Transcriptomic removal and mass balance of polycyclic aromatic hydrocarbons in waste spent coolant oil: Gene discovery, enzyme identification and metabolic pathway

The study identified the catabolic genes, enzymes and metabolic pathways involved in spent coolant oil waste (SCW) degradation by mutant S. vacuolatus (MSv) and wild S. vacuolatus cultivated without SCW and with SCW using RNA transcriptomic analysis. Moreover, total petroleum hydrocarbon (TPH) degradation and the metabolites released were determined using GC–MS. Major hydrocarbon (HC) degraded were naphthalene, decane, and benzene,1,3-dimethyl with highly enriched gene ontology obtained that provided strong evidence of enhanced cellular metabolic activities that enabled the oxidation of various hydrocarbons (HCs) present in SCW. Significant residual mass balances (>70 % degradation) were obtained for the polycyclic aromatics (PAHs) and their derivatives. Also, distinct transcripts involved in SCW degradation include 6-CoA-linked acetaldehyde dehydrogenase, 3-coatomer subunit alpha-3 and 1-arginine deiminase. Additionally, a key transcript CoA-linked acetaldehyde dehydrogenase encoding alcohol dehydrogenase for the degradation of naphthalene HCs via a naphthalene degradation pathway was identified. These findings provide a major insight into HC degradation genes and enzymes that can further be exploited for the bioremediation of HC polluted water environments.