Screening And Performmance Study Of Surfactant-producing Oil-degrading Bacteria

Grease wastewater is highly concentrated organic wastewater.The discharge of untreated grease wastewater into the environment directly will put the ecosystem at risk.Biological method is one of the important methods to treat grease wastewater,but the hydrophobicity of grease limits its bioavailability.Biosurfactants can increase the affinity of strains to grease and promote the absorption and utilization of grease by strains,thereby increasing the degradation rate.Therefore,this study is to screen out surfactant-producing oil-degrading bacteria,analyze the types and physical and chemical properties of the surfactants produced,and optimize the cultivation conditions of the strains to explore the effects of different types of surfactants on the biodegradation of oils by strains.The main results and conclusions obtained are as follows:(1)After enrichment and domestication,one strain of surfactant-producing oil degrading bacteria C11 was screened out.The surface tension is 37.1 m N·m^-1,the diameter of the oil discharge ring is 6.1 cm,and the oil degradation rate is 52.16%.After morphology,physiology and biochemistry,fatty acid determination and molecular identification,the strain C11 is determined to be Burkholderia sp.C11.(2)The surfactant produced by strain C11 was identified as glycolipid.The critical micelle concentration(CMC)of this surfactant is 200 mg·L^-1,and the yield is 1.6 g·L^-1;the emulsification performance is good,and the emulsification index of liquid paraffin after 84 h is still about 60%;This strain can tolerant high salinity and temperature.It has good emulsification performance and surface activity under the initial pH 5?10,temperature0?120? and salinity 0?16%.(3)Through single factor test and Box-Behnken response surface test,it was determined that under the conditions of temperature 33.28?,oil concentration of 9.31 g·L^-1 and initial pH of 7.92,the oil degradation rate of strain C11 could reach 71.70%,and the yield of surfactant is 2.7 g·L^-1.The degradation kinetics of strain C11 conforms to the Haldane model.(4)Low-concentration(0.5?1 CMC)biosurfactants(rhamnolipids and sophorolipids)and nonionic surfactants(Tween 80)can improve the degradation effect of strains on oils.Adding rhamnolipids(1 CMC),Sophorolipid(0.5 CMC)and Tween 80(1 CMC)can increase the oil degradation rate by 10.56%,8.17%and 7.84%respectively;adding linear alkyl benzene sulfonate(LAS)and hexadecyl Trimethylammonium bromide(CTAB)can reduce the effect of oil degradation,and CTAB has a greater inhibitory effect on strains to degrade oil than LAS.