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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 OPEO 3 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 3 -OPEO 9 observed to accumulate and reduced after 70 h. MC biodegradation was accomplished via the initial accumulation of OPEO 3 -OPEO 9. The amounts of OPEO 3 increased and others reduced; however, OPEO 3 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. [Display omitted] • Selective biodegradation: short OPEO n accumulation and long OPEO n depletion. • OPEO n length and structures influence biodegradation. • Pseudomonas , Sphingobium and Flavobacterium spp. were dominant during degradation. • Bacterial physiological traits changed before and after biodegradation. [ABSTRACT FROM AUTHOR]

Octylphenol polyethoxylate (OPEO) surfactants are widely used as commercial cleaning products and agricultural pesticides. Sewage effluents containing high levels of OPEOs are often discharged into soil–slurry systems. OPEOs have been identified as endocrine-disrupting compounds and are a threat to organisms present in ecological systems. Several studies have previously investigated methods to degrade OPEOs; however, clarifications regarding the impact on environmental ecology and bacterial physiological changes are required. This study aimed to evaluate the changes in bacterial community and physiological characteristics that occur during OPEO biodegradation in terms of abiotic factors. The results show that adsorption of OPEO on soil can be described using the Freundlich adsorption isotherm. The rates of OPEO biodegradation in different environmental matrices were compared and the results are as follows: aqueous system > clay–slurry system > natural soil–slurry system, all of which can be identified by their distinct community-level physiological profiles (CLPPs). OPEO biodegradation is always faster in the monomer state than in the micelle state. Bacterial numbers are maintained at high level and range from 107 to 108 CFU/mL; Pseudomonas spp. is dominant and likely plays an important role in OPEO biodegradation. Fluctuations in the utilisation of carboxylic acid groups were found. The enzymatic activity of esterases was significant, ranging from 12.5–54.1%. Phosphatase activity in the soil slurries ranged from 2.1–45.8%. The responses in terms of physiological characteristics indicate the soil ecology state during OPEO biodegradation. [Display omitted] • Effective OPEO biodegradation by an indigenous mixed bacterial culture. • The influence of abiotic factors on OPEO biodegradation was evaluated. • The dominant Pseudomonas spp. plays an important role in OPEO biodegradation. • Excellent ecological indicators of carboxylic acid and esterase during degradation. [ABSTRACT FROM AUTHOR]