Effect of Rhamnolip on Microbial Degradation of Petroleum Hydrocarbon

Objective:Microbial degradation of petroleum hydrocarbon was studied. Method: By determinating biomass and observating cell surface,the effect of rhamnolip on the strain was studied.By designing orthogonal tests,effective factors of degradation rate was determined.Through degradation rate of petroleum hydrocarbon determinated,synergistic effect of rhamnolip and deep oxidation in the microbial degradation of petroleum hydrocarbons was discussed.Result: The degradation rate of diesel oil by the strain reached 53%.The degradation rate of petroleum hydrocarbon was significantly enhanced by the amendment of rhamnolipid biosurfactant.The degradation rate of petroleum hydrocarbon was 12%~20% higher than that without rhamnolipid.It indicated that rhamnolipid increased microbial biodegradation and cell surface hydrophobicity.The orthogonal tests showed that culture time was the most important factor,followed by the culture time and rhamnolipid concentration.Orthogonal design showed that the best combination was A3B2C1,Which was culture time of seven days,culture temperature of 35℃ and rhamnolipid concentration of 60 mg/L.With three of the best combination of factors,the degradation rate of petroleum hydrocarbon was 82%.Biodegradation rate of petroleum hydrocarbon was increased from 82% to 97% by a hydrogen peroxide dosage of 200 mg/L.Conclusion: Rhamnolipid promoted the growth of the strains.Synergistic effect of rhamnolip and deep oxidation would be helpful to increase the biodegradation rate of petroleum hydrocarbon contaminants.