Breeding Of Alkane-Degrading Strains And Metabolic Study Of A Predominant Strain

There is serious pollution problem during the oil exploration, mining, transportation, storage and processing. The major chemical components of oil are hydrocarbons, benzene, toluene, xylene and aromatic hydrocarbon, which are mostly carcinogenic, mutagenic, and teratogenic. In this study, the predominant microorganisms utilizing alkane were screened from polluted soil to study their potential in bioremidation and production of commercial products.Firstly,14 isolates were obtained from the enrichments with n-heptane as the sole carbon sources. Secondly, through the identification of morphology and 16S rDNA sequencing, the result showed that G2, G9 and G14 belonged to Rhodococcus sp.; G3 and G27 belonged to Ochrobactrum sp.; G4 and G7 belonged to Bacillus sp.; G5, G10, G15, and G25 belonged to Arthrobacter sp.; G16 belonged to Brevundimonas diminuta; G17 and G22 belonged to Stenotrophomonas sp.. Among them, Rhodococcus sp. G2 was one of the predominant strains in the alkane-degradation. The degradation of n-heptane, n-dodecane and xylene by Rhodococcus sp. G2 was also conducted. Furthermore, the effect of salt on growth and the mechanism of degradation when glucose and alkane co-existed as carbon source were discussed. Additioanlly, the metabolites produced in the utilizationof alkane werepreliminarily analyzed.The result indicated that Rhodococcus sp. G2 could degrade alkane with different carbon chain length including n-heptane, n-dodecane and xylene. When Rhodococcus sp. G2 was cultivated on n-heptane, the major product was an organic acid. The n-dodecane was a better carbon source compared with n-heptane and xylene, and the biomass could reach approximately 12 OD600 in 18 hours. Biosurfactant produced mainly on the cultivation with n-dodecane had 67.44% emulsification ability. And the metabolites produced were also studied by GC-MS, which were keptones and esters. lOg/L of salt benefitted the growth of Rhodococcus sp. G2. Through the fermentation process optimization, the ratio of n-dodecane and ammonium sulfate is 8:1.Although glucose was always preferred for most of the microorganisms, this strain could utilize them at the same time. This result suggested that there were several mechanisms of alkane oxidation taking effect simultaneously in the strain.