Study On The Isolation,Identification And Characteristics Of A Strain Of Medium-long Chain Alkane Degrading Bacteria

With the constant development of petroleum, the petroleum pollution is worsening, which not only destroy the environment, but also harm human health.Accordingly, people pay more attention to the treatment of petroleum. The Bioremediation of petroleum pollution is a economical, environmentally friendly,and efficient method. But now, it is still lack of in-depth study on the efficiency,stability and strong adaptability of petroleum degrading strains that it is crucial for controlling petroleum pollution.In this study, we choose samples from petroleum that was long-term polluted by petroleum, and the crude petroleum is the sole carbon source, through a series of screening and purification, We could get a hydrocarbon degradation strain and named it TWJ22. Through the preliminary identification using morphological study, physiological and biochemical research, and 16 s rDNA phylogenetic analysis, the strain belonged to gram-negative bacterium, which is Oxidase negative, not spore and capsul. And shape of the single cell was short, about0.5~0.8μm×0.9~2.0μm. It has a higher similarity on physiological and biochemical property with Serratia liquefaciens and Serratia proteamaculans. But with the further analyse using 16 s rDNA phylogenetic analysis, the final identification of the strains was Serratia proteamaculans.In this article, we researched the optimum growth condition of the strain in LB liquid nutrient medium, and found that the optimum was temperature 30℃,pH 7.0, and bed rotation speed 180 rpm. Experiment results showed, the inorganic salt nutrient medium of the sole carbon source obtained 1% glycerin is the optimum seed nutrient medium. In optimum seed nutrient medium, strain TWJ22 entered to logarithmic growth phase after the delay period of 2h, and reached stable growth period about 16 h. Study on the degradation of the strain found, that the strain could decompose C12, C14, C16, C18, C20, C22, C24, C28, C32, and the degradation effect of C22 was the best. When Strain TWJ22 was transferred to the inorganic salt nutrient medium that used C22(2% W / V) as the sole carbon source,the optimum condition to decompose C22 was temperature 30℃, pH 7.0, 0—1%of NaCl, and 3% of inoculation amount. The degradation rate could be up to 70%at the optimum condition.The concentration of metal ions in the petroleum affects the growth of petroleum degrading strains, therefore, we also researched the effects of metal ions on the growth of the strain TWJ22. The research found, the Ag+, Ni2+ with avery low concentrations under 0.01 mmol / L has a strong inhibition effect on the growth of strain, and it also showed that Ag+, Ni2+ had a strong toxicity to strain TWJ22; when the concentration of Cr3+, Fe3+, Pb2+, Ti4+ were less than0.05mmol/L, the inhibition on the growth of the strain was not obvious; when the concentration more than 0.06mmol/L, the inhibition was very strong. When the concentration of Co2+, Cu2+ was below 0.01mmol/L, it had a certain promotion function to the growth of the strain, when the concentration more than0.03mmol/L, the inhibition was very strong. When the concentration of Fe2+ 、Mn2+、Ba2+、K+ less than 0.06mmol/L, it had a certain promotion function to the growth of the strain, and the inhibitory effect was gradually increased as the concentration gradually increased. When the concentration of Ca2+、Mg2+ more than 0.06mmol/L, it had a promotion function to the growth of strain TWJ22. The results for the treat of petroleum wastewater had certain guiding significance.