Isolation, characterization and growth kinetics of phenol hyper-tolerant bacteria from sewage-fed aquaculture system

Pollution of aquatic resources is increasing day-by-day, and phenolic compounds are common pollutants negatively impacting aquatic biodiversity and production. This study aimed at isolation of phenol hyper-tolerant bacteria from polluted aquaculture resource so that they might be useful in aquaculture systems. Four phenol hyper-tolerant bacterial strains were isolated from sewage fed East Kolkata Wetlands, a Ramsar site. By 16S rDNA sequence, cell morphology and biochemical characteristics the strains PDB2, PDB13, PDB16, and PDB26 were identified as Acinetobacter sp., Acinetobacter junii, Pseudomonas citronellolis, and Bacillus cereus, respectively. Pseudomonas citronellolis strain PDB16, described in this study, is possibly the first report of phenol hyper-tolerant strain in this species. All the four strains degraded 600 mg L-1 phenol within 5 days and expressed catechol 1,2-dioxygenase but lacked catechol 2,3-dioxygenase enzyme suggesting that the bacteria used the ortho-cleavage pathway for phenol degradation. In growth kinetic study Edwards and Aiba model, rather than the most popular Haldane model, gave the best fit indicating behavioral divergence of these strains with those from petroleum contaminated environments. The phenol degrading bacteria isolated from a polluted sewage fed aquaculture system might be useful in degradation and remediation of polluted aquaculture resources as well as inland open waters.