Selective biodegradation of octylphenol polyethoxylates with different ethoxylate length chains by aerobic bacterial culture.

Octylphenol polyethoxylates (OPEO) are composed of a hydrophobic octylphenol (OP) group and a hydrophilic polyethylene oxide (EO) chain and are widely used in commercial products. Shorter EO chains and OPEO biometabolites have been identified as endocrine-disrupting contaminants and can threaten biotic factors in the ecosystem. In this study, OPEO at three EO lengths (TX-45, TX-114, and TX-165) were selected in monomer (MN) or micelle (MC) state for batch experiments under aerobic conditions, with results showing biodegradation rates of 90 % within 35-70 h. The pseudo-first-order constant (k) of OPEO biodegradation was observed in the order TX-45 (0.1414 h) > TX-114 (0.0556 h) > TX-165 (0.0485 h), with biomineralisation reaching at least 80 % for all OPEO. The selective biodegradation of EO chains was also measured, with initial accumulation of OPEO observed along with the depletion of longer EO chains for TX-45 and TX-114 in both the MN and MC states. A similar trend was observed for the MN state of TX-165, with OPEO-OPEO observed to accumulate and reduced after 70 h. MC biodegradation was accomplished via the initial accumulation of OPEO-OPEO. The amounts of OPEO increased and others reduced; however, OPEO remained high at the end of biodegradation for TX-165. Bacterial community analysis indicated that the genera Sphingobium spp., Pseudomonas spp., Flavobacterium spp., Comamonas spp., and Sphingopyxis spp. dominate OPEO biodegradation, and they have their roles during biodegradation, and the community-level physiological profile (CLPP) was also changed by biodegradation in both the MN and MC states.