Developing a bioprocess for a novel trehalose tetraester biosurfactant from Rhodococcus erythropolis KB1 and evaluating its efficacy in PAH bioremediation

The bioremediation of petroleum hydrocarbons in cold environments remains a significant challenge, necessitating novel biosurfactants with superior low-temperature performance. This study investigates a unique trehalose tetraester (TTEs) from the cryotolerant strain Rhodococcus erythropolis KB1. This TTEs, featuring a unique mixed-ester structure, exhibits excellent properties, including high PAH-solubilization efficacy at 10 °C, a low critical micelle concentration (CMC, 100 mg/L), and high emulsification activity (E₂₄ > 90 % for crude oil). A high-yield bioprocess was developed, achieving 2.5 g/L on crude oil with excellent productivity and substrate conversion efficiency, and was scaled up to 3.3 g/L on sorbitol, with kinetic analysis supporting industrial fed-batch strategies. Furthermore, a putative biosynthetic pathway was proposed via genomic analysis, and the molecular basis for the strain's cryotolerance was elucidated through multi-omics. In phenanthrene-contaminated soil, a synergistic strategy combining the strain and its TTEs achieved the highest degradation efficiency (90.9 %)-significantly outperforming a chemical surfactant-by actively engineering the soil microbiome, promoting key indigenous degraders while suppressing competitors. These findings establish the KB1/TTEs system as a potent, ecologically sound platform for developing advanced, community-driven bioremediation technologies, especially for cold environments.