Production and Characterization of Bioemulsifiers by Thermotolerant Bacteria for Enhanced Oil Recovery Potential

Abstract

Three bacterial strains were isolated from oil contaminated soil samples in Yumen oilfield of China and selected due to their capacity of growing under extreme conditions and production of bioemulsifier. The isolates were identified as Brevibacillus sp. XS1, Geobacillus sp. XS2 and Geobacillus sp. XS3 according to 16S rDNA sequence and physiological methods, respectively. The isolates XS1, XS2 and XS3 were thermotolerant with the optimum growth temperature of 50 °C, 60 °C and 55 °C, respectively. All the three isolates were able to produce bioemulsifiers which had little effect on surface tension reduction. The bioemusifiers produced by the three isolates were purified with a production yield of 2.98g/L, 4.24g/L and 3.82 g/L, respectively. The bioemulsifiers were identified as anionic heteropolysaccharides by FTIR analysis and their average molecular weight and polydispersity were investigated by GPC method. The bioemulsifiers produced by Geobacillus sp. XS2 and XS3 exhibited a perfect stability over various temperature (up to 100 °C), pH (range from 2.0 to 12.0) and salinity (up to 30.0% of NaCl concentration) and were considered to be ideal candidates in MEOR process.