Isolation and characterization of a hydrocarbon-degrading strain of Compostibacillus

Abstract:

[Background] By implementing multiple cycles of microbial oil recovery, the reservoir produced liquid bacteria concentration reached more than 106 CFU/mL, forming a stable microbial fermentation field in the reservoir. To further improve the effect of microbial oil recovery, the crude oil-emulsifying and hydrocarbon-degrading bacteria from the reservoir was selected to cultivate for microbial oil recovery application in the reservoir. [Objective] The strains with good performance of crude oil-emulsifying and hydrocarbon-degrading capacity are screened out to carry out multiple taxonomic identification and performance evaluation. [Methods] Crude oil was chosen as substrate for strains selection. Through morphological observation, biochemical and physiological characteristics and 16S rRNA gene sequence, the taxonomic position of the strain BLG74 was identified. The crude oil-emulsifying and hydrocarbon-degrading capacity of the strain BLG74 were investigated by emulsifying ability and degrading rate. [Results] strain BLG74 was selected from the production water sample of Huabei oil field. 16S rRNA gene sequence analysis showed that the strain belonged to the genus Compostibacillus and most closely related to Compostibacillus humi with identity of 99.6%. Its growth environment has a pH of 6.5 to 9.5 (optimum at pH 7.0), a temperature of 30 °C to 60 °C (optimum at 45 °C) and a salinity of 0% to 7%. Strain BLG74 was cultured in crude oil degradation medium. The surface tension of the fermentation broth was 56.3 mN/m, and the emulsifying capacity was about 95%. It was cultured for 20 days under the initial crude oil mass concentration of 0.5% and temperature of 45 °C, resulting in the degradation rate of up to 40.8%. [Conclusion] Strain BLG74 is a new member of bacteria capable of emulsifying and degrading crude oil, presenting a remarkable potential in microbial enhanced oil recovery with its crude oil-emulsifying and hydrocarbon-degrading capacity under hot salt conditions.