Molecular Identification of a Bacillus mojavensis UMF۲۹ Producing a Novel Raw-starch Degrading Alpha-amylase

Microbial alpha-amylases demonstrate more compatibility with industrial demands. These industrial enzymes have potential applications in various industrial parts, e.g., starch processing, brewing, baking bread, pharmaceuticals, and detergents. In this study, a mesophyll bacterium, Bacillus mojavensis strain UMF۲۹, has been identified based on the ۱۶S rDNA sequence and phylogenetic tree. After ۷۲ h of incubation at ۳۷ °C, the plates were inoculated with Lugol’s iodine, and the alpha-amylase-producing isolates were distinguished by clear zones in the blue background of starch agar plate around the colonies. Biochemical characterization of this enzyme was also investigated. Results showed that the optimal activity of this enzyme was at ۵۰ °C, and pH of ۷.۰. In addition, the alpha-amylase exhibited optimum stability at ۴۰ °C, and pH of ۷.۰. Some metal ions including Mn۲+, Cu۲+, Ca۲+, Fe۲+, Zn۲+, Hg۲+, and Mg۲+ stimulated the alpha-amylase activity by about ۱۲۲, ۱۰۵, ۶۱, ۴۷, ۴۶, ۲۳ and ۱۶%, respectively. The best activity of this enzyme was achieved in ۰.۵ M of KCl (۸۱% enhancement), and ۱.۵ M of NaCl (۹% enhancement). This alpha-amylase hydrolyzed a wide range of raw-starch granules (۱.۰ %, w/v) including potato, corn, grain, rice, and wheat and optimally was effective on wheat starch (۱۶%, w/v) at ۴۵ °C for ۶ h with relative hydrolyses of ~۱۰ U/ml. To our knowledge, it was also found that the alpha-amylase was a Ca۲+-dependent enzyme for hydrolyzing higher concentrations of raw wheat starch (۹۰-۱۸۰ mg/ml) after ۶ h of incubation at ۴۵ ℃. Finally, these results indicated that UMF۲۹ alpha-amylase showed high capacity in the degradation of the raw starch.

کلیدواژه ها:

Alpha-amylase ، Bacillus mojavensis ، Biochemical characterization ، Molecular identification ، Raw-starch degrading