The optimum pH of a-amylase is 5.0-8.0 , and that of glucoacleavage of polysaccharide chains are reduced at pH 3.0 and 6.0. Starch was only hydrolyzed by acid at an initial pH of 3.0. The co-immobilization of M. purpureus and S. cerevisiae resulted in enhanced consumption of residual sugars at all tested pH, and the ethanol production rates showed a different picture. . The initial pH 4.0 gave the highest ethanol production of 3.17% .
, followed by 3.11%) at pH 3.0, and 2.66% at pH 6.0. The highest ethanol yield and production rate were achieved at an initial pH 4.0