Improved production, purification and some properties of α-amylase from Streptomyces clavifer

Abstract

Improvement of the α-amylase productivity of Streptomyces clavifer was achieved through studying the effect of some nutritional factors and ultra violet (UV) mutagenesis. Modification in the formula of liquid starch medium by decreasing the concentration of soluble starch to 1%, increasing the corn steep liquor to 2%, and adding 0.75% glucose and 0.01% L-valine caused significant increase in the enzyme productivity from 8640 to 23450 U/L. UV variants of high amylase productivity (54620 U/L) was isolated from the parent strain. A promising level of α-amylase production (50850 U/L) at large scale level was obtained by cultivating the tested strain in the optimum condition using laboratory fermentor of 14 L. Enzyme purification was achieved by ethanol precipitation, diethylaminoethyl cellulose (DEAE-C), and Sephadex G-100 gel filtration chromatography. The final preparation had 22.0% activity recovery and approximately 156.1 fold purification. The purified enzyme had molecular weight of approximately 50 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The purified enzyme exhibits maximum activity at pH 6 and 60°C and showed maximum stability at pH 6 and up to 40°C.

Key words: Streptomyces clavifer, α-amylase, UV mutagenesis, purification.