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Extracellular Microbial Lipids as Biosurfactants
Abstract
During the past 10 years there have been rapid developments in the detection and characterization of surface-active agents formed by bacteria, yeasts and fungi. The present paper reviews the available information on microbial processes which result in the formation of such compounds — biosurfactants —, i.e. appropriate conditions as well as the known chemical structures and physico-chemical properties of isolated biosurfactants. The physiological importance of extracellular surface-active compounds is discussed, particularly with respect to their possible role in the microbial degradation of water-insoluble carbon-sources and their possible biocidic effects. A survey on commercial applications is given and conclusions for further research work are presented.
... These are desirable properties to bioremediation strategies and processes. The properties of various microbial produced biosurfactants had been studied (Haferburg et al. 1986; Cooper and Goldenberg 1987; Georgiou et al. 1992; Rosenberg and Ron 1997). Biosurfactant properties make them suitable for a wide range of industrial applications involving: detergency, emulsification, lubrication , foaming ability, wetting ability, solubilization, and phases dispersion (Ashis and Das 2010). ...
... On the contrary, a few studies state that in some situations biosurfactant production is inhibited in B. subtilis cultures (i.e., for adding hexadecane). Although even in these instances an increased biomass still occurred (Haferburg et al. 1986). Interestingly, oil added to BH broth as a sole carbon source resulted in the lowest B. subtilis biomass production (0.67 g L −1 ). ...
Microbial pollutant removal capabilities can be determined and exploited to accomplish bioremediation of hydrocarbon-polluted environments. Thus, increasing knowledge on environmental behavior of different petroleum products can lead to better bioremediation strategies. Biodegradation can be enhanced by adding biosurfactants to hydrocarbon-degrading microorganism consortia. This work aimed to improve petroleum products biodegradation by using a biosurfactant produced by Bacillus subtilis. The produced biosurfactant was added to biodegradation assays containing crude oil, diesel, and kerosene. Biodegradation was monitored by a respirometric technique capable of evaluating CO2 production in an aerobic simulated wastewater environment. The biosurfactant yielded optimal surface tension reduction (30.9 mN m(-1)) and emulsification results (46.90 % with kerosene). Biodegradation successfully occurred and different profiles were observed for each substance. Precise mathematical modeling of biosurfactant effects on petroleum degradation profile was designed, hence allowing long-term kinetics prediction. Assays containing biosurfactant yielded a higher overall CO2 output. Higher emulsification and an enhanced CO2 production dataset on assays containing biosurfactants was observed, especially in crude oil and kerosene.
... Hence, optimization of these conditions may lead to high and safe biosurfactants production. Most of the studies to date describe biosurfactants production by bacteria grown on hydrocarbons but a few have reported biosurfactants produced by bacteria growing on carbohydrates [35]. Most of the world's total oil and fat production is derived from plants. ...
Rhamnolipids mainly are produced by Pseudomonas aeruginosa and another microorganism that have been found to have good surface activity. Rhamnolipids are used in various application areas, including environmental, health, food, cosmetic, oil industries, pharmaceuticals and environmental bio remediation particularly in enhanced oil recovery (EOR) and cleaning of oil spills. Many kinds of bio surfactant such as, rhamnolipids are already being used in industry but it is important to develop indigenous technology for the production of rhamnolipids produced by the microorganisms of local origin which would be more suitable for the application to that specific areas. Rhamnolipids have several beneficial uses: they are easily degradable, nontoxic, nonmutagenic, and have the highest surface-tension-reduction index of any surface-tension reducing agent currently in use. In this review, I summarize the definition, preparation, properties, and the application in different areas especially in food and agriculture, and industrial potential of rhamnolipids, as the next generation of biosurfactants.
... Thus with the processes of fermentation we can get the " biosurfactants " , also known as " green surfactants " , obtained by microorganisms or extracted from biomass, or obtained from these after biotransformation[9]. Biosurfactants are structurally diverse, depending on the microorganism from which they derived, the substrates employed in the bioprocess, and the fermentation conditions. They are generally classified into acylpolyols[10], glycolipids[11], and lipopeptides[12]. However, surfactants synthesized from natural sources are considered " natural " , such as alkyl polyglycosides, sugar fatty acid esters, amino acid-based surfactants, and polyglycerol esters of fatty acids[3,13141516. ...
During recent years, microwave irradiation has been extensively used for performing green organic synthesis. The aim of this study was to synthesize, through a microwave-assisted irradiation process, a natural surfactant with O/W emulsifying properties. Our attention was focused on polyglycerol esters of fatty acids that are biocompatible and biodegradable non-ionic surfactants widely used in food and cosmetic products. The emulsifier was obtained using vegetable raw material from renewable sources: polyglycerol derived from vegetable glycerol and rice bran oil fatty acids. The natural emulsifier obtained was then characterized and evaluated for its emulsifying properties using different doses, oil phases, rheological additives, waxes, etc. The potential application in solar products, in comparison with other natural emulsifiers, was also evaluated.
... A variety of microbial biosurfactants are available. Their type, quantity , and quality are mostly influenced by the nature of the carbon substrate (Georgiou et al., 1992), and the concentration of nitrogen, phosphorous, magnesium, iron, and manganese ions in the medium (Guerra-Santos et al., 1986; Haferburg et al., 1986; Abu-Ruwaida et al., 1991b ) and culture conditions , which include pH, temperature, agitation, dilution rate, etc. (GuerraSantos et al., 1986; Abu-Ruwaida et al., 1991a; Drouin and Cooper, 1992; Lin et al., 1994). The selection of microorganisms for the use of microbial enhanced oil recovery based on varying conditions, which they use such as temperature, pressure, pH, and salinity, must be given priority (Khire and Khan, 1994). ...
Biosurfactants are surface-active biomolecules produced by microbes (bacteria, fungi, and yeast) and have several advantages over the chemical surfactants, such as lower toxicity, higher biodegradability, better environmental compatibility, higher foaming, high selectivity, and specific activity under extreme conditions
such as temperature, pH, and salinity. Almost all the surfactants now available in the market are chemically synthesized. Recently, attention toward the biosurfactants was doubled, which is mainly due to their wide range of functional properties and the diverse synthetic capabilities of the microbes. Microbial biosurfactants are found to have a wide range of applications in environmental protection, which include enhancing oil recovery, controlling oil spills, biodegradation, and detoxification of oil-contaminated industrial effluents and soils. Biosurfactants produced by microorganisms have potential applications in pharmaceutical/medicine, food, cosmetic, pesticide, oil, and biodegradation industries. In this review article, we concentrated on three important aspects such as various types of biosurfactants, the group of microbes involved in the production of biosurfactants, and application of microbial biosurfactants.
... In general, biosurfactants have microbial and plant based origin. However, the use of biosurfactants of microbial origin is limited because the lack of large scale industrial production due to high recovery or separation costs and some possess antimicrobial properties too171819. In recent times, the use of eco-friendly surfactants from renewable plant sources for soil and water remediation is of great importance. ...
... According to Hallman et al. (2007) , biodegradation of hydrocarbons also produces biogenic acids as secondary metabolites during in vitro biodegradation experiments. Haferburg et al. (1986) and Watson et al. (2002) also reported the production of significant amounts of acids during biodegradation assays in the laboratory. In these reports, rapid production followed by rapid biodegradation of medium molecular weight (C 10 –C 20 ) acids was also observed. ...
The detection of microorganisms with potential for biodeterioration and biodegradation in petroleum fields is of great relevance, since these organisms may be related to a decrease in petroleum quality in the reservoirs or damage in the production facilities. In this sense, petroleum formation water and oil samples were collected from the Campos Basin, Brazil, with the aim of isolating microorganisms and evaluating their ability to degrade distinct classes of hydrocarbon biomarkers (9,10-dihydrophenanthrene, phytane, nonadecanoic acid and 5α-cholestane). Twenty eight bacterial isolates were recovered and identified by sequencing their 16S rRNA genes. Biodegradation assays revealed that bacterial metabolism of hydrocarbons occurred through reactions based on oxidation, carbon–carbon bond cleavage and generation of new bonds or by the physical incorporation of hydrocarbons into microbial cell walls. Based on the biodegradation results, selective PCR-based systems were developed for direct detection in petroleum samples of bacterial groups of interest, namely Bacillus spp., Micrococcus spp., Achromobacter xylosoxidans, Dietzia spp. and Bacillus pumilus. Primer sets targeting 16S rRNA genes were designed and their specificity was confirmed in silico (i.e. computational analysis) and in PCR reactions using DNA from reference strains as positive and negative controls. Total DNA from oil was purified and the amplification tests revealed the presence of the target bacteria in the samples, unraveling a significant potential for petroleum deterioration in the reservoirs sampled, once proper conditions are present for hydrocarbon degradation. The application of molecular methods for rapid detection of specific microorganisms in environmental samples would be valuable as a supporting tool for the evaluation of oil quality in production reservoirs.
... Ever since the discovery of sophorolipids, many efforts have been made to increase the production effectiveness, which resulted in final concentrations of more than 300 g/ L (Daniel et al., Davila et al. [3, 4]) or yields of Y P/S of 0.54 in semi-continuous processes described by Rau et al. [5]. Furthermore, sophorolipids have been tested for use in technical applications, mainly as surfactants (Haferburg et al., Willumsen and Karlson and Van Bogaert et al.678) but also pharmaceutically as sperm and HIV-inhibitors (Shah et al. [9]) and for sepsis treatment (Bluth et al. [10]). The technical potential of C. bombicola culminated in studies of its genetic Correspondence: Professor Siegmund Lang, Institute of Biochemistry and Biotechnology, Braunschweig University of Technology, Biotechnology Group, Spielmannstr., Braunschweig, Germany E-mail: s.lang@tu-bs.de ...
The yeast Candida bombicola ATCC 22214 is well-known to produce mixtures of glycolipids containing the sugar sophorose, the so-called sophorolipids, especially when cultivated on hydrophobic carbon sources as co-substrates. To improve cultivation efficiency, an integrated process was developed using ultrasound separation technology. Since this technology is new for use with C. bombicola, it was first characterized in batch experiments and afterwards implemented in an integrated production process. In this process, separation efficiencies of about 99% C. bombicola cells could be achieved, leading to 8 g/L of nearly cell-free sophorolipid product and a total amount of 73.8 g/L sophorolipids. Furthermore, a technical mixture of unusual branched fatty alcohols containing mainly 2-hexyl-1-decanol was used as co-substrate with glucose in a shake flask study. This resulted in the production of a new product, 1-O-β-glucopyranosyl-2-hexyldecanol, a molecule containing glucose as the sugar moiety and 2-hexyl-1-decanol as a branched hydrophobic side chain.
... The biosurfactant density (at that dilution) was the same as the water density; therefore, the CMC of the biosurfactant was 430 mg/l. This result indicates that the CMC is higher than the CMC of the biosurfactants produced by other microorganisms (10 −3 to 10 mg/l) (Haferburg et al. 1986; Mulligan et al. 1989; Bongolo 1999) nevertheless, this CMC is lower than those obtained with synthetic surfactants (590 mg/l of linear alkyl benzene sulphonate), and, in general, lower than that of other synthetic surfactants: BRIJ-35, Tergitol NP 10, and Genapol X-100 (90,000, 36,000, and 150,000 mg/l, respectively) used for soil bioremediation (Volke-Sepúlveda and Velasco-Trejo 2003). Therefore, the biosurfactant produced by P. putida could enhance bioremediation of soils contaminated with PAHs. ...
A culture medium formulation was established using a Box-Behnken experimental design aimed at enhancing biosurfactant production
and phenanthrene removal by Pseudomonas putida CB-100. The independent variables selected (+, 0, −, levels) were: glucose (9.1, 13.6, and 18.2g/l), NH4Cl (0.5, 0.75, and 1.0g/l), and yeast extract (0.005, 0.0075, and 0.01g/l), with 200mg/l phenanthrene at 37°C, shaken at
150rpm, at pH7, for 5days. Analyses of results by one-way analysis of variance showed that biosurfactant production was
improved by the glucose–ammonium chloride interaction at high values (p < 0.004). Phenanthrene removal was enhanced by the ammonium chloride-yeast extract interaction at low and high values, respectively
(p < 0.02). The highest phenanthrene removal (82.4%) was observed in formulation 11, which had a C:N ratio of 5:1 and a C:P
ratio of 10:1. In addition, 47.5mN/m surface tension, 20% emulsion capacity, and 23.5mg/l biosurfactant production were
obtained. With this medium, we followed the kinetic growth of P. putida for 118h, the culture conditions were the same as those used in the experimental design. At 46h, we obtained 57.8% phenanthrene
removal and 27mg/l biosurfactant production. The critical micelle concentration of the biosurfactant was 430mg/l. The biosurfactant
produced by P. putida was characterized as a rhamnolipid type.
KeywordsCell culture–Experimental design–HPLC–Kinetic–Rhamnolipid
A polar head and an apolar tail chemically characterize surfactants, they show different properties and are categorized by different factors such as head charge and molecular weight. They work by reducing the surface tension between oil and water phases to facilitate the formation of one homogeneous mixture. In this respect, they represent unavoidable ingredients, their main application is in the production of detergents, one of if not the most important categories of cosmetics. Their role is very important, it should be remembered that it was precisely soaps and hygiene that defeated the main infectious diseases at the beginning of the last century. Due to their positive environmental impact, the potential uses of microbial sourced surfactants are actively investigated. These compounds are produced with different mechanisms by microorganisms in the aims to defend themselves from external threats, to improve the mobility in the environment, etc. In the cosmetic field, biosurfactants, restricted in the present work to those described above, can carry high advantages, in comparison to traditional surfactants, especially in the field of sustainable and safer approaches. Besiede this, costs still remain an obsatcle to their diffusion; in this regard, exploration of possible multifunctional actions could help to contain application costs. To highlight their features and possible multifunctional role, on the light of specific biological profiles yet underestimated, we have approached the present review work.
This chapter focuses on the role of biosurfactants in the remediation of petroleum hydrocarbon by microbes over chemical surfactants. An emphasis has also been placed on the common types, properties, and characteristics of biosurfactants involved in hydrocarbon bioremediation. The potential microbes involved in the cleanup of hydrocarbon-contaminated environments with biosurfactant synthesis are also addressed. The aim is also to introduce the constraints and challenges of biosurfactant production and its use in hydrocarbon remediation. The recent advances in biosurfactant production processes are also elaborated. The strategies for improvement in production of natural surfactants by microbes, cost-effectiveness, and the commercialization of biosurfactants for petroleum hydrocarbon are also emphasized.
Contamination with petroleum hydrocarbons causes extensive damage to ecological systems. On oil-contaminated sites, alkanes are major components; many indigenous bacteria can access and/or degrade alkanes. However, their ability to do so is affected by external properties of the soil, including nutrient cations. This study used Raman microspectroscopy to study how nutrient cations affect alkanes' bioavailability to Acinetobacter baylyi ADP1 (a known degrader). Treated with Na, K, Mg, and Ca at 10 mM, A. baylyi was exposed to seven n-alkanes (decane, dodecane, tetradecane, hexadecane, nonadecane, eicosane, and tetracosane) and one alkane mixture (mineral oil). Raman spectral analysis indicated that bioavailability of alkanes varied with carbon chain lengths, and additional cations altered the bacterial response to n-alkanes. Sodium significantly increased the bacterial affinity toward decane and dodecane, and K and Mg enhanced the bioavailability of tetradecane and hexadecane. In contrast, the bacterial response was inhibited by Ca for all alkanes. Similar results were observed in mineral oil exposure. Our study employed Raman spectral assay to offer a deep insight into how nutrient cations affect the bioavailability of alkanes, suggesting that nutrient cations can play a key role in influencing the harmful effects of hydrocarbons and could be optimized to enhance the bioremediation strategy.
The chemical and physical properties of extracellular rhamnolipid synthesized by a nonfluorescent Pseudomonas species soil isolate, identified as DYNA270, is described, along with characteristics of rhamnolipid production under varying growth conditions and substrates. The biosurfactant is determined to be an anionic, extracellular glycolipid consisting of two major components, the rhamnopyranoside β-1-3-hydroxydecanoyl-3-hydroxydecanoic acid (GU-6) and rhamnopyranosyl β→β2-rhamnopyranoside-β1-3-hydroxydecanoyl-3-hydroxydecanoic acid (GL-2), of molecular weight 504 and 649 daltons, respectively. These glycolipids are produced in a stoichiometric ratio of 1:3, respectively. The purified rhamnolipid mixture exhibits a critical micelle concentration of 20 mg/L, minimum surface (air/water interface) tension of 22 mN/m, and minimum interfacial tension values of 0.005 mN/m (against hexane). The pH optimum, critical micelle concentration, and effective alkane carbon number were established for Pseudomonas species DYNA270 and compared to those of rhamnolipid produced by Pseudomonas aeruginosa PG201. Significant differences are documented in the physical properties of extracellular rhamnolipids derived from these two microorganisms. The surface properties of this rhamnolipid are unique in that ultra-low surface and interfacial tension values are present in both purified rhamnolipid and culture broth containing the rhamnolipid complex (GU6 and GL2). We are not aware of prior studies reporting surface activity values this low for rhamnolipids. An exception is noted for an extracellular trehalose glycolipid produced by Rhodococcus species H13-A, which measured 0.00005 mN/m in the presence of the co-agent pentanol (Singer et al. 1990). Similar CMC values of 20 mg/L have been reported for rhamnolipids, a few being recorded as 5–10 mg/L for Pseudomonas species DSM2874 (Lang et al. 1984).
Bioemulsifiers (BE) and biosurfactants (BS) are considered as multifunctional biomolecules of 21st century because of their functional abilities and eco‐friendly properties. They are produced by various microorganisms under versatile and extreme environmental conditions. They have tremendous applications in various industries such as petroleum, food, medicine, pharmaceutical, chemical, paper & pulp, textile, and cosmetics. Currently, they are also considered as “green molecules” because of their wide applications in bioremediation of soil. Their importance has been increasing day by day in the global market as they are the natural resources with high‐aggregate value. Although, there are numerous reports on BE and BS production by different bacteria, Acinetobacter spp. acquired special attention among all. This is because it is the earliest member known for the production of bioemulsifier. Emulsan and Alasan are the best examples of the commercially used BE produced by Acinetobacter spp. These BE are mainly used in microbial enhanced oil recovery and biodegradation of toxic compounds. This review is focused on BE and BS produced by Acinetobacter spp., their characterization and applications in different fields. This is the first review on genus Acinetobacter which defines independently about different types of BE and BS produced by it. It will also address the need of exploration of these molecules from various sources and their applications for the benefit of mankind and sustainable environment.
This study was carried out to evaluate the ability of two cyanobacterial isolates, Anabaena flose-aquae and Westiellopsis prolifica, to degrade Iraqi crude oil in batch cultures with the addition of linear alkyl benzene sulfonate. The degree of oil removal was measured after a 15-d culture period. According to biomass and gas-chromatography data, axenic cultures of both strains were able to degrade crude oil, showing complete removal of some hydrocarbon compounds during the 15-d exposure period. The strains produced biosurfactants at a final concentration of 2–3.1 g/L, which was further evidence of their oil-degrading capabilities.
Biosurfactants or microbial surfactants are a diverse group of nonconventional surface active substances synthesized from microorganisms such as bacteria, fungi, and yeast. The hydrophilic moiety of biosurfactants can either be an amino acid, peptide group, phosphate group, carbohydrate (mono-, di-, or polysaccharides), or some other compounds, whereas the hydrophobic group is generally made up of long hydrocarbon tail. Commonly, biosurfactants are neutral or anionic in nature. On the basis of their mass, they are broadly classified in two categories namely low- and high-mass biosurfactants. Glycolipids, phospholipids, lipopeptides, lipoproteins, and neutral lipids are low-mass biosurfactants, whereas polymeric and particulate biosurfactants are high-mass biosurfactants. Some commonly known examples of biosurfactants are surfactin produced from Bacillus subtilis, rhamnolipids produced from Pseudomonas aeruginosa, emulsan produced from Acinetobacter calcoaceticus, and sophorolipids produced from Candida bombicola. The nature of carbon and nitrogen sources, pH, temperature, and agitation are usually the factors that influence the production of biosurfactants. Their varied surface active properties such as excellent ability to lower the surface tension and interfacial tension, low CMC (critical micelle concentration) values, emulsification and de-emulsification, HLB (hydrophilic–lipophilic balance), and better pH and thermal stability are due to their specific structure. Low or no toxicity, fast biodegradation, and specific structural properties of biosurfactants label them as green and sustainable materials. These properties make them superior over chemically synthesized counterparts and stimulate the interest of researchers and industry for their extensive use. Their easy dispersability, emulsifying and de-emulsifying property, good wettability, and corrosion inhibition property are exploited in many industries such as detergent, agriculture, laundry, polymer, pharmaceuticals, cosmetics, food, and in microbial enhanced oil recovery. Despite having a large number of advantages, a few disadvantages are also linked with biosurfactants/microbial surfactants. The two most specific disadvantages are their production cost and purification. Biotechnological processes involved in the synthesis of biosurfactants are pretty expensive, and purification of surfactants is a bit problematic. Various research groups are working especially for the cost cutting of biosurfactants' production by using easily available and renewable bioresources as raw materials for the production of biosurfactants. Use of biosurfactants at commercial level is the need of the hour to reduce of the harmful effects of conventional synthetic surfactants on environment. Disadvantages associated with them are to be surmounted by the scientists. Full potential of these sustainable versatile surfactants may be achieved by the economic balance between their production cost and benefits.
Biosurfactant are surface-active substances synthesized by living cells-in the majority of cases by microorganisms. Metallic contaminants in the soil are poisonous and their accumulation in plants and water may be dangerous. Microorganisms are known to absorb; adsorb and accumulate heavy metals and they can be made use of in solving major problems associated with metals. The extensive use of chromium in different industries such as leather, textile, metal electro plating etc has resulted in the discharge of chromium compounds into aquatic system. Among the fungal isolates, Mucor sp. ATS 5 was predominant using inactive cells about 84% chromium was removed, whereas in resting cells it was found to be 79%. In the case of bacterial population, Pseudomonas sp. ATS-08 was predominant about 86% chromium was removed using inactive cells followed by resting cells (75%). Among the actinomycetes isolates, Nocardia sp. ATS-2 was predominant. 90% chromium was removed using inactive cells of Nocardia sp. followed by resting cells (84%). From the above study, it is concluded that the actinomycetes was the best effective followed by bacteria and fungi and could be used for treating industrial effluents having high amount of chromium.
IntroductionBiosurfactant ClassesBiosynthesisBiosurfactant ProductionBiosurfactant Properties of Interest for CosmeticsMedical and Pharmaceutical ApplicationsBiosurfactants in FoodsBiosurfactants for Environmental ControlBio-De-EmulsifiersReferences
http://saber.ucv.ve/jspui/handle/123456789/8875
El presente estudio está enmarcado dentro del proyecto Misión Ciencia “Desarrollo y Validación de Nuevas Tecnologías para el Saneamiento Ambiental de Pasivos Generados por la Actividad Petrolera”, dentro del subprefecto “Caracterización del Medio Físico Natural en Áreas Impactadas con Hidrocarburos”
Se caracterizó funcionalmente la comunidad bacteriana del suelo en la zona de descarga de la fosa petrolera Bare 9; Se destacaron grupos con capacidad para degradar sustratos complejos, para crecer en hidrocarburos y producir biosurfactantes. Se evaluaron dos cuadratas (B9I y B9D) dentro de la zona de descarga, caracterizada por derrame de petróleo y otra en la zona de vegetación (B9V), con valores de abundancia del orden de 10^9 UFC/gr de suelo en áreas impactadas, y sobre el orden de 10^12 UFC/gr de suelo en la zona sin impacto.
La caracterización bioquímica de las poblaciones, debido a su crecimiento en diferentes sustratos utilizando una única fuente de carbono, refleja un gran número de cepas capaces de degradar azúcares simples como la glucosa (80%), utilizando fuentes de nitrógeno y nitratos e hidrolizantes de urea y Proteínas (80%) y un bajo número de cepas capaces de degradar sustratos complejos tales como celulosa, lignina y pectina con valores cercanos o inferiores al 20%.
El análisis multivariante Clúster agrupó cepas con características similares en su actividad enzimática, formando los llamados grupos funcionales (GF). Se determinó que la diversidad funcional era mayor en el área impactada (B9I) que en el área con vegetación, donde se espera y a pesar de encontrar números similares de grupos funcionales entre las diferentes comunidades. GF se agruparon en función de la actividad proteolítica, urea, agentes reductores de nitrato y con la capacidad de utilizar el acetato como única fuente de carbono, características presentes en todas las localidades evaluadas. Se encontró una mayor similitud entre la comunidad impactada B9D y el área con vegetación (B9V).
Las cepas de interés se destacaron por su potencial biotecnológico para ser utilizadas en procesos de biorremediación a los que se realizaron bioensayos para determinar la producción de compuestos tensioactivos
The bacterial community of the soil in the zone of discharge of the oil pit (Bare-9) was functionally characterized in the present study; groups with ability to degrade complex substrates, to grow on hydrocarbons and produce biosurfactants were highlighted. Two quadrats (B9I and B9D) were evaluated within the discharge zone, characterized by oil spill and other one on the vegetation zone (B9V), abundance values found were of the order of 10^9 CFU/gr of soil in impacted areas, and up to 10^12 UFC/gr of soil in the area without impact.
The biochemical characterization of the populations, due to their growth in different substrates using a single source of carbon, reflects a large number of strains capable of degrading simple sugars such as glucose (80%), using nitrogen sources and nitrates and hydrolyzing urea and Proteins (80%) and a low number of strains capable of degrading complex substrates such as cellulose, lignin and pectin with values close to or below 20%.
Cluster multivariate analysis grouped strains with similar characteristics in their enzymatic activity, forming the so-called functional groups (GF). It was determined that the functional diversity was higher in the impacted area (B9I) than in the area with vegetation, where it is expected and despite finding a similar number of functional groups among the different communities.
GF were grouped according to proteolytic activity, urea, nitrate reducing agents and with the capacity to use acetate as the only carbon source, characteristics present in all the evaluated localities. A greater similarity was found between the impacted community B9D and the area with vegetation (B9V).
The strains of interest were highlighted for their biotechnological potential to be used in bioremediation processes to which bioassays were carried out to determine the production of surfactant compounds
Aromatic hydrocarbons represent a group of ring structured hydrophobic and reduced compounds which are industrially significant and toxic in nature. Due to their presence in nature through anthropogenic and biological routes, micro-organisms have evolved/adapted to degrade these compounds. Aerobic bacteria initialize their degradation by incorporation of oxygen atoms by a group of enzymes ‘oxygenases’ which leads to the formation of cis-dihydrodiols. Subsequent formation of catechol intermediates followed by ortho- or meta-ring cleavage leads to intermediates which enter Kreb’s cycle. The reaction sequences are repeated for additional rings in case of polycyclic aromatic compounds. A large array of metabolic diversity exists within these strains and several parameters regulate the efficient utilization of such compounds. Hence, an ideal microbial culture should have following features for its effective application in sustainable environmental development strategies: (i) ability to metabolize wide range of aromatic compounds even at high concentrations with novel pathways and enzymes, (ii) complete degradation of toxic pollutants without formation of toxic by-products, (iii) production of biosurfactants for solubilization and uptake of hydrophobic xenobiotic compounds and (iv) absence of carbon catabolite repression.
A wide variety of unprotected sugars were acylated in high-yields with non-activated fatty acids in a regioselective manner using commercial lipase preparations. The reactions were performed in a (mainly) solid phase in the presence of an organic solvent, serving as adjuvant to maintain a small catalytic liquid phase. Optimum conditions were found using solvents with a low log P value such as acetone or dioxane, lipase from Candida antarctica (Novo SP 435) and saturated fatty acids with chain lengths from C12 to C18 as acyl donors. The esterification ofβ-D(+)-glucose with palmitic acid resulted in up to 86% conversion after 48 h and a productivity of 0.4 mmol 6-O-β-D(+)-glucose palmitate per gram lipase and hour. α-D(+)-Glucose, sorbitol, D(+)-mannose and mannitol were also successfully acylated.
Biosurfactants are generally microbial metabolites with the typical amphiphilic structure of a surfactant. This study investigated potential biosurfactants production of Pseudomonas aeruginosa ATCC-10145 and Bacillus subtilis NCTC-1040 using glucose and n-hexadecane as substrates separately and compared it with the production in conventional medium. Pseudomonas aeruginosa growing in BHMS (Bushnell hass mineral salt) medium with glucose as substrate decreased the surface tension from 72 of distilled water to 32 mN/m, this strain had higher reduction than Bacillus subtilis among all the substrates tested. The selection of Pseudomonas aeruginosa for the separation of biosurfactant was determined. The crude biosurfactant was extracted from the supernatant and the yield of the crude biosurfactant was about 1 g/l. Some surface properties of rhamnolipids biosurfactant were evaluated. It also showed antimicrobial activity against different bacteria and fungi strains. The crude biosurfactant showed good action as antimicrobial activity against different bacterial and fungal species.
Microbiological analyses of an urban river continuously polluted with hydrocarbons resulted in the isolation of 33 strains of Gram negative bacteria capable of growing on n-hexadecane. One Acinetobacter strain (B2-2) was selected and several parameters that are likely to affect the growth of this strain on n-hexadecane were evaluated. Temperature, pH, inoculum size, effect of the presence of yeast extract and n-hexadecane concentration were analysed. At pH 7.5, 25°C and an initial concentration of 0.5% of n-hexadecane, 82% of the hydrocarbon was degraded in the first stage of the culture (50 h) and, at 124 h only 10% of the n-hexadecane remained undegraded. During growth, an extracellular surfactant was produced and a decrease in the surface tension of the culture media was observed. This study shows how the performance of an n-hexadecane degrader strain is affected by several factors and therefore could be helpful for the design of strategies for the bioremediation of contaminated sites.
Highly regioselective lipase catalyzed macrolactonization has been used in synthesizing first feedstock based glycolipid analogs. These macrolides containing common disaccharides maltose (4-O-α-d-glucopyranosyl-β-d-glucose) and melibiose (6-O-α-d-galactopyranosyl-β-d-glucose) were synthesized by employing chemoenzymatic methodologies. Maltose and Melibiose were coupled with methyl 15-hydroxy pentadecanoate and then subjected to a highly regioselective macrolactonization at the C-6″ position using Candida antarctica lipase-B to yield the desired products.
Pseudomonas aeruginosa RS29, the native
biosurfactant-producing strain isolated from the oil fields
of Assam, India was used to investigate the influence of the
carbon nitrogen ratio on production of the biosurfactant.
The biosurfactant producing ability of the strain was
measured based on surface tension (ST) reduction of the
culture medium and the emulsification (E24) index. Production
was greatly influenced by the sources of nitrogen
and carbon as well as the carbon to nitrogen (C/N) ratio.
Sodium nitrate was the best nitrogen source and the water
miscible carbon source, glycerol was observed as the best
carbon source for maximum biosurfactant production. The
C/N ratio 12.5 allowed the maximum production of biosurfactant
by the RS29 strain. At this C/N ratio, 55 % ST of
the culture medium was reduced by the produced biosurfactant.
Concentrations of crude and rhamnolipid biosurfactant
obtained at this particular C/N ratio were 5.6 and
0.8 g/l respectively. The RS29 strain was novel as it was
able to produce a sufficient amount of biosurfactant utilizing
a much lower amount of the water miscible carbon
source, glycerol. Extraction of the biosurfactant by a
chloroform–methanol (2:1) mixture was the best method to
obtain the highest biosurfactant from the culture medium of
the strain. The biosurfactant was confirmed as a mixture of
mono and di-rhamnolipid congeners, Rha–C10–C10–CH3
being the most abundant one. The biosurfactant was a good
foaming and emulsifying agent.
Keywords: Pseudomonas aeruginosa � C/N ratio �
Biosurfactant � Rhamnolipid
Bioavailability is herein defined as the accessibility of a substrate by a microorganism. Further, bioavailability is governed by (1) the substrate concentration that the cell membrane “sees,” (i.e., the “directly bioavailable” pool) as well as (2) the rate of mass transfer from potentially bioavailable (e.g., nonaqueous) phases to the directly bioavailable (e.g., aqueous) phase. Mechanisms by which sorbed (bio)surfactants influence these two processes are discussed. We propose the hypothesis that the sorption of (bio)surfactants at the solid-liquid interface is partially responsible for the increased bioavailabdity of surface-bound nutrients, and offer this as a basis for suggesting the development of engineered in-situ bioremediation technologies that take advantage of low (bio)surfactant concentrations. In addition, other industrial systems where bioavailability phenomena should be considered are addressed.
Biosurfactants are surface-active compounds synthesized by a wide variety of microorganisms. They are molecules that have both hydrophobic and hydrophilic domains and are capable of lowering the surface tension and the interfacial tension of the growth medium. Biosurfactants possess different chemical structures — lipopeptides, glycolipids, neutral lipids, and fatty acids. They are nontoxic biomolecules that are biodegradable. Biosurfactants also exhibit strong emulsification of hydrophobic compounds and form stable emulsions. Polycyclic aromatic hydrocarbons (PAHs) can be toxic, mutagenic, and carcinogenic compounds that pollute the environment. They are released to the environment as a result of spillage of oil and byproducts of coal treatment processes. The low water solubility of PAHs limits their availability to microorganisms, which is a potential problem for bioremediation of PAH-contaminated sites. Microbially produced surfactants enhance the bioavailability of these hydrophobic compounds for bioremediation. Therefore, biosurfactant-enhanced solubility of PAHs has potential applications in bioremediation.
Gegenstand der Untersuchungen sind langkettige Fettsäuren mit einer Methylgruppe in unterschiedlicher Position zur Carboxylgruppe sowie Fettsäuren mit unterschiedlich langen Alkylresten in α-Position. Die analytische Razemattrennung als Methylester mittels GC an einer chiralen Säule hängt stark von der Struktur der verzweigten Fettsäure ab. Präparativ wurden razemische α-verzweigte Fettsäuren als diastereomere Amide getrennt. Die verzweigten Fettsäuren wurden in 1,2-Diacyl-, 1-Acyl-2-hexadecyl- und 2-Acyl-1-hexadecyl-glycerophosphocholine eingebaut, deren physikochemisches Verhalten mit verschiedenen Methoden (Mikrokalorimetrie, Röntgendiffraktion) untersucht wurde. Durch HPLC und präparative Säulenchromatographie gelang die Trennung von diastereomeren Phospholipiden mit verzweigten Fettsäuren.
Analytics and biophysics of branched fatty acids in lipids. Objects of our investigations are long chain fatty acids with methyl groups in different positions and fatty acids with a different length of the sidegroup in α-position. The separation of racemic branched fatty acid methyl esters by gas chromatography on a chiral column depends on the structure of the branched fatty acid. Diastereomeric amides and phosphatidylcholines with α-branched fatty acid residues were separated preparatively. The branched fatty acids were incorporated into 1,2-diacyl-, 1-acyl-2-hexadecyl- and 2-acyl-1-hexadecyl-glycerophosphocholines and characterized by differential scanning calorimetry and X-ray diffraction.
Bacillus subtilis experiments for surface tension evaluation were accomplished with culture medium containing 0.4% nitrate ions and 4% glucose basic nutrient in the presence of crude oil. Surfactin production was observed by surface tension reduction of the culture broth. Surfactin was isolated from Bacillus subtilis fermented broth, by acid-precipitation followed by extraction with chloroform-methanol. Evaluation of the linear alkanes composition was performed by capillary gas chromatography. We observed a significant reduction of the surface tension of the fermented broth indicating that the biosurfactant production was not inhibited by the crude oil presence, and that the light paraffins might have been consumed.
The effect of ammonium on growth ofCandida apicola and on production of sophorose lipid was studied. Sophorose lipid production increased with increasing initial ammonium sulphate concentration. Both growth and product formation were strongly reduced at 73.6mm ammonium. With 58.9mm ammonium a microcrystalline sophorose lipid was formed. The ratio of the two isomers of the sophorose lipid, harbouring either ?- or ?-1 hydroxy fatty acid, was influenced by the initial concentration of ammonium. Both production kinetics, yields and profiles of the total cellular fatty acids express alterations with enlarged ammonium concentrations. These results suggest regulatory effects of ammonium onC. apicola and its sophorose lipid synthesis.
This study reports the production of biosurfactant by a psychrophilic strain ofArthrobacter protophormiae during growth on an immiscible carbon source, w-hexadecane. The biosurfactant reduces the surface tension of the medium from
68.0 mN/m to 30.60 mN/m and exhibits good emulsification activity. The strain could grow and produce biosurfactant in the
presence of high NaCl concentrations (10.0 to 100.0 g/1). Although the biosurfactant was isolated by growing the organism
under psychrophilic conditions (10‡C) it exhibited stable activity over a wide range of temperature (30‡C to 100‡C). It retained
its surface-active properties at pH2 to 12. The biosurfactant was effective in recovering up to 90% of residual oil from an oil saturated sandpack column, indicating
its potential value in enhanced oil recovery.
A study was undertaken to investigate the distribution of biosurfactant producing and crude oil degrading bacteria in the oil contaminated environment. This research revealed that hydrocarbon contaminated sites are the potent sources for oil degraders. Among 32 oil degrading bacteria isolated from ten different oil contaminated sites of gasoline and diesel fuel stations, 80% exhibited biosurfactant production. The quantity and emulsification activity of the biosurfactants varied. Pseudomonas sp. DS10-129 produced a maximum of 7.5 ± 0.4 g/l of biosurfactant with a corresponding reduction in surface tension from 68 mN/m to 29.4 ± 0.7 mN/m at 84 h incubation. The isolates Micrococcus sp. GS2-22, Bacillus sp. DS6-86, Corynebacterium sp. GS5-66, Flavobacterium sp. DS5-73, Pseudomonas sp. DS10-129, Pseudomonas sp. DS9-119 and Acinetobacter sp. DS5-74 emulsified xylene, benzene, n-hexane, Bombay High crude oil, kerosene, gasoline, diesel fuel and olive oil. The first five of the above isolates had the highest emulsification activity and crude oil degradation ability and were selected for the preparation of a mixed bacterial consortium, which was also an efficient biosurfactant producing oil emulsifying and degrading culture. During this study, biosurfactant production and emulsification activity were detected in Moraxella sp., Flavobacterium sp. and in a mixed bacterial consortium, which have not been reported before.
Summary Surfactant (BL86) was isolated from foam produced during growth ofBacillus licheniformis 86 by acid-precipitation followed by extraction into tetrahydrofuran or methanol. The surfactant is anionic and dissolves in tetrahydrofuran, methanol, chloroform, dichloromethane, xylene, toluene, and alkaline water. The surfactant lowers the surface tension of water to 27 dynes/cm, and achieves the critical micelle concentration with as little as 10 µg surfactant/ml. Its interfacial tension can reach 0.36 dynes/cm when measured in 4% sodium chloride againstn-hexadecane. The surfactant is stable from pH 4.0 to 13.0, at temperatures ranging from 25 to 120°C, and in salt solutions ranging from 0 to 30% NaCl. Preliminary analytical results indicate that the surfactant is a mixture of lipopeptides different from previously reportedBacillus produced surfactants.
A Rhodococcus species, the best of 99 oil-emulsifying bacteria isolated from globally distributed seawater samples, was characterized. The bacterium produced very stable oil-in-water emulsions from different crude oils with various contents of aliphatic and aromatic compounds by utilizing the C11 to C33n-alkanes as carbon and energy sources. The presence of alkanes induced the formation of a hydrophobic cell surface that permitted oil-associated exponential growth and where an extensive emulsification of the residual oil and accumulation of acidic oxidation products occurred. The acidic products were consumed in a second step characterized by linear growth and an increasing number of cells growing in the water phase. Adhesion of cells resulted in some stabilization of oil droplets, but the most extensive emulsification occurred at the end of the exponential phase and coincided with an increasing number of cells in the water phase. No surfactant could be detected in the water phase during exponential growth, but a polymeric compound with emulsifying activity, tightly bound to the oil droplets, could be isolated. This suggests that the emulsification was caused by the release of the hydrophobic cell surface discarded by the cells during conditions of growth limitations.Key words: Rhodococcus,emulsification, adhesion, n-alkanes, hydrophobicity.
Surfactants have the ability to increase aqueous concentrations of poorly soluble compounds and interfacial areas between immiscible fluids, thus potentially improving the accessibility of these substrates to microorganisms. However, both enhancements and inhibitions of biodegradation of organic compounds in the presence of surfactants have been reported. The mechanisms behind these phenomena are not well understood. To better understand the factors involved and the current state of knowledge in this field, a search of the literature concerning the influence of commercial surfactants and biosurfactants on microbial metabolism has been conducted. Factors pertaining to surfactant‐substrate interactions such as emulsification, solubilization, and partitioning of hydrocarbons between phases, all of which can influence accessibility of substrates to microorganisms, are of concern. Also, due to the direct interaction of surfactants with microorganisms, it appears that steric or conformational compatibility of surfactants with cell membrane lipids and enzymes is an important metabolic factor. Weaknesses in the general data base are evident, such as the lack of research involving Gram‐positive organisms and ionic surfactants. It is also worthy to note that research involving commercial surfactants and mixed microbial cultures has shown a correlation between inhibited biodegradation of hydrocarbons and surfactant concentrations above the critical micelle concentration. This is a significant point of interest when remedial efforts involving indigenous organisms in natural environments are being considered.
Biotransformation of [1-13C] labelled hexadecane, hexadecanol and hexadecanoic acid have been investigated using the yeast Torulopsis apicola. The yeast produces a microcrystalline mixture of two glycolipids, the lipophilic moiety of which consists of ω- or (ω-l)-hydroxylated hexadecanoic acid. Biosynthesis of these glycolipids takes place via hydroxylation of hexadecane, oxidation to hexadecanoic acid and ω or (ω-l)-hydroxylation of hexadecanoic acid. Feeding the cell cultures with a mixture of hexadecane and [1-13C] labelled hexadecane derivatives one observes 13C enrichment ratios which indicate that neither of the biohydroxylation or oxidation steps are rate limiting in the formation of the glycolipids, furthermore, two different monooxygenase systems appear to be involved in hydroxylation of hexadecane and hexadecanoic acid.
Abstract While a class of yeasts excrete lipid-containing surfactants, oleaginous yeasts produce and store lipids similar to vegetable oils and fats. Recovery of the oleaginous yeast lipids is problematic because of their intracellular nature and protection by well-knit biopolymers of the cell wall and other membrane systems. There is no suitable method of choice that ensures 100% recovery of intracellular lipids without affecting the native state during different unit operations. Several laboratory methods are available, but none can be adopted directly for commercial extractions due to technological limitations. However, as a result of the emergence of new downstream processing techniques, there is a positive indication for commercialization of yeast-lipid production in the future. Although most of the oleaginous yeasts are nonpathogenic, it is mandatory to analyze and report quality as well as toxicity of their lipids prior to market introduction as a component of human diet. This warrants specially formulated codes for edibility of yeast lipids and, in general, for similar products from other microbial sources.
IntroductionBiosurfactant ClassesBiosynthesisBiosurfactant ProductionBiosurfactant Properties of Interest for CosmeticsMedical and Pharmaceutical ApplicationsBiosurfactants in FoodsBiosurfactants for Environmental ControlBio-De-EmulsifiersReferences
Surfactants find applications in a wide variety of industrial processes. Biomolecules that are amphiphilic and partition preferentially at interfaces are classified as biosurfactants. In terms of surface activity, heat and pH stability, many biosurfactants are comparable to synthetic surfactants. Therefore, as the environmental compatibility is becoming an increasingly important factor in selecting industrial chemicals, the commercialization of biosurfactant is gaining much attention. In this paper, the general properties and functions of biosurfactants are introduced. Strategies for development of biosurfactant assay, enhanced biosurfactant production, large scale fermentation, and product recovery are discussed. Also discussed are recent advances in the genetic engineering of biosurfactant production. The potential applications of biosurfactants in industrial processes and bioremediation are presented. Finally, comments on the application of enzymes for the production of surfactants are also made.
BACKGROUND: Biosurfactant production was investigated using two strains of Bacillus subtilis, one being a reference strain (B. subtilis 1012) and the other a recombinant of this (B. subtilis W1012) made able to produce the green fluorescent protein (GFP).
RESULTS: Batch cultivations carried out at different initial levels of glucose (G0) in the presence of 10 g L−1 casein demonstrated that the reference strain was able to release higher levels of biosurfactants in the medium at 5.0≤G0≤10 g L−1 (Bmax = 104–110 mg L−1). The recombinant strain exhibited slightly lower levels of biosurfactants (Bmax = 90–104 mg L−1) but only at higher glucose concentrations (G0 ≥ 20 g L−1). Under these nutritional conditions, the fluorescence intensity linked to the production of GFP was shown to be associated with the cell concentration even after achievement of the stationary phase.
CONCLUSION: The ability of the genetically-modified strain to simultaneously overproduce biosurfactant and GFP even at low biomass concentration makes it an interesting candidate for use as a biological indicator to monitor indirectly the biosurfactant production in bioremediation treatments. Copyright
The Nocardia sp. L-417 strain grown with n-hexadecane as a carbon source produced two types of biosurfactant that have different characteristics. These biosurfactants were purified by procedures that included ammonium sulphate fractionation, chilled acetone and hexane treatments, silica-gel column chromatography and Sephadex LH-20 gel filtration. The purified biosurfactants were very stable over a broad range of pHs (2–12) and temperatures (100 °C, 3 h). The biosurfactant type I had strong properties as an emulsifying agent and as an emulsion-stabilizing agent, whereas type II had a strong ability to reduce surface tension.
This study presents novel information useful for addressing the question how species of the genus Alcanivorax discharge triacylglycerols (TAG) and/or wax esters (WE). The observed structures were referred as “blebs” according to Gauthier et al.1 to avoid confusion with other discharging phenomena. The cells were aerobically cultivated on solid media and not in liquid media to maintain the cells in the native state, and were investigated by transmission electron microscopic (TEM) and scanning electron microscopic (SEM) methods to document the surface structures of the cells. The phenomenon of lipid export could be allocated to three phases: phase I: protrusion formation of the cell membrane occurred; phase II: discharging progressed further with blebs becoming larger; and phase III: the blebs at the cell surface were separated from the cells. Using freeze-fracture micrographs by TEM, vesicle experiments and TLC, we have shown that the blebs contained TAGs and WEs. The results shown in this study will support further research to unravel the unknown discharging mechanism. In addition, the formation of an extensive extracellular matrix was observed by SEM.
Pseudomonas fluorescens in free suspension and immobilized to a commercially available biosupport (Biofix) and a biosorbent (Drizit), were used as bioremediation agents in an aqueous system with petrol (Slovene diesel) as the carbon source. Analysis of cellular growth and estimation of rhamnolipid production was carried out on the free suspension of the free and immobilized systems over 5 d. An increase in growth and rhamnolipid production was seen in the immobilized systems in comparison to the free system. EDTA was shown to be an inhibitor of rhamnolipid production. Its addition to the aqueous suspensions of all systems resulted in a fall in production of the surface-active agent in all cases, with no corresponding decrease in growth. This indicates the bacteria can rely on contact between the cell and the oil droplet for hydrocarbon transport into the cell. The data from this study indicated that immobilization resulted in a combination of increased contact between cell and hydrocarbon droplets and enhanced levels of rhamnolipid production.
Biosurfactants are biologically-produced, natural surface active agents and are synthesized by a range of microorganisms. These compounds include glycolipids, lipopeptides and phospholipids. The yields of biosurfactants in microbial fermentations may be as high as 150g l−1 and may be increased by optimizing production conditions and by strain improvement. Biosurfactants display very low critical micelle concentration (CMC) values when compared with conventional surfactants and are stable at a wide range of temperatures, pH values and salinities. They show many promising characteristics for cosmetic applications.
Biotensio-actifs pour applications cosmétiques
Les biotensio-actifs sont produits biologiquement, ce sont des agents actifs en surface qui sont synthétisés par une série de micro-organismes. Ces composés comprennent les glycolipides, les lipopeptides et les phospholipides. L'activité des biotensio-actifs dans la fermentation microbienne peut atteindre 150gl-1 et peut ětre augmentée en optimisant les conditions de formation et en améliorant leur qualité. Les biotensio-actifs ont des valeurs concentration micellaire critique (CMC) très basses par rapport aux tensio-actifs conventionnels et sont stables sur un écart important de températures, de valeurs de pH et de salinité. Ils montrent des caractéristiques très prometteuses pour les applications cosmétiques.
Lipase-catalyzed synthesis of sugar fatty acid esters was performed in a heterogeneous reaction system in the presence of an organic solvent serving as adjuvant. Although the sugar is almost insoluble in such a system, high conversions to the corresponding sugar esters were achieved, due to crystallization of the product. Acylation occurred regioselectively at the primary hydroxyl group and subsequent diacylation was observed only in the case of caprylic acid (2–5%). Best conditions were found for solvents having low log P values and low product solubility such as acetone, using immobilized lipase from Candida antarctica (CAL-B, Novo SP435) and fatty acids with chain lengths from C12 to C8 as acyl donors. The esterification of β-D(+)-glucose with stearic acid resulted in up to 100% conversion after 48 hours equal to a productivity of 0.4 mmol sugar ester per gram lipase and hour.
Lipase-katalysierte Synthese von Zuckerestern. Die Lipase-katalysierte Synthese von Zucker-Fettsäureestern erfolgte in einem heterogenen Reaktionssystem in Gegenwart eines organischen Lösungsmittels als Adjuvant. Obwohl die Zucker in diesem System nahezu unlöslich sind, wurden hohe Umsetzungen zu den entsprechenden Zuckerestern erzielt, was auf die Kristallisation des Produktes zurückzuführen ist. Die Veresterung erfolgte regioselektiv an der primären Hydroxylgruppe des Zuckers, eine nachfolgende Acylierung zum Diester wurde nur bei Caprylsäure (2–5%) beobachtet. Beste Reaktionsbedingungen ergaben sich bei Verwendung von Lösungsmitteln mit niedrigen log P-Werten, die eine geringe Produktlöslichkeit aufweisen (z.B. Aceton), mit Lipase aus Candida antarctica (CAL-B, Novo SP435) und Fettsäuren mit Kettenlängen zwischen C12 und C18 als Acyldonoren. Die Veresterung von β-D(+)-Glucose mit Stearinsäure ergab bis zu 100% Umsatz nach 48 Stunden, entsprechend einer Produktivität von 0,4 mmol Zuckerester pro Gramm Lipase und Stunde.
Biosurfactants capable of emulsifying pesticides have great potential to assist in microbial degradation of the pesticides. Solid State Fermentation (SSF) due to several advantages, is one of the efficient ways of producing these surfactants and seldom receives attention for commercial exploitation. In this study, a packed column bioreactor with wheat bran as the raw material and Bacillus subtilis has been used to produce a biosurfactant specific to disperse Fenthion, an organophosphrous pesticide. The emulsifier activity (EA) and surface tension from the packed column bioreactor were compared with flask fermentation experiments, which served as control. Airflow rate in the packed column bioreactor was varied from 10-20 l/min. Maximum EA and minimum surface tension occurred at airflow rate of 20 l/min. Peak EA in the control was 1.2 at 29 h while it was 1.9 in the bioreactor. The least surface tension of 24 dynes/cm was noticed at 54 h in the bioreactor, which was 33% better than the control at the same time period. The results indicate that the packed column bioreactor can become a more acceptable solid state fermentation system for commercial exploitation of Fenthion specific biosurfactant production.
During screening for biosurfactants among marine, n-alkane-utilizing bacteria, low- and high-molecular surface-active substances were detected. The marine bacterial strain MM1 was found to synthesize a novel glycolipid that has not so far been cited in the literature. Both 1H, 13C-nuclear magnetic resonance spectroscopic and positive ion fast atom bombardment mass spectrometer studies led to the identification of a glucose lipid consisting of four 3-OH-decanoic acids, which are linked together by ester bonds. The lipophilic moiety is coupled glycosidically with C-1 of glucose. The glucolipid reduced the surface tension from 72 mN/m to 30 mN/m while the minimum interfacial tension towards n-hexadecane was lowered to values smaller than 5 mN/m.
Fifty-seven bacterial strains were isolated from PAH-contaminated soils using PAH-amended minimal medium. The isolates were screened for their production of biosurfactants and bioemulsifiers when grown in liquid media containing selected PAHs. The results suggest that many, but not all, of the isolates are able to produce biosurfactants or bioemulsifiers under the experimental conditions. The majority of the strains isolated on phenanthrene, pyrene, and fluoranthene were better emulsifiers than surface tension reducers and the stability of the formed emulsions was in general high. The strains isolated on anthracene were in general better in lowering the surface tension than in forming emulsions. In all strains, reduction of surface tension and emulsion formation did not correlate. However, in the majority of strains the two factors were associated with the bacterial cell surfaces, rather than the culture supernatants. Nevertheless, supernatants from selected surfactant-producing anthracene isolates increased the aqueous solubility of anthracene. Although a significant potential for surfactant and emulsifier production in the microbiota of the PAH-contaminated soils was found in this study, the ability of individual strains to mineralize PAHs did not coincide with production of surface-active compounds.
1. Crude extracts prepared by sonicating Candida bogoriensis cells contained glucosyltransferases catalyzing the transfer of glucose from UDP-[¹⁴C]glucose to 13-hydroxydocosanoic acid (HDA) (transferase 1) and methyl 13-glucopyranosyloxydocosanoate (methyl GlcHDA) (transferase 2) when these lipids were added as acceptors. The enzymatic products were characterized by thin layer chromatographic and gas-liquid chromatographic comparison to derivatives of GlcHDA and 13-glucopyranosylglucopyranosyloxydocosanoate (Glc2HDA) prepared from cultures of C. bogoriensis.
2. The transferases were purified 20- and 30-fold, respectively, with no separation of the two activities and with a constant ratio of the two activities obtained in successive peak fractions from a DEAE-Sephadex column, a hydroxyl-apatite column, a gel filtration column, and a disc gel electrophoresis fractionation.
3. Both transferases were specific for UDP-glucose, showing apparent Km values of 104 and 88 µm, respectively, for this compound.
4. Glucosyltransferase 1 showed 4- to 5-fold greater activity with HDA than with its methyl ester. A series of hydroxystearate isomers also showed acceptor activity. The activity with 9-hydroxystearate was 60% of that with HDA, whereas the acceptor activity decreased as the hydroxyl group was moved toward either the methyl or carboxyl end of the fatty acid chain.
5. Glucosyltransferase 2 exhibited severe substrate inhibition with GlcHDA as acceptor and a much higher reaction velocity when the methyl ester of GlcHDA was utilized as acceptor.
6. Crude extracts of C. bogoriensis also contained acetyltransferase(s) catalyzing incorporation of [¹⁴C]acetate from [¹⁴C]acetyl coenzyme A into Ac2Glc2HDA (the diacetate of Glc2HDA) characterized by thin layer chromatographic comparison with the glycolipid isolated from C. bogoriensis cultures.
7. Acetone extraction of the lyophilized extracts, followed by DEAE-Sephadex chromatography, freed the acetyl-transferase(s) of endogenous acceptor, making activity dependent upon added methyl Glc2HDA or its monoacetate as acceptor. Methyl GlcHDA was a poor acceptor for the acetyl groups.
8. In fermentor cultures the peak of glucosyltransferase 1 and 2 activities was reached in 1½ days and the peak of acetyltransferase activity was reached in 3 days. This time course is consistent with involvement of these enzymes in the biosynthesis of extracellular Ac2Glc2HDA, and with the tentative conclusion that extracellular AcGlc2HDA and Glc2HDA were formed by deacetylation of Ac2Glc2HDA.
Crude extracts prepared by sonicating Candida bogoriensis cells catalyzed the incorporation of radioactivity from UDP-[¹⁴C]glucose into a lipid different from the hydroxydocosanoic acid glycosides also formed by this organism. 1-Butanol-acetone extraction of lyophilized crude extract made the glycosyltransferase dependent upon added C. bogoriensis lipids. The active lipid acceptor was purified and identified as ergosterol, and both authentic ergosterol and cholesterol were effective in stimulating glucosyltransferase activity. Incubation of the 1-butanol-acetone extract with UDP-[¹⁴C]glucose and [1,2-³H]cholesterol yielded a glycolipid product containing equimolar amounts of ¹⁴C and ³H. The product was stable to sodium methoxide but was hydrolyzed in methanolic HCl, and therefore has the properties of cholesteryl glucoside. The crude UDP-glucose: sterol glucosyltransferase was stimulated by ethanol in the range of 7 to 15% by volume, and retained activity in up to 20% ethanol.
Earlier (Godchaux, W., and Leadbetter, E. R. (1980) J. Bacteriol. 144, 592-602; (1983) J. Bacteriol. 153, 1238-1246) we demonstrated that an unusual class of sulfonolipids are major components of the cell envelope of gliding bacteria of the genus Cytophaga and of closely related genera. One of these lipids, to which we have assigned the trivial name capnine, was purified and was shown to be 2-amino-3-hydroxy-15-methylhexadecane-1-sulfonic acid (which might also be named as 1-deoxy-15-methylhexadecasphinganine-1-sulfonic acid). Though capnine accumulates as such in the cells of some Capnocytophaga spp., most organisms of the Cytophaga-like genera contain, instead, sulfonolipids that are less polar than capnine. These less polar lipids have been purified from a Capnocytophaga sp., a marine Cytophaga sp., Cytophaga johnsonae, and a Flexibacter sp. Acid methanolysis of the lipids yielded both aminosulfonates and a collection of fatty acid methyl esters. The infrared absorption spectra of the lipids indicated that the fatty acids were in amide (and not ester) linkage to the aminosulfonates. In every instance, analysis by mass spectrometry and other methods revealed that most, if not all, of the aminosulfonates obtained by methanolysis were structurally identical to capnine (though small amounts of variants of that compound may be present in some cases). The less polar sulfonolipids are, therefore, predominantly N-fatty acyl capnines, 1-deoxy-1-sulfonic acid analogs of ceramides. The fatty acid methyl esters obtained from the lipids were heterogeneous, but in all cases were rich in hydroxylated fatty acyl groups, which constituted 66 to 95% of the total.
Rhodococcus erythropolis DSM 43215 produced a surface-active trehalose lipid whose formation was induced by n-alkanes to a maximum of 2.1 g l-1 in a 50 l batch culture on 2% (w/v) n-alkanes of chain length C12 to C18. The glycolipid was extracted from the biomass with n-hexane and was purified by repeated chromatography on silica gel. It contained α,α-trehalose as the sole non-reducing sugar. The lipid moiety was characterized by 13C nuclear magnetic resonance spectroscopy and mass spectrometry and consisted predominantly of saturated long-chain α-branched β-hydroxy fatty acids (mycolic acids) ranging from C32H64O3 to C38H76O3, of which C34H68O3 and C35H70O3 predominated. The molar ratio of trehalose to mycolic acids was 1:2. 13C nuclear magnetic resonance analysis of the O-hexamethyltrehalose obtained by saponification of the permethylated trehalose dimycolates revealed, with the aid of deuterium exchange, that the ester linkages of mycolic acids are to both primary alcohol groups at the C-6 and C-6’ positions of the trehalose.
Torulopsis bombicola produces extracellular sophorolipids when it is grown on
water-insoluble alkanes. Sophorolipids and related model compounds, which
were not themselves used for growth, were found to stimulate markedly the
growth of T. bombicola on alkanes. This stimulatory effect was restricted to
growth on C10 to C20 alkanes, whereas no significant influence was observed for
growth on fatty alcohols, fatty acids, glucose, or glycerol. The nonionic methyl
ester of the glycolipid supported the greatest cell yield. However, a number of
synthetic nonionic surfactants were unable to replace the glycolipid. When
organisms were grown on hexadecane, stimulation of growth by sophorolipids
was observed almost exclusively with strains of Torulopsis yeasts. In contrast, the
growth of other typical alkane-utilizing yeasts, such as Candida and Pichia
strains, was inhibited or not affected. It appears that sophorolipids are involved in
alkane dissimilation by T. bombicola through an undetermined mechanism.
Strain MR-12 which was derived from Candida cloacae M-l as a mutant unable to assimilate n-alkane showed marked increase in dicarboxylic acid (DC) productivity from n-alkane.
Resting cells of strain MR-12 produced 42.7g/liter of n-tetradecane 1,14-dicarboxylic acid (DC-16) from n-hexadecane (n-C16) after 72 hr’ incubation. DC degradation activities of strain M-1 and MR-12 were found to be markedly reduced and their activities against DC-16 decreased to 40% and 10% of that of the parent strain, respectively.
Strain M-1 and MR-12 produced DC from the various oxidized derivatives of n-alkane such as alcohol, diol, aldehyde, fatty acid and methyl- or ethylester of fatty acid other than n-alkane.
The carbon balance in n-C16 oxidation was determined by using resting cells of strain MR-12 and about 60% of utilized carbon was recovered as DC-16 and about 40% was recovered as CO2.
The growth of microorganisms on hydrocarbons is often associated with the production of surfactants. These metabolites are involved in the mechanism for the initial interaction of hydrocarbons with the microbial cell. The production and function of α,α-trehalose-6,6Ȳ-dimycolate and α,α-trehalose-6-monomycolate from Rhodococcus erythropolis grown on n-alcanes are described. The influence of these glycolipids on the reduction of surface tension and interfacial tension depending on the salinity of the water phase are discussed. A short account about the application of the trehaloselipids in enhanced oil recovery concludes the paper.
During the production of nucleotides with Brevibacterium ammoniagenes abnormally shaped elongated cells are induced by depletion of manganese ions. Proteins including enzymes for the biosynthesis of nucleotides are released into the medium. Cells have a lowered phospholipid content under manganese deficient conditions. In particular the phosphatidyl glycerol and cardiolipin content was increased. The inhibition of DNA synthesis can be reversed by the addition of manganese ions. From inhibition experiments it may be concluded that the reduction of ribonucleotides to deoxyribonucleotides is the primary target of manganese starvation.
Screening test for obtaining growth stimulant (GS) produced by a hydrocarbon-utilizing bacterium, Pseudomonas aeruginosa S7B1, was carried out. In consequence, the anthrone positive substance was most effective on the growth of this strain. Although the growth of this strain on glucose medium had no relation with the addition of GS, the growth on n-hexadecane medium was remarkably stimulated by the addition of GS. This effect of GS seemed to be specific on the growth of P. aeruginosa. GS which had a strong surface activity and emulsifying power was comfirmed to be rhamnolipid.
Prof, (now Sir Brian) Flowers deserves all praise from universities for what he has done for their computing facilities. Having launched the famous 'Flowers' Report in 1965, he has chaired the Computer Board since its establishment in 1966, and he now reports on the first two years of the Board's work.
One characteristic feature of many phytopathogenic organisms is their ability to produce an array of enzymes capable of degrading the complex polysaccharides of the plant cell wall (Bateman and Millar, 1966; Wood, 1967; Albersheim et al., 1969; Wood, 1973) and membrane constituents (Porter, 1966; Tseng and Bateman, 1968). These enzymes usually are produced inductively. Generally, they are extracellular, highly stable and present in infected host tissues. In most plant diseases caused by microbial agents, cell walls are penetrated, tissues are colonized, and permeability of host cells is altered. A brief summary of our understanding of cell wall and membrane structure, coupled with knowledge of the enzymes capable of degrading the components of these structures, and an analysis of the association of these enzymes with diseased tissue, should enable us to make an appraisal of their involvement in pathogenesis and point the way to an objective consideration of this area of disease physiology.
Two kinds of glycolipids (R-l and R-2) were produced in the culture media by several strains of Pseudomonas aeruginosa when grown on n paraffin (mixture of C12, C13. and C14 fractions). These compounds were isolated through the extraction of the culture broth with ethylacetate and the chromatography on silicic acid column. On the basis of chemical analysis, these lipids were characterized as 2-O-α-L-rhamnopyranosyl-α-L-rhamnopyranosyl-β- hydroxydecanoyl-β-hydroxydecanoate (R-l) and L-α-rhamnopyranosyl-β- hydroxydecanoyl-β-hydroxydecanoate (R-2). Bactericidal activity of R-2 which is postulated to be a precursor of R-1 was remarked against grampositive bacteria. Further, these compounds also demonstrated mycoplasmacidal and antiviral activities in vitro.
Partly acylated ustilagic acids 8 [from Ustilago maydis (DC) (= U. zeae Unger) PRL-119], consisting of partially esterified β-cellobiosyl residues glucosidically linked to long-chain, hydroxylated fatty acids, and a mixture of partially acylated derivatives of 4-O-β-D-mannopyranosyl-D-erythritol from Ustilago sp. [probably U. nuda (Jens.) Rostr. = U. tritici (Pers.) Rostr.] PRL-627 were acetalated with methyl vinyl ether, deacylated, and methylated. Vigorous acid hydrolysis of a methylated 8 gave 2- and 6-O-methyl-D-glucose (11:9 molar ratio) corresponding to 2′- and 6-O-acyl substitution of the cellobiose residue. Graded acid hydrolysis of methylated 8 gave an O-methyl derivative (9) which yielded, on Smith degradation, glycerol and 4-O-methyl-D-erythritol. Comparison of the p.m.r. spectra of 8 and the product of its oxidation by lead tetraacetate suggested C-6 and C-2′ as the locations of the acetate and hydroxy acid ester-groups, respectively. Vigorous acid hydrolysis of the methylated PRL-627 glycolipid gave d-mannose, its 2- and 4-methyl, and 2,6- and 4,6-dimethyl ethers, and erythritol and its D-1- and 2-methyl-, and 1,3-dimethyl ethers. The positions of the methyl groups corresponded to those of the ester groups in the glycolipid.
Twenty-three hydrocarbon-utilising bacteria and one yeast were isolated, using enrichment techniques, from water and sediment samples. Vibrio and Pseudomonas were the predominant genera. Of the different organisms screened, Bacillus, Candida and Arthrobacter sp. exhibited the widest range of hydrocarbon-utilising profiles. Arabian Sea crude and kerosene supported the growth of most of the isolates.
Methyl [(17L)-17-3H1]stearate, methyl [(17D)-17-3H1]stearate, and methyl [(17DL)-17-3H1]stearate have been prepared. Each of these compounds, mixed with methyl [U-14C]stearate, has been incubated with Torulopsis gropengiesseri, to give, after work-up, methyl 17-L-hydroxystearate and dimethyl octadecane-1,18-dioate. Determination of the 3H : 14C ratios of the latter compounds has established (a) that ω-hydroxylation and ω-1-hydroxylation of stearic acid are independent reactions which involve overall a direct substitution of a hydrogen atom by a hydroxy-group, (b) that the ω-1-hydroxylation of stearic acid is a stereospecific process which takes place with retention of configuration, and (c) that a kinetic isotope effect probably operates during the hydroxylation of [(17L)-17-3H1]stearic acid. A mixture of 1-bromo[(16DL)-16-3H1]heptadecane and 1-bromo[U-14C]heptadecane has been oxidised with T. gropengiesseri, to give, after work-up, dimethyl heptadecane-1,17-dioate. No change in the 3H : 14C ratio was observed during this transformation. This result has been interpreted as evidence that alk-1-enes are not intermediates in the terminal oxidation of alkanes by the yeast.
In a medium containing glucose, the yeast Torulopsis gropengiesseri effects the following transformations: (a) long-chain 1-halogenoalkanes to αω-alkanedioic acids; (b) 1-cyanohexadecane to the cyanohydrin derivative of 16-oxohexadecanoic acid; (c) long-chain 1-methoxyalkanes and 1-ethoxyalkanes to ω-hydroxyalkanoic acids; (d) long-chain 1-propoxyalkanes to ω- and ω-1-hydroxyalkoxyalkanoic acids. The transformation products separate from the culture medium as glycolipids. Metabolic pathways which account for these transformations are proposed.
In a medium containing glucose, the yeast Torulopsis gropengiesseri converts long-chain methyl-branched alkanes into glycolipids by one or more of three metabolic pathways, namely, (i) alkane → alkan-1-ol → alkanoic acid →ω- and/or ω-1-hydroxyalkanoic acid → glycolipid, (ii) alkane → alkan-1-ol → glycolipid, and (iii) alkane → alkan-1-ol →ω- and/or ω-1-hydroxyalkan-1-ol → glycolipid. Pathways (ii) and (iii) are important for the metabolism of alkan-1-ols whose dehydrogenation to alkanoic acids is inhibited by one or more methyl substituents close to the primary alcohol group. Initial oxidation of 2,2-dimethylhexadecane occurs exclusively at the less hindered terminal position which is the predominant site of the initial oxidation of 2-methyl-hexadecane. Alkanoic acids and alkan-1-ols which have methyl substituents close to the functional group give ω- and ω-1-hydroxy-derivatives; alkanoic acids and alkan-1-ols which have methyl substituents at the ω-1-position give ω-hydroxy-derivatives.
This chapter discusses the metabolism of α,α-trehalose. The chapter outlines the various reactions that have been shown to be involved in the metabolism of trehalose. The other isomers of trehalose containing D-glucopyranose—that is, α,β-trehalose and β,β-trehalose have been synthesized chemically. However, except for a few rare cases, these isomers of trehalose do not appear to be naturally occurring. The mechanism of biosynthesis of α,α-trehalose. To determine the role of trehalose in Mycobacterium the levels of free and “bound” (that is, lipid-associated) trehalose and glycogen during growth of Mycobacterium smegmutis under various conditions of nitrogen limitation is examined. Whereas the glycogen levels increased markedly as the nitrogen content of the medium was lowered, the levels of trehalose remained fairly constant. The results of labeling studies suggested that the free trehalose in these cells may be utilized for purposes except as an energy reserve, whereas glycogen is probably stored mainly as a reserve. Synthesis and degradation of trehalose constitute a mechanism for the resorption of D-glucose in the kidney and, perhaps, also in the intestine. It has also been suggested that trehalose—like another naturally occurring, nonreducing disaccharide, sucrose—could function in the movement of carbohydrate, .i.e., as a translocate in plants or insects, or both.
Bacterial adherence to hydrocarbons (BATH) is a simple and rapid technique for determining cell-surface hydrophobicity. During recent years, this method has found application in the study of the surface characteristics of a wide variety of bacteria and bacterial mixtures. Correlations have been found between the adherence of bacteria to hydrocarbons and their attachment to other surfaces, including non-wettable plastics, epithelial cells, and teeth. A slight modification of the assay enables the isolation of nonhydrophobic mutants. The present publication briefly describes the technique and its modifications, summarizes results obtained using this method, and suggests several directions for further investigation.
Acinetobacter calcoaceticus 69-V is capable of utilizing n-alkanes as the sole carbon source. By conventional and high voltage electron microscopy the fine-structure of these bacteria grown on hexadecane (with or without addition of DL-carnitine), succinate or yeast extract was analysed. A. calcoaceticus grown on hexadecane exhibited intracytoplasmic unit membrane aggregates in contrast to controls grown on the nonhydrocarbon substrates. Probably these aggregates are formed by the cytoplasmic membrane. Most of these membranes are surrounding and penetrating hexadecane inclusions. Ultrastructurally no essential difference caused by addition of carnitine could be seen. The results suggest that the membrane aggregates are the sites of enzymes which are required for the utilization of hexadecane.
Past and present research on Enhanced Oil Recovery is reviewed with emphasis on the surface phenomena involved. The nature of capillary pressure phenomena in porous media has been understood for some time, and much research has been devoted towards the alteration of the surface forces which prevent the efficient displacement of oil by water. Early work often treated surface active agents as wetting agents designed to remove the oil from the solid surface by classical detergent action. More recent work has recognized the strong influence of oil-water interfacial tension on the displacement of discontinuous oil blobs or ganglia. Therefore, surfactant systems are now being developed to produce the lowest possible oil-water interfacial tensions by adjusting the various components and thus, the phase behavior in the total system. In addition to inter-facial tension, the phase behavior itself can strongly influence the oil displacement. The surfactant work, current work in blob mechanics, current research in CO2 flooding, and past results in alcohol flooding all indicate that an expanding oil phase is very important for effective oil displacement. Therefore, much current research is directed toward methods which utilize materials (including gases such as CO2 and mobility control agents) to dislodge oil blobs, or to prevent their entrapment by maintaining a continuous oil phase and improving sweep efficiency during displacement. The general direction of future research on enhanced oil recovery is predicted.
THE effect of non-polar groups on the structural properties of liquid water is of interest in several fields of enquiry. The most direct method of studying such systems is by the determination of hydrocarbon solubilities, but, until recently, reliable experimental data have been confined to the four lowest members of the paraffin series1,2. McAuliffe has provided a valuable extension to the existing data by his study of the solubilities of twenty-three aliphatic and aromatic hydrocarbons3. His results show good agreement with earlier data for the C1-C4 paraffins1,2, but his values for the C5-C8 members of the series are lower by more than one order of magnitude than the only other recorded solubilities of these hydrocarbons4.
Microorganisms and microbial products can be used to recover oil from reservoirs. To be successful, the complexity of oil and the physical constraints in the reservoir must be taken into account. The three general approaches are: stimulation of the endogenous microbial population; injection of microorganisms with proven ability to perform well in situ; and the use of microbial products, such as xanthan gum, produced by Xanthomonas campestris.
The following groups of glycolipids are reviewed: 1.(1)|The toxic cord factors (6,6′-diesters of trehalose),2.(2)|Wax D, a macromolecular peptidoglycolipid having adjuvant activity,3.(3)|The mycosides A, B and C, which are deoxyhexose containing “type-specific” glycolipids of mycobacterial origin,4.(4)|The phosphatidyl myo-inositol mannosides,5.(5)|Carotenol-glycosides.Wherever possible, chemical structure, biosynthesis and biological activities are considered.
Ether-soluble "oils" of specific gravity > 1 were produced extracellularly in yields of over 16 gm./liter fermentation mixture by strains of Ustilago zeae growing in shaken flasks on medium containing cerelose, urea, and sugar beet molasses. The bulk of the oily material was shown to be a glycoside of mannose and erythritol, and in addition, itaconic acid and dianthrone were shown to be present. Yields of itaconic acid as determined by a bromine–iodine method at pH 1.2 (Friedkin) reached values of over 15 gm./liter but such values were considerably higher than those indicated by quantitative isolation of this acid. One hundred and eighty isolates of Ustilago were grown on medium with and without calcium carbonate and some 45 isolates produced extracellular oily material, 98 produced ustilagic acid, and 50 produced both crystals and oil. Ether-soluble substances from freeze-dried fermentation mixtures of different isolates ranged from 1 to 12 gm./liter, while methanol-soluble substances from ether-extracted freeze-dried fermentation mixtures ranged from 1 to 45 gm./liter.
Bei den Lipoiden der Mycobakterien lassen sich drei große Gruppen unterscheiden: Fette, Phospholipoide und Wachse. Es sind vor allem Ester verzweigter Fettsäuren mit Zuckern, Zuckeralkoholen, Glycerin und höhermolekularen, verzweigten, aliphatischen Alkoholen. Besonders interessante Substanzen sind der toxisch wirkende Cord-Faktor und die D-Wachse. Die Struktur des Cord-Faktors konnte durch Abbau und Synthese gesichert werden. Es handelt sich um ein Trehalose-6.6′-dimycolat. Molekulargewicht und Zusammensetzung der D-Wachse variieren mit dem Bakterienstamm, aus dem sie isoliert werden. Sie bestehen je zur Hälfte aus Mycolsäuren und einem stickstoff-haltigen Polysaccharid. Die D-Wachse humaner Stämme zeigen Adjuvanswirkung.
A kinetic model is presented to explain microbial growth using liquid n-alkanes as substrate. The model is based on the assumption that growth occurs on the soluble alkane and that the metabolite produced by the growing cells helps the dissolution of liquid alkanes in the aqueous medium. Growth curves based on that model fit well with growth data for batch and continuous culture reported by various authors. The model also explains the differences between the relative length of exponential and linear phases of growth reported earlier.
Several strains of Pseudomonas, Nocardia and incompletely identified soil isolates have been grown in a mineral salts plus hydrocarbon medium, and the fatty acids produced by the organisms have been isolated, identified and estimated. The results of an estimation of the percentage conversion to these acids under varying experimental conditions is discussed in relation to the metabolic systems involved. Some indication has been obtained that the hydrocarbon breakdown pathway by these organisms is that of ω oxidation followed by β oxidation. Preliminary experiments carried out with one strain of organism, Pseudomonas aeruginosa 5940, indicate that there may be some difference in the utilization of odd- and even-chain hydrocarbons by this organism. An improvement of 3 ·8-fold was obtained by using nitrate instead of ammonium nitrogen; 13-fold by using continuous instead of batch operation; and 8-fold by the use of liquid instead of solid paraffins, giving a total improvement of yield of 400-fold.