A novel ∼34-kDa α-amylase from psychrotroph Exiguobacterium sp. SH3: 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 SH3, was purified from culture medium of this bacterium using acetone precipitation and DEAE-Sepharose anion-exchange chromatography. The molecular mass of the enzyme was estimated about 34 kDa using SDS-PAGE. Biochemical characterization of Amy SH3 revealed that the optimum temperature for maximum activity of Amy SH3 was 37°C. However, Amy SH3 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 SH3 was pH 7, whereas the amylase was active over a pH range of 5 to 10. The activity of Amy SH3 was enhanced by Co²⁺ but decreased by Mg²⁺, Mn²⁺, Zn²⁺, Fe²⁺, and Ca²⁺. Amy SH3 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 SH3 seems very promising for applications at ambient temperature.