Biodegradation of short-chain phthalate esters (PAEs) by Sinomonas sp. S2 isolated from a soil contaminated by metal(loid)s smelting

Abstract

Phthalate esters (PAEs) are widely used as plasticizers and beneficiation flotation agents in ore smelters, which are ubiquitously distributed emerging contaminants in the environment. The biodegradation of PAEs by degrading microbes is a promising method for their remediation. In this study, we isolated a novel PAE-degrading bacteria, Sinomonas sp. S2, from a contaminated area of a metal(loid) smelter in Guangxi Zhuang Autonomous Region, China. Strain S2 is capable of degrading short-chain PAEs, including dimethyl phthalate (DMP), diethyl phthalate (DEP), di-iso-butyl phthalate (DIBP) and di-n-butyl phthalate (DBP). Sinomonas sp. S2 can completely degrade DBP at concentrations of 400 mg·L^-1 within 24 h. The degradation kinetics of PAEs followed the modified Gompertz model. Strain S2 demonstrated good environmental adaptability thriving at pH ranging from 5 to 9 and temperatures between 20 and 40 °C, indicated by its growth on DBP. The optimal pH and temperature for degradation were found to be 7 and 40 °C, respectively. Additionally, several metabolites of DBP were identified, including phthalic acid (PA), butyl acetate, ethyl propionate and methyl 2-methylbutyrate. The reconstructed degradation pathway of DBP may involve protocatechuic acid, β-carboxy-cis, cis-mucronate and γ-carboxy muconolactone, ultimately leading to the tricarboxylic acid (TCA). In a bioaugmentation experiment involving soil artificially contaminated with DBP, strain S2 could promote the degradation of DBP in soil. The results indicate that strain S2 had high degradation capacity and environmental tolerance, which had the potential to be applied in the bioremediation of DBP-contaminated environments.

Keywords: Sinomonas strains; Biodegradation; Di-n-butyl phthalate; Metal(loid)s smelter; Short-chain PAEs.