Gaseous environments modify physiology in the brewing yeast Saccharomyces cerevisiae during batch alcoholic fermentation.

AIMS: To investigate the impact of different gaseous atmospheres on different physiological parameters in the brewing yeast Saccharomyces cerevisiae BRAS291 during batch fermentation. METHODS AND RESULTS: Yeasts were cultivated on a defined medium with a continuous sparging of hydrogen, helium and oxygen or without gas, permitting to obtain three values of external redox. High differences were observed concerning viable cell number, size and metabolites produced during the cultures. The ethanol yields were diminished whereas glycerol, succinate, acetoin, acetate and acetaldehyde yields were enhanced significantly. Moreover, we observed major changes in the intracellular NADH/NAD(+) and GSH/GSSG ratio. CONCLUSIONS: The use of gas led to drastic changes in the cell size, primary energy metabolism and internal redox balance and E(h). These changes were different depending on the gas applied throughout the culture. SIGNIFICANCE AND IMPACT OF THE STUDY: For the first time, our study describes the influence of various gases on the physiology of the brewing yeast S. cerevisiae. These influences concern mainly yeast growth, cell structure, carbon and redox metabolisms. This work may have important implications in alcohol-related industries, where different strategies are currently developed to control better the production of metabolites with a particular attention to glycerol and ethanol.

Glucosamine measurement as indirect method for biomass estimation of Cunninghamella elegans grown in solid state cultivation conditions.

Glucosamine measurement has been tested as the indirect method to estimate the biomass produced by Cunninghamella elegans during solid state cultivation (SSC). The independence of this cell constituent content from the age and the conditions of the culture have been verified. The influence of the medium composition, in particular the nature of the carbon source on glucosamine amount is presented. Glucosamine can be considered as a well-adapted biomass indicator, with the necessity to establish for each medium tested a prior correlation between biomass and glucosamine amount. This correlation should be defined in submerged conditions before applying the biomass estimating method in SSC.

Use of solid state fermentation to produce Beauveria bassiana for the biological control of European corn borer.

The production process of a new bioinsecticide against european corn borer is described. The entomopathogenic fungus, Beauveria bassiana, is cultivated by Solid State Fermentation (SSF). The culture support chosen, clay microgranules, humidified with optimal nutritive solution, is incubated in optimal conditions during 48 hours, then dried for 5 days. The bioinsecticide can be directly used after harvesting, without formulation. This process is original for several reasons : - The granulometry (500 microm) and the bulk density (0.6) of the microgranules are compatible with the mechanical standard application of pesticides on corn. - The bioinsecticide could be produced in a pilot reactor of 1600 1 capacity, on 0.5m-thick-layer.- The biomass bound to microgranules conserves its efficiency after storage for 12 months at 4 degrees C, unlike pure cells. - Like the chemical insecticides usually used, this bioproduct has a field efficiency of 80%. Moreover, the efficiency of the product persists during 3 weeks.