Duan X, Zhu Q, Zhang X, Shen Z, Huang Y. Expression, biochemical and structural characterization of high-specific-activity β-amylase from Bacillus aryabhattai GEL-09 for application in starch hydrolysis.
Microb Cell Fact 2021;
20:182. [PMID:
34537082 PMCID:
PMC8449922 DOI:
10.1186/s12934-021-01649-5]
[Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 08/03/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND
β-amylase (EC 3.2.1.2) is an exo-enzyme that shows high specificity for cleaving the α-1,4-glucosidic linkage of starch from the non-reducing end, thereby liberating maltose. In this study, we heterologously expressed and characterized a novel β-amylase from Bacillus aryabhattai.
RESULTS
The amino acid-sequence alignment showed that the enzyme shared the highest sequence identity with β-amylase from Bacillus flexus (80.73%) followed by Bacillus cereus (71.38%). Structural comparison revealed the existence of an additional starch-binding domain (SBD) at the C-terminus of B. aryabhattai β-amylase, which is notably different from plant β-amylases. The recombinant enzyme purified 4.7-fold to homogeneity, with a molecular weight of ~ 57.6 kDa and maximal activity at pH 6.5 and 50 °C. Notably, the enzyme exhibited the highest specific activity (3798.9 U/mg) among reported mesothermal microbial β-amylases and the highest specificity for soluble starch, followed by corn starch. Kinetic analysis showed that the Km and kcat values were 9.9 mg/mL and 116961.1 s- 1, respectively. The optimal reaction conditions to produce maltose from starch resulted in a maximal yield of 87.0%. Moreover, molecular docking suggested that B. aryabhattai β-amylase could efficiently recognize and hydrolyze maltotetraose substrate.
CONCLUSIONS
These results suggested that B. aryabhattai β-amylase could be a potential candidate for use in the industrial production of maltose from starch.
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