Condition optimization, molecular mechanism and metabolic pathway of p-chloroaniline biodegradation enhanced by aniline as the co-substrate

Aromatic amines, the common organic metabolites of chemical raw materials and herbicides, has attracted wide attention due to its difficult degradation and carcinogenic risk. This study aims to use microbial co-metabolism technology to efficiently degrade p-chloroaniline (PCA), which is a highly toxic aromatic amine. From the perspective of enzyme substrate specificity, a system for efficient degradation of PCA using aniline as a co-substrate was constructed. The degradation conditions were optimized by response surface methodology, and the degradation efficiency of PCA was 81.12 % (50 mg/L). Further, the co-metabolism mechanism was clarified by multiple methods. Enzyme activity assay preliminarily showed that aniline induced catechol 2,3-dioxygenase activity. Then the intermediates of PCA and aniline degradation was identified and two possible PCA degradation pathways were proposed. Transcriptomic analyzed the molecular mechanism of aniline-enhanced PCA degradation: Nitrogen utilization efficiency was accelerated by up-regulation of nitrogen metabolism-related genes. Several oxidoreductases including catechol 2,3-dioxygenase were significantly up-regulated. TCA cycle and ATP synthesis were accelerated, facilitating cell metabolism and energy supply. The work contributes a worthy theory for the remediation of PCA-aniline co-contaminated sites.