Influence of mixed culture system on the growth performance of Aspergillus oryzae and Saccharomyces cerevisiae

This study describes a novel strategy to improve the α-galactosidase and invertase production of Saccharomyces cerevisiae by co-cultivating it with Aspergillus oryzae. In the mixed culture, the growth of the both strains was repressed, and the protein synthesis for the yeast cell wall was promoted significantly. As a result, α-galactosidase and invertase activities of the mixed culture reached 85.16 and 561.60 Uml-1, over 9 and 15 fold greater than the values obtained in the cultures of single strain, respectively. During the simultaneous saccharification and fermentation procedure, ethanol with the concentration of 15.2% (v/v) was obtained from soybean sirup in 60 h at 30°C, and the conversion efficiency of total sugar to ethanol was 96.3% of the theoretical ethanol yield.   Key words: Co-cultivation, Aspergillus oryzae, Saccharomyces cerevisiae, α-galactosidase, invertase.