Degradation of dibutyl phthalate (DBP) by a bacterial consortium and characterization of two novel esterases capable of hydrolyzing PAEs sequentially

Ecotoxicol Environ Saf. 2020 Jun 1:195:110517. doi: 10.1016/j.ecoenv.2020.110517. Epub 2020 Mar 25.

Abstract

Phthalate esters (PAEs), a class of toxic anthropogenic compounds, have been predominantly used as additives or plasticizers, and great concern and interests have been raised regarding its environmental behavior and degradation mechanism. In the present study, a bacterial consortium consisting of Microbacterium sp. PAE-1 and Pandoraea sp. PAE-2 was isolated by the enrichment method, which could degrade dibutyl phthalate (DBP) completely by biochemical cooperation. DBP was converted to phthalic acid (PA) via monobutyl phthalate (MBP) by two sequential hydrolysis steps in strain PAE-1, and then PA was further degraded by strain PAE-2. Strain PAE-1 could hydrolyze many dialkyl Phthalate esters (PAEs) including dimethyl, diethyl, dibutyl, dipentyl, benzyl butyl, dihexyl, di-(2-ethyhexyl) and their corresponding monoalkyl PAEs. Two esterase genes named dpeH and mpeH, located in the same transcription unit, were cloned from strain PAE-1 by the shotgun method and heterologously expressed in Escherichia. coli (DE3). The Km and kcat values of DpeH for DBP were 9.60 ± 0.97 μM and (2.72 ± 0.06) × 106 s-1, while those of MpeH for MBP were 18.61 ± 2.00 μM and (5.83 ± 1.00) × 105 s-1, respectively. DpeH could only hydrolyze dialkyl PAEs to the corresponding monoalkyl PAEs, which were then hydrolyzed to PA by MpeH. DpeH shares the highest similarity (53%) with an alpha/beta hydrolase from Microbacterium sp. MED-G48 and MpeH shows only 25% identity with a secreted lipase from Trichophyton benhamiae CBS 112371, indicating that DpeH and MpeH are two novel hydrolases against PAEs.

Keywords: Consortium; Degradation; Dibutyl phthalate (DBP); dpeH; mpeH.

MeSH terms

  • Actinobacteria / drug effects
  • Actinobacteria / enzymology
  • Burkholderiaceae / drug effects
  • Burkholderiaceae / enzymology
  • Dibutyl Phthalate / analysis*
  • Dibutyl Phthalate / chemistry
  • Environmental Pollutants / analysis*
  • Environmental Pollutants / chemistry
  • Esterases / genetics*
  • Genes, Bacterial
  • Hydrolysis
  • Lipase / genetics
  • Microbial Consortia / drug effects*
  • Microbial Consortia / genetics
  • Phthalic Acids / analysis
  • Plasticizers / analysis*
  • Plasticizers / chemistry

Substances

  • Environmental Pollutants
  • Phthalic Acids
  • Plasticizers
  • Dibutyl Phthalate
  • Esterases
  • Lipase
  • monobutyl phthalate