In this work, the biodegradation of the crude oil by the potential biosurfactant producing Bacillus subtilis A1 was investigated. The isolate had the ability to synthesize degradative enzymes such as alkane hydroxylase and alcohol dehydrogenase at the time of biodegradation of hydrocarbon. The biosurfactant producing conditions were optimized as pH 7.0, temperature 40°C, 2% sucrose and 3% of yeast extract as best carbon and nitrogen sources for maximum production of biosurfactant (4.85 g l-1). Specifically, the low molecular weight compounds, i.e., C10–C14 were completely degraded, while C15–C19 were degraded up to 97% from the total hydrocarbon pools. Overall crude oil degradation efficiency of the strain A1 was about 87% within a short period of time (7 days). The accumulated biosurfactant from the biodegradation medium was characterized to be lipopeptide in nature. The strain A1 was found to be more robust than other reported biosurfactant producing bacteria in degradation efficiency of crude oil due to their enzyme production capability and therefore can be used to remove the hydrocarbon pollutants from contaminated environment.

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In latest years, various techniques and chemicals have been used for the control of microbial influenced corrosion (MIC) of metals. The application of botanicalbased biocides is one of the effective and practical techniques in the fight against MIC. In the present study, the role of aqueous extract of ginger (Zingiber officinale) (GIE) as green biocide to control MIC of mild steel 1010 (MS) in a cooling water system was investigated. Biocorrosion behavior of Bacillus thuringiensis EN2 on MS and its control by GIE was analyzed by electrochemical measurements. Polarization, electrochemical studies (ES), weight loss measurements (WL), and surface analysis (XRD, X-ray diffraction spectroscopy, and FTIR, Fourier transform infra-red spectroscopy) were performed under various incubation periods up to 4 weeks. We observed that EN2 forms a thick biofilm on the MS metal surface at the end of the incubation period and the WL significantly increased to 993 mg at fourth week when compared to the initial immersion period (194 ± 2 mg). In contrast, with addition of GIE, WL was reduced about 41 ± 2 mg over biotic system (993 ± 2 mg). GC-MS analysis confirmed the adsorption of active component of GIE (b-turmerone) on the metal surface as a protective layer to prevent the biofilm formation and thus leads to reduction of corrosion. The optimum 20 ppm of GIE was found to be effective corrosion inhibition efficiency which was about 80%. From the results of WL, ES, XRD, FTIR, and GC-MS, GIE was identified as biocide and thus inhibits the bacterial growth on MS metal surface and it leads to control MIC. XRD showed that the GIE with EN2 resulted in less formation of corrosion products over biotic and abiotic systems. Overall, this research first shed light on the antibacterial activity of GIE inhibiting biofilm formation, thus reducing the corrosion of MS in cooling water systems.