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Publications (77)
The problems of malnutrition constitute a major challenge in South Africa, particularly affecting the underprivileged populations of the Eastern Cape and Limpopo provinces. The present study aimed to gain an understanding of how to improve the nutritional intake of South African university student mothers and their children by the introduction of M...
Native to India, Moringa oleifera Lam. is a plant with high nutritional value, which is now grown across the world, especially in tropical and subtropical regions. This study determined the knowledge, consumption, attitudes and beliefs toward Moringa oleifera in some African countries (Nigeria, Ghana, and South Africa) and in India to gain a better...
Hemp protein concentrates were obtained from hemp seed cake by extraction at high alkaline pH (10 and 12) followed by an ultrafiltration/diafiltration (UF) purification step and spray‐drying. The composition, thermal, nutritional, and functional properties of the resulting protein samples were evaluated. The UF treatment increased protein purity of...
African locust bean (AfLB) protein isolates could be an interesting alternative to the use of soy as an ingredient for the development of new protein-rich products. From AfLB seed flour, the protein extractability yields by aqueous extraction were determined as a function of pH and ionic strength. Then thermally induced gelation of various protein...
Moringa oleifera is a nutrient-rich plant, known as a miracle tree, and commonly used as a food supplement. Despite its popularity, there are scant empirical findings on its real nutritional benefits and acceptance among consumers when added to food. To fill this gap, we added Moringa Dried Leaves (MDL) to biscuits. A consumer test was implemented...
In the present paper, the Layer by Layer (LbL) method using β-lactoglobulin and sodium alginate was performed to individually encapsulate Saccharomyces cerevisiae cells in microorganized shells in order to protect them against stresses during dehydration. Higher survival (∼1 log) for encapsulated yeast cells was effectively observed after air dehyd...
During industrial yeast production, cells are often subjected to deleterious hydric variations during dehydration, which reduces their viability and cellular activity. This study is focused on the yeast Lachancea thermotolerans, particularly sensitive to dehydration. The aim was to understand the modifications of single-cells biophysical profiles d...
The purpose of this paper was to study the extraction conditions of hemp proteins from undelipidated press‐cakes. The effects of different hydration conditions on protein recovery yield and polypeptide profile were evaluated: pH (2 to 12), ionic strength (0 to 500 mM NaCl) and press‐cake/liquid weight ratio (2% to 22%). pH was the most impacting fa...
The development of new fermented foods and beverages requires more and more the use of new dehydrated yeasts species. In this context, the non-Saccharomyces (NS) yeasts Torulaspora delbrueckii, Metschnikowia pulcherrima and Lachancea thermotolerans are developed especially in winemaking as co-culture in the fermentation of the must or for the must...
the manufacture of novel blended dairy gels (called “mixed gels” here) containing fava bean (Vicia faba) globular proteins on both protein composition and metabolism when given to young rats. Three mixed dairy gels containing casein micelles and fava bean proteins were produced either by chemical acidification (A) with glucono-δ-lactone (GDL) or by...
In food industry and winemaking, the use of active dehydrated yeast (ADY) Saccharomyces cerevisiae is a frequent practice because of the long-term stability and high efficiency of ADY. Nowadays, there is an increasing interest for new yeasts strains, such as Torulaspora delbrueckii (Td), Metschnikowia pulcherrima (Mp) and Lachancea thermotolerans (...
Introduction et but de l’étude
L’impact environnemental et les risques pour la santé associés à la production et la consommation excessive de sources de protéines animales pourraient être limités par l’augmentation de la part des protéines végétales dans notre alimentation. Les protéines végétales sont parfois déficitaires en certains acides aminés...
Actuellement, pour assurer des produits de haute qualité, les industries agroalimentaires ont besoin de grandes quantités de levures sèches. Les procédés de stabilisation et notamment la déshydratation sont des situations stressantes pour les micro-organismes qui peuvent affecter leurs performances technologiques. Afin de faire face au stress engen...
Fluidized bed drying is a dehydration process often applied to microorganisms and used for food particles stabilization. Despite its common use in yeast production, this process can lead to cell death depending on the strain and the growth conditions. During fermentation, yeasts undergo nutritional stressful environments according to media composit...
The behavior of pea albumins (Alb) and globulins (Glob) in a denatured state toward microbial transglutaminase (MTGase) treatment was studied by SDS-PAGE analysis, free amine group determination, dynamic rheology and confocal laser scanning microscopy. The denaturation of pea proteins by chemical reduction with dithiothreitol (DTT) or by thermal tr...
For the first time, synchrotron infrared was performed on yeast during dehydration processes in real time with simultaneously controlling relative humidity and temperature. This leaded us to investigate the biochemical modification in relation to dehydration of Saccharomyces cerevisiae. The correlation between hydration level and yeast survival was...
Fluidized bed drying is a dehydration process often applied for microorganisms and food particles stabilization. Despite its common use in the industry of yeast, this process can lead to cell death depending on the strain and the growth conditions. During fermentation, yeasts undergo nutritional stressful environments according to media composition...
We report herein an efficient synthesis of news naphtalimide-based fluorescent derivatives functionalized with an α,β-unsaturated carbonyl group. Probes were synthesized from reaction of an amino-naphtalimide precursor with maleic anhydride. Photophysical study of fluorescent probes and cells labelling were performed, and showed that the reactive d...
The presence of selected dehydrogenases, including alcohol dehydrogenase (ADH-YL) and aldehyde dehydrogenase (ALDH-YL), in Yarrowia lipolytica JMY 861, and their potential role in flavor synthesis were investigated. The experimental findings showed that using reduced form of nicotinamide adenine dinucleotide (NADH) as cofactor, the ADH-YL activity...
In the development of new food consumers’ acceptability is a critical factor. This study aimed at evaluating the possibility to introduce pea proteins as new fermented food. For this purpose, mixtures of cow and pea milks with different ratios of pea (0, 10, 20, 30, 40 and 100%) were fermented with French commercial yogurt-ferment. Consumer accepta...
In this work, techniques for monitoring the intramolecular transglutaminase cross-links of pea proteins, based on protein size determination, were developed. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles of transglutaminase-treated low concentration (0.01% w/w) pea albumin samples, compared to the untreated one (control), showe...
The present study aimed to entrap probiotic lactic acid bacteria (LAB) in a sodium alginate and sodium caseinate aqueous two-phase gel system. The natural acidifying properties of two therapeutic probiotic LAB were exploited to liberate calcium ions progressively from calcium carbonate (CaCO3), which caused the gelation of the co-existing phases. B...
Five mixtures of milk and pea protein (0-40 g pea protein/100 g total protein) were fermented by ten starter cultures of lactic acid bacteria (LAB) to select the cocktails that can lead to products similar to a conventional yoghurt. Generally speaking, an increase in pea concentration leads to products with higher acidity, higher syneresis and lowe...
The encapsulation techniques are applied in various fields and for various applications. The layer-by-layer self-assembly (LbL), one of the encapsulation techniques, is built by the electrostatic attraction between oppositely charged polyelectrolytes, and the topmost layer determines essentially the sur-face properties of the edifice. This techniqu...
Du fait de l’augmentation de la population de la planète, la production de protéines pour l’alimentation des populations et l’évaluation de la qualité de ces protéines pour satisfaire les besoins de l’Homme pourraient devenir des questions majeures dans les décennies à venir pour l’ensemble du monde. Le développement de nouveaux aliments optimisant...
Active dried yeast cells have been widely used in the food industry for several applications in baking, wine and beer production, etc. These organisms are unstable when being removed from their environment and exposed to stabilization processes (drying, freezing, freeze drying...) (1, 4). The high temperature gradients currently applied in these pr...
Saccharomyces cerevisiae, a eukaryotic model organism, plays a key role in the oxidative stability of fermented products. In order to protect cells against environmental stresses, we report a method of modifying the cell surface architecture while maintaining the internal working properties of the system. The objective was to encapsulate living yea...
A new method based on 1H NMR spectroscopy was developed for monitoring transglutaminase crosslinking reaction with model molecules (CBZ-Gln-Gly and N-α-acetyl-lysine). The transglutaminase reaction led to the appearance of new resonances on NMR spectrum as well as significant decrease in others. The new observed resonances, originated from newly fo...
Commercial lipases, from porcine pancreas (PPL), Candida rugosa (CRL), and Thermomyces lanuginosus (Lipozyme TL IM), were investigated in terms of their efficiency for the hydrolysis of safflower oil (SO) for the liberation of free linoleic acid (LA), used as a flavor precursor. Although PPL, under the optimized conditions, showed a high degree of...
The behavior of pea albumin (Alb) and globulin (Glob) in their native state upon microbial transglutaminase (MTGase) treatment was studied. Only Glob was able to form a gel, at up to a 10% (w/w) concentration, with a minimum gelling concentration of 6% (w/w), and with a cross-linking degree of 25%. The most affected Glob subunits were convicilin (7...
The objective of the research was the synthesis of linoleic acid hydroperoxides (HPOD) and their recovery, using selected sources of linoleic acid (LA) as substrate. This is part of on-going work aimed at the development of an economically viable biotechnological process for the production of natural flavors. The investigated sources included pure...
Ten starter cultures of lactic acid bacteria were used to ferment five mixtures of milk and pea protein (0%, 10%, 20%, 30%, and 40% of pea) to select the cocktail of starters that could lead to products similar to traditional yogurt. Product quality evaluation was performed by comparing the sensory profiles of 49 formulated products with the profil...
In tropical countries, traditional fermented foods are usually home-made products obtained through spontaneous fermentation or backslopping. They are now facing an evolution aiming at responding to quality, safety and mass production issues. This requires acquisition of knowledge on raw materials, microbial ecosystems and fermentation processes. Vi...
Biocatalysis with hydroperoxide lyase (HPL) in extracts from Penicillium camemberti, in neat organic solvent media has been investigated. The effects of reaction conditions including organic solvent mixtures, initial water activity (aw) and reaction temperature as well as the effect of the lyoprotectants, KCl and dextran 1 kDa, on HPL activity were...
Skiathos Island, GREECE - 30 May - 02 June 2013
This research investigates the cultural influence on beliefs about and attitudes towards soy foods (French from France vs. Vietnamese from Vietnam) and possible change of beliefs and attitudes and soy consumption habits with a change in cultural environment (French from France vs. French from Vietnam, Vietnamese from Vietnam vs. Vietnamese from Fra...
An in vitro method to determine the infectious potency of an unknown suspension of the protozoan parasite Toxoplasma gondii based on kinetics of host cells lysis was developed. Mic1-3KO a mutant strain of T. gondii RH tachyzoites was inoculated in 25-cm² flasks containing a 90% confluent monolayer of human foreskin fibroblasts. Lysis kinetics was m...
Pretreatment of lignocellulosic residues like water hyacinth (WH) and wheat straw (WS) using crude glycerol (CG) and ionic liquids (IL) pretreatment was evaluated and compared with conventional dilute acid pretreatment (DAT) in terms of enzymatic hydrolysis yield and fermentation yield of pretreated samples. In the case of WS, 1-butyl-3-methylimida...
This study investigated the cultural differences in description and preference of soy yogurts formulated for French market between French and Vietnamese panellists, two cultures with important differences in soy and dairy product consumption habits. Two trained panels assessed the in-mouth perceptions of eight soy yogurts and four milk yogurts, usi...
In-mouth perceptions including texture, taste and aroma of eight soy-yogurts and four milk-yogurts were assessed by one French trained panel and one Vietnamese trained panel, two cultures with important differences in soy and dairy product consumption habits, using a quantitative descriptive analysis (QDA) method. A Multiple Factor Analysis (MFA) s...
Fatty acid hydroperoxide lyase (HPL) is a member of the cytochrome P450 family acting on fatty acid hydroperoxides in many organisms. The active green bell pepper HPL, cloned and expressed in the yeast Yarrowia lipolytica, was purified by immobilized metal-ion affinity chromatography (IMAC) in the presence of 2% of Triton X-100R. The secondary stru...
Lactococcus lactis can decrease the redox potential at pH 7 (E(h7)) from 200 to -200 mV in oxygen free Man-Rogosa-Sharpe media. Neither the consumption of oxidizing compounds or the release of reducing compounds during lactic acid fermentation were involved in the decrease in E(h7) by the bacteria. Thiol groups located on the bacterial cell surface...
Hexanal produced by cells of a recombinant Yarrowia lipolytica yeast expressing the hydroperoxide lyase (HPL) from green bell pepper fruit was studied under oxido-reducing conditions using the reducing dithiotreitol and oxidizing potassium ferricyanide compounds. The combined effect of pH, linoleic acid 13-hydroperoxides concentration, temperature...
An enzymatic extract from Penicillium camemberti, containing lipoxygenase (LOX) and hydroperoxide lyase (HPL) activities, was immobilized on oxirane acrylic beads, Eupergit C and Eupergit C250L-iminodiacetic acid (IDA). The optimum pH for LOX activity was determined to be 4.0 and 6.0 for the free enzyme extract and 6.0 for the immobilized one, wher...
Circular dichroism (CD) spectroscopy of secondary structure conformation of the purified green bell pepper hydroperoxide lyase (HPL), cloned in the yeast Yarrowia lipolytica, was investigated. The CD spectra of HPL in iso-octane, obtained at 60°C, in the presence of the reducing agent dithiothreitol showed dramatic increase in α-helix content. The...
The aim of this study was to investigate the action mechanism of linoleic acid hydroperoxides (HPOD), which are the major substrates of hydroperoxide lyase for the production of flavour compounds, on the yeast Yarrowia lipolytica by evaluating their effect on the oxidative state of the cells. The total antioxidant capacity (TAC) and the activity of...
The stabilization of an enzymatic extract, obtained from Penicillium camemberti containing lipoxygenase (LOX) and hydroperoxide lyase (HPL) activities, was investigated using selected additives. Although the addition of KCl (86%, w/w) to the enzymatic extract decreased slightly (7%) the LOX activity, it increased HPL activity by 2.25 fold; however,...
Linoleic acid hydroperoxide (HPOD), substrate of hydroperoxide lyase, an enzyme of the lipoxygenase pathway, can be transformed into many aromatic compounds, the so-called "green notes". The presence of linoleic acid hydroperoxide in the culture medium of Yarrowia lipolytica, the yeast expressing the cloned hydroperoxide lyase of green bell pepper,...
The optimization of the expression of recombinant 6-His-tagged HPO lyase in Yarrowia lipolytica is described: 1800 U/L of culture was detected at 24 h of culture on a medium containing olive oil as the sole carbon source. The enzyme was purified by IMAC and showed an optimal pH at 5.5, an optimal temperature at 20 °C and a Km value of 9 μM with 13-...
The occurrence of styrene in food may be an important aroma defect (celluloid odour), even at very low concentrations (Miltz et al. 1980) causing consumer rejection and is therefore a problem for the food industry. We examined the biosynthetic pathway leading to styrene formation by Penicillium camemberti using labelled compounds. As styrene is str...
Responding to consumer' demand for natural products, biotechnology is constantly seeking new biocatalysts. In the field of hydrophobic substrate degradation, some yeast species known some years ago as non-conventional, have acquired their right to be considered as good biocatalysts. These Candida, Yarrowia, Sporobolomyces ... are now used for thems...
The aim of this study was to investigate the effect of redox potential (Eh) on the growth of the yeast Yarrowia lipolytica in both oxidizing (Eh = +350 mV) and reducing (Eh = −150 mV) media and its effect on the expression and activity of hydroperoxide lyase (HPL). HPL activity was assayed in media with Eh values ranging from −250 to +720 mV. In or...
Responding to consumer demand for natural products, biotechnology is constantly seeking new biocata-lysts. In the field of hydrophobic substrate degradation, some yeast species known some years ago as non-conventional, have acquired their right to be considered as good biocatalysts. These Candida, Yarrowia, Sporobolomyces ... are now used for thems...
Lipoxygenases (LOX; EC 1.13.11.12) are an important class of non-heme iron enzymes that catalyze the di-oxidation of PUFA
to hydroperoxy FA, which can be measured by the xylenol orange method (FOX). To determine the enzymatic production of these
FA in organic solvent media, the FOX assay was optimized using the standard cumene hydroperoxide. An inc...
Biomass of Penicillium candidum was harvested and homogenized prior to centrifugation. The resultant supernatant, considered as the crude enzymatic extract, was enriched by ammonium sulphate precipitation. The enriched enzymatic extract was assayed for its lipoxygenase (LOX) activity, using selected polyunsaturated fatty acids (PUFAs) as substrates...
Biomass production of Penicillium camemberti was investigated in selected media, including synthetic media supplemented with either linoleic acid or soybean oil and a dairy medium containing soybean oil and found to be 6.5, 8.3 and 61 g/l, respectively. The presence of soybean oil in the synthetic medium enhanced the production of 1-octen-3-ol, in...
Fatty acid hydroperoxide lyase (HPO lyase) is a cytochrome P450 acting on fatty acid hydroperoxides in many organisms. The expression of green bell pepper HPO lyase in the yeast Yarrowia lipolytica is described for the first time. HPO lyase activity from yeast extract and whole yeast cells is measured and aldehydes production from yeast extract and...
Aspergillus niger was grown for 6 days, and the harvested biomass was homogenized; the resultant supernatant, considered as the crude enzymatic extract, was enriched by ammonium sulfate precipitation. The extract was assayed for its lipoxygenase (LOX) activity using a wide range of polyunsaturated fatty acids (PUFAs), including linoleic, linolenic...
Surfactants play a key role in the biotechnological degradation of hydrophobic substrates, however this role is often misunderstood. During the biotransformation of methyl ricinoleate into the aroma compound gamma-decalactone by the yeast Yarrowia lipolytica, a direct contact occurs between the surface of the cells and the small droplets of substra...
The yeast Yarrowia lipolytica possesses five acyl-CoA oxidases (Aox1p to 5), the enzyme catalysing the first reaction of β-oxidation. The understanding of the specific role of each acyl-CoA oxidase is important to construct a yeast strain growing at a good rate and able to produce without degrading the aroma compound γ-decalactone. In this study we...
The effect of induction by linoleic acid on the biomass production, glucose consumption, change in pH values and 1-octen-3-ol profile were investigated during the growth of Penicillium camemberti. The results showed that the presence of 1 g of linoleic acid per liter of culture medium increased the biomass from 3.0 to 7.0 g/l. In addition, incubati...
Crude enzymatic extracts obtained from Penicillium camemberti and Penicillium roqueforti were incubated with the 9-, 10-, 12- and 13-hydroperoxide isomers of linoleic acid (HPODs), used as substrates. The 10-HPOD isomer was the only substrate to be enzymatically converted into selected aldehydes, alcohols and acids by both enzymatic extracts. Gas–l...
The aim of this work was to compare the efficiency of different extracts of hydroperoxide lyase from green bell peppers in producing aldehydes: a crude extract, a chloroplastic fraction, and a purified enzyme were investigated. From a crude extract, the HPO lyase was purified by ion-exchange chromatography with a 22.3-fold increase in purification...
The biogeneration of 1-octen-3-ol by lipoxygenase and associated hydroperoxide lyase activities of a homogenate of the cultivated mushroom Agaricus bisporus was investigated using linoleic acid as a substrate. The optimal substrate and protein concentrations were 1.5 mM and 1.5 mg ml−1, respectively. The Vmax value for the enzymic coupled reaction...
Biomass of the fungus Fusarium proliferatum was produced in liquid medium and used to obtain a crude enzymatic extract. Several methods were tested to obtain this extract: sonication, cryofracture and protoplasts disintegration. A lipoxygenase activity was found in this crude extract, which was highly induced when the fungus was grown in a medium c...
The fungus Fusarium proliferatum was grown in a soya oil- and glucose-supplemented medium. Induction of lipoxygenase activity (13-fold) in an extract of Fusarium biomass has been observed at day four on soya oil culture medium. A band at 232 kDa was detected using a specific lipoxygenase stain combined with native PAGE. The method of fungal homogen...
In response to gibberellic acid, aleurone layers isolated from dormant barley (Hordeum distichumL. cv. Triumph) kernels produced significantly lessalpha-amylase than aleurones from non-dormant kernels. Light microscopical investigations using the dye acridine orange as well as electron microscopical studies showed that the relatively lowalpha-amyla...
The major surface immunodominant antigen (P30) of Toxoplasma gondii was purified by two methods (i) SDS-PAGE and (ii) immunoaffinity chromatography. The secondary elements within this protein were assessed by circular dichroism and spectra obtained were compared to those proposed by Manavalan & Johnson (1983). The results allowed us to determine an...
Ultrastructural localization of four immunodominant antigens of Toxoplasma gondii was investigated quantitatively on thin sections and replicas by an immunogold technique using four monoclonal antibodies (Mab). On immunoblot Mab IV47, GII9, II38 and IE10 identified proteins of 28, 30, 45 and 66-70 kDa, respectively. Use of digital image analyzer an...
Four monoclonal antibodies in which diagnostic usefulness has been observed, concerning congenital, acquired, and reactivated toxoplasmosis, were raised against Toxoplasma gondii tachyzoïtes in order to localize immunodominant antigens. On immunoblots, it appears that McAb IV47, McAB GII9, McAb II38, and McAb IE10 identify families of proteins with...
Four immunodominant antigens frequently observed in congenital, acquired and reactivated toxoplasmosis have been localized on Toxoplasma gondii ultrathin sections using four monoclonal antibodies (Mab GII 9 , IV 47 , IE 10 II 38 ) which detect membrane and cytoplasmic antigens. Thin sections as well as the whole surface of RH tachyzoïtes of Toxopla...
