The effect of soyabean flour on alcohol and cell concentration in alcohol fermentation of molasses.

The effects of soy flour on alcohol fermentation of molasses by different yeast strains were investigated. Six strains of Saccharomyces cerevisiae and one Saccharomyces bayanus were used. It was found that soy flour affected fermentation time, alcohol concentration and total cell count in all strains. But the degree of this effect was different among strains. The maximum ethanol concentration were 63.9 g/l in Saccharomyces cerevisiae N3 strains. The maximum theoritical yield, however was 91.6% in Saccharomyces cerevisiae W4 strains. Compared with the control, the largest increment in ethanol concentration was in Saccharomyces bayanus 1A as 12.2%. Furthermore, addition of soy flour incerased cell counts of all strains and the increment level varied with the concentration of soy flour and strains used. The maximum cell counts were (1.5x10 7 cfu.ml -1 ) determined by Saccharomyces cerevisiae W4 strain at 3% soy flour concentration but the same cell density was reached at 9% soy flour concentraton with the Saccharomyces cerevisiae N3 strain. Results of the statistical analysis showed that alcohol concentration, yield and yeast concentration were affected by yeast strains and soy flour concentration, significantly. The addition of soy flour also resulted in approximately 15% decrease in the fermentation time in all of the strains.