No abstract

We examined the changes in three biomass constituents (glucosamine, ergosterol, total sugar), sucrose consumption and conidia formation, during cultivation of Beauveria bassiana on agar plates or clay granules. We showed that glucosamine can be considered a good biomass indicator on condition that the media had the same constituents but not necessarily the same C/N.ratio. Total sugar was not constant during the different growth phases and cannot accurately represent biomass changes. The ergosterol amounts changed during the different growth phases but, for a fixed process, it can be a good indicator of conidiation. Good correlations were obtained between glucosamine and sucrose consumption allowing biomass yield calculations.

Two m e t h o d s for on-line b i o m a s s m e a s u r em e n t were tested with success: (a) infrared (IR) estimation o f cell c o m p o n e n t s (glucosamine a n d ergosterol) and m e d i u m residues (sucrose and nitrogen) directly on solid m e d i u m ; (b) the CO2 evolution rate during cultivation. These m e t h o d s were very satisfactory for following b i o m a s s changes during a d e f i n e d process. The I R m e a s u r e m e n t s c o r r e l a t e d well with m a n u a l m e t h o d s . The c o r r e l a t i o n b e t w e e n CO2 a n d g l u c o s a m i n e m e asurements was very satisfactory with g o o d precision. However, they did not p e r m i t c o m p a r i s o n b e t w e e n processes.

No abstract

No abstract

No abstract

No abstract

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 Eh. 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.