Ball-milled biochar can act as a preferable biocompatibility material to enhance phenanthrene degradation by stimulating bacterial metabolism

The aim of this study was to evaluate the impact of different concentrations of ball-milled biochar pyrolyzed at 300-700 °C on the lethality, growth, metabolism, and degradability of gram-negative petroleum-degrading bacteria. BM-biochar was not toxic to Acinetobacter venetianus, only slowing the growth rate and extending the logarithmic phase. The ability of A. venetianus to produce extracellular polymeric substances (EPS) and biosurfactants was positive with ROS level. The highest degradation efficiency of phenanthrene (PHE) was 2.84-fold that of the control. Mechanism analysis revealed that increased EPS stimulated the adsorption of PHE and biosurfactant enhanced PHE solubility. The improved PHE biodegradability of A. venetianus through phthalic acid pathway is mainly owing to the intensify of PHE bioavailability and accessibility. These findings provide new insights into effects of BM-biochar on cellular responses and indicate that BM-biochar can act as a biocompatible material to enhance the degradation of organic pollutants.