Joseph Boudrant

ABSTRACT During fermentation the cellular reactions can be subdivided into three classes: degradation of nutrients, biosynthesis of small molecules, biosynthesis of large molecules (besides transport of ionic and neutral substances, mechanical work required for cell division and motion). The number of different chemical reactions necessary for sustenance of cell life is of the order of 1000 or more. Each reaction is catalyzed by at least one enzyme. Many reacting substances within the cell can be attacked simultaneously by several different enzymes. Thus the sequences of reactions occurring in the cell intersect and overlap in complex ways.

ABSTRACT Modelling of microorganism hydrodynamic stress by CFD has been done for stirredtank bioreactor for process of lactic acid production. Maximum dissipation rate has been taken as one of the characteristics of shear stress (as a type of mechanical stress in bioreactor). The zone of high mechanical influence on microorganisms (stress zone) has been defined. It was established the dependencies of stress zone specific volume versus impeller rates in bioreactor for different initial concentrations of substrate that allowed to define the range of recommended impeller rate values.

In Russia the most popular juice tastes are orange, apple, tomato and peach. From 52 up to 66 per cent of consumers use these kinds of juice or nectar regularly or occasionally. The most important criterions for the choice of a juice are its taste quality and nutritional value. The present work had two main proposes: firstly, the creation of a glossary of sensory attributes for these four most popular juices and the development and the adaptation of the procedure of control of sensory quality in regard of the industry needs; secondly, the definition of the most important sensory attributes for consumer appreciation of these high-grade juices, which are important or necessary to control during the choice of raw material and the manufacture processing. This work allowed us to create the sensory attributes glossary for three kinds of fruit juices and one vegetable juice and to developed and adapt the procedure of control of sensory quality for the industry need. Besides, this work allo...

Food and beverages high in vitamins, minerals and fibres are regarded today as precautions, which can prevent people from civilisation diseases. Fruit and vegetables belong to this group of food. Best beverages, which can be equivalent fresh fruits and vegetables, are juices and nectars. In Russia the most popular juice tastes are orange, apple, tomato and peach. From 52 up to 66 per cent of consumers use these kinds of juice or nectar regularly or occasionally. The most important criterions for the choice of a juice are its taste quality and nutritional value. In this study, various kinds of fruit juices and nectars were analysed for their sensory characteristics and changes depending on quality of used concentrates in order to define most important sensory attributes for quality control procedure. The present work had two main proposes: firstly, the creation of a glossary of sensory attributes for the most popular juices and nectars and the development and the adaptation of the pr...

A cDNA encoding human liver UDP-glucuronosyltransferase 2B4, which glucuronidates the bile acid hyodeoxycholic acid, has been expressed in Escherichia coli as a fusion protein with Staphylococcus aureus protein A. The expression of this protein, under the control of the thermo-inducible λ-PR promoter, was induced by a shift in culture temperature. In order to increase both the biomass and the amount of recombinant protein, the temperature profile in the batch culture and especially the influence of the time of induction have been studied. A lag phase of 35°C, followed by exponential and stationary phases of 42 and 28°C respectively, allowed an increase of about 27% of UGT2B4 per litre of culture compared to the typical 28–42°C late induced batch culture.

Yeast flocculation is a complex phenomenon. The present work concerns the effect of different factors on the flocculation dispersion of Kluyveromyces lactis. This study employs mother and hybrid strains, the latter being obtained by mating a flocculent and a non-flocculent mother strain. The optimum pH of flocculation was around 4·5. Flocculation dispersion depends upon the nature of carbohydrate present, galactose

A modelling approach is proposed to represent the decreasing evolutions observed on cell concentration, biosynthetic activity and substrate consumption at late fermentation times during processing when using a cell recycling (membrane) apparatus and continuous feeding. Indeed, during such processes, which are over rather long time periods, the cell populations may have to withstand various stresses (physical, environmental and chemical) involving

Extracellular cholesterol oxidase (COX) (EC 1.1.3.6) was produced by Rhodococcus sp. GK1 cells grown in a defined mineral salt medium containing a mixture of phytosterols (sitosterol, campesterol, stigmasterol) as the sole source of carbon and energy. In the same time, the sterols acted as enzyme inducers. The medium was enriched with yeast extract in order to stimulate enzyme secretion. COX was purified from the culture supernatants by affinity-like chromatography on a column packed with kieselguhr and cholesterol. Enzyme bound onto the column was eluted with 0.05 M phosphate buffer pH 7.0 containing Triton X-100 at 0.1% (w/v). Some properties of the purified COX were determined. Its specific activity at pH 7.0 and 30 °C, was around 5.5 units mg-1. The molecular mass of the enzyme, as estimated by SDS-PAGE, was 59 kDa. Its isoelectrofocusing point was around pH 8.9. The C-5 double bond and the alkyl chain moiety in sterol molecules were necessary for an adequate oxidation of the st...

At high glucose concentrations, Escherichia coli produces acetate (Crabtree effect). To look for the influence of glucose and/or acetate in the medium on the expression of a recombinant gene in E. coli, the effect of a pulse addition of glucose, on transcription of a cloned E. coli gapA gene and the resulting glyceraldehyde-3P-dehydrogenase activity (GAPDH), was tested during continuous cultivation of E. coli HB101 transformed with the plasmid pBR::EcogapA. Stable continuous cultures were established in a semi-synthetic medium supplemented with 5 g/L of glucose. After the addition of 7 g of glucose within a few seconds, gapA gene expression was strongly and very rapidly induced. As shown by primer-extension analysis, promoter P1, one of the four transcriptional promoters of the gapA gene, was strongly activated, and GAPDH activity increased. However, after rapid glucose consumption, acetate was produced and acetate concentrations above 2 g/L induced stress conditions. This is shown by a strong activation of promoter P2, that is recognized by the stress specific Esigma32 RNA polymerase. During this period, the total cellular RNA content was strongly diminished. Later, when acetate was partially consumed a high level of total RNA was restored, translation was efficient and a regular increase of the GAPDH-specific activity was observed. The transitions between glucose metabolism, acetate production and the end of acetate consumption, were marked by large increases in RNase and protease activities. For comparison, pulse-addition experiments were also performed with serine and alanine. A transient increase of GAPDH production associated with an increase in biomass was also found for serine that can be utilized as an energy source, whereas the addition of alanine, which is only incorporated into newly synthesized proteins, did not increase GAPDH production. The implication of these data for overproduction of recombinant proteins in E. coli is discussed.