Evaluation of a Locally Isolated Phenol Degrading Bacterium under different Physiological Conditions

Phenol is an organic pollutant accumulated into the environment either naturally or by anthropogenic activity which adversely affects all living forms regarding mortality, health, quality and production. The elimination of phenol is obligatory to meet the goal of the untainted environment and sustainable agriculture. Bioremediation plays a vital role and preferred over physiochemical methods owing to its environment-friendly nature and low cost. The objectives of this study were to evaluate bacterial strains for phenol degradation at different physiological conditions and detection of phenol metabolic pathway. Eight bacterial strains were isolated from different environmental samples through enrichment in MSM containing 100 mg L-1 phenol, among them Lysinibacillus spp. NIGAB-4 showed good growth on phenol plates and was further assessed to check its phenol mineralization efficiency. This isolate was identified through 16S rRNA gene as a member of the genus Lysinibacillus. This strain tolerated up to 1200 mg L-1 phenol when supplied as a sole source of carbon and energy and has the potential to degrade 800 mg L-1 phenol in 96 h. Phenol (200 and 400 mg L-1) degradation at different temperature, pH, and NaCl was checked. It was found that this strain has the potential to degrade phenol in the range 20-45 degrees C, while optimum degradation was achieved at 30 degrees C. Lysinibacillus spp. NIGAB-4 has the potential to degrade these phenol concentrations in the pH range 6-9, while complete phenol degradation was observed at pH 7. This strain was able to degrade 200 mg L-1 completely at 0 and 2% NaCl concentrations. However, at 4% NaCl a notable amount of phenol degradation was also observed. Phenol degradation pathway was detected by observing the amplification of catechol 1,2-dioxygenase (C12O) and catechol 2,3-dioxygenase (C23O) gene and PCR amplification of C23O gene actively provided the evidence of phenol degradation via meta-pathway. These findings suggest that this strain could be efficient in phenol degradation at adverse environmental conditions and helpful in remediation of phenol where the salt concentration is high. (C) 2020 Friends Science Publishers