Isolation Of Petroleum Degradation Bacteria And Optimization Of Conditions For Degradation

Oil pollution is showing a serious trend with the development of oil industry, whichhas caused severe threat to human health and environmental safety. Bioremediationtechnology has become a hotspot in recent years with the advantages such as safety,extensive sources, well effect and so on. Though the petroleum-degrading bacteria arewidely existed in nature, its growth and degradation abilities are affected by many factorssuch as temperature, pH, pollutant concentration and so on.Firstly, five strains with high degradation ability are screened from Suzhou factorysoil and dropping crude soil which named S1, S3, S7, N1and N2, respectively. They arepreliminary identified to be Pseudomonas, Bacillus Cohn and Flavobacterium throughmorphologic observation and a series of physiological and biochemical experiments.Secondly, infrared spectrophotometry (IR) and high performance liquidchromatography (HPLC) were used to detect the content and components of oil. Thedegradation of single strain rates are59.75%,45.89%,62.35,51.8%and35.7%and themixed strains degradation rates are71.6%(S1+S7),59.2%(S1+S3),61.95%(S3+S7),65%(S1+S3+S7) and52.3%(N1+N2). The degradation efficiency of mixed bacteria ishigher than the single one. What’s more, S7and N1are of good comprehensive propertiesand can also have good degradation effect on polycyclic aromatic hydrocarbon and theother strains prefer to degrade alkanes.Finally, the degradation conditions are optimized by single factor experiment to verifythe relations with the optimal growth conditions and contrast the degradation effect underdifferent environment. The influence of solid carrier on degradation efficiency and thedegradation effect under low temperature are preliminary studied. It is showed that theoptimum degradation temperature of strains in soil are29℃,29℃,30℃,30℃and29℃;the optimum pH respectively are7,7,7,8,8; the optimum nitrogen source are KNO3,KNO3, NH4NO3, KNO3, and KNO3; the optimum phosphorus source are allK2HPO4+KH2PO4(1:1); the optimum nitrogen source concentration are all750mg/L; the optimum phosphorus source concentration are all200mg/L; the optimum soil moisturecontent respectively are25%～30%,25%,25%～30%,20%and20%; the optimuminoculation concentration are all15%; the optimum incubation time respectively are13d,11d,12d,13d and12d; the addition of mineral culture can degradate better.The optimum degradation temperature of strains in mineral oil medium respectivelyare30℃,30℃,30℃,29℃and30℃; the optimum pH are all8; the optimum nitrogen andphosphorus source are all KNO3and K2HPO4+KH2PO4(1:1); the optimum nitrogen andphosphorus source concentration are all750mg/L and200mg/L; the optimum inoculationconcentration are15%,15%,10%,10%and15%; the optimum incubation time are11d,10d,11d,11d and10d; the optimum initial oil concentration are600～1000mg/kg,600mg/kg,600～1000mg/kg,2000mg/kg and1000mg/kg.The optimal degradation conditions and growth conditions are not consistent by thecontrast. The degradation effect in medium is overall better than soil but the rangeability insoil is smaller than medium. The solid dispersion polyethylene glycol can enhance thedegradation rate and the degradation effectiveness is as low as15℃. After synthesizing theoptimum conditions, the degradation rate on total petroleum hydrocarbon (TPH) of singlestrain in Suzhou plant and dropping crude are increased by30%and20%, the degradationrate of mixed strains respectively are increased by20%～30%and10%. The degradationrate on polycyclic aromatic hydrocarbon (PAH) is increased by6%～12%.