A novel raw starch digesting alpha-amylase from a newly isolated Bacillus sp. YX-1: purification and characterization.

This study reports the purification and characterization of a novel raw starch digesting alpha-amylase from a newly isolated Bacillus sp. YX-1. Maximum alpha-amylase activity (53 U mL(-1)) was obtained at 45 degrees C after 44 h of incubation. The enzyme was purified using ammonium sulfate precipitation, ion exchange and gel filtration chromatography, and showed a molecular weight of 56 kDa by SDS-PAGE. This enzyme exhibited maximum activity at pH 5.0, performed stability over a broad range of pH 4.5-11.0, and was optimally active at 40-50 degrees C. The enzyme preparation had a strong digesting ability towards various raw starches and efficiently hydrolyzed raw corn starch at a concentration of 20% and pH 5.0, which were normally used in the starch industries, in a period of 12h. By analyzing its partial amino acid sequences, the enzyme was proposed to be a novel alpha-amylase.