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Analysis of the respiro-fermentative growth of Saccharomyces cerevisiae on glucose in a fed-batch fermentation strategy for accurate parameter estimation

Ejiofer, A.O., Solomon, B.O., Posten, C., Deckwer, W.D.
Applied microbiology and biotechnology 1994 v.41 no.6 pp. 664-669
Saccharomyces cerevisiae, fermentation, carbohydrate metabolism, glucose, ethanol
Analysis of the respiro-fermentative growth of a strain of Saccharomyces cerevisiae, DSM 2155 on glucose, in a simulated 5-phase feeding strategy of fedbatch cultures executed on the Universal BIoprocess CONtrol (UBICON) system, was carried out. There was a good agreement between the estimated and the simulated values of specific growth rates. In this study, which was designed to span 0.20-0.23 h-1 growth rates before returning to lower growth rates, the critical dilution rate at which the switch between purely oxidative and respiro-fermentative growth takes place was not observed. The biomass yield, specific substrate uptake and O2 consumption rates as well as the consistency of the data using both carbon and available electron balances were examined. A high average value of true biomass energetic yield, eta(max) = 0.707, and a low value of maintenance coefficient, Me = 0.0114 h-1, were obtained indicating that the organism was in no danger from the ethanol produced as a high-density fermentation with a yeast concentration above 54 g 1-1 was possible within a period of 24 h. The yeast produced also had good dough-leavening characteristics. Thus it is possible to operate a yeast plant without resorting to using respiratory quotient, which may be problematic, as the controlling parameter.