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

Octylphenol polyethoxylates (OPEO_n) 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_n biometabolites have been identified as endocrine-disrupting contaminants and can threaten biotic factors in the ecosystem. In this study, OPEO_n 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_n biodegradation was observed in the order TX-45 (0.1414 h^-1) > TX-114 (0.0556 h^-1) > TX-165 (0.0485 h^-1), with biomineralisation reaching at least 80 % for all OPEO_n. The selective biodegradation of EO chains was also measured, with initial accumulation of OPEO₃ 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 OPEO₃-OPEO₉ observed to accumulate and reduced after 70 h. MC biodegradation was accomplished via the initial accumulation of OPEO₃-OPEO₉. The amounts of OPEO₃ increased and others reduced; however, OPEO₃ 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_n 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.