Efficiency and kinetics of Assam crude oil degradation by Pseudomonas aeruginosa and Bacillus sp.

We report kinetics of Assam crude oil degradation by Pseudomonas aeruginosa AKS1 and Bacillus sp. AKS2, both isolated from Assam refinery sediments. The isolates exhibited appreciable degrees of hydrophobicity, emulsification index and biosurfactant production. Crude oil degradation efficiency of isolates was assessed in (1) liquid medium amended with 1% v/v crude oil and (2) microcosm sediments (125 mg crude oil/ 10 g sand). In liquid culture, biodegradation rate (k) and half-life (t1/2) values were found to be 0.038 day-1 and 18.09 days for P. aeruginosa AKS1, and 0.020 day-1 and 33.97 days in case of Bacillus sp. AKS2, respectively. In microcosm sediments, the estimated k and t 1/2 values were 0.014 day-1 and 50 days for P. aeruginosa AKS1, and 0.011 day-1 and 61.34 days in case of Bacillus sp. AKS2. The level of nutrient treatment in microcosm sand sediment was 125 µg N and 62.5 µg P/g sediment in case of P. aeruginosa AKS1 and 375 µg N and 37.5 µg P/g sediment in case of Bacillus sp. AKS2. In microcosms without inorganic nutrients, values of k and t1/2 were found to be 0.007 day-1 and 100 days for P. aeruginosa AKS1 and for Bacillus sp. AKS2, the respective values were 0.005 day-1 and 150.68 days. Our data provides important information for predictive hydrocarbon degradation in liquid medium and contaminated sediments.