Beta-amylase (EC 3.2.1.2), catalyzing the hydrolysis of the second alfa-1,4 glycosidic bond from non-reducing end of amylose or amylopectin, is a exo-type enzyme that plays a significant role in the production of maltose syrup. In this study, a novel beta-amylase (amyB) was characterized from Bacillus aryabhattai GEL-09. It showed that the amyB encoding gene was composed of 1542 bp, which encodes a protein containing 514 amino acid residues. The amino acid sequence alignment revealed that the beta-amylase from Bacillus aryabhattai shared the highest identity of 74% with that from Bacillus cereus. The amyB was over-expressed in E. coli BL21(DE3) and the recombinant enzyme was purified to homogeneity. The molecular weight of the recombinant beta-amylase was estimated to be about 57.6 kDa by SDS-PAGE. The recombinant beta-amylase has maximum activity at 50 degrees Celsius, and pH 6.0, and it maintained 53, 72 and 94% relative activity at 30, 40 and 60 degrees Celsius, respectively. In the presence of Co2+, the activity of the recombinase was enhanced and was inhibited by EDTA, and other metal ions had little effect on the activation or inhibition of the enzyme. The kinetic analysis showed that when the soluble starch was used as the substrate, the michaelis constant (Km) was 1.85 mM, the catalytic constant (Kcat) was 1202.72 s-1, and the Kcat/Km was 649.07 mM−1s−1. The enzyme showed the highest specificity for soluble starch, followed by corn starch. Then the recombinant beta-amylase was used to transform soluble starch (10%) into maltose, the yield of maltose reached 55.14% (w/w) after 24 h. The beta-amylase identified in this study has potential applications in the starch sugar industry.

Identification and characterization of a high catalytic efficiency beta-amylase from Bacillus aryabhattai GEL-09

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.