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.
Highlights
At present, the environmental pollution that is caused by human intervention has become a global problem
Sci. 2018, 19, 2803 inhibited under the strong acid or alkaline environment. These results indicated that strain YC-JH1 was a strong candidate applied to bioremediation under a broad pH range
According to result of molecular dynamics (MD) simulation, the conserved catalytic triad S125-H291-D259 was located in a hydrophobic cavity (Figure 6A,B), and all of the monoalkyl phthalates (MAPs) were situated in this cavity (Figure 6C–F)
Summary
The environmental pollution that is caused by human intervention has become a global problem. The strains with high degradation efficiency under a broad range of environmental conditions are urgently required for the remediation of PAEs-contaminated environment. According to the results here, the strain YC-JH1 had high degradation efficiency toward PAEs and good adaptability to environment of strong alkaline and high temperature. Sci. 2018, 19, 2803 inhibited under the strong acid (pH 4.0) or alkaline (pH 13.0) environment These results indicated that strain YC-JH1 was a strong candidate applied to bioremediation under a broad pH range. The degradation process was not completely inhibited under the strong acid (pH 4.0) or alkaline (pH 13.0) environment The β-strands were sandwiched between the domain composed of α1 and
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