Studies On Screening And Degradation Characteristics Of Bacterial Strains For Biodegradation Of Lubricating Oil

Lubricants applied in industrial production widely.Waste lubricants contains alkanes,naphthenes,aromatic hydrocarbons,heavy metals and other components which is not easy to degrade.Without treatment,it will cause environmental pollution.Although the physical and chemical methods achieved certain effects of degrading,the secondary pollution was serious.However,the biological method could regard toxic pollutants as a substrate for degradation.The development of efficient degradation of bacteria is the core of the Bioremediation technology.The purpose of this experiment is to screen out the strains which degrade the waste lubricating oil and to study its biodegradability.The following conclusions were obtained:(1)Two strains of degrading lubricating oil were selected from the soil which was contaminated by crude oil.Among them,strain X1 and X2 had high effect of degrading.Its 16 Sr DNA sequencing were carried out to obtain the gene sequences.The accession numbers of KX620435 and KX620436 were obtained in GenBank,respectively.Blast and evolutionary tree analysis inferred that strains X1 and X2 were Escherichia vulneris and Pseudomonas lutea strain(2)Compared strain X1 with X2,the degradability of strain X1 is better than X2.The optimal degradation rate of strain X1 was 40.83%,and we choose strain X1 for research.The optimal medium of strain X1 was obtained by orthogonal design.The results showed that the degree of influence of the components of medium is that peptone is more effective than beef extract and beef extract is more effective than sodium chloride.The optimized components were pH7.0,beef extract 5.0 g,water 1 L,NaCl 4.5 g,and peptone 10.0 g.The dry weight of strain X1 increased from 1.485 g/L to 1.905 g/L,which increased 1.28 times.The optimal conditions were as follows: temperature of 35?,pH 7.5,rotation speed of 160 r/min,and the dry weight of strain X1 was 2.342 g/L after 24 h culturing time.(3)Study on Degradation of Lubricating Oil of Strain X1 was concluded as follows:(1)The optimum inoculation amount of the strain was 4%,the optimal pH was 7.5 and the lower the lubricating oil concentration,the better degradability of strain X1,and the lower sodium chloride concentration,the better the degradation of strain X1.(2)Degradation effect of strain X1 nitrogen sources was as follows: NaNO3 > NH4 Cl > NH4NO3 >(NH4)2SO4 > CO(NH2)2 and degradation effect of strain X1 by C was as follows: Maltose > Glucose > Starch > Citric acid > Sucrose.(3)The affecting factors of the degradation of strain X1 were tested by orthogonal test,including inoculation amount,temperature,maltose concentration and initial lubricating oil concentration.The optimum formulation of strain X1 degrading lubricating oil was as follows: temperature of 35?,inoculation 6%,Maltose 0%,crude oil concentration 1000 mg/L,and the degradation efficiency was 63.44%.(4)Strains of X1 and X2 were mixed to study the degradation of lubricating oil :When the strain X1: X2 = 1: 3,the total amount of inoculum was 8%,the degradation efficiency was 80.92%,indicating that strain X1 and X2 were synergetic to promote the degradation of lubricating oil.(5)The kinetics of growth and degradation of strain X1 showed that the growth kinetics is accorded with logistic model,and first-order ratel model for degradation kinetics.