Characterization and Degradation Pathways of Microbacterium resistens MZT7, A Novel 17β-Estradiol-Degrading Bacterium

Abstract

Due to the ecotoxicity of 17β-estradiol (E2), residual E2 in the environment poses potential risks to human and animal health and ecosystems. Biodegradation is considered one of the most effective strategies to remove E2 from the environment. Here, a novel, efficient E2-degrading bacterial strain Microbacterium resistens MZT7 was isolated from activated sludge and characterized. The genome of strain MZT7 contained 4,011,347 bp nucleotides with 71.26% G + C content and 3785 coding genes. There was 86.7% transformation efficiency of 10 mg/L E2 by strain MZT7 after incubation for 5 d at optimal temperature (30 °C) and pH (7.0). This strain was highly tolerant to ranges in pH (5.0–11.0), temperature (20–40 °C), and salinity (2–8%). Adding sources of carbon (glucose, maltose, sucrose, or lactose) or nitrogen sources (urea, peptone, or beef extract) promoted the degradation of E2 by strain MZT7. However, when yeast extract was added as a nitrogen source, the degradation efficiency of E2 was inhibited. Metabolites were analyzed by LC-MS and three metabolic pathways of E2 degradation were proposed. Further, the intermediates dehydroepiandrosterone and androsta-1,4-diene-3,17-dione were detected, as well as identification of kshB and fadD3 genes by KEGG, confirming one E2 degradation pathway. This study provided some insights into E2 biodegradation.

Characterization of 17β-estradiol-degrading enzyme from Microbacterium sp. MZT7 and its function on E2 biodegradation in wastewater

“…It is well known that the E2 biodegradation occurs mainly through enzyme catalysis. In most of the reported E2-degrading bacteria, enzyme-catalyzed conversion of E2 to estrone (E1) is considered as the first reaction step in E2 degradation [ 7 , 20 – 22 ]. This step of reaction is the key and restriction step for E2 to be biodegraded [ 23 ].…”

“…Microbacterium resistens MZT7 ( M. resistens MZT7) was isolated from dairy farm activated sludge and was subjected to whole genome sequencing (Accession number CP082781) [ 22 ]. Previous studies have shown that strain MZT7 can degrade E2 to E1 [ 22 ].…”

“…Microbacterium resistens MZT7 ( M. resistens MZT7) was isolated from dairy farm activated sludge and was subjected to whole genome sequencing (Accession number CP082781) [ 22 ]. Previous studies have shown that strain MZT7 can degrade E2 to E1 [ 22 ]. In another recent study, a heterologously expressed short-chain dehydrogenase gene (MZT7_GM000095, locus_tag = K8F61_00480) was confirmed to transform E2 to E1 [ 34 ].…”