Studies On The Isolation Of Marine Oil-Degrading Bacteria And Their Biodegradation Characteristics

With the development of petroleum industry,the pollution caused by the petroleum becomes more and more serious.At the same time when petroleum brings great economic benefits,it poses serious threat to the environment.Presently petroleum is one of the main contaminant in seawater,which has severely damaged seashore environments.In order to get rid of the petroleum from the environment,lots of scientific researches have been carried out by scientists to seek the safe,economic and reliable techniques wiping out petroleum.The present disposal ways of oil pollution includes physical,chemical and bioremediation techniques,of which, bioremediation is the most efficient technique,with the advantages of high efficiency, economic,free of second pollution and wide application.This thesis has shown up some important information such as oil constitutions, dangers of oil in seawater,common species of marine oil-degrading microorganisms, degradation mechanisms and methods.Based on the above information,the important thing is to obtain better strains and to understand their biodegradation characteristics. Therefore,screening marine oil-degrading strains from environment samples and studies on the biodegradation characteristics are the main contents of this thesis.By enriching manual marine culture with crude oil as a sole carbon source,10 strains of bacteria were obtained from oil contaminated water samples which had been collected from Shengli Oil Field,Shandong Province.Through measuring the degradation rates of 10 stains of bacteria,strain HB-1 had the highest oil-degradation capacity and its degradation rate was 54.74%(natural degradation rate had been deducted from total) after incubating for six days.In terms of physiological characteristics and 16S rDNA sequence analysis,strain HB-1 was identified as Acinetobacter sp.The experimental results indicated the optimal conditions for growth and degradation is:the incubation temperature is 25～32℃,the initial pH of the incubation media is 6.5～7.5,the NaCl concentration is 3%,the crude oil concentration is 1% (v/v),the shaking rate is 200 r·min^-1,the predominant nitrogen source is ammonium nitrate(NH₄NO₃) and the ratio of N to P is 3.18:1.Strain HB-1 could grow in freshwater or seawater medium;however,the effect of oil degradation was much better in seawater than in freshwater medium.The biodegradation of each chemical component was analyzed to probe the rule by GC-MS.The result indicated a significant degradation effect on long chain aliphatic alkanes.The surfactants such as Tween 80 played an important role in oil-degradation.It could enhance the degradability of crude oil by strain HB-1.Strain HB-1 could produce certain biosurfactant to facilitated the absorption of hydrocarbons.The biodegradation mechanism of petroleum still need further to research deeply in order that strain HB-1 can be applied in practical environmental engineering.