Amylase production under solid state fermentation by a bacterial isolate W74

Abstract

This study was concerned with the screening of a suitable isolate and optimization of cultural conditions for the biosynthesis of thermostable amylase under solid state fermentation (SSF). Twenty seven isolates were screened for amylase production out of which one isolate designated as W74 showed maximal amylase activity at 70°C and a pH of 6.5 and selected for further optimization of cultural conditions under SSF. Among the different carbon and nitrogen sources supplemented to wheat bran, starch (96.7 U/g) and casein (107.3 U/g) enhanced maximum amylase production. Addition of exogenous glucose repressed secretion of amylase, demonstrating that a classical glucose effect was operative in this organism. Cultural optimization was undertaken to evaluate the effect of main process parameters as incubation period (144 h), moisture (66.7%), inoculum size (40%), and initial medium pH (6.5) on enzyme production. The enzyme was optimally active at 70°C and in pH range of 5.5-6.5.