An efficient phthalate ester-degrading Bacillus subtilis: Degradation kinetics, metabolic pathway, and catalytic mechanism of the key enzyme

Youqiang Xu; Xiao Liu; Jingrong Zhao; Huiqin Huang; Mengqin Wu; Xiuting Li; Weiwei Li; Xiaotao Sun; Baoguo Sun

doi:10.1016/j.envpol.2021.116461

An efficient phthalate ester-degrading Bacillus subtilis: Degradation kinetics, metabolic pathway, and catalytic mechanism of the key enzyme

Environ Pollut. 2021 Jan 15:273:116461. doi: 10.1016/j.envpol.2021.116461. Online ahead of print.

Authors

Youqiang Xu¹, Xiao Liu², Jingrong Zhao², Huiqin Huang², Mengqin Wu², Xiuting Li³, Weiwei Li², Xiaotao Sun⁴, Baoguo Sun¹

Affiliations

¹ Beijing Advanced Innovation Center for Food Nutrition and Human Health, Beijing Technology and Business University, Beijing, 100048, China; Key Laboratory of Brewing Molecular Engineering of China Light Industry, Beijing Technology and Business University, Beijing, 100048, China; Beijing Engineering and Technology Research Center of Food Additives, Beijing Technology & Business University, Beijing, 100048, China.
² Beijing Advanced Innovation Center for Food Nutrition and Human Health, Beijing Technology and Business University, Beijing, 100048, China.
³ Beijing Advanced Innovation Center for Food Nutrition and Human Health, Beijing Technology and Business University, Beijing, 100048, China; Key Laboratory of Brewing Molecular Engineering of China Light Industry, Beijing Technology and Business University, Beijing, 100048, China; Beijing Engineering and Technology Research Center of Food Additives, Beijing Technology & Business University, Beijing, 100048, China. Electronic address: lixt@btbu.edu.cn.
⁴ Beijing Advanced Innovation Center for Food Nutrition and Human Health, Beijing Technology and Business University, Beijing, 100048, China; Key Laboratory of Brewing Molecular Engineering of China Light Industry, Beijing Technology and Business University, Beijing, 100048, China.

PMID: 33485001
DOI: 10.1016/j.envpol.2021.116461

Abstract

Phthalate ester pollution in the environment and food chain is frequently reported. Microbial treatment is a green and efficient method for solving this problem. The isolation and systematic investigation of microorganisms generally recognized as safe (GRAS) will provide useful resources. A GRAS Bacillus subtilis strain, BJQ0005, was isolated from Baijiu fermentation starter and efficiently degraded phthalate esters (PAEs). The half-lives for di-isobutyl phthalate, di-butyl phthalate and di-(2-ethylhexyl) phthalate were 3.93, 4.28, and 25.49 h, respectively, from the initial amount of 10 mg per 10 mL reaction mixture, which are records using wild-type strains. Genome sequencing and metabolic intermediate analysis generated the whole metabolic pathway. Eighteen enzymes from the α/β hydrolase family were expressed. Enzymes GTW28_09400 and GTW28_13725 were capable of single ester bond hydrolysis of PAEs, while GTW28_17760 hydrolyzed di-ester bonds of PAEs. Using molecular docking, a possible mechanism affecting enzymatic ester bond hydrolysis of mono-butyl phthalate was proposed of GTW28_17760. The carboxyl group generated by the first hydrolysis step interacted with histidine in the catalytic active center, which negatively affected enzymatic hydrolysis. Isolation and systematic investigation of the PAE degradation characteristics of B. subtilis will promote the green and safe treatment of PAEs in the environment and food industry.

Keywords: Bacillus subtilis; Baijiu; Di-ester bond hydrolase; Generally recognized as safe; Phthalate ester.