The study of growth kinetics of Bacillus subtilis BMT4i (MTCC 9447) using diesel as the sole carbon and energy source
2012
The present study aimed at studying the growth kinetics of an efficient high molecular weight polycyclic aromatic hydrocarbon (HMW-PAH) degrader Bacillus subtilis BMT4i (MTCC 9447) using diesel oil as the sole carbon and energy source. The study was carried out in order to understand and reveal the morphological and growth variations in benzo-a-pyrene (BaP) degrading BMT4i imposed by the stress environment of diesel oil. The morphological variations were determined by growing Bacillus subtilis BMT4i in basal salt medium (BSM) with diesel oil (2%: BSMD) as sole carbon and energy source at various time durations using Gram staining and spore staining (Schaeffer-Fulton method) followed by viability and growth assessment using colony forming units (CFU)/ml method. The result demonstrated that the diesel oil has visible effect on the shape and size of BMT4i cells. Majority of the BMT4i cells undergone endospore formation within 24 h of diesel oil exposure and some of them were released as exospores (free spores) after 24 h. The growth kinetics demonstrated exponential increase in the cell number of BMT4i in BSMD with increase in incubation duration up to 3 days reaching maxima of 4.16 x 10₁₉ showing approx. 2x10¹¹-fold increase in cell numberand there after it declined. About 2x10¹¹ fold enhancements in the CFU number is directly correlated with the ability of Bacillus subtilis BMT4i to utilize diesel oil as the sole source of carbon and energy which leads to high increase in cell number within just 3 days. Therefore, it could be concluded that Bacillus subtilis BMT4i (MTCC 9447) is very efficient in using diesel oil as the sole source of carbon and energy and it could be employed for bioremediation of diesel oil and PAH contaminated sites.
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