Stochastic modelling of micro-organisms displacements in a stirred-tank bioreactor

Poster (2010)

An Improved Test to Study the Changes in Membrane Permeability During Rehydration of Freeze-Dried Weissella paramesenteroides LC11

in The Open Biotechnology Journal (2010), 4

The objective of this study was to assess changes in membrane permeability during rehydration of freeze-dried Weissella paramesenteroides LC11. Viability was assessed using the electrical conductivity ... [more ▼]

The objective of this study was to assess changes in membrane permeability during rehydration of freeze-dried Weissella paramesenteroides LC11. Viability was assessed using the electrical conductivity measurement (ms cm-1 g-1 dry weight) and the plate count method (cfu g-1 dry weight). The symptoms of injury included an increase in the electrolyte leakage during the first 4 h of rehydration in Milli Q water and a decrease in the survival rate (about 64%), suggesting an increase in membrane permeability during dehydration. During rehydration of the freeze-dried strain, an increase in the temperature, NaCl or monosodium glutamate concentration and a decrease in H+ concentration resulted in an increase in the electrolyte leakage and a decrease in the survival rate (from about 5% to 97%, with respect to the treatment made). However, a decrease in the electrolyte leakage was observed with increasing glycerol, sucrose or maltodextrin and resulted in the maintenance of cell viability. Change in membrane permeability might lead to electrolyte leakage during rehydration and, ultimately, cell death. The electrolyte leakage assay associated with the plate count method, a quick and inexpensive method, could be used to evaluate dried bacteria resistance to dehydration. [less ▲]

Influence of bioreactor hydraulic characteristics on a Saccharomyces cerevisiae fed-batch culture: hydrodynamic modelling and scale-down investigations.

in Journal of Industrial Microbiology & Biotechnology (2010), 37

Yeast is a widely used microorganism at the industrial level because of its biomass and metabolite production capabilities. However, due to its sensitivity to the glucose effect, problems occur during ... [more ▼]

Yeast is a widely used microorganism at the industrial level because of its biomass and metabolite production capabilities. However, due to its sensitivity to the glucose effect, problems occur during scale-up to the industrial scale. Hydrodynamic conditions are not ideal in large-scale bioreactors, and glucose concentration gradients can arise when these bioreactors are operating in fed-batch mode. We have studied the effects of such gradients in a scale-down reactor, which consists of a mixed part linked to a non-mixed part by a recirculation pump, in order to mimic the hydrodynamic conditions encountered at the large scale. During the fermentation tests in the scale-down reactor, there was a drop in both biomass yield (ratio between the biomass produced and the glucose added) and trehalose production and an increase in both fermentation time (time between inoculation and beginning of stationary phase) and ethanol production. We have developed a stochastic model which explains these effects as the result of an induction process determined mainly by the hydrodynamic conditions. The concentration profiles experienced by the microorganisms during the scale-down tests were expressed and linked to the biomass yields of the scale-down tests. [less ▲]

Trehalose as a stress marker of the physiological impact of mixing on yeast production: scale-down reactors and mini-bioreactors investigations

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010), 14

Optimisation of culture conditions for biological hydrogen production by Citrobacter freundii CWBI952 in batch, sequenced-batch and semicontinuous operating mode

in International Journal of Hydrogen Energy (2010), 35

Investigations were carried out to determine the effect of the pH, the nitrogen source, iron and the dilution rate (h 1) on fermentative hydrogen production from glucose by the newly isolated strain ... [more ▼]

Investigations were carried out to determine the effect of the pH, the nitrogen source, iron and the dilution rate (h 1) on fermentative hydrogen production from glucose by the newly isolated strain Citrobacter freundii CWBI952. The hydrogen production rate (HPR), hydrogen yield, biomass and soluble metabolites were monitored at 30 C in 100 mL serum bottles and in a 2.3 L bioreactor operated in batch, sequenced-batch and semicontinuous mode. The results indicate that hydrogen production activity, formate biosynthesis and glucose intake rates are very sensitive to the culture pH, and that additional formate bioconversion and production of hydrogen with lower biomass yields can be obtained at pH 5.9. In a further series of cultures casein peptone was replaced by (NH4)2SO4, a low cost alternative nitrogen source. The ammonia-based substitute was found to be suitable for H2 production when a concentration of 0.045 g/L FeSO4 was provided. Optimal overall performances (ca. an HPR of 33.2 mL H2/L h and a yield of 0:83 molH2 =molglucose) were obtained in the semicontinuous culture applying the previously optimized parameters for pH, nitrogen, and iron with a dilution rate of 0.012 h 1 and degassing of biogas by N2 at a 28 mL/min flow rate. [less ▲]

Hydrolysis of starch by sorghum malt for maltodextrin production

Poster (2009, December 16)

Maltodextrin is a mixture of saccharides with a molecular weight between polysaccharides and oligosaccharides with DE lower than 20. Maltodextrin is more soluble in water than native starches, also is ... [more ▼]

Maltodextrin is a mixture of saccharides with a molecular weight between polysaccharides and oligosaccharides with DE lower than 20. Maltodextrin is more soluble in water than native starches, also is cheaper in comparison with other major edible hydrocolloids. Maltodextrin is obtained by moderate enzymatic or acidic hydrolysis of starch. The hydrolysis of starch, catalyzed by amylases, is the most important commercial enzyme process. The hydrolyzed products are widely applied in food, paper and textile industries. Because of the increasing demand for these enzymes in various industries, there is enormous interest in developing enzymes with better properties, such as raw starch-degrading amylases suitable for industrial applications and their cost-effective production techniques. Sorghum (Sorghum bicolor) is a widely grown crop in Africa. Obtaining enzymes from sorghum requires a transformation. The objective of this study was application of sorghum amylase for maltodextrin. Sorghum seeds were supplied by the ISRA (Bambey, Senegal). Seeds were germinated in the laboratory at 30°C for 72 h and the sorghum malt was dried at 40°C for 48 h. Corn starch (from Roquette, France) hydrolysis was assayed in a bioreactor of 2 l at a temperature of 65°C gently stirred. Raw starch was slurried in water (30% w/v) and sorghum malt was introduced, chloride calcium was added, pH was adjusted to 6. Maltodextrin was characterized in term of the dextrose equivalent (DE) during the hydrolysis. The yield of hydrolysis was evaluated by soluble solids (° BRIX) at different hydrolysis time. The glucose concentration released was measured by DNS method (Miller method). [less ▲]

Fermentative biohydrogen production by a Clostridium butyricum sp. strain in a novel continuous rotating cylinder bioreactor

Poster (2009, December 16)

Investigation of hydrogenase molecular markers to optimize hydrogen production from organic waste and agro-food industries effluents

Poster (2009, December 16)

Rapport de recherche (mission du 1er mars 2008 au 6 novembre 2009): Valorisation par la volaille des hydrates de carbone de structure issus des industries agro-alimentaires: effets des enzymes fibrolytiques ruminales

Report (2009)

Le développement de starters lactiques : de la cellule au produit fini.

Conference (2009, November)