only a few of these molds can cause illness in humans such as Aspergillus flavus, Aspergillus niger, and Aspergillus fumigatus causing aspergillosis. ...
The wheat crop is one of the most cultivated and consumed commodities all over the world. Fungal diseases are of particular concern for wheat cultivation since they cause great losses and reduced quality, and also for the accumulation of toxin compounds into the final product. In this scenario, optimal disease management strategies are a key point to boosting food production and sustainability in agriculture. Innovative and point-of-care diagnostic technologies represent a powerful weapon for early detection of fungal pathogens and preventively counteract diseases on wheat with the aim to drastically reduce the fungicides as inputs. Indeed, in-field diagnostics devices are fast, sensitive, and ready-to-use technologies able to promptly detect a low inoculum concentration even at the pre-symptomatic stage of the disease. Promising isothermal molecular and phenomics-based methods have been developed to detect wheat fungal pathogens directly in the field. Such technologies could be potentially coupled to directly detect the presence of a certain pathogen and indirectly disclose the plant-pathogen interactions since spectral-based methodologies detect host perturbations following the infection. The present review reports the main in-field isothermal molecular-based and phenomics-based detection technologies for fungal pathogens in wheat discussing their advantages, disadvantages, and potential applications in the near future.
A total of 20 samples of green and roasted coffee beans (the same varieties as green coffee beans were used) [Coffea arabica L. (19 samples) and Coffea robusta L. (1 sample)] were collected from the various coffee roasters in Slovakia (2017/2020) and their mycobiota were analyzed. Mycological analysis was carried using standard media with focus on genera Aspergillus and Penicillium. To determine endogenous and exogenous mycobiota the method of direct placing of surface-sterilized coffee beans (green and roasted) on agar plates and the plate dilution method were used. All obtained pure cultures were classified into the genera and identified to the species according to micro- and macromorphological properties. Next the potentially toxigenic isolates were tested on their ability to produce mycotoxins (cyclopiazonic acid, penitrem A, sterigmatocystin, aflatoxins (AFB1, AFG1), ochratoxin A, patulin, roquefortine C, citrinin, and griseofulvin). From green coffee samples with higher isolation frequency (FR%) and relative density (RD%) were the genus Aspergillus (FR 100% and RD 67.39%) and the genus Penicillium (FR 90% and RD 24.60%) recorded. Aspergillus section Nigri was the most widespread in green coffee samples (RD 47.7%). The genus Aspergillus was the most occurred genus in roasted coffee bean samples, too (RD 36.58%; FR 90%). In green and roasted coffee samples were detected mainly producers of aflatoxins (AFB1 and AFG1), cyclopiazonic acid, OA, sterigmatocystin and patulin. Due to the detected presence of mycotoxins in green as well as in roasted coffee bean samples, it is very important to prevent fungal contamination and control of coffee beans before and after roasting process.
Copper and zinc are essential trace elements for several biological activities and play an important role in living organisms. In this study, the role of siderophores obtained from 16 microorganisms isolated from iron‐rich environment was evaluated in the transport of zinc and copper in yeast. In addition, siderophores showing relevant transport activity were used in the preparation of metal‐enriched yeast. Siderophores TZT‐SH5I and TZT‐ZTH2X significantly improved tolerance of Saccharomyces cerevisiae during growth under high concentrations of zinc/copper. Strains producing siderophores TZT‐SH5I and TZT‐ZTH2X were identified as Aspergillus sp and Penicillium sp, respectively. The orthogonal method was used to determine optimized conditions for siderophore‐assisted copper and zinc enrichment of S. cerevisiae. Final intracellular content of organic Cu and Zn in S. cerevisiae grown in siderophore‐containing medium was 60.76 mg/g and 44.22 mg/g. This study provides a convenient and feasible new strategy for the preparation of supplements rich in organic trace elements.
Aflatoxin B1 (AFB1) exposure often causes serious food safety problems and illnesses in humans and animals even at extremely low content. Therefore, ultrasensitive detection and effective degradation of AFB1 is vitally significant. Photoelectrochemical (PEC) approach has been widely applied in sensing and catalysis fields. For achieving robust PEC performance, exploring highly photoactive semiconductor materials is critical. Herein, we constructed a novel and dual-functional copper oxide/bismuth oxychloride (CuO/BiOCl) composite by in-situ growth of CuO on BiOCl surface. The photo-absorption region of CuO/BiOCl was efficaciously broadened from UV to visible range, making for enhanced light harvest. Meanwhile, the p-n heterostructure in CuO/BiOCl clarified that the formed built-in internal electric field could accelerate band-band transfer of carriers. Driven by this, PEC response of CuO/BiOCl was greatly boosted comparing with that of pure CuO or BiOCl. Further combing with the specific aptamer, a favorable CuO/BiOCl-based PEC biosensor was fabricated for AFB1 detection with ultra-sensitivity (detection limit of 0.07 pg mL⁻¹) and satisfactory recoveries (96.4% ∼ 105.7%) in real maize samples. Subsequently, under light irradiation and suitable bias voltage, a degradation rate of ∼81.3% was facilely attained for 5.0 µg mL⁻¹ AFB1, indicating excellent photoelectrocatalytic activity of CuO/BiOCl material. The catalytic mechanism and the main product of AFB1 degradation were analyzed. Taken together, the heterostructured CuO/BiOCl -based PEC assay provides a potential way for monitoring and controlling the AFB1contamination in the food security areas.
The photocatalytic efficiency of activated carbon supported TiO2 catalyst (AC/TiO2) for degradation of aflatoxin B1 (AFB1) under UV–Vis light was evaluated in this study. AC/TiO2 was prepared by simple hydrothermal synthesis and characterized by scanning electron micrograph (SEM), X-ray diffraction (XRD) and FT-IR. The various factors including catalyst dosage, pH value and light source affecting the degradation efficiency of AFB1 were also investigated. The higher degradation efficiency of AFB1 by AC/TiO2 composite (98%) than bare TiO2 (76%) were attributed to a higher surface area and enhanced visible light intensity by the synergy of AC and TiO2. The degradation process of AFB1 was fitted with the pseudo-first-order kinetic model. In addition, the catalyst can be easily separated from the solution and keep good activity. The hole (h⁺) and the hydroxyl radicals (•OH) were found to play an important role in the degradation of AFB1. These results demonstrated that AC/TiO2 possess synergy of high absorption capacity and photoactivity, thus supplying a simple, efficient and green approach for the degradation of AFB1.
Aspergillus fumigatus is a ubiquitous opportunistic fungus. In this study, systematic analyses were carried out to study the temperature adaptability of A. fumigatus. A total of 241 glycoside hydrolases and 69 proteases in the secretome revealed the strong capability of A. fumigatus to degrade plant biomass and protein substrates. In total, 129 pathogenesis-related proteins detected in the secretome were strongly correlated with glycoside hydrolases and proteases. The variety and abundance of proteins remained at temperatures of 34°C–45°C. The percentage of endo-1,4-xylanase increased when the temperature was lowered to 20°C, while the percentage of cellobiohydrolase increased as temperature was increased, suggesting that the strain obtains carbon mainly by degrading xylan and cellulose, and the main types of proteases in the secretome were aminopeptidases and carboxypeptidases. Only half of the proteins were retained and their abundance declined to 9.7% at 55°C. The activities of the remaining β-glycosidases and proteases were merely 35% and 24%, respectively, when the secretome was treated at 60°C for 2 h. Therefore, temperatures >60°C restrict the growth of A. fumigatus.
This study explored the feasibility of degrading aflatoxin B1 (AFB1) in contaminated peanut meal by extrusion cooking. Peanut meal contaminated with AFB1 (35.8 ± 1.5 μg/kg) was extrusion-cooked in a twin-screw extruder and AFB1 was quantified by ELISA. The effects of barrel temperature, material moisture content, feed rate, and screw speed as well as their interactions on the reduction rate of AFB1 in peanuts meal were evaluated by Response surface methodology (RSM) to optimize the extrusion conditions. Under the optimal conditions (barrel temperature of 150 °C, material moisture content of 40 g/100 g, feed rate of 17 g/min, and screw speed of 152 rpm), 77.6 ± 2.2% of AFB1 was degraded. The barrel temperature and material moisture have significant influences (P < 0.01) on the degradation rate of AFB1, while the feed rate or screw speed has no significant influence.
The possibility to control mould growth by Lactobacillus rhamnosus VT1 and Lactobacillus reuteri CCM 3625 in a milk environment was assessed using the milk agar plate method. Higher antifungal activity was exhibited by actively growing cells of both lactobacilli strains compared with the MRS broth supernatants of both bacterial strains containing metabolites with antifungal activity. The control of mould growth by Lactobacillus reuteri CCM 3625 was proved to be associated with the production of the mixture of lactic (0.9% w/w), acetic (0.2% w/w), and succinic (0.2% w/w) acids. The mechanism of mould growth control by Lactobacillus rhamnosus VT1 probably consists in the production of lactic acid (1.2% w/w) together with some other metabolite(s) of non-proteinaceous and non-saccharidic nature with antifungal activity
To investigate the enzyme production from Aspergillus oryzae S. NPUST-FS-206-A1, different combinations of soybean and wheat bran (40%:60%, 50%:50%, and 60%:40% w/w) in koji were used as substrates in soybean koji fermentation. During cultivation period, pH change of various samples was similar. However, moisture content of koji obviously decreased. Koji with high content of soybean conducted high protease activity. After 48 h of cultivation, koji containing 60% soybean showed the highest neutral protease activity of 84.38 U/g dry weight. Sample with high amount of wheat bran presented high amylase activity of 731.53 U/g dry weight. Reducing sugar content of koji was related to amylase activity. Moreover, different inoculum sizes of A. oryzae S. spore had no effect on the enzyme production. (C) 2012 Published by Elsevier B.V. Selection and/or peer review under responsibility of Asia-Pacific Chemical, Biological & Environmental Engineering Society
Strains of the Aspergillus flavus/oryzae complex are frequently isolated from meju, a fermented soybean product, that is used as the starting material for ganjang (soy sauce) and doenjang (soybean paste) production. In this study, we examined the aflatoxin producing capacity of A. flavus/oryzae strains isolated from meju. 192 strains of A. flavus/oryzae were isolated from more than 100 meju samples collected from diverse regions of Korea from 2008 to 2011, and the norB-cypA, omtA, and aflR genes in the aflatoxin biosynthesis gene cluster were analyzed. We found that 178 strains (92.7%) belonged to non-aflatoxigenic group (Type I of norB-cypA, IB-L-B-, IC-AO, or IA-L-B- of omtA, and AO type of aflR), and 14 strains (7.3%) belonged to aflatoxin-producible group (Type II of norB-cypA, IC-L-B+/B- or IC-L-B+ of omtA, and AF type of aflR). Only 7 strains (3.6%) in the aflatoxin-producible group produced aflatoxins on Czapek yeast-extract medium. The aflatoxin-producing capability of A. flavus/oryzae strains from other sources in Korea were also investigated, and 92.9% (52/56) strains from air, 93.9% (31/33) strains from rice straw, 91.7% (11/12) strains from soybean, 81.3% (13/16) strains from corn, 82% (41/50) strains from peanut, and 73.2% (41/56) strains from arable soil were included in the non-aflatoxigenic group. The proportion of non-aflatoxigenicity of meju strains was similar to that of strains from soybean, air and rice straw, all of which have an effect on the fermentation of meju. The data suggest that meju does not have a preference for non-aflatoxigenic or aflatoxin-producible strains of A. flavus/oryzae from the environment of meju. The non-aflatoxigenic meju strains are proposed to be named A. oryzae, while the meju strains that can produce aflatoxins should be referred to A. flavus in this study.
Fungi are ubiquitous and formation of mycotoxins can occur in all agricultural commodities under appropriate field or storage conditions throughout the animal feed supply chain. In this increasingly complex area, the salient features of a fungal growth and mycotoxin production are outlined with strategies to mitigate their accumulation. Overall, there are a number of approaches that can be taken to minimise mycotoxin contamination in animal feeds and these involve prevention of fungal growth and therefore mycotoxin formation, and strategies to reduce or eliminate mycotoxins from contaminated commodities, especially feed additives. The major problem associated with mycotoxin contaminated animal feed is not acute disease episodes but low level toxin ingestion which may cause an array of metabolic disturbances resulting in poor animal productivity. In studies with pigs and poultry it has been shown that low level mycotoxin intake can result in reduced feed intake, poor growth rate, lower egg production, changes in carcass quality, reduced fertility and hatchability of eggs and immunosuppression. It is concluded that mycotoxins constitute a significant problem for the animal feed industry and an ongoing risk to feed supply security.
Vegetative compatibility (VC) of Aspergillus flavus isolates from peanut seed was studied to evaluate preliminary diversity and its association with mycotoxin production and sclerotia production and number. A. parasiticus isolates also were included as a comparative group. Isolates were divided into five categories based on mycotoxin production combination. Five of the A. flavus isolates were considered atypical because they simultaneously produced aflatoxins B, G, and cyclopiazonic acid (CPA). Vegetative compatibility groups (VCGs) were determined through complementation tests between nitrate-nonutilizing mutants. Sclerotia diameters and the number of sclerotia produced per square centimeter were determined for each isolate. Out of 32 isolates of A. flavus, 25 combined in 13 VCGs, whereas the remaining could not be assigned to any particular group. Each VCG included isolates of the same mycotoxin category, with only one exception. Also, all isolates within the same VCG were characterized by their ability to produce or not produce sclerotia. Isolates between VCGs showed significant differences in number of sclerotia per square centimeter, but differences in sclerotia size were not evident. Atypical isolates simultaneously producing aflatoxins B, G, and CPA formed a single and exclusive VCG.
Specific lactic acid bacterial strains remove toxins from liquid media by physical binding. The stability of the aflatoxin B1 complexes formed with 12 bacterial strains in both viable and nonviable (heat- or acid-treated) forms was assessed by repetitive aqueous extraction. By the fifth extraction, up to 71% of the total aflatoxin B1 remained bound. Nonviable bacteria retained the highest amount of aflatoxin B1. Lactobacillus rhamnosus strain GG (ATCC 53103) and L. rhamnosus strain LC-705 (DSM 7061) removed aflatoxin B1 from solution most efficiently and were selected for further study. The accessibility of bound aflatoxin B1 to an antibody in an indirect competitive inhibition enzyme-linked immunosorbent assay suggests that surface components of these bacteria are involved in binding. Further evidence is the recovery of around 90% of the bound aflatoxin from the bacteria by solvent extraction. Autoclaving and sonication did not release any detectable aflatoxin B1. Variation in temperature (4 to 37°C) and pH (2 to 10) did not have any significant effect on the amount of aflatoxin B1 released. Binding of aflatoxin B1 appears to be predominantly extracellular for viable and heat-treated bacteria. Acid treatment may permit intracellular binding. In all cases, binding is of a reversible nature, but the stability of the complexes formed depends on strain, treatment, and environmental conditions. Food contaminants entering the body through the oral route are directly exposed to the action of gut microflora. Normal healthy intestinal microflora contains many strains of lactic acid bacteria (LAB), some of which have been isolated, as- cribed health benefits, and termed probiotic strains (22). The protective effect of LAB against food mutagens such as het- erocyclic amines, N-nitroso compounds, and aflatoxins has been reported (8, 12, 19, 24, 27). Many of these studies have involved Lactobacillus strains, and physical binding has been proposed as one mechanism of mutagen removal. This study focuses on the nature of the binding of aflatoxin B1 (AFB1) by 12 LAB strains. The potent mycotoxin AFB1 is a secondary metabolite of Aspergillus fungi that grow on a variety of food and feed commodities at any stage during growth, harvest, storage, and transportation. The occurrence of aflatoxin contamination is global, with severe problems es- pecially prevalent in developing countries (11). Aflatoxins are of great concern because of their detrimental effects on the health of humans and animals, including carcinogenic, muta- genic, teratogenic, and immunosuppressive effects (3). Aflatox- ins are also of industrial importance due to the economic losses resulting from condemnation of contaminated crops, cheese defects, and impaired growth and feed efficiency of animals fed contaminated feeds. Consequently there is a great demand for
Aspergillus flavus is the main producer of the well known carcinogenic aflatoxins. The presence of this fungus and aflatoxins is of huge concern in terms of food safety. The identification of A. flavus is not straightforward due to similarities with closely related species (e.g. A. parasiticus and A. nomius). Also, from the biochemical point of view the closely-related species are able to produce different mycotoxins. In order to clarify the differentiation between species the identification schemes is revisited. Selective media, data from mycotoxins production and molecular biology tools are discussed in order to clarify the concept of A. flavus species.
Fungi cause human illness in different ways. Mycoses are the best-known diseases of fungal etiology, but toxic secondary metabolites produced by saprophytic species are also an important health hazard. The term mycotoxin is an artificial rubric used to describe pharmacologically active mold metabolites characterized by vertebrate toxicity. They fall into several chemically unrelated classes, are produced in a strain-specific way, and elicit some complicated and overlapping toxigenic activities in sensitive species that include carcinogenicity, inhibition of protein synthesis, immunosuppression, dermal irritation, and other metabolic perturbations. Mycotoxins usually enter the body via ingestion of contaminated foods, but inhalation of toxigenic spores and direct dermal contact are also important routes. It is difficult to prove that a disease is a mycotoxicosis. Molds may be present without producing any toxin. Thus, the demonstration of mold contamination is not the same thing as the demonstration of mycotoxin contamination. Moreover, even when mycotoxins are detected, it is not easy to show that they are the etiological agents in a given veterinary or human health problem. Nevertheless, there is sufficient evidence from animal models and human epidemiological data to conclude that mycotoxins pose an important danger to human and animal health, albeit one that is hard to pin down. The incidence of mycotoxicoses may be more common than suspected. It is easy to attribute the symptoms of acute mycotoxin poisoning to other causes; the opposite is true of etiology. It is not easy to prove that cancer and other chronic conditions are caused by mycotoxin exposure. In summary, in the absence of appropriate investigative criteria and reliable laboratory tests, the mycotoxicoses will remain diagnostically daunting diseases.
The classification of the genus Aspergillus has been studied by many taxonomists. The most important monograph on which most taxonomies are derived from is strictly based on phenotypical characters. Later revisions of certain Aspergillus sections have been predominantly nomenclatural changes and primarily used morphological criteria. Many new taxa were added particularly in the genera Emericella and Neosartorya. Identification of the most common and often important species remains problematic due to the variability in the phenotypic characters. This has caused errors in the literature, especially concerning the links to mycotoxin formation. The new taxonomies are based on a polyphasic approach using phenotypical characters together with multigene DNA sequences. In a polyphasic approach micro-and macromorphology, physiology, metabolites produced and molecular data are all important, and in principle no particular method should be overemphasized. In particular extrolite profiles have proven to be specific for the taxa and this has contributed to a stable species concept, but DNA sequence data have also been very valuable in critical revisions of species and their taxonomy and phylogeny. Examples of new classifications for species in section Circumdati, Flavi, Fumigati and Nigri are presented. Although the polyphasic approach might reveal clear cut species, problems may arise for some species if they are to be separated based only on their microscopic features and few physiological features. Suggestions for new methods in order to carry out more fast and precise identifications will be discussed. Full genome sequencing and DNA arrays offers exciting new bases for identifying the Aspergilli, but recent methods based on image analysis of accurately fingerprinted phenotypes are also very promising. However both methods require a stable and well resolved taxonomy and nomenclature. Validated careful phenotypic classification (taxonomy) together with phylogenetic treatment of DNA sequence data is a prerequisite for reliable rapid identification methods and database formation. Concerning identification, DNA bar coding will be possible in the future, either based on molecular methods or certain phenotypic features.
Mycotoxins represent one of the important classes of naturally occurring toxicants in food, posing considerable health risk. Biological decontamination of mycotoxins using microorganisms is one of the well-known strategies for the management of mycotoxins in foods and feeds. Among the different potential decontaminating microorganisms, Saccharomyces cerevisiae and lactic acid bacteria represent unique groups, which are widely used in food fermentation and preservation. This review discusses the available literature on the mycotoxin binding by S. cerevisiae and lactic acid bacteria and the scope of developments in the field.
Saccharomyces cerevisiae and Lactic acid bacteria (Lactobacillus rhamnosus GG and Lactobacillus rhamnosus LC705) potentially inhibited Aspegillus flavus growth and aflatoxins production in YES liquid media. Six groups of rats orally administrated SC (1011 CFU / ml) and LGG & LC705 (109 CFU/ ml) daily for 15 days alone or with 2 mg / ml aflatoxin B1 (AFB1) in corn oil, significantly reduced serum ALT, AST, GGT, creatinine, and BUN compared with AFB1-tereated group. No deaths occurred in any combined treatment with AFB1, while a 30% mortality rate was recorded in the AFB1-treated group. Blood glutathione (GSH) levels significantly increased in groups treated with single-treatment of S. cerevisiae, LGG & LC705 or concomitant with AFB1; however, AFB1-treatment alone severely depleted GSH level more than other treatments. Histopathological examination of liver and kidney in rats treated with AFB1 showed necrosis, vacuolar degeneration and fatty changes in hepatocytes; cellular swelling and pyknotic nuclei of proximal convoluted tubules in renal tissue. DNA content decreased significantly in liver and kidney tissues with AFB1-administration, these findings were ameliorated by probiotec bacteria and S.cervisiae treatment. Conclusion: These probiotics may have good medical benefits to diminish the aflatoxins production in vitro and in vivo studies.
Fungal secondary metabolites have been considered promising resources in the search for novel bioactive compounds. Given the high potential of fungi as genetic resources, it is essential to find an efficient way to link biosynthetic genes to the product in a heterologous system, because many genes for the secondary metabolite in the original strain are silent under standard laboratory conditions. In a previous study, we constructed a heterologous expression system for a biosynthetic gene cluster using Aspergillus oryzae as the host. To make the host more versatile for the expression of secondary metabolism genes, the expression levels of a global regulator, laeA, were increased by placing the A. oryzae laeA gene under the control of the constitutive active pgk promoter. In the A. oryzae overexpressing laeA, two clusters of heterologous biosynthetic genes [the monacolin K (MK) gene cluster from Monascus pilosus and the terrequinone A (TQ) gene cluster from Aspergillus nidulans] were successfully overexpressed, resulting in the production of the corresponding metabolite, MK or TQ. The successful production of secondary metabolites belonging to different structural groups, namely MK as a polyketide and TQ as a hybrid of amino acid and isoprenoid, indicated that the laeA-enriched A. oryzae was a versatile host for the heterologous expression of the biosynthetic gene cluster.
Aspergillus subgenus Circumdati section Flavi includes species with usually biseriate conidial heads, in shades of yellow-green to brown, and dark sclerotia. Several species assigned to this section are either important mycotoxin producers including aflatoxins, cyclopiazonic acid, ochratoxins and kojic acid, or are used in oriental food fermentation processes and as hosts for heterologous gene expression. A polyphasic approach was applied using morphological characters, extrolite data and partial calmodulin, β-tubulin and ITS sequences to examine the evolutionary relationships within this section. The data indicate that Aspergillus section Flavi involves 22 species, which can be grouped into seven clades. Two new species, A. pseudocaelatus sp. nov. and A. pseudonomius sp. nov. have been discovered, and can be distinguished from other species in this section based on sequence data and extrolite profiles. Aspergillus pseudocaelatus is represented by a single isolate collected from Arachis burkartii leaf in Argentina, is closely related to the non-aflatoxin producing A. caelatus, and produces aflatoxins B & G, cyclopiazonic acid and kojic acid, while A. pseudonomius was isolated from insects and soil in the USA. This species is related to A. nomius, and produces aflatoxin B(1) (but not G-type aflatoxins), chrysogine and kojic acid. In order to prove the aflatoxin producing abilities of the isolates, phylogenetic analysis of three genes taking part in aflatoxin biosynthesis, including the transcriptional regulator aflR, norsolonic acid reductase and O-methyltransferase were also carried out. A detailed overview of the species accepted in Aspergillus section Flavi is presented.
Filamentous fungi are the cause of serious human and plant diseases but are also exploited in biotechnology as production platforms. Comparative genomics has documented their genetic diversity, and functional genomics and systems biology approaches are under way to understand the functions and interaction of fungal genes and proteins. In these approaches, gene functions are usually inferred from deletion or overexpression mutants. However, studies at these extreme points give only limited information. Moreover, many overexpression studies use metabolism-dependent promoters, often causing pleiotropic effects and thus limitations in their significance. We therefore established and systematically evaluated a tunable expression system for Aspergillus niger that is independent of carbon and nitrogen metabolism and silent under noninduced conditions. The system consists of two expression modules jointly targeted to a defined genomic locus. One module ensures constitutive expression of the tetracycline-dependent transactivator rtTA2(S)-M2, and one module harbors the rtTA2(S)-M2-dependent promoter that controls expression of the gene of interest (the Tet-on system). We show here that the system is tight, responds within minutes after inducer addition, and allows fine-tuning based on the inducer concentration or gene copy number up to expression levels higher than the expression levels of the gpdA promoter. We also validate the Tet-on system for the generation of conditional overexpression mutants and demonstrate its power when combined with a gene deletion approach. Finally, we show that the system is especially suitable when the functions of essential genes must be examined.
Worldwide, Aspergillus flavus is the second leading cause of allergic, invasive and colonizing fungal diseases in humans. However, it is the most common species causing fungal rhinosinusitis and eye infections in tropical countries. Despite the growing challenges due to A. flavus, the molecular epidemiology of this fungus has not been well studied. We evaluated the use of microsatellites for high resolution genotyping of A. flavus from India and a possible connection between clinical presentation and genotype of the involved isolate.
A panel of nine microsatellite markers were selected from the genome of A. flavus NRRL 3357. These markers were used to type 162 clinical isolates of A. flavus. All nine markers proved to be polymorphic displaying up to 33 alleles per marker. Thirteen isolates proved to be a mixture of different genotypes. Among the 149 pure isolates, 124 different genotypes could be recognized. The discriminatory power (D) for the individual markers ranged from 0.657 to 0.954. The D value of the panel of nine markers combined was 0.997. The multiplex multicolor approach was instrumental in rapid typing of a large number of isolates. There was no correlation between genotype and the clinical presentation of the infection.
There is a large genotypic diversity in clinical A. flavus isolates from India. The presence of more than one genotype in clinical samples illustrates the possibility that persons may be colonized by multiple genotypes and that any isolate from a clinical specimen is not necessarily the one actually causing infection. Microsatellites are excellent typing targets for discriminating between A. flavus isolates from various origins.
Wheat and its derivatives are a very important staple food for North African populations. The aim of this study was to analyze populations of Aspergillus section Flavi from local wheat based on aflatoxins (AFs), cyclopiazonic acid (CPA) and sclerotia production, and also to evaluate AFs-contaminated wheat collected from two different climatic regions in Algeria. A total of 108 samples of wheat were collected during the following phases: pre-harvest, storage in silos and after processing. The results revealed that among the Aspergillus species isolated, those belonging to section Flavi were predominant. Of the 150 strains of Aspergillus section Flavi isolated, 144 were identified as Aspergillus flavus and 6 as Aspergillus tamarii. We showed that 72% and 10% of the A. flavus strains produced AFs and CPA, respectively. Among the 150 strains tested, 60 produced amounts of AFB1 ranging from 12.1 to 234.6 microg/g of CYA medium. Also, we showed that most strains produced large sclerotia. AFB1was detected by HPLC in 56.6% of the wheat samples and derived products (flour, semolina and bran) with contamination levels ranging from 0.13 to 37.42 microg/kg.
Growth and mycotoxin production by molds is influenced by the environment, including other microorganisms. Lactic acid bacteria (LAB), Bacillus species and sourdough bread cultures have been reported to inhibit mold growth which may result from competition for space and nutrients in general, competition for nutrients required for mycotoxin production but not for growth, and production of antimycotic and antimycotoxigenic metabolites. Changes in the pH of the substrate through production of organic acids, such as lactic, propionic and acetic, along with hydroxyl fatty acids, reuterin and low-molecular-weight peptides may account in part for this activity. LAB have also been reported as capable of binding mycotoxins, which shows promise for the possible use of these organisms as sequestering agents in fermented and other processed foods, as well as in the gut. In the literature there is also evidence of microbial degradation of mycotoxins, and while this area of research is promising, there are some risks associated with potential production of toxic by-products or only partial detoxification that need further study. In general, the "generally recognized as safe"(GRAS) status of LAB and sourdough cultures enhances the potential of this group of bacteria to be used in commercial applications as biological control agents in processed foods to prevent mold growth, to improve the shelf life of fermented products and to reduce potential health hazards associated with mycotoxins.
This study was carried out to investigate the effects of adding baker yeast (BY), chlortetracycline (CTC) and both BY + CTC to a control diet containing 200 ng/g of aflatoxin B I (C + AFB,)on performance, serum parameters and pathologyc alterations of broilers. A total 100chicks (Ross PM 3) were divided into five groups in individual cages and each containing 20 animals. BY, a rich source of protein and vitamin B complex, was mixed into the diets at 2.0 %, CTC was mixed into the diet at 2.5 ng/g. Feed consumption, body weight and feed efficiency were recorded weekly. Serum parameters and pathologyc alterations were determined at the end of the study. Dead animals were recorded daily. Liver changes were clearly apparent in the C+AFB(1), and C+AFB(1),+CTC most of the livers were enlarged, yellow and had pethecial hemorrhages. Canalicula cholestosis was absent in group C+AFB(1), and C+AFB(1) +CTC, but not others. When compared to the control (C) group, alkaline phosphatase (ALP), appear to be significantly increased in the C+AFB(1) and C+CTC+AFB(1) groups. Serum glutamic oxalacetic transaminase (GOT)was increased in C+AFB(1) birds. Serum alphaphetoprotein was not affected by the treatments. Feed consumption and body weight were significantly reduced in group AFB(1). Birds receiving BY + AFB(1),(,) CTC + AFB, and BY + CTC + AFB(1) had a significantly higher body weight than group C+AFB Feed efficiency was better in group CTC + AFB, than the others. The findings of this research suggest tha BY (2%) can partly counteract some of the toxic effects of AFB.
In this work, the effect of pretreatment on the biochemical methane potential (BMP) of sweet sorghum biomass was determined. Various pretreatment methods, such as thermal (1 h at 121 °C), enzymatic [through the addition of the enzyme Celluclast 1.5L (Cellulase from Trichoderma reesei, ATCC 26921) or by the addition of a mixture of Celluclast 1.5L and Novozyme 188 (Cellobiase from Aspergillus niger) at a ratio of (3:1)], chemical [through alkali (NaOH) or acid (H2SO4) addition, at concentrations of 0–2 % w/v] or combination of the above methods (thermal acid and thermal alkaline) were tested, in order to evaluate their effect on carbohydrate solubilization (saccharification) and on the methane yield. The experimental results showed that thermal acid treatment and enzymatic treatment for all enzymes concentrations tested improved saccharification. Under thermal alkaline treatment at NaOH concentrations above 0.5 % w/v, a significant decrease in soluble carbohydrates concentration was observed meaning that a high portion of sugars also contained in sorghum biomass was degraded or was transformed into other components. BMP experiments showed that the chemical pretreatment methods did not enhance methane generation compared to the raw substrates. This could be attributed either to inhibitory compounds released during pretreatment, or to high salts (cations of sodium during alkaline treatment) concentration, causing in both cases methanogenic bacteria inhibition. On the other hand, thermal treatment improved the methane yield from 253 to 288 LCH4/kg sorghum. During enzymatic pretreatment, the methane production was enhanced either with only one or with the mixture of enzymes.
Mycotoxins are abiotic hazards produced by certain fungi that can grow on a variety of crops. Consequently, their prevalence in plant raw materials may be relatively high. The concentration of mycotoxins in finished products is usually lower than in raw materials. In this review, occurrence and toxicology of the main mycotoxins are summarised. Furthermore, methodological approaches for exposure assessment are described. Existing exposure assessments, both through contamination and consumption data and biomarkers of exposure, for the main mycotoxins are also discussed.
a b s t r a c t The adsorption of lead on Aspergillus versicolor biomass (AVB) has been investigated in aqueous solu-tion with special reference to binding mechanism in order to explore the possibilities of the biomass to address environmental pollution. AVB, being the most potent of all the fungal biomasses tested, has been successfully employed for reducing the lead content of the effluents of battery industries to permissi-ble limit (1.0 mg L −1) before discharging into waterbodies. The results establish that 1.0 g of the biomass adsorbs 45.0 mg of lead and the adsorption process is found to depend on the pH of the solution with an optimum at pH 5.0. The rate of adsorption of lead by AVB is very fast initially attaining equilibrium within 3 h following pseudo second order rate model. The adsorption process can better be described by Redlich–Peterson isotherm model compared to other ones tested. Scanning electron micrograph demon-strates conspicuous changes in the surface morphology of the biomass as a result of lead adsorption. Zeta potential values, chemical modification of the functional groups and Fourier transform infrared spectroscopy reveal that binding of lead on AVB occurs through complexation as well as electrostatic interaction.
This pioneering work describes how simply, inexpensively and efficiently novel fungi utilize the alarming plasticizer, di(2-ethylhexyl)phthalate (DEHP) blended in PVC blood storage bags (BB). In order to quantify total DEHP (33.5%, w/w) present in BB, it was extracted using n-hexane and confirmed by GC-MS. Three mycelial fungi, viz., Aspergillus parasiticus, Fusarium subglutinans and Penicillium funiculosum isolated in our laboratory form heavily plastics-contaminated soil - either singly or in consortium - completely consumed intact DEHP physically bound to BB by static submerged growth (28°C) in simple basal salt medium (BSM). A two-stage cultivation strategy was adopted for the complete removal of DEHP from BB in situ. During the first growth stage, almost 70% DEHP contained in the BB was consumed in 2 weeks, accompanied by increased fungal biomass (∼0.15-0.35g/g BB; OD ∼7 at 600nm) and a sharp declining (3.3) of initial pH (7.2). Spent BSM was replaced at this stagnant growth state (low pH), thus in the second stage, remaining DEHP bound to BB utilized completely (over 99%). Furthermore, A. parasiticus and F. subglutinans also grew well on scrapes of PVC water pipes in BSM. F. subglutinans was as efficient independently as consortium in completely utilizing the DEHP bound to BB, and these fungi offer great potentials for the inexpensive and eco-friendly bioremediation of phthalates in medical and allied PVC wastes on a large scale through a batch process in alleviating the plactics waste management issue.
Recent outbreaks of Aspergillosis in chickens on farms throughout Trinidad have left the chicken consuming population shocked and frightened. At present there exists very little published information available to the population on Aspergillosis and its effect on health and food safety. The present paper examines some of the fundamental questions associated with the pathogenesis of Aspergillus, health implications and recommendation for public health food safety. It is hoped through education and access to information on Aspergillus will serve to alleviate fears about Aspergillus and to empower farmers and the chicken consuming population about methods of reducing, preventing and eliminating Aspergillus, thereby restoring confidence through the adoption of good agriculture practices, safe food handling practices, good sanitation practices and good hygienic practices when rearing, handling, processing, preparing, storing and transporting poultry.
Recognizing the high incidence of paranasal sinus mycoses in north India, we analysed retrospectively the clinical, mycological and management aspects of 178 patients with proven disease attending our institute. On the basis of clinical, radiological, histopathological and mycological findings, the patients could be categorized into those with allergic (8), non-invasive (92) and invasive (78) disease types. Bony erosion without mucosal invasion by fungi was seen in 16 patients with non-invasive disease. Young men from rural areas were the most commonly affected. Rhinorrhoea with nasal polyposis (45.8%) and proptosis (46.4%) was the most common presentation. Concurrent involvement of the maxillary and ethmoid sinuses was common in these patients, whereas isolated sphenoid and frontal sinuses were involved in the invasive variety only. Orbital and intracranial extensions were detected in 100% and 13.2%, respectively, of patients with the invasive type of disease. Aspergillus flavus (79.7%) was the most common isolate. Surgical debridement and sinus ventilation were adequate for the effective management of the non-invasive disease. However, adjuvant medical therapy was included in treatment of the semi-invasive and invasive varieties of the disease. Itraconazole was found to be most useful in prevention of recurrence in the invasive type, Mortality was highest (33.3%) among patients with zygomycotic infection. Invasive fungal granuloma with orbital and intracranial invasion is a distinct entity in terms of its clinical course and treatment compared with noninvasive fungal sinusitis, and it needs to be treated aggressively with surgical excision and postoperative itraconazole.
Maize (Zea mays L) germplasm is needed with resistance to infection by Aspergillus flavus and/or subsequent contamination by aflatoxin B1 (AFB1). A select group of maize populations were evaluated for their resistance to AFB1 contamination at three locations. Four populations (Ibadan B and three others derived from crosses between Corn Belt inbreds and diploid perennial teosinte. Zea diploperennis) were compared with a susceptible hybrid check in a randomised complete block experiment with 10 replicates in Georgia, Missouri and South Carolina for two years. Ears were not inoculated, and naturally occurring concentrations of AFB1 in harvested grain were analysed for population differences. Ibadan B and Mo2 W × Z diploperennis had significantly lower average amounts of AFB1, 19 μg kg−1 and 18 μg kg−1, respectively, than other test entries. Backcrossing to susceptible Corn Belt inbreds produced populations as susceptible as the check when resistance was measured as the concentrations of AFB1 in the grain. The consistency and significance of low AFB1 concentrations for Ibadan B and Mo20W × Z diploperennis suggest that these may be useful sources of resistance.
Aspergillus section Flavi isolates, predominately A. flavus, from different crops and soils differed significantly in production of aflatoxin and sclerotia. About 50% of the isolates from corn, soil and peanut produced large sclerotia, while only 20% of the rice isolates produced large sclerotia. There was a higher frequency of small sclerotia-producing isolates from rice compared to the other sources and isolates that did not produce sclerotia were significantly less likely to be toxigenic than strains that produced large sclerotia.
Six isolates of Bacillus pumilus were tested for their ability to inhibit aflatoxin production of Aspergillus parasiticus
NRRL 2999 in yeast extract sucrose (YES) broth. Aflatoxin production was inhibited in both simultaneous and deferred antagonism
assays, suggesting that the inhibitory activity was due to extracellular metabolite(s) produced in cell-free supernatant fluids
of cultured broth. The inhibition was not due to organic acids or hydrogen peroxide produced by B. pumilus since the inhibitory
activity was not lost after pH adjustment or treatment of supernatant fluids with catalase. A range of media tested for the
production of inhibitory metabolite(s) in supernatant fluids showed that all media supported bacterial growth and production
of the metabolite(s). The metabolite(s) were produced over a wide range of temperature (25 to 37°C) and pH (4 to 9) of growth
of B. pumilus. They were stable over a wide range of pH (4 to 10) and were not inactivated after autoclaving at 121°C for
30 minutes.
Chesse flavor is a manifestation of complex interactions of volatile and non-volatile flavor-active compounds plus tactual perception. Numerous agents, including lactic acid bacteria, procece the flavou sensations. The effect of lactic acid bacteria is more dominant in cheese varieties with limited growth of secondary flora. This review describes the indirect and direct impacts of lactic acid bacteria in cheese with emphasis on carbohydrate fermentation, changes in oxidation-reduction potential, interactions with non-starter bacteria, autolysis, proteolytic and peptidolytic activities, transport of metabolites and flavor production.
Lactic acid bacteria (LAB) are the most important bacteria used in food fermentations. Apart from general demands for starter cultures from the view of safety, technological effectiveness and economics, numerous specific aspects have to be considered when selecting strains for the different food fermentations. Therefore selection criteria for LAB depend on the type and the desired characteristics of the final product, the desired metabolic activities, the characteristics of the raw materials and the applied technology. Special selection criteria for LAB for use in the fermentation of sausages and vegetables as well as for the malolactic fermentation in wine are discussed.
Globalisation of the trade in agricultural commodities has contributed significantly to the discussion about potential hazards involved and has increased in particular the awareness of mycotoxins. Safety awareness in food and feed production has also risen due to the simple fact that methods for testing residues and undesirable substances have become noticeably more sophisticated and more available at all points of the supply chain.A 2-year survey program was initiated by feed additive producer Biomin® in order to evaluate the incidence of mycotoxins in feed and feed raw materials in some of the major animal production regions. Fusarium mycotoxins tested were those known for their impact on feed industry and animal husbandry, namely deoxynivalenol (DON), T-2 toxin, zearalenone (ZON), fumonisins B1, B2, and B3. In addition, ochratoxin A and aflatoxin B1, which are not produced by Fusarium, were tested and are reported herein since interactions between Fusarium toxins and other non-Fusarium mycotoxins are possible. A total of 2753 analyses were performed on 1507 samples sourced from European and Mediterranean markets, and 6391 analyses were undertaken on 1291 samples originating from the Asian-Pacific region. More than half of materials sampled in Europe were contaminated at levels above the limit of quantification of methods applied, while one third of tests on Asian-Pacific sourced samples were positive. European samples had DON, ZON and T-2 toxin as major contaminants, materials from Asia and the Pacific tended to be contaminated with DON, ZON, fumonisins, and aflatoxins.
Aspergillus flavus andAspergillus oryzae are difficult to differentiate using standard morphologically based characteristics. This survey, using several restriction enzymes, showed thatSmaI digestions of total DNA could be used to differentiate these two closely related species ofAspergillus. A different electrophoretic pattern was associated with each of the two species, while within a species the pattern remained constant. CsCl banding of DNA from one isolate of each species indicated the DNA that produced the species-specific pattern was associated with the nuclear DNA fraction.
Aspergillus flavus is a common filamentous fungus that produces aflatoxins and presents a major threat to agriculture and human health. Previous phylogenetic studies of A. flavus have shown that it consists of two subgroups, called groups I and II, and morphological studies indicated that it consists of two morphological groups based on sclerotium size, called “S” and “L.” The industrially important non-aflatoxin-producing fungus A. oryzae is nested within group I. Three different gene regions, including part of a gene involved in aflatoxin biosynthesis (omt12), were sequenced in 33 S and L strains of A. flavus collected from various regions around the world, along with three isolates of A. oryzae and two isolates of A. parasiticus that were used as outgroups. The production of B and G aflatoxins and cyclopiazonic acid was analyzed in the A. flavus isolates, and each isolate was identified as “S” or “L” based on sclerotium size. Phylogenetic analysis of all three genes confirmed the inference that group I and group II represent a deep divergence within A. flavus. Most group I strains produced B aflatoxins to some degree, and none produced G aflatoxins. Four of six group II strains produced both B and G aflatoxins. All group II isolates were of the “S” sclerotium phenotype, whereas group I strains consisted of both “S” and “L” isolates. Based on the omt12 gene region, phylogenetic structure in sclerotium phenotype and aflatoxin production was evident within group I. Some non-aflatoxin-producing isolates of group I had an omt12 allele that was identical to that found in isolates of A. oryzae.
Several resistance sources and resistance mechanisms to aflatoxin formation and corn earworm (Helicoverpazea Boddie) damage to maize (Zeamays L.) have been identified. Based on this knowledge, experiments were initiated toward achievement of the following objectives: (1) to confirm earlier determinations on resistance traits of germplasm sources and to identify quantitative trait loci (QTL) associated with each of the traits, and (2) upon estimation of the degree of QTL effects on each trait, to generate a maize population, with chemical and physical resistance to Aspergillus spp. and ear-feeding insects, for inbred development. A 2-year field experiment to evaluate selected genotypes inoculated with A. flavus and infested with corn earworm revealed that significant variation exists among the genotypes for aflatoxin contamination and corn earworm damage. The protection of maize ears against aflatoxin contamination was primarily dependent on resistance to fungal infection and ear-feeding insects, and excellent husk coverage and tightness. A major QTL (p1) identified on chromosome 1S had effects of 54.0, 42.1, and 28.3% on the phenotypic variability for concentrations of silk maysin, 3′-methoxymaysin+apimaysin, and chlorogenic acid, respectively. Markers/QTLs for husk phenotypic traits and total aflatoxin concentrations have been determined, but more detailed mapping of these chromosomic regions will be necessary to locate precise markers/QTLs for husk traits and aflatoxin production. Realizing the complexity of the Aspergillus–aflatoxin-maize system and the factors affecting aflatoxin contamination, we are directing our program toward marker-assisted breeding to enhance or improve general genetic resistance to ear-feeding insects and invasion by Aspergillus spp.
Mycotoxins are natural food and feed contaminants, mainly produced by moulds of genera Aspergillus, Penicillium and Fusarium. The number of mycotoxins known to exert toxic effect on human and animal health is constantly increasing as well as the legislative provisions taken to control their presence in food and feed. Morocco, a North African country, surrounded by the Mediterranean Sea and Atlantic Ocean, has a climate characterized by high humidity and high temperature which favor growth of moulds. This paper gives an overview about the contamination levels and the occurrence of some mycotoxins (e.g. aflatoxins, ochratoxin A, and Fusarium toxins) in cereals, bread, milk, spices, wine, olives, poultry feeds, dried fruits and nuts; the average of contaminated samples was often above 50%. A section on mycotoxin regulations by Moroccan authorities is discussed with a comparison with international and European limits. Recent data about the contamination of foods and feed from Morocco by mycotoxins are considered in this review. Finally, the paper gives a last part with conclusions and principal prospectives and recommendations that should be undertaken by authorities and scientists during monitoring of mycotoxins in food and feed produced and/or commercialized in Morocco.
Turmeric is well known for a wide range of medicinal properties. Essential oil of turmeric leaves (Curcuma longa L.) were evaluated at varying concentrations of 0.01, 0.05, 0.1, 0.5, 0.75, 1.0 and 1.5% (v/v) in Yeast Extract Sucrose (YES) broth inoculated with spore suspension of Aspergillus flavus of 10(6)conidia/ml. These were evaluated for their potential in the control of aflatoxigenic fungus A. flavus and aflatoxin production. Turmeric leaf oil exhibited 95.3% and 100% inhibition of toxin production respectively at 1.0% and 1.5%. The extent of inhibition of fungal growth and aflatoxin production was dependent on the concentration of essential oil used. The oil exhibited significant inhibition of fungal growth as well as aflatoxins B(1) and G(1) production. The LD(50) and LD(90) were also determined. GC-MS analysis of the oil showed α-phellandrene, p-cymene and terpinolene as the major components in turmeric leaf oil. The possibility of using these phytochemical components as bio-preservatives for storage of spices is discussed.
Response surface methodology involving three variables with five level second order central composite experimental design was employed to optimize conditions for maximum dye removal by Aspergillus lentulus FJ172995. The interaction between three variables; glucose, urea and initial dye concentration was studied and modeled for two responses: dye removal and biomass production. The results indicate that urea is the main factor influencing dye removal whereas glucose plays a major role in biomass production. Also, initial dye concentration has depreciative effect on dye removal thereby suggesting that for the treatment of effluent containing higher concentrations of dye, nutrient input should be increased. A high dye removal efficiency (99.97%) and high uptake capacity (97.54 mg/g) was obtained in 24h using optimum process variables.
An anthracene-degrading strain, identified as Aspergillus fumigatus, showed a favorable ability in degradation of anthracene. The degradation efficiency could be maintained at about 60% after 5d with initial pH of the medium kept between 5 and 7.5, and the optimal temperature of 30 °C. The activity of this strain was not affected significantly by high salinity. Exploration on co-metabolism showed that the highest degradation efficiency was reached at equal concentration of lactose and anthracene. Excessive carbon source would actually hamper the degradation efficiency. Meanwhile, the strain could utilize some aromatic hydrocarbons such as benzene, toluene, phenol etc. as sole source of carbon and energy, indicating its degradation diversity. Experiments on enzymatic degradation indicated that extracellular enzymes secreted by A. fumigatus could metabolize anthracene effectively, in which the lignin peroxidase may be the most important constituent. Analysis of ion chromatography showed that the release of anions of A. fumigatus was not affected by addition of anthracene. GC-MS analysis revealed that the molecular structure of anthracene changed with the action of the microbe, generating a series of intermediate compounds such as phthalic anhydride, anthrone and anthraquinone by ring-cleavage reactions.
Studies with non-immunocompromised mice have demonstrated that Aspergillus flavus is more virulent than almost all other Aspergillus species. However, the type of immune response this fungus induces in mammals has not been investigated thoroughly. The study was carried out to analyze the sequential pathogenesis of pulmonary A. flavus infection and the role of cytokines in host response in BALB/c mice. Two distinct phases were observed in mice: First, an intense rate of clearance of A. flavus occurred, most likely through recruited neutrophils and the resident alveolar macrophages with concurrent release of pro-inflammatory cytokines and second, fungal and cellular debris were cleaned by recruited monocytes, pro-inflammatory cytokine production rapidly decreased and infection self-healed. The pro-inflammatory cytokine IFN-γ demonstrated an upward trend up to 24h PI followed by a steady decline. The titers of TNF-α (a pro-inflammatory Th1 cytokine) were, however, inversely related to the titers of IL-10 an anti-inflammatory Th2 cytokine. The anti-inflammatory cytokine IL-4 showed slightly decreasing trend between 12 and 48 h PI, beyond that it again reached to the titers observed at 6h PI. The infected mice produced signs of Th1 type response with self healing capabilities.
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Fusarium species are among the most studied plant-pathogenic fungi, with several species causing diseases on maize, wheat, barley, and other food and feed grains. Decreased yield, as well as diminished quality and value of the grain, results in significant worldwide economic losses. Additionally, Fusarium species produce a chemically diverse array of mycotoxins such as diacetoxyscirpenol, deoxynivalenol, nivalenol, T-2 toxin, zearalenone, fumonisins, fusarin C, beauvericin, moniliformin, and fusaproliferin. The dominant Fusarium species associated with feed grain that produce these mycotoxins are reviewed with emphasis on their current taxonomy, phylogenetic relationships, and general biology. Ecological and environmental factors associated with plant-fungal interactions and potential mycotoxin contamination of feed also are discussed with primary emphasis on two main diseases: head blight of small grains and ear rot of maize. The past quarter-century has provided much detail on the morphology, physiology, genetics and genomics of Fusarium species. Such data are critical for understanding these fungi and for managing their impact on the safety, value, and yield of quality grain.
Dairy propionibacteria are important organisms for the manufacture of Swiss-type cheese, for the biological production of propionate and vitamin B and have probiotic properties. In ail these application, their metabolic activities play a critical role. A complete understanding of propionate fermentation and of the metabolic routes used is therefore necessary. Dairy propionibacteria have a complex metabolism and involves several cycles. Lactate or sugars utilisation yields pyruvate which can be reduced to produce propionate via the transcarboxylase cycles, or oxidised to yield acetate and CO2. During the coupled oxidation-reduction, ATP is produced by an electron transport system and fumarate acts as the final acceptor. Although propionibacteria are mainly anaerobes, the electron transport system can be used in the presence of oxygen and they possess the citrate cycle, but can not grow under normal atmosphere oxygen pressure. The proportions of propionate acetate and CO2 produced vary depending on the strain used and this can be explained, to some extent. By their relative ability to utilise private via reactions of the citrate cycle. The physico-chemical environment during growth affects propionic acid fermentation; it is impaired by the presence of oxygen and nitrate, but fermentation at acidic pHs enhances propionate production. Fermentation in presence of more than one substrate is complex and still poorly understood. When both L- and D-lactate isomers are available, L-lactate is used preferentially. Although sugar fermentation is more efficient, in the presence of lactate and sugars, there is an évidence that lactate is used preferentially. Propionic acid fermentation is affected by the utilisation of amino acids, especially aspartate; co-metabolism of lactate and aspirate results in a lower propionate production and a decrease of the ratio propionate:acetate. There is evidence that the utilisation of the products of proteolysis is an important event in the ripening of Swiss-type cheese and could account for the low propionate:acetate ratios observed in Swiss-type cheese. © Inra / Elsevier, Paris. Les bactéries propioniques laitières sont importantes pour la fabrication de fromages de type emmental, pour la production biologique de propionate et de vitamine B12, ainsi que pour leurs propriétés probiotiques. Dans ces domaines, leurs activités métaboliques ont un rôle crucial. Il est donc nécessaire de comprendre de façon approfondie la fermentation propionique et les voies métaboliques empruntée. Les bactéries propioniques possèdent un métabolisme complexe impliquant plusieurs cycles. Le pyruvate issu de l'utilisation du lactate et des sucres peut être réduit, ce qui conduit à la production de propionate via les cycles de la transcarboxylase. Le pyruvate peut aussi être oxydé en acétate et en CO2.Au cours de ces réactions d'oxydation-réduction, un transport d'électron, dans lequel l'accepteur final est le fumarate. produit de l' ATP. Bien que les bactéries propioniques soient principalement anaérobies, le transport d'électron est possible en présence d'oxygène et elles possèdent le cycle des acides tricarboxyliques. Elles ne peuvent cependant pas se développer sous les pressions partielles en oxygène atmosphériques habituelles. Les proportions de propionate, d'acétate et de CO2 produites sont variables en fonction de la souche utilisée ; ceci peut être en partie expliqué par la proportion de pyruvate utilisée via les réactions du cycle des acides tricarboxyliques. L'environnement physico-chimique influence la fermentation propionique. Elle est inhibée par la présence d'oxygène et de nitrate alors que la production de propionate est accrue à des pH acides. La fermentation en présence de plusieurs substrats est complexe et mal comprise. Lorsque les deux isomères du lactate sont présents, le L-Iactate est utilisé de façon préférentielle. La fermentation propionique est affectée par l'utilisation d'acides aminés, et plus particulièrement en présence d'acide aspartique. L'utilisation de l'aspartate pendant la fermentation du lactate provoque une diminution de la quantité de propionate produite ainsi que du ratio propionate : acetate. Au cours de l'affinage des fromages de type emmental, l'utilisation des produits de la protéolyse est un événement important qui pourrait être corrélé aux faibles ratios propionate : acetate observés. © Inra / Elsevier. Paris.
The lipase produced by the Aspergillus niger strain AC-54 has been widely studied due to its enantioselectivity for racemic mixtures. This study aimed to optimize the production of this enzyme using statistical methodology. Initially a Plackett-Burman (PB) design was used to evaluate the effects of the culture medium components and the culture conditions. Twelve factors were screened: water content, glucose, yeast extract, peptone, olive oil, temperature, NaH(2)P0(4), KH(2)P0(4), MgS0(4)-7H(2)0, CaCl(2), NaCI, and MnS0(4). The screening showed that the significant factors were water content, glucose, yeast extract, peptone, NaH(2)P0(4), and KH(2)P0(4), which were optimized using response surface methodology (RSM) and a mathematical model obtained to explain the behavioral process. The best lipase activity was attained using the following conditions: water content (20%), glucose (4.8%), yeast extract (4.0%), and NaH2P04 (4.0%). The predicted lipase activity was 33.03 U/ml and the experimental data confirmed the validity of the model. The enzymatic activity was expressed as micromoles of oleic acid released per minute of reaction (micromol/min).