Process optimization for hyperproduction of 1,4-alpha-D-glucan glucanohydrolase from locally isolated <em>Bacillus subtilis</em> BBT6 under solid state fermentation

Abstract

The extracellular enzyme 1,4-alpha-D-glucan glucano-hydrolase (AMY) has wide application in clinical, medicinal and analytical chemistry and are used in industries such as food, textile, paper, etc. The ɑ-amylase (AMY) produced from microbial sources, particularly bacterial is preferred over fungal, because of characteristic advantages, such as rapid growth rate and ability to release proteins into the extracellular medium. The current study deals with the isolation of novel bacterial strain and process optimization of AMY. Primary screening was performed on the basis of starch hydrolysis zone. Secondary screening was carried out using solid state fermentation (SSF). Molecular characterization using16S r RNA gene sequencing technique was performed for the strain showing highest AMY production as compared to other isolates. The selected strain exhibited 91% similarity with the reference strain in the Gene Bank and identified as <em>Bacillus subtilis</em> on the basis of molecular characterization and analytical profile index testing. Different agricultural byproducts such as rice bran, rice husk, wheat bran, potato peel and coconut oil cake was tested. Among all, wheat bran proved to be the best for AMY production. Effect of other variables including incubation time, temperature, pH, inoculum size, carbon and nitrogen sources, surfactant and metal ion have also been investigated. Optimal production of AMY was obtained at 48 h of incubation period, 37°C, pH 7 and inoculum size 1 mL; 1 % ammonium sulphate and peptone as the best inorganic and organic nitrogen sources and 1.5 % starch, 0.2 % SDS found best for optimal production of enzyme.