Investigation of important factors in Solid State Fermentation for alkaline protease production by Bacillus thuringiensis aizawai HD283

Abstract

Objective: this paper investigates the critical factors in solid state fermentation (SSF) for improved production of alkaline protease by Bacillus thuringiensis aizawai HD283 and explores some biochemical properties of the crude enzyme. Methods: One factor at a time method was used in this investigation. Tested factors include: nutritive substrate, moisture content, inoculums size and incubation period. Explored assay parameters include: enzyme concentration, time, pH and temperature. Results: Among others, the agro-industrial byproduct wheat bran was found to be a superior nutritive substrate for alkaline protease production by Bacillus thuringiensis aizawai HD283. Further supplementation with carbon source such as fructose or mannitol has enhanced the production by almost 2 folds. The optimum levels of alkaline protease were obtained using wheat bran of particle size <1mm, 200% moisture content, inoculums size of 60% and incubation period for 5 days. The optimum activity of crude enzyme was obtained at pH 9 and 50°C. However, crude enzyme was active over a wide range of temperature ranging from 40 to 80°C. Conclusion: Under optimized conditions of SSF, the production of alkaline protease by Bacillus thuringiensis aizawai HD283 could be improved by at least 2-3 folds. Crude enzyme activity over a wide range of temperature (40 to 80°C) suits well many biotechnological applications such as detergent industry, leather and textile industry and waste water treatment.