Abstract
The intrinsic biodegradability of hydrocarbons and the distribution of proficient degrading microorganisms in the environment are very crucial for the implementation of bioremediation practices. Among others, one of the most favorable methods that can enhance the effectiveness of bioremediation of hydrocarbon-contaminated environment is the application of biosurfactant producing microbes. In the present study, the biodegradation capacities of native bacterial consortia toward total petroleum hydrocarbons (TPH) with special emphasis to poly aromatic hydrocarbons were determined. The purpose of the study was to isolate TPH degrading bacterial strains from various petroleum contaminated soil of Assam, India and develop a robust bacterial consortium for bioremediation of crude oil of this native land. From a total of 23 bacterial isolates obtained from three different hydrocarbons contaminated samples five isolates, namely KS2, PG1, PG5, R1, and R2 were selected as efficient crude oil degraders with respect to their growth on crude oil enriched samples. Isolates KS2, PG1, and R2 are biosurfactant producers and PG5, R1 are non-producers. Fourteen different consortia were designed involving both biosurfactant producing and non-producing isolates. Consortium 10, which comprises two Bacillus strains namely, Bacillus pumilus KS2 and B. cereus R2 (identified by 16s rRNA sequencing) has shown the best result in the desired degradation of crude oil. The consortium showed degradation up to 84.15% of TPH after 5 weeks of incubation, as revealed from gravimetric analysis. FTIR (Fourier transform infrared) and GCMS (Gas chromatography-mass spectrometer) analyses were correlated with gravimetric data which reveals that the consortium has removed a wide range of petroleum hydrocarbons in comparison with abiotic control including different aliphatic and aromatic hydrocarbons.
Highlights
Assam (26.1400◦ N, 91.7700◦ E) is the oldest oil producing land from North to East India as oil drilling activity in Asia was first initiated in Digboi, Assam
The previously isolated KS2 was identified as B. pumilus KS2 (Genbank accession no. gb|KF021245|; Patowary et al, 2014)
Biosurfactant producer strain B. pumilus KS2 which was isolated from Lakwa oilfield soil, showed excellent crude oil degradation ability
Summary
Assam (26.1400◦ N, 91.7700◦ E) is the oldest oil producing land from North to East India as oil drilling activity in Asia was first initiated in Digboi, Assam. This profuseness of petroleum in Assam stands both as a blessing and a curse, because most of the crude oil drilling sites and group gathering stations (GGS; where crude oil is collected from different wells) are based at the periphery of human settlement including the agricultural belts. Some of the constituents of petroleum oil have the potential to bio-accumulate within susceptible aquatic organisms and can be transferred to the subsequent level of the food chain by trophic transfer (Orisakwe et al, 2004). This problem is more triggered because of unsafe disposal methods owing to the associated higher cost of safe and proper disposal (Rahman et al, 2003). Bacteria have long been considered as one of the predominant hydrocarbon degrading agents found in the environment, which are free living and ubiquitous (Dasgupta et al, 2013)
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