Mechanisms Underlying Efficient n‐Eicosane Degradation and Physiological Adaptation in Rhodococcus erythropolis KB1

Low temperature limits microbial remediation of petroleum hydrocarbon–contaminated environments, yet the physiological basis for long‐chain alkane degradation under cold stress remains insufficiently understood. In this study, Rhodococcus erythropolis KB1 was cultured with n‐eicosane as the sole carbon source at 4°C, 16°C, and 30°C for 5, 10, and 15 days. Degradation performance, growth‐associated traits, surface tension, membrane permeability, redox‐energy metabolism, key enzyme activities, and putative GC–MS signals were evaluated. KB1 showed the highest n‐eicosane degradation efficiency at 30°C, reaching 86.84 ± 0.21% by Day 15, accompanied by enhanced biomass accumulation, protein content, cytochrome P450 monooxygenase (CYP450) activity, adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (NADPH) contents, and Na + –K + ‐ATPase and Ca 2+ –Mg 2+ ‐ATPase activities. Notably, KB1 retained substantial low‐temperature degradation capacity, achieving 60.13 ± 0.44% degradation at 4°C by Day 15. Correlation analysis indicated that degradation efficiency was associated with membrane permeability, reducing‐power supply, ion‐transport activity, biomass accumulation, and interfacial regulation rather than a single enzymatic response. Gas chromatography–mass spectrometry (GC–MS) analysis detected 23 putative compounds, including shorter‐chain alkane‐related signals, fatty alcohols, and fatty acid methyl esters, supporting a pathway involving terminal oxidation, β‐oxidation, and downstream tricarboxylic acid (TCA)‐cycle‐related metabolism. Overall, R. erythropolis KB1 coordinates membrane‐interface remodeling, redox‐energy coupling, ion transport, and oxidative transformation to sustain n‐eicosane degradation across temperature gradients. These findings identify KB1 as a promising cold‐adapted microbial resource for petroleum hydrocarbon bioremediation.