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See detailInvestigation of the effect of different extracellular factors on the lipase production by Yarrowia lipolityca on the basis of a scale-down approach
Kar, Tambi ULg; Delvigne, Frank ULg; Masson et al

in JOURNAL OF INDUSTRIAL MICROBIOLOGY & BIOTECHNOLOGY (2008), 35(9), 1053-1059

The influence of three extracellular factors (namely, the methyl oleate dispersion in the broth, the dissolved oxygen variations, and the pH fluctuation) on the lipase production by Y. lipolytica in batch ... [more ▼]

The influence of three extracellular factors (namely, the methyl oleate dispersion in the broth, the dissolved oxygen variations, and the pH fluctuation) on the lipase production by Y. lipolytica in batch bioreactor has been investigated in different scale-down apparatus. These systems allow to reproduce the hydrodynamic phenomena encountered in large-scale equipments for the three specified factors. The effects of the extracellular factors have been observed at three distinct levels: the microbial growth, the extracellular lipase production, and the induction of the gene LIP2 encoding for the main lipase of Y. lipolytica. Among the set of environmental factors investigated, the dissolved oxygen fluctuations generated in a controlled scale-down reactor (C-SDR) have led to the more pronounced physiological effect by decreasing the LIP2 gene expression level. The other environmental factors observed in a partitioned scale-down reactor, i.e., the methyl oleate dispersion and the pH fluctuations, have led to a less severe stress traduced only by a decrease of the microbial yield and thus of the extracellular lipase specific production rate. [less ▲]

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See detailComparison Of Yarrowia Lipolytica Lipase Immobilization Yield Of Entrapment, Adsorption, And Covalent Bond Techniques
Alloue, Wam.; Destain, Jacqueline ULg; El Mejdoub, Thami ULg et al

in Applied Biochemistry and Biotechnology (2008), 150(1),

The purpose of this study was to immobilize lipase from Yarrowia lipolytica using three methods including inclusion, adsorption, and covalent bond to study enzyme leaching, storage, and catalytic ... [more ▼]

The purpose of this study was to immobilize lipase from Yarrowia lipolytica using three methods including inclusion, adsorption, and covalent bond to study enzyme leaching, storage, and catalytic properties. Sodium alginate and chitosan were the polymers selected to immobilize lipase by inclusion. The beads of each polymer were dried by freeze drying and fluidization. The results show that chitosan was more adapted to the inclusion of lipase. Even though freeze dried, bead activity was low compared to that of fluidized beads. The freeze-drying process seems to produce suitable beads for storage at 4 and 20 °C. The immobilization by adsorption was carried out on both celite and silica gel. Maximum immobilization yield of 76% was obtained with celite followed by 43% in silica gel. The enzyme adsorbed on the two supports exhibited greater stability at a certain temperature (50 °C) and in no polar solvents (Isooctane, n-heptane, and n-hexane). In addition, the lipase immobilized by covalent bond retained residual activity equitable to 70%. It was demonstrated that the enzyme immobilized by covalent bond showed greater activity (80%) after 5 months of storage. [less ▲]

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See detailSugar beet leaves as new source of hydroperoxide lyase in a bioprocess producing green-note aldehydes.
Rabetafika, Holy-Nadia ULg; Gigot, Cédric ULg; Fauconnier, Marie-Laure ULg et al

in Biotechnology Letters (2008), 30(6), 1115-9

Hydroperoxide lyase activity was found in sugar beet leaves. Its optimum pH and temperature were, respectively, 6.7 and 22 degrees C. Under these conditions, conversion of linolenic acid 13-hydroperoxide ... [more ▼]

Hydroperoxide lyase activity was found in sugar beet leaves. Its optimum pH and temperature were, respectively, 6.7 and 22 degrees C. Under these conditions, conversion of linolenic acid 13-hydroperoxide to cis-3-hexenal with a maximum yield of 80% was reached after only 2 min. The stability of cis-3-hexenal was improved by acidifying the reaction medium. Based on these studies, a bioprocess producing green-note aldehydes in a laboratory-scale was achieved. [less ▲]

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See detailImmobilized lipases and their applications
Alloue, Waze Aimee Mireille; Aguedo, Mario ULg; Destain, Jacqueline ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2008), 12(1), 57-68

Lipases are able to catalyse the hydrolysis of glyceridic esters in aqueous media and the synthesis of esters in non-aqueous media. They are thus able to catalyse numerous reactions of industrial interest ... [more ▼]

Lipases are able to catalyse the hydrolysis of glyceridic esters in aqueous media and the synthesis of esters in non-aqueous media. They are thus able to catalyse numerous reactions of industrial interest. Whether it is by inclusion, by adsorption or by covalent link, the immobilisation of lipases aims at conferring them a good stability that enables a reuse of the enzymes after a reaction and the development of continuous processes. The reactions of triglycerides hydrolysis constitute main applications for immobilised lipases, however their use in different types of esterification reactions has also arose: there exist processes involving reactions of transesterification, of interesterification or of esters synthesis. The production of structured lipids by interesterification is one example. Although the reaction conditions dissent from those of hydrolysis, the same lipases have been used in both cases. A lipase specifically adapted for esterification though would be a highly capable tool: a series of strategies is in progress in order to reach this goal. [less ▲]

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See detailEffect of monopropylene glycol and gamma irradiation on Yarrowia lipolytica lipase stabilization
Alloué, Wazé Aimée Mireille; Destain, Jacqueline ULg; Ongena, Marc ULg et al

in Preparative Biochemistry & Biotechnology (2008), 38(3), 217-228

This work investigated the effects of monopropylene glycol, protease inhibitor, and gamma irradiation on Yarrowia lipolytica lipase stability during storage. Enzyme liquid stabilization was achieved by ... [more ▼]

This work investigated the effects of monopropylene glycol, protease inhibitor, and gamma irradiation on Yarrowia lipolytica lipase stability during storage. Enzyme liquid stabilization was achieved by addition of monopropylene glycol (MPG) at respective concentrations of 50, 75, and 90%, the protease inhibitors (P2714 and P8215) at 0.1%, and the gamma irradiation with 10kGy, 15kGy, and 25kGy doses. The results showed that monopropylene glycol limited the microorganism growth and decreased the enzymatic activity at high concentration (up to 50%), at two temperatures (20 and 4 degrees C). Enzyme stored at 20 degrees C lost its activity by 80% after two months. This loss was attributed to the protease's effect. At this temperature, the protease's activities have been limited by the specific inhibitors. The gamma irradiations improve microbial safety of liquid enzyme. [less ▲]

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See detailCharacterization of lactic acid bacteria isolated from poultry farms in Senegal
Coulibaly, Ibourahema ULg; Dubois Dauphin, Robin ULg; Destain, Jacqueline ULg et al

in African Journal of Biotechnology (2008), 7(12), 2006-2012

The group that includes the lactic acid bacteria is one of the most diverse groups of bacteria known and these organisms have been characterized extensively by using different techniques. In this study ... [more ▼]

The group that includes the lactic acid bacteria is one of the most diverse groups of bacteria known and these organisms have been characterized extensively by using different techniques. In this study, thirty lactic acid bacterial strains were isolated from soils chicken faeces and feathers. A total of nineteen isolates were obtained and by sequential screening for catalase activity and Gram-staining, eight were determined to be LAB out of which six were established to be homofermentative by the gel plug test. Five isolates were identified by use of the API 50CHL kit and four Lactobacilli strains and one Lactococci strain were selected to study their growth and lactic acid production profiles in a time course experiment. The Lactobacilli strains, both isolated from faeces, produced higher amounts of cells and lactic acid from soils as compared to the lactococci strain isolated from feathers. L (+)-lactic acid is the only optical isomer for use in pharmaceutical and food industries because is only adapted to assimilate this form. The optical isomers of lactic acid were examined by L (+) and D (-) lactate dehydrogenase kit. Lactobacilli strains produced combination of both optical isomers of lactic acid. Among them, Lactobacillus casei subsp. casei produced the low amount of D (-)-lactic (2%). The optimum rates of glucose for lactic acid production by Lactobacillus strains were 180 and 120 g/l for Lactobacillus plantarum and Lactobacillus paraplantarum, respectively. [less ▲]

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See detailIn Vitro Detection And Characterization Of Bacteriocin-Like Inhibitory Activity Of Lactic Acid Bacteria (Lab) Isolated From Senegalese Local Food Products
Diop, Mb.; Dubois Dauphin, Robin ULg; Dortu, C. et al

in African Journal of Microbiology Research [=AJMR] (2008), 2(8),

The prevalence of lactic acid bacteria (LAB) in Senegalese local food products was determined to be 109 CFU/g in millet flour and milk products, and 103 CFU/g in seafood products. These food products are ... [more ▼]

The prevalence of lactic acid bacteria (LAB) in Senegalese local food products was determined to be 109 CFU/g in millet flour and milk products, and 103 CFU/g in seafood products. These food products are generally preserved by spontaneous fermentation (without addition of starters). Of 220 lactic acid bacteria strains randomly selected from such products, 12 isolates capable of producing bacteriocin-like substances (bac+) were detected. Based on the use of API 50 CH test kits and 16S rDNA sequencing, 11 isolates were characterized as Lactococcus lactis subsp. lactis strains and one as an Enterococcus faecium strain. Nisin- and enterocin B-encoding genes were respectively identified in the bac+ lactococcal strains and the E. faecium strain. Since the bac+ Lc. lactis strains were isolated from different products, it suggests a high potential of growth by these strains in variable ecological environments. Expression of the nisin gene was indicated for one of the lactococcal strains, designated Lc. lactis subsp. lactis CWBI-B1410, which showed the highest in vitro antibacterial activity. An antibacterial preparation prepared from the CWBI-B1410 strain showed many similarities with nisin with regards to its inhibitory effects, heat resistance, protease sensitivity profile, as well as retention time of the antibacterial substances on a C18 column. These results suggest that a nisin-like substance is produced by the CWBI-B1410 strain. This strain has been selected for application as an additional barrier to supplementation with sodium chloride as a means to improve the bacterial quality of fish commodities in Senegal. [less ▲]

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See detailImprovement of xylanase production by Penicillium canescens 10-10c in solid-state fermentation
Assamoi, antoine; Delvigne, Frank ULg; Aldric, Jean-Marc ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2008)

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See detailEthanolic fermentation as a tool for high added value products purification from biomass
Destain, Jacqueline ULg; Laurent, Pascal ULg; Thonart, Philippe ULg et al

Poster (2008)

The biorefinery concept implies the development of processes in order to valorise the whole part of a crop. In this concept, white biotechnologies are usually considered for the production of new ... [more ▼]

The biorefinery concept implies the development of processes in order to valorise the whole part of a crop. In this concept, white biotechnologies are usually considered for the production of new compounds or compounds actually derived from the oil industry. For example, interest in ethanolic fermentation is growing nowadays, mainly for its energetic applications, starting from starch or saccharose. Biorefinery integrating lignocellulosic materials are under development. Whatever the initial substrate may be, wet technologies would produce sugars and other soluble materials from the biomass. Different results could be expected:most of the hydrolysates molecules are used by the microorganisms;some molecules could be inhibitors for the fermentation;some molecules are "indifferent ones" and could be concentrated by the fermentation proccess followed by distillation. In the latest case, these molecules are concentrated in the residual medium and could be more easily recuperated. An example of this exists in the production of ethanol from beet. The different juices (diffusion, clarified, ...) contain molecules such as raffinose, glutamine, betaine, saponins or pectic materials. Some products are used by the yeasts and other are concentrated. Our purpose is to summary the results obtained, allowing the development of the concept in other biorefinery applications. [less ▲]

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See detailBioethanol subproducts as a basis of plant biorefinery
Destain, Jacqueline ULg; Laurent, Pascal ULg; Ndoye, Bassirou et al

Poster (2008)

The philosophy of our research is built on the behaviour of non-sugar compounds from biomass during ethanolic fermentation. Saccharomyces cerevisiae, industrially used to bioconvert sugar into ethanol ... [more ▼]

The philosophy of our research is built on the behaviour of non-sugar compounds from biomass during ethanolic fermentation. Saccharomyces cerevisiae, industrially used to bioconvert sugar into ethanol under anaerobic conditions, assimilates some compounds present in the fermentable juice (proteins, amino acids,...). But others compounds are not used by the yeast. They leave in the vinasse after ethanol distillation and are thus concentrated by the process. Our purpose is to discuss the behaviour of betaine, saponins and raffinose in sugar juices (raw juice, thin juice, thick juice) and in vinasse after ethanolic fermentation. An attention will be given to some high added value products (like betaine) and the potentialities to use fermentation as a tool of purification in white chemistry. [less ▲]

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See detailEnhancing The Antilisterial Effect Of Lactobacillus Curvatus Cwbi-B28 In Pork Meat And Cocultures By Limiting Bacteriocin Degradation
Kouakou, P.; Ghalfi, H.; Destain, Jacqueline ULg et al

in Meat Science (2008), 80(3),

This work focused on Listeria monocytogenes growth inhibition and growth rebound in raw and cooked pork meat inoculated with Lactobacillus curvatus strains. During storage of raw meat homogenates in the ... [more ▼]

This work focused on Listeria monocytogenes growth inhibition and growth rebound in raw and cooked pork meat inoculated with Lactobacillus curvatus strains. During storage of raw meat homogenates in the presence of the bacteriocin-producing strain Lactobacillus curvatus CWBI-B28wt, the Listeria monocytogenes cfu count was initially reduced to an undetectable level, but a growth rebound occurred after two weeks, coinciding with loss of 70% of the bacteriocin activity present at the end of week 2. The Listeria growth rebound was suppressed when proteolysis of bacteriocin was countered by the absence of proteases (bacteriocin addition to cooked meat) or the presence of 1% soy flour (added to provide competing substrates). Further experiments confirmed that bacteriocin is sensitive to the action of proteolytic enzymes isolated from both Lactobacillus curvatus CWBI-B28wt and the meat matrix. Bacteriocin proteolysis thus emerges as a cause of Listeria growth rebound. [less ▲]

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See detailPreservation of vinegar acetic acid bacteria
Ndoye, B.; Ceenwerck, I.; Destain, Jacqueline ULg et al

in Vinegars of the world (2008)

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See detailLes lipases sont des hydrolases atypiques : principales caractéristiques et applications
Fickers, Patrick ULg; Destain, Jacqueline ULg; Thonart, Philippe ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2008), 12(2), 119-130

Due to their kinetic and substrate specificities, triacylglycerol acyl-hydrolases or lipases are atypical enzymes. In function of their microenvironment, lipases are able to act as hydrolases in aqueous ... [more ▼]

Due to their kinetic and substrate specificities, triacylglycerol acyl-hydrolases or lipases are atypical enzymes. In function of their microenvironment, lipases are able to act as hydrolases in aqueous solution or as biocatalysts in organic synthesis. As hydrolases, they are responsible of the triglycerids catabolism into fatty acids and glycerol. In many organisms, this reaction plays a major role in the fat and lipid metabolism. In addition, lipases are also able to hydrolyse phospholipids and cholesterol esters. In organic solvent, lipases could catalyse reactions such as esterifications, acidolysis or alcoolysis with enantio-, regio- and chimioselectivity. Lipases form a mixed class of enzyme due to their animal, vegetal or microbial origins. All those properties led to the development of many applications in the food and chemical industries but also in the medical and therapeutic field. [less ▲]

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See detailProteolytic Breakdown Of Gliadin By Enterococcus Faecalis Isolated From Tunisian Fermented Dough
M'Hir, S.; Aldric, Jean-Marc ULg; El Mejdoub, Thami ULg et al

in World Journal of Microbiology & Biotechnology (2008), 24(12),

The aim of this work was to select strains with proteolytic activity on wheat gliadin, among lactic acid bacteria, previously isolated from Tunisian fermented wheat dough. Hydrolysis of gliadin, as sole ... [more ▼]

The aim of this work was to select strains with proteolytic activity on wheat gliadin, among lactic acid bacteria, previously isolated from Tunisian fermented wheat dough. Hydrolysis of gliadin, as sole nitrogen source, in an agar medium was visualized by a clear zone surrounding colonies. The increase in absorbance due to gliadin breakdown was measured spectrophotometrically using Ophthaldialdehyde (OPA) on Gliadin Glucose Broth medium. Fermented liquid dough inoculated with individual selected Enterococcus faecalis, showed a decrease of the gliadin concentration from 45 g/kg to 18 g/kg determined by sandwich ELISA test (R-7001). Only the enterococci strains show an hydrolysis of gliadin proteins. Strains showing proteolytic activity are gaining more and more importance in cereal based fermented foods and may help to reduce gliadin involved in coeliac disease. [less ▲]

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