Purification and Characterization of Endoglucanase from Sorghum (S. bi-color) and Millet (Pennisetum typhoides and Digitaria exilis) Malts

Endoglucanase (EC3.2.1.4) from sorghum (S. bi-color) and millet (Pennisetum typhoides & Digitaria exilis) malts were purified to homogeneity through the methods of ammonium sulphate precipitation and gel filtration. Molecular mass of 35 KDa and 41 KDa were determined by SDS-PAGE. The purified enzymes catalyzed the hydrolysis of carboxy-methylcellulose with optimum activity at pH of 4.8, 5.0, 6.0, and temperature of 60ºC, 60ºC and 70ºC for Digitaria exilis, S. bi-color and Pennisetum typhoides respectively. More than 90% activity was retained in S. bi-color and Pennisetum typhoides and 73% activity in Digitaria exilis after 1.0 hour pre-incubation at 60ºC. Km values of 0.11, 0.09, 0.20 mM and Vmax 17.53, 15.0 and 11.10 U/mg/min were obtained for S. bi-color, Pennisetum typhoides and Digitaria exilis respectively. Co2+ inhibited endoglucanase activity whereas Ca2+, Ba2+, and Zn2+ enhanced enzyme activity. The enzyme was inactivated by glucose, a major end product of cellulose hydrolysis. Results indicate that endoglucanase of S. bi-color and Pennisetum typhoides are more suitable for malting and a blend of the two will produce high quality malt.