A High Salt Stable ɑ-Amylase by Bacillus Sp. MRS6 Isolated from Municipal Solid Waste; Purification, Characterization and Solid State Fermentation

Abstract

Salt-tolerant alkaline amylase producing Bacillus sp. MRS6 was isolated from three municipal waste disposal site of Medinipur town in the Paschim Medinipur district of southern West Bengal, India. The strain had been characterized from a polyphasic approach. Extracellular enzyme production was carried out in mineral salt media at pH-7, 35°C with 2% soluble starch as sole carbon source. It was found that the amylase, produced by the salttolerant strain possessed high activity in a range of alkaline pH (6-9), with pH-8 as optimum. An incubation period of 30 min at 35°C was found as optimum temperature condition of its activity. This alkaliphilic, salt-tolerant enzyme was found to stay stable upto 80°C, 4M NaCl. Mn 2+, Ca 2+ plays critical role in >80% increasing of this enzyme activity. EDTA, β-merkeptoethanol and detergents strongly inhibit enzyme activity. A solid state fermentation for production of this enzyme was performed with 85% moisture content where wheat bran was found as most effective and cheap carbon source. This enzyme was purified partially by cold acetone precipitation followed by gel filtration chromatography (seralose 6B) and the molecular mass was found to be 55 kDa by SDS PAGE. The present findings suggested the enzyme to be halophilic alkaline amylase. The present enzyme is of great significance in present day biotechnology with applications ranging from food, fermentation, textile, detergent to paper industries.