Molecular Identification of a Bacillus mojavensis UMF29 Producing a Novel Raw-starch Degrading Alpha-amylase

Abstract

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 UMF29, has been identified based on the 16S rDNA sequence and phylogenetic tree. After 72 h of incubation at 37 °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 50 °C, and pH of 7.0. In addition, the alpha-amylase exhibited optimum stability at 40 °C, and pH of 7.0. Some metal ions including Mn2+, Cu2+, Ca2+, Fe2+, Zn2+, Hg2+, and Mg2+ stimulated the alpha-amylase activity by about 122, 105, 61, 47, 46, 23 and 16%, respectively. The best activity of this enzyme was achieved in 0.5 M of KCl (81% enhancement), and 1.5 M of NaCl (9% enhancement). This alpha-amylase hydrolyzed a wide range of raw-starch granules (1.0 %, w/v) including potato, corn, grain, rice, and wheat and optimally was effective on wheat starch (16%, w/v) at 45 °C for 6 h with relative hydrolyses of ~10 U/ml. To our knowledge, it was also found that the alpha-amylase was a Ca2+-dependent enzyme for hydrolyzing higher concentrations of raw wheat starch (90-180 mg/ml) after 6 h of incubation at 45 ℃. Finally, these results indicated that UMF29 alpha-amylase showed high capacity in the degradation of the raw starch.

Keywords

• alpha-amylase
• bacillus mojavensis
• biochemical characterization
• molecular identification
• raw-starch degrading