Simultaneous o-cresol degradation and biosurfactant production by indigenous bacterial monoculture: kinetics and genotoxic risk assessment.

Use of a novel bacterial isolate in environmental cleanup from toxic o-cresol along with valuable biosurfactant generation has been simultaneously explored, and a relevant correlation between the two has been obtained in this study. Paper pulp effluent from Durgapur, West Bengal, India, was screened to obtain indigenous o-cresol-tolerating bacteria, identified to be Pseudomonas fluorescens (NITDPY Accession no. KM111571). The bacteria showed significant stimulatory growth in o-cresol concentration of 5 mg L-1 and tolerance up to 200 mg L-1. Monod model fitted well at initial lower concentrations, whereas at higher concentration range (100-1,000 mg L-1), model Aiba was found to be the best fit. The rate of degradation of o-cresol showed observable correlation with bacterial growth fitting best with Aiba model. The role of enzymes in o-cresol-degrading pathway was studied, where enzyme catechol 1,2-dioxygenase was found to be involved in ortho-cleavage pathway. The role of interesting amphiphillic microbial metabolites and biosurfactants participating in o-cresol degradation was explored. Biosurfactant was being produced by the bacterial isolate and was revealed by specific assays (emulsification assay, oil spreading assay, foam height assay, etc.). Surface tension of water was lowered down to 44 mN m-1. Thin layer chromatography and Fourier transform infra-red spectroscopy studies confirmed the specific characteristics coinciding with the nature of biosurfactants. Induction of biosurfactant production via o-cresol was found to be 2.5 fold. Nonhazardous eco-friendly nature of the biotreatment has been unwrapped by cytotoxicity and genotoxicity assays, where reduction of toxicity was prominently detected in bacteria-treated o-cresol on Allium cepa as compared with untreated control. Comet assay for genotoxicity assessment, which has been rarely explored in the area of study, revealed similar results. [ABSTRACT FROM AUTHOR]