Efficient biodegradation of phthalate esters by Bacillus tequilensis L26: Identification and surface display of functional phthalate ester hydrolase

Phthalate esters (PAEs) are ubiquitous organic contaminants in agricultural soils and are increasingly recognized as a critical threat to food safety and ecological sustainability due to their endocrine-disrupting properties. Here, a PAE-degrading bacterium, Bacillus tequilensis L26, was isolated from industrial sludge and evaluated for its biodegradation capacity. Strain L26 efficiently utilized dimethyl phthalate (DMP) as the sole carbon source, achieving 91% removal of 200 mg/L within 5 days under optimized conditions (36.9°C, pH 10.0, inoculum 12.8%). The degradation process followed first-order kinetics over 50‒600 mg/L, with half-lives ranging from 1.1 to 1.6 days. Genome analysis identified a putative esterase gene, carE19, potentially involved in PAE hydrolysis. To elucidate its functional role and expand its application potential, carE19 was expressed on the surface of Escherichia coli, generating a stable whole-cell biocatalyst. The engineered strain efficiently degraded multiple PAEs, including DMP, diethyl phthalate, and diisobutyl phthalate. The surface-displayed CarE19 exhibited optimal catalytic activity at pH 8.0 and 50 °C, and showed substrate preference for medium-chain esters, indicating its classification as a medium-chain ester hydrolase. Overall, this study demonstrates an integrated strategy combining microbial resource mining and enzyme surface engineering to improve PAEs biodegradation. The developed whole-cell catalyst provides a potential and scalable approach for removal of plasticizers from contaminated environments.