Enhanced pyrene degradation by a biosurfactant producing Acinetobacter baumannii BJ5: Growth kinetics, toxicity and substrate inhibition studies

Microbial community isolated from petroleum oil contaminated soil was enriched in minimal medium with pyrene as the only carbon source. One of the isolates exhibiting growth with increased concentrations of pyrene was identified as Acinetobacter baumannii BJ5 by 16S rRNA analysis. Growth, toxicity, and substrate inhibition models were studied with the enriched strain BJ5 over the range of 10-600 mg/L of pyrene. The specific growth rate increased linearly from 0.0163-0.0346 h(-1) up to a concentration of 300 mg/L, with a decrease at higher levels, as confirmed by cell viability test. However, the absolute amount of pyrene metabolised increased linearly with an increase in initial concentration to the maximum of 336 mg/L in 14 days (C-initial = 600 mg/L). Kinetic parameters derived by nonlinear regression of the substrate inhibition model (Haldane Andrew model) were mu(max) = 0.033, K-s=16.58 mg/L, and K-i=503.9 mg/L, respectively, indicating good tolerance and adaptation of the BJ5 strain to high concentrations of pyrene. With the production of a glycolipid biosurfactant (as characterised by FTIR, NMR and GC-MS) during growth with pyrene, the strain BJ5 exhibits a promising application for reclamation of Polyaromatic Hydrocarbons contaminated sites, adversely affecting the health of the exposed. (c) 2020 Published by Elsevier B.V.