An Enriched Microbial Consortium XYS for Anaerobic Degradation of Petroleum Hydrocarbons: Characterization, Community Structure and Its Emulsification to Crude Oil

Microbial enhanced oil recovery (MEOR) and biogasification of residual oil have received increasing attention as biotechnologies for exploitation of oil and gas resources. Oil reservoirs have with the anoxic and hydrocarbons-rich characteristics. Microbial resources anaerobically degrading petroleum hydrocarbons have significant research value and application prospects for both MEOR and residual oil gasification. In this study, the microbial consortium XYS for anaerobic degradation of crude oil was obtained from oil reservoir in Xinjiang Oilfield (China) produced fluids through anaerobic enrichment. The microbial consortium XYS anaerobically degrades 30.08 ± 2.31% of crude oil. The surface tension of XYS culture was lower than 40 mN/m. The crude oil was emulsified and dispersed in anaerobic tubes. Metagenomic sequencing analysis showed that the enriched microbial consortium XYS included mainly bacteria. The dominant species detected were Nocardioides iriomotensis (4.9%), Stenotrophomonas acidaminiphila (4.2%), Alphaproteobacteria bacterium (3.8%), Nocardioides sp. (2.7%), Stenotrophomonas sp. (1.8%), Saccharomonospora marina (1.7%), Pseudomonas sp. (1.4%) and Gemmatimonadetes bacterium (1.4%). Genes masD and bamA involved in anaerobic biodegradation of alkanes and aromatic hydrocarbons were detected with 104 and 106 copies/mL in anaerobic culture of the enriched microbial consortium XYS, respectively. Crude oil was emulsified to micrometer scale by the microbial consortium XYS, and 80% of oil droplets were within 15 μm in diameter. The enriched microbial consortium XYS can anaerobically degrade crude oil and emulsify crude oil, exhibiting great potential for MEOR and initiation of residual oil gasification.