Abstract

An alkaliphilic bacterium producing organic solvent-tolerant and thermostable alkaline protease was isolated from poultry litter site and identified as Bacillus coagulans PSB-07. Protease production under different submerged fermentation conditions were investigated with the aim of optimizing yield of enzyme. B. coagulans PSB-07 produced protease optimally at the beginning of stationary phase over broad pH range of 6.0 to 11.0 and temperature range of 30 to 50°C. The optimum enzyme production was at 37°C and pH 8.0. The media composition that supported maximum yield of protease (760.4 U/ml) contained sucrose (0.5%), peptone (0.75%), NaCl (0.05%) and MgSO4.7H₂O (0.01%). The protease had optimum activity at 60°C and pH 8.0 with casein as substrate. The enzyme was stable over a broad pH of 6.0 to 12.0 and showed good thermostability retaining 91.4 and 50.5% of its original activity after incubation at 50 and 60°C for 60 min at pH 8.0 in the presence of CaCl₂. The protease was strongly activated by metal ions, Ca²⁺ and Mg²⁺. The enzyme showed remarkable activity and stability in the presence of all organic solvents studied except benzene. The exhibited properties of the protease suggest the suitability of the enzyme for applications in peptide synthesis, detergent formulation and bio-transformation in non-aqueous medium.

Key words: Alkaline protease, Bacillus coagulans PSB-07, organic solvent-tolerant, thermostable, production.