Chiang Mai Journal of Science

      Microbial Enhanced Oil Recovery (MEOR) is an effective alternative method for oil recovery in reservoirs using microorganisms or their secondary metabolites. This research aimed to evaluate the indigenous bacteria from Mae Soon reservoir by culture-dependent and culture-independent methods and to investigate the potential of biosurfactant-producing bacteria using a drop-collapsed assay. Indigenous bacteria were isolated from the oil sands of the reserved core of Mae Soon reservoir using five different media (nutrient, Luria-Bertani, mineral salt, tryptic soy, and peptone yeast extract). Fifty-four facultative anaerobic bacterial isolates were obtained. Seven isolates showed their potential as biosurfactant producers in the drop-collapse assay. Based on 16S rRNA gene analysis, six of the biosurfactant-producing bacterial isolates belonged to the species Bacillus licheniformis and one belonged to the species B. subtilis. The biosurfactant producers and microbial community in the oil sands were determined using Denaturing Gradient Gel Electrophoresis (DGGE). Interestingly, DGGE bands corresponding to bacteria belonging to the genus Geobacillus sp. were detected. Overall, the results obtained from this work showed that indigenous bacteria in Mae Soon reservoir oil well were prospective for use in MEOR.