Optimization of Xylanase and α-Amylase Production by Alkaline and Thermophilic Bacillus Isolate KH-13

Abstract

Alkaline, and thermophilic Bacillus sp. strain KH-13, which produces α-amylase and xylanase was isolated from Caspian Sea in Iran. Characterization of strain KH-13 by 16S rRNA gene analysis found it closest member of Bacillus sp. M26with a similarity of 98%. This bacterial isolate was mutagenized by treatment with Ethidium bromide (EtBr) and 4 mutant variants were obtained. Wild type strain KH-13 and its mutant variants KH13-M3, and KH13-M4 were selected for partial characterization. Maximum α-amylase productions were achieved at the end of 12 h of growth for KH-13 and KH13-M3. Besides, maximum xylanase productions were achieved at the end of 24 and 48 h of growth for KH-13 and KH13-M4, respectively. The optimum temperature values of the KH-13 and KH13-M3 α-amylases were found to be 40 and 50 °C, respectively. An optimum pH value of the both enzymes was 6.5. The optimum temperature values of the KH-13 and KH13-M4 xylanases were found to be 50 and 60 °C, respectively. An optimum pH value of the both enzymes was 9.5.