The growth of Methylobacterium radiotolerans SH771 on 4-t-octylphenol and metabolite analysis

• Main Authors: Sook-Yeng Foo, 胡菽蕓
• Other Authors: Shir-Ly Huang
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/00242516026974245557

碩士 === 國立中央大學 === 生命科學研究所 === 99 === Alkylphenol polyethoxylates (APEOn) are an important group of non-ionic surfactants used in the agricultural, industrial and domestic detergents, and many other applications. In addition, nonylphenol and octylphenol are known as the major metabolites from APEOn. The prior studies have demonstrated that octylphenol is 10 to 20 folds higher in the estrogenic effect than nonylphenol. 4-t-octylphenol was used as the sole carbon source for the isolation of octylphenol-degrading bacteria in Taiwan. Seventeen octylphenol-degrading bacteria were isolated from paddy farm topsoil, soil microcosm and 4-t-octylphenol reagent bottles by previous works. Methylobacterium radiotolerans SH771 is belong to alpha proteobacteria and was isolated from a reagent bottle containing 4-tert-octylphenol in our lab. In many reports had shown Methylobacterium radiotolerans has biotechnology and bioremediation potential. The aim of this study was to analyze the key metabolites from octylphenol degradation by Methylobacterium radiotolerans SH771 and propose the degradation pathway. Octylphenol and its metabolites were analyzed by high-performance chromatography (HPLC) system equipped with an electrospray ionization-mass spectrometer (MS). The chromatogram was shown the octylphenol gradually decreased with time and produced 1,2,4-trihydroxyenzene. We proposed that the octylphenol can go two pathways then transformed to the ring cleavage compound. The first octylphenol would central cleavage into 2,4,4-trimethyl-2-pentanol and hydroquinone. The other one, octylphenol can via the aromatic ring-hydroxylating oxygenase, multicomponent phenol hydroxylase (Tuan et al., 2011), transformed octylphenol to octylcatechol (OC) then central cleavage to 1,2,4-trihydroxybenzene and 2,4,4-trimethyl-2-pentanol. 1,2,4-trihydroxybenzene is a common metabolite of this two pathway then ortho-cleavage into maleylacetate and meta-cleavage into semialdehyde. The estrogenic activity of octylphenol is decreased due to the central cleavage and ring fission by aromatic ring cleavage dioxygenases because of the collapse of the phenolic and hydrophobic moiety that interact with the estrogen receptor. However, the mechanism is remaining unclear. The octylphenol degradation pathway is anticipated to be completed in Methylobacterium radiotolerans.