Improvement of gluco-amylase B excretion by Aspergillus oryzae in a biofilm reactor

Poster (2013, April 29)

Modulation de l'effet scale-down chez Saccharomyces cerevisiae par ajout d'acide oléique

Master's dissertation (2011)

Scale-down technology allows to simulate heterogeneities created in an industrial reactor at a laboratory scale. In this kind of bioreactor, fed-batch production of Saccharomyces cerevisiae on glucose ... [more ▼]

Scale-down technology allows to simulate heterogeneities created in an industrial reactor at a laboratory scale. In this kind of bioreactor, fed-batch production of Saccharomyces cerevisiae on glucose induces the apparition of the scale-down effect. It means a decrease in biomass synthesis and an increase in ethanol production as time of culture in comparison with an ideal bioreactor where the mixing operation is perfect. In a recent study, FERIA-GERVASIO et al., (2008) notice that ethanol production is delayed on behalf biomass synthesis when a glucose pulse occurs in a chemostat glucose/oleic acid. The goal of this work is to study the modulation of the scale-down effect by the presence of oleic acid in a fed-batch production of Saccharomyces cerevisiae (boulardii). The methodology is separated in three parts: - development of a yeast conditioning protocol with oleic acid - yeast production with a mixed substrate composed of glucose and oleic acid in a scale-down reactor - computer simulation of glucose gradients experienced by yeast during their displacement in the bioreactor In addition to the measurements performed to describe growth kinetic of yeast on this mixed substrate, an original phenotypic analysis of yeast has been achieved throughout each culture thanks to flow cytometry. At the end of this work, vacuoles staining with fluoro-isothiocyanate has revealed the induction of peroxisomes infered during the yeast conditioning by flow cytometry. Then, it was demonstrated that in a culture in a scale-down reactor preceded by the conditioning, oleic acid naturally reduces ethanol production for the benefit of the biomass synthesis in comparison with a yeast cultivated on glucose only in scale-down reactors. Flow cytometry has not identified a negative influence of oleic acid on cell viability. Finally, simulation of glucose gradients experienced by yeast in the scale-down reactor with oleic acid has demonstrated that yeast feel important extracellular fluctuations in the recycle loop. [less ▲]