Screening Of Diesel Oil Degradable Microorganisms And Characterization Of The Diesel Oil Degradation

Petroleum and its related products are widely used in modern life and thus playimportant roles in securating energy and resources supply, promoting innovation of industryand progress of human society. However, the increasing comsumption of petroleum causedthe world-wide crisis of environmental pollution, threatening the sustainable development ofhuman being.Diesel oil is utilized as fuel for many vehicles such as car, tractor, ship and machines. Itis mainly composed of hydrocarbons with the chain length varies from C8to C30. Diesel oilis a kind of light oil and insoluble in water. Once it was leaked, it was hard to be removed andlikely lead to serious pollution. Many efforts have been made to overcome this problem.Among them, biological degradation of diesel oil by microbial attracted more attention due toits advantages of high efficiency, low cost and envirometal-friendship. Nowdays, it has beendeveloped to be the most popular method for dealing with diesel pollution.This work aimed to find new microbials for diesel degradation and study its degradationcapacity as well as degradation mechanism. The main results of this work are listed asfollowing:1. Nine micarobial strains with potential diesel oil degradation capacity were isolatedfrom hydrocarbons polluted soil by culture using diesel oil as the sole carbon source. Amongthem, strain A and C were chosen for further study due to its relatively rapid growth rate andhigher degradation rate (34%and30%for A and C, respectively).2. Strain A and C were identified to be Bacillus pumilus and Bacillus subtilis,respectively, by morphology analysis, physiological and biochemical assay and16S rDNAsequences.3According to single factor experiment and orthogonal experiment, found the theoptimal degradation conditions, in10mL/L of diesel degradation cultures, Bacillus pumilus Athe optimum temperature for37℃, pH8.0, incolumn concentration15%, in the7th day thedegradation rate reached43%; Bacillus subtilis C the optimum temperature for37℃, pH7.5,incolumn concentration10%, in the7th day the degradation rate reached41%.4In the laboratory conditions, investigate the biodegradation of diesel oil in the soil.5gsoil with1mL diesel oil, temperature37℃, maintain the humidity40%-50%, continuouslydegradated for5weeks, found in the first week degradation rate exceeded50%, more suitablefor diesel oil degradation in the soil, at the5th week, degradation rate was above70%.5Investigate the biodegradation characteristics, B. pumilus A has a lower lipophilic thanB. subtilis C. In the degradation process, the two strains both produce surfactant which causesurface tension decrease, extract the surfactants and FTIR show that they are lipopeptidemolecules, GC/MS testing demonstrate the broken down of components in the process ofdiesel oil degradation.