Substrate Report for: Diisobutyl-phthalate

A promising bacterial strain for biodegrading dibutyl phthalate (DBP) was successfully isolated from activated sludge and characterized as a potential novel Microbacterium sp. USTB-Y based on 16S rRNA sequence analysis and whole genome average nucleotide identity (ANI). Initial DBP of 50 mg/L could be completely biodegraded by USTB-Y both in mineral salt medium and in DBP artificially contaminated soil within 12 h at the optimal culture conditions of pH 7.5 and 30 degC, which indicates that USTB-Y has a strong ability in DBP biodegradation. Phthalic acid (PA) was identified as the end-product of DBP biodegraded by USTB-Y using GC/MS. The draft genome of USTB-Y was sequenced by Illumina NovaSeq and 29 and 188 genes encoding for putative esterase/carboxylesterase and hydrolase/alpha/beta hydrolase were annotated based on NR (non redundant protein sequence database) analysis, respectively. Gene3781 and gene3780 from strain USTB-Y showed 100% identity with dpeH and mpeH from Microbacterium sp. PAE-1. But no phthalate catabolic gene (pht) cluster was found in the genome of strain USTB-Y. The results in the present study are valuable for obtaining a more holistic understanding on diverse genetic mechanisms of PAEs biodegrading Microbacterium sp. strains.

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 muM and (2.72 +/- 0.06) x 10(6) s(-1), while those of MpeH for MBP were 18.61 +/- 2.00 muM and (5.83 +/- 1.00) x 10(5) 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.

Phthalate esters (PAEs) are harmful to human health and have been repeatedly identified in Baijiu samples. In our study, the distribution and degradation characteristics of 14 PAEs in Baijiu raw materials (BRMs) and Baijiu during distillation were detected using QuEChERS or vortex-assisted surfactant-enhanced-emulsification liquid-liquid micro-extraction (VSLLME) methods coupled with gas chromatography-mass spectrometry. The same five PAEs were detected in all tested samples, values ranged from 0.003 to 0.292 mg/kg; however, higher concentrations existed in BRMs compared to Baijiu samples. Using multivariate statistical analysis, detailed distinctions between different varieties of Baijiu and BRMs and separation-related PAE markers were revealed. PAEs concentration during Baijiu distillation showed a decreasing trend. The highest concentrations detected in distillate heads, were 1.6-, 2.3-, and 8.1-fold higher than those in heart1, heart2, and tail distillates, respectively. These findings revealed that PAEs may migrate from BRMs; moreover, that PAEs content can be regulated by distillation.