A novel ∼34‐kDa α‐amylase from psychrotroph Exiguobacterium sp. SH 3: Production, purification, and characterization

An amylase‐producing psychrotroph bacterium was isolated from soil and identified as belonging to the genus Exiguobacterium . A novel cold‐adapted α‐amylase, Amy SH 3, was purified from culture medium of this bacterium using acetone precipitation and DEAE ‐ S epharose anion‐exchange chromatography. The molecular mass of the enzyme was estimated about 34 kDa using SDS ‐ PAGE . Biochemical characterization of Amy SH 3 revealed that the optimum temperature for maximum activity of Amy SH 3 was 37°C. However, Amy SH 3 was also active at cold temperatures, showing 13% and 39% activity at 0 and 10°C, respectively. The optimum pH for maximum activity of Amy SH 3 was pH 7, whereas the amylase was active over a pH range of 5 to 10. The activity of Amy SH 3 was enhanced by Co 2+ but decreased by Mg 2+ , Mn 2+ , Zn 2+ , Fe 2+ , and Ca 2+ . Amy SH 3 was able to retain 76% of its activity in the presence of 0.5% SDS . The K m and V max of the enzyme were calculated to be 0.06 mg/mL and 4,010 U/mL, respectively. The cold‐adapted Amy SH 3 seems very promising for applications at ambient temperature.