A bacterial strain was isolated and cultured from the oil excavation areas in tropical zone in northern China. The biochemical characteristics and partial sequenced 16S rRNA gene of isolate, WJ-1, was identical to those of cultured representatives of the species Pseudomonas aeruginosa. This bacterium was able to produce a type of biosurfactant. Compositional analysis revealed that the extracted biosurfactant was composed of high percentage lipid (∼74%, w/w) and carbohydrate (∼20%, w/w) in addition to a minor fraction of protein (∼6%, w/w). The best production of 50.2 g/l was obtained when the cells were grown on minimal salt medium containing 6.0% (w/v) glucose and 0.75% (w/v) sodium nitrate supplemented with 0.1% (v/v) element solution at 37 °C and 180 rpm after 96 h. The optimum biosurfactant production pH value was found to be 6.0-8.0. The biosurfactant of WJ-1, with the critical micelle concentration of 0.014 g/L, could reduce surface tension to 24.5 mN/m and emulsified kerosene up to EI(24) ≈95. The results obtained from time course study indicated that the surface tension reduction and emulsification potential was increased in the same way to cell growth. However, maximum biosurfactant production occurred and established in the stationary growth phase (after 90 h). Thin layer chromatography, Fourier transform infrared spectrum, and mass spectrum analysis indicate the extracted biosurfactant was affiliated with rhamnolipid. The core holder flooding experiments demonstrated that the oil recovery efficiency of strain and its biosurfactant was 23.02% residual oil.
This study stimulated functional microbial adaptation to the extreme environment of the Luliang oilfield reservoir and assessed the impact of indigenous microbial enhanced oil recovery treatment on the microbial community and oil recovery. By high-resolution pyro-sequencing, Acinetobacter, Pseudomonas, Sphingomonas, Thauera, Arcobacter and Hyphomonas were regarded as suitable candidates and a customised nutrient mixture was selected to activate the target microbes. The interfacial tension of crude oil and water decreased from 29.76 mN m À1 to 0.65 mN m À1 and the emulsion stability index increased from 5% to 92% after customised nutrient culture. The oil biodegradation experiments after the cultivation exhibited positive effects in degrading aromatics, resins and asphaltenes fractions and improving the mobility. Six target genera were activated markedly after 96 h of incubation. The oil recovery was enhanced from 51.2% to 60.7% using fermentation broth injection. Thus, injecting a customised nutrient mixture with injection brine into the stratum to stimulate functional microbes has the potential to enhance oil recovery in the Luliang oilfield.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.