Identification of a Strain with Carboxylesterase and Its Enzymatic Character

Objective: Microbial species level identification in Chinese liquor fermentation, key enzymatic character and enzymatic mechanism study benefits to improve quality of Chinese liquor. Methods: Based on the morphological and physiological characteristics, 16S rRNA, gyrB gene and antiSMASH analysis to identify a micro-organism. 3D model by 3D structure modeling was gained and the mechanism regulating by molecular docking was insighted. Results: The strain was identified as gram-negative Bacillus velezensis with carboxylesterase gene. The growth curve was typical S-shaped growth curve. Product curve was typical S-shaped. The range of carboxylesterase-activity was from pH5.0 to pH9.0. Molecular docking indicated that Phe21A was responsible for the primarily hydrolysis reaction in catalytic site where glyceryl tributyrate was hydrolyzed into glycerol and butyric acid. Glyceryl tributyrate experiencing conformational changes were transported into catalytic site and then hydrolysed; Interactions of hydrophilic and hydrophobic interface were beneficial to the substrate transferred downward. The hydrolyzed substrates went to the enzyme surface from hydrophobic channel. Conclusion: The stain is identificated as gram-negative Bacillus velezensis with carboxylesterase gene and this study provides a new view of substrate recognition, transfer and catalysis mechanism when carboxylesterase hydrolyzes substances, such as glyceryl tributyrate.