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In order to identify an optimal aeration strategy for intensifying bio-fuel ethanol production in fermentation processes where growth and production have to be managed simultaneously, we quantified the effect of aeration conditions—oxygen limited vs non limited culture (micro-aerobic vs aerobic culture)—on the dynamic behaviour of Saccharomyces cerevisiae cultivated in very high ethanol performance fed-batch cultures. Fermentation parameters and kinetics were established within a range of ethanol concentrations (up to 147 g l-1), which very few studies have addressed. Higher ethanol titres (147 vs 131 g l-1 in 45 h) and average productivity (3.3 vs 2.6 g l-1 h-1) were obtained in cultures without oxygen limitation. Compared to micro-aerobic culture, full aeration led to a 23% increase in the viable cell mass as a result of the concomitant increase in growth rate and yield, with lower ethanol inhibition. The second beneficial effect of aeration was better management of by-product production, with production of glycerol, the main by-product, being strongly reduced from 12 to 4 g l-1. We demonstrate that aeration strategy is as much a determining factor as vitamin feeding (Alfenore et al. 2002) in very high ethanol performance (147 g l-1 in 45 h) in order to achieve a highly competitive dynamic process. [ABSTRACT FROM AUTHOR]

Several bottlenecks in the alcoholic fermentation process must be overcome to reach a very high and competitive performance of bioethanol production by the yeast Saccharomyces cerevisiae. In this paper, a nutritional strategy is described that allowed S. cerevisiae to produce a final ethanol titre of 19% (v/v) ethanol in 45 h in a fed-batch culture at 30°C. This performance was achieved by implementing exponential feeding of vitamins throughout the fermentation process. In comparison to an initial addition of a vitamin cocktail, an increase in the amount of vitamins and an exponential vitamin feeding strategy improved the final ethanol titre from 126 g l–1 to 135 g l–1 and 147 g l–1, respectively. A maximum instantaneous productivity of 9.5 g l–1 h–1 was reached in the best fermentation. These performances resulted from improvements in growth, the specific ethanol production rate, and the concentration of viable cells in response to the nutritional strategy. [ABSTRACT FROM AUTHOR]