Abstract
The selected bacterial strain, Bacillus subtilis D19 was inoculated into the solid residues such as, wheat bran, banana peel, orange peel, rice bran and pine apple peel. Among the tested solid wastes, wheat bran showed enhanced the production of amylase (640 U/g) than other tested substrates. The carbon and nitrogen sources were initially screened by traditional method using wheat bran medium. Amylase activity was high in the wheat bran substrate supplemented with starch (670 U/g). The tested nitrogen sources enhanced amylase activity. Among the selected nitrogen sources, yeast extract stimulated maximum production of amylase (594 U/g). In two level full factorial experimental design, maximum activity (1239 U/g) was obtained at pH 9.0, 70% (v/w) moisture, 1% (w/w) starch, 1% (w/w) yeast extract and 5% (v/w) inoculums. Central composite design and response surface methodology was used to optimize the required medium concentration (pH, moisture content of the medium and starch concentrations) for the maximum production of amylase. All three selected variables enhanced amylase production over 3 fold in optimized medium. (C) 2019 The Author(s). Published by Elsevier B.V. on behalf of King Saud University.