Elucidating styrene tolerance mechanisms in Gluconobacter oxydans through adaptive laboratory evolution

Biodegradation of styrene utilizing Gluconobacter oxydans (G. oxydans) is affected by the inhibitory and toxic effects of styrene concentrations. In this study, evolution experiments were conducted at low concentrations to mimic typical wastewater conditions to develop G. oxydans mutants with enhanced styrene tolerance. Physiological and biochemical analyses reveal that styrene hinders normal cell growth and damages cell membrane function and motility. Nevertheless, phenotypic heterogeneity and enhanced biofilm formation emerged as primary factors contributing to high styrene tolerance. Mutations in the flagella protein FlgE primarily affects cell motility, chemotaxis, and biofilm formation. TFs MarR and HipB positively regulate the tolerance phenotypes, with MarR playing a more pivotal role than HipB in regulating styrene tolerance, supporting tolerance up to 22 g·L^-1 of styrene. This study clarifies potential mechanisms underlying styrene tolerance and, offering valuable insights for the application of G. oxydans in treating styrene-laden wastewater.