Cyclohexanecarboxylic acid degradation with simultaneous nitrate removal by Marinobacter sp. SJ18

Abstract

Naphthenic acid (NA), a new kind of toxic pollutants, is labeled as the potential threat to human health.However, the transformations of NAs in marine environments are still unclear. In this study, the characteristics and pathways of cyclohexylcarboxylic acid (CHCA) biodegradation were explored in the presence of nitrate. Results showed that CHCA was completely degraded with pseudo-rst-order kinetic reaction under aerobic and anaerobic conditions, accompanied by nitrate removal rates exceeding 70%, which was positively correlated with CHCA degradation(P<0.05). Degradation pathways of CHCA were proposed the cyclohexane was dehydrogenated to form cyclohexene, then ring-opened to generated fatty acid by dioxygenase under aerobic conditions, yet the cyclohexene was cleaved through β-oxidations under anaerobic condition. Whole genome analysis indicated that nitrate was removed via assimilation and dissimilation pathways and denitri cation pathways under aerobic and anaerobic conditions, respectively. This study provides a basis for the combined pollution of NA and nitrate in marine environments.Highlights 1.CHCA degradation in the presence of nitrate in marine environment was rstly studied 2.Strain SJ18 could rapidly degraded the combined pollutants of CHCA and nitrate 3.CHCA degradation pathways were proposed under aerobic and anaerobic conditions 4.Strain SJ18 contained functional genes for CHCA degradation and nitrate removal