Excellent Degradation Performance of a Versatile Phthalic Acid Esters-Degrading Bacterium and Catalytic Mechanism of Monoalkyl Phthalate Hydrolase

Abstract

Despites lots of characterized microorganisms that are capable of degrading phthalic acid esters (PAEs), there are few isolated strains with high activity towards PAEs under a broad range of environmental conditions. In this study, Gordonia sp. YC-JH1 had advantages over its counterparts in terms of di(2-ethylhexyl) phthalate (DEHP) degradation performance. It possessed an excellent degradation ability in the range of 20–50 °C, pH 5.0–12.0, or 0–8% NaCl with the optimal degradation condition 40 °C and pH 10.0. Therefore, strain YC-JH1 appeared suitable for bioremediation application at various conditions. Metabolites analysis revealed that DEHP was sequentially hydrolyzed by strain YC-JH1 to mono(2-ethylhexyl) phthalate (MEHP) and phthalic acid (PA). The hydrolase MphG1 from strain YC-JH1 hydrolyzed monoethyl phthalate (MEP), mono-n-butyl phthalate (MBP), mono-n-hexyl phthalate (MHP), and MEHP to PA. According to molecular docking and molecular dynamics simulation between MphG1 and monoalkyl phthalates (MAPs), some key residues were detected, including the catalytic triad (S125-H291-D259) and the residues R126 and F54 potentially binding substrates. The mutation of these residues accounted for the reduced activity. Together, the mechanism of MphG1 catalyzing MAPs was elucidated, and would shed insights into catalytic mechanism of more hydrolases.

Characterization of a novel family VIII esterase EstM2 from soil metagenome capable of hydrolyzing estrogenic phthalates

“…Interestingly, the esterase is capable of hydrolyzing both phthalate diesters and phthalate monoesters and is active over a wide range of temperature and pH without any cofactor requirement. Although phthalate hydrolases have long been isolated from cultured microbial sources and typically possess the catalytic serine within the consensus G-x-S-x-G motif [36][37][38]40], to the best of our knowledge, EstM2 is the first phthalate hydrolase, isolated from a soil metagenomic library that belongs to family VIII esterases possessing a β-lactamase like catalytic triad for phthalate ester hydrolysis. It is believed that structural modification of the enzyme by site-directed mutagenesis may further enhance the catalytic performance of EstM2 towards various estrogenic phthalates and may find use to counter the growing pollution caused by phthalate-based plasticizers in diverse geological environment and in other aspects of biotechnological applications.…”

“…As far as metabolism of phthalate esters is concerned, there are only a few reports on the purified dialkyl phthalate esterase enzymes, which are capable of specifically hydrolyzing only one of the ester bonds of the diester to generate the corresponding monoalkyl phthalate esters [28,[30][31][32][33][34][35]. On the other hand, there are only limited reports of specific monoalkyl phthalate esterases that hydrolyze monoalkyl phthalates to furnish phthalic acid but are incapable of hydrolyzing phthalate diesters [5,[36][37][38][39][40]. Recently, another esterase isolated from naphthalene-enriched soil community, was shown to hydrolyze various polyaromatic esters besides dimethyl phthalate [41].…”

Integrated multi-omics investigations reveal the key role of synergistic microbial networks in removing plasticizer di-(2-ethylhexyl) phthalate from estuarine sediments

“…The amino acid sequences of alpha/beta hydrolases in the genome of Acidovorax sp. 210-6 and hydrolases derived from several aerobic o -phthalic acid-degrading Actinobacteria [14–16, 67, 75–77], Alphaproteobacteria (78, 79), Firmicutes [80], Gammaproteobacteria [81], and uncultured bacterium [82] were used for inferring maximum likelihood tree. The bacterial source, substrate specificity, and accession number of these aerobic hydrolases are listed in Table S1 .…”

“…Several studies have reported aerobic microbial degradation pathways for different PAEs [3]. In the aerobic pathway, DEHP is initially transformed into ophthalic acid and 2-ethylhexanol through mono-(2-ethylhexyl) phthalate (MEHP) by dialkyl phthalate hydrolase and monoalkyl phthalate hydrolase [14][15][16][17] (Fig. 1).…”

Integrated Multi-omics Investigations Reveal the Key Role of Synergistic Microbial Networks in Removing Plasticizer Di-(2-Ethylhexyl) Phthalate from Estuarine Sediments

“…Several studies have reported aerobic microbial degradation pathways for different PAEs ( 4 ). In the aerobic pathway, DEHP is initially transformed into o -phthalic acid and 2-ethylhexanol through mono-(2-ethylhexyl) phthalate (MEHP) by dialkyl phthalate hydrolase and monoalkyl phthalate hydrolase ( 14 – 16 ) ( Fig. 1 ).…”