Prevention and mitigation of paraffin deposition by biosurfactant-producing and paraffin-degrading Bacillus amyloliquefaciens strain 6-2c

Abstract

Paraffin deposition during oil production and transportation results in pipeline blockage and increases the cost of petroleum production. Conventional mechanical, thermal, and chemical methods to clear paraffin deposition are problematic; microbiological approaches are an effective alternative. Bacillus spp. that possesses exceptional survival abilities and can degrade paraffins in the environment of oil wells is often used as potential microbe for paraffin removal. In this study, we investigated a biosurfactant-producing bacterial strain, Bacillus amyloliquefaciens 6-2c that was recently isolated from oil-contaminated soil in the Ansai oilfield, northwest China. The performance of bacterial treatment in prevention and mitigation of paraffin deposition was assessed. Strain 6-2c efficiently improved the solubility of paraffin in n-hexane and the paraffin solubility rate (SR%) reached 79.15%, increased by 5.39% compared to the control. The morphology of paraffin crystals markedly changed after bacterial degradation, having a rough surface and a loose structure. Strain 6-2c produced a biosurfactant that reduced the surface and interfacial tension to 25.51 ± 0.035 mN m−1 and 1.55 ± 0.014 mN m−1, respectively. The biosurfactant formed stable emulsions with a wide range of hydrocarbons, and showed high stability over a wide range of temperature (20–120 °C), pH (2–13), and salinity (0–15%, w/v). The paraffin removal efficiency of strain 6-2c ranged from 50.82% to 95.17%. Interestingly, strain 6-2c cells attached to the surface of steel pipes inhibited paraffin coalescence. These findings indicate the potential of this biosurfactant-producing bacterial strain in paraffin degradation and enhanced oil recovery.