Study On Screening And Identification Of Engine Oil Degrading Bacteria And Their Soil Remediation Effect

Engine oil is one of many petroleum products,and it is widely used as a mechanical lubricant,metal rust inhibitor and emulsifier.Because of its wide range of uses and huge annual consumption,waste engine oil is also generated.There are management irregularities in the transportation,storage and treatment of waste engine oil,which inevitably leads to soil and water pollution by waste engine oil,which has a significant impact on the environment and poses a huge threat to human health.Bioremediation has the advantages of high efficiency,strong adaptability,low cost and no secondary pollution.It has received widespread attention and is regarded as the most promising petroleum hydrocarbon pollution treatment technology.In this paper,five strains that can degrade motor oil were selected from the petroleum-hydrocarbon contaminated soil.After re-screening,the strain ML-1 with the best degradation effect was finally selected,and then the strain ML-1 was identified as Rigidoporus vinctus.Through single factor test and response surface method to optimize the factors affecting the degradation of ML-1 engine oil,the best degradation conditions are finally obtained as follows:temperature is 26?,p H is 7.4,initial concentration of engine oil is 4600mg/L,and the dosage of bacteria liquid is 5%,The degradation rate of ML-1 to engine oil is the highest when the incubation time is 4d.The theoretical maximum value of engine oil degradation rate is 99.13%,and the actual verification result is 94.74%.Under the optimal conditions,the process of ML-1 degradation of engine oil conforms to the first-order reaction kinetic equation.ML-1 has a significant effect on the degradation of alkanes with carbon chain lengths of C₁₇-C₃₄.It can completely degrade alkanes with carbon chain lengths of C₁₀-C₁₇.It also has a certain degradation of long-chain alkanes and some aromatic hydrocarbons with carbon chain lengths greater than C₃₄.effect.The microbial remediation test on soil with an initial oil concentration of 10000mg/kg showed that the addition of 10m L ML-1 to 50g oil contaminated soil has the best effect.On this basis,the addition of different auxiliary carbon sources is compared to the soil contaminated by engine oil.It is found that the oil degradation rate of the treatment with auxiliary carbon source is significantly improved compared with the treatment with only the bacteria liquid.Among them,the effect of adding sucrose is the best,and the oil degradation rate of 30d treatment reaches 51.56%;The highest oil degradation rate is 74.22%when the additive amount is 25%.Finally,the effect of adding sucrose treatment on the number of microorganisms in the soil was studied,and it was found that the number of microorganisms in the treatment group added with sucrose increased significantly,which has a positive impact on the disposal of oil contaminated soil.After bio-enhanced remediation of oil-contaminated soil,soil microbial diversity is significantly reduced.The dominant bacterial phyla of unrepaired oil-contaminated soil are actinobacteria(27.86%),proteobacteria(25.24%),acidobacteria(15.74%),and Chloroflexi(Chloroflexi).,9.40%),Firmicutes(Firmicutes,2.22%);The dominant fungal phyla is Ascomycota(ascomycota,68.29%).The dominant bacterial genus is pseudonocardia(9.5%),lysobacter(8.95%),nocaradioides(8.58%),and the dominant fungal genus is Talaromyces(Talaromyces,52.03%).After bio-enhancement treatment,the oil contaminates the soil.Firmicutes(75.62%)in the bacterial community become the most dominant phyla,Actinobacteria(10.57%)and Proteobacteria(12.03%)As a secondary phylum;Ascomycota(61.14%)and Basidiomycota(37.86%)in the fungal community became the dominant phyla.At the genus level,Bacillus(41.71%)in the bacterial community became the most dominant genus,Paenibacillus(15.21%)and Pseudomonas(7.34%)became the second dominant genus.Aspergillus,56.42%)and Rhodotorula(37.87%)in the fungal community became the dominant genus.