Abstract

Growth and ethanol production by three strains of the bacterium Zymomonas mobilis were tested, at 40°C, in a medium containing cellulose hydrolysate (hexose fraction) as carbon source. The thermotolerant mutant C107 exhibited the best growth compared to wild type ZM4 and to the osmotolerant mutant SBE15. When cultivated in media supplemented with various nutrients, growth was only observed in presence of yeast extract (10 g/l) which acted both as a vitamin supplier and pH stabilizer. Using calcium pantothenate instead of yeast extract and sodium acetate to control pH resulted in growth inhibition by the high medium osmolality. Batch fermentation with pH control (KOH addition) showed good growth and ethanol production with the mineral medium.

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