Ways of using Zymomonas mobilis in alcohol fermentation
1992
Ravasz, K. (Szeszip. Kut. Int. (Hungary))
The alcoholic fermentation of Zymomonas mobilis was studied at 30 C/degrees/ and pH 5.0 using molasses as raw material. When the Z. mobilis data were compared with similar data for the recharging fermentation of Saccharomyces cerevisiae under identical conditions, it was found that the biomass production of Z. mobilis on molasses was only 1/3 of the cell yield recorded for S. cerevisiae, while the bacterium strain had lower alcohol tolerance than the yeast. The final concentration of alcohol had a maximum value of 7.9 (V/V) o/o, but due to the alcohol inhibition the fermentation of Z. mobilis slowed down after 5 (V/V) o/o, so the fermentation period was longer (6-8 days) than for S. cerevisiae (4-5 days). The best specific value (320.5 g M50/100 g abs. alcohol) was obtained in one-step fermentation with the addition of yeast extract (2.5 g/l) with a molasses concentration of 200 g/l, the final alcohol concentration was 6.24 (V/V) o/o. The absolute alcohol produced in the course of molasses fermentation by Z. mobilis contained as a contaminant an easily eliminated volatile component, not present in that obtained with S. cerevisiae, but the quantity of fusel oils was considerably lower
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