Research On Screening, Identification Of Bacteria Producing Surfactant And Degradation Property On Petroleum Hydrocarbons

As the rapid development of global economy, oil is widely used in manyareas, and has become one of the important energy, however, the wide use ofpetroleum hydrocarbons has caused serious harm to natural environment andhuman, so the governance of oil pollution is imperative. Oil pollutionremediation methods，it includes physical remediation, chemical remediation andbioremediation, of which microbial remediation is paid widely attention for itslow toxicity and no secondary pollution to the environment. Microorganism, themain force in bioremediation, is an important member of ecosystem, and it playsan important role in pollutant removal. The hydrophobic of petroleumhydrocarbon may limit the degradation of organisms in the remediation processof oil pollution. Some microbial cells metabolites, which are calledbiosurfactants, are secreted by microorganism under certain conditions and areamphiphilic compounds with combined structure of hydrophilic group andhydrophobic group in a molecule. These biosurfactants can promote oil emulsion,improve the dispersion of the oil, increase the contact opportunity between strainand oil bead and promote absorption and degradation of petroleumhydrocarbons.Seven degrading oil strains producing surfactant were isolated fromlong-term oil-contaminated soil in this paper and they were numbered as bacteria1, bacteria2, bacteria3, bacteria4, bacteria5, bacteria6, bacteria7, of whichbacteria1and bacteria2were identified as gram-negative bacteria Serratiamarcescens, bacteria3as gram-negative bacteria Raoultella planticola, bacteria4,6, and7as gram-negative bacteria Klebsiella pneumonia, Klebsiella variicola,Klebsiella variicola, bacteria5as gram-positive bacteria Bacillus cereus bymorphological observation, Biolog identification and16S rDNA gene sequence analysis. Bacteria3Raoultella planticola,4Klebsiella pneumonia and5Bacilluscereus enabled the surface tension of the fermentation liquid reduce from36.1mN/m to20.2mN/m,20.74mN/m and21.78mN/m, indicating the surfactantsproduced by the bacteriums have a strong emulsification crude capacity andshow great potential.The relationship between7screening bacteria growth and the surfactantmaterial secretion was studied and found all the whole trend was that OD valueincreased while surface tension decreased with the increase of time. Extractionproducts of7strains were examined by thin-layer chromatography, ion-typeanalysis and IR spectroscopy. Anionic Glycolipid was found as the maincomponents. Oil degradation capabilities of different strains were measuredconsidering four single factor, pH, initial oil mass concentration, inoculationvolume and salinity. Bacteria Raoultella planticola and bacteria Bacillus cereushad better degradation performance. Response surface methodology was used tostudy on Bacillus cereus degradation conditions. Its optimum degradationconditions were pH of5.02, oil mass concentration of3g/L, inoculation amount1199.98μL, salt mass concentration of0.5g/L. In this condition, the oildegradation rate was66.94%.In addition, degradation mechanism of petroleum hydrocarbons of bacteria3Raoultella planticola was preliminary discussed by measuring the relationshipbetween surface tension and the degradation rate in the process of petroleummaterial degradation and selecting hexadecane in the alkane, cyclohexane in thenaphthene, naphthalene in the Aromatic hydrocarbon as represented material toobserve its degradation effect. The results indicated that the metabolic stability ofthe strain was during72h, when a large number of surfactant materials wasgenerated to promote the degradation of petroleum material; Bacteria Raoultellaplanticola has some degradation ability on the alkane and the Aromatichydrocarbon, while has poor degradation on the naphthene.