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The present study focuses on the optimization of biosurfactant (BS) production using two potential biosurfactant producer NA3 and MN3 and role of enzymes in the biodegradation of crude oil. The optimal conditions for NA3 and MN3 for biodegradation were pH of 8 and 7; temperature of 30 and 40 °C, respectively. NA3 and MN3 produced 3.81 and 4.68 g/L of BS, respectively. Gas chromatography mass spectrometry confirmed that BS was mainly composed of fatty acids. Furthermore, the role of the degradative enzymes, alkane hydroxylase, alcohol dehydrogenase and laccase on biodegradation of crude oil are explained. Maximum biodegradation efficiency (BE) was recorded for mixed consortia (86%) followed by strain NA3 (84%). Both bacterial strains were found to be vigorous biodegraders of crude oil than other biosurfactant-producing bacteria due to their enzyme production capabilities and our results suggests that the bacterial isolates can be used for effective degradation of crude oil within short time periods.

Removal of long-chain hydrocarbons and nalkanes from oil-contaminated environments are mere important to reduce the ecological damages, while bioaugmentation is a very promising technology that requires highly efficient microbes. In present study, the efficiency of pure isolates, i.e., Geobacillus thermoparaffinivorans IR2, Geobacillus stearothermophillus IR4 and Bacillus licheniformis MN6 and mixed consortium on degradation of long-chain n-alkanes C 32 and C 40 was investigated by batch cultivation test. Biodegradation efficiencies were found high for C 32 by mixed consortium (90%) than pure strains, while the pure strains were better in degradation of C 40 than mixed consortium (87%). In contrast, the maximum alkane hydroxylase activities (161 lmol mg -1 protein) were recorded in mixed consortium system that had supplied with C 40 as sole carbon source. Also, the alcohol dehydrogenase (71 lmol mg -1 protein) and lipase activity (57 lmol mg -1 protein) were found high. Along with the enzyme activities, the hydrophobicity natures of the bacterial strains were found to determine the degradation efficiency of the hydrocarbons. Thus, the study suggested that the hydrophobicity of the bacteria is a critical parameter to understand the biodegradation of n-alkanes.

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The role of biosurfactants producing hydrocarbon-degrading bacteria (HDB) on biodegradation and bio-corrosion was evaluated. Biodegradation efficiency (BE) of Streptomyces parvus B7 was found to be 82% when compared to other bacteria. Increased production of biosurfactants directly influences the rate of crude oil BE. Corrosion of carbon steel was found to be more severe in mixed bacterial consortia (1.493 ± 0.015 mm/y). X-ray diffraction confirmed the presence of high intensity of ferric oxide (Fe 2 O 3), iron oxide (Fe 3 O 4), manganese oxide (Mn 3 O 4), and manganese dioxide (MnO 2) in corrosion product of mixed bacterial system. Biofilm formation was assist to pit formation on the carbon steel surface and it was evidenced from the atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis. Corrosion current was increased in the presence of mixed consortia 1.6 ± 0.2 × 10-3 A/cm-2 , compared to abiotic control 1.2 ± 0.15 × 10-4 A/cm-2 , this values were well supported with charge transfer values and these observations confirmed that mixed bacterial consortia play key role in the corrosion of carbon steel. This is the first report to show degradation of crude oil by Streptomyces parvus B7 and its effects on the corrosion of carbon steel in oil reservoir.