Purification and characterization of a novel thermostable β-amylase from Aspergillus foetidus MTCC-508. β-amylase from Aspergillus foetidus MTCC-508

Abstract

An extracellular β-amylase was produced from Aspergillus foetidus MTCC-508, and was purified 254.8-fold with 14.6 yields by precipitation with acetone and by column chromatographies with DEAE-Sephadex A-50 and Sephadex G-100. The purified enzyme was homogeneous on polyacrylamide gel electrophoresis. The band of enzyme was visible around 20 kDa on SDS-PAGE while around 80 kDa on Native-PAGE, showing its homotetrameric nature. The enzyme was optimally active at pH-6.0 and 50°C temperature. It was fully stable at 50°C for 2 h. The activity was strongly inhibited by Hg2+, Zn2+and Co2+, while Mg2+marginally enhanced the enzyme activity. The enzyme was able to hydrolyze the raw starches of potato, wheat, rice, maize, and Trapa natans, with the highest degree of saccharification of maize starch. The Kmand Vmaxvalues for this enzyme against boiled soluble starch were found 2.7 mg/mL and 2,100 U/mg of protein, respectively.