Purification and Characterization of Endoglucanase from Sorghum (S. bi-color) and Millet (Pennisetum typhoides and Digitaria exilis) Malts
D. I. Ukairo *
Department of Biochemistry, School of Biological Sciences, Federal University of Technology, Owerri, Nigeria.
H. C. Nzelibe
Department of Biochemistry, Ahmadu Bello University, Zaria, Nigeria.
C. I. Iheme
Department of Biochemistry, School of Biological Sciences, Federal University of Technology, Owerri, Nigeria.
E. C. Udenze
Department of Biochemistry, School of Biological Sciences, Federal University of Technology, Owerri, Nigeria.
C. P. Ihedimbu
Department of Biochemistry, School of Biological Sciences, Federal University of Technology, Owerri, Nigeria.
A. U. Ezirim
Department of Biochemistry, School of Biological Sciences, Federal University of Technology, Owerri, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
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.
Keywords: Endoglucanase, sorghum, millet, malting, enzyme purification