Research Of The Characteristics And Applications In The Hydrocarbon Degradation Of Trehalose Lipids Produced By Strain Rhodococcus Erythropolis FF

Biological surfactants are secondary metabolites of microorganisms.Compared with chemical surfactants,their functional groups are diverse,the surface activity is stable,biodegradable and non-toxic,and it can replace chemical surfactants on many occasions,especially in food and cosmetics related products.Trehalose lipids are kinds of important biosurfactants,but there are few studies on their fermentations and applications.A strain named FF of Rhodococcus erythropolis was isolated and identified in the early stage of our research projects'group.It was found that FF strain could secrete a large amount of trehalose lipids in vitro when it degraded hydrocarbon pollutants.Therefore,the characteristics of trehalose lipids's produced by FF strain were studied in this paper.The structure and composition of trehalose lipids were analyzed by FT-IR and LCMS-IT-TOF,and the effects of them on the degradations of hydrocarbon organic pollutants by FF strain were also discussed.The following results were achieved:?1?By optimizing the carbon and nitrogen sources of fermentation,the optimum carbon sources and nitrogen sources for trehalose lipids produced by FF strain were n-hexadecane:oleic acid?1:1?and urea,respectively.Under this condition,the yield of trehalose lipids could reach 7.97g/L,the conversion of carbon source was 19.92%,the critical micelle concentration of produced trehalose lipids was 85mg/L,and the highest emulsification index(EI₂₄)was 91.75%.The composition of carbon sources not only affected the yield of trehalose lipids secreted by FF strain,but also affected the structural composition.The results of FT-IR and LCMS-IT-TOF showed that when n-hexadecane:oleic acid?1:1?were used as carbon source for fermentation,the trehalose lipids produced by FF strain were a mixture of trehalose tetraester while the trehalose lipids fermented by n-hexadecane:maltose?1:3?were the mixtures of trehalose triesters and trehalose tetraesters.?2?FF strain can grow with aromatic hydrocarbons such as naphthalene and anthracene as sole carbon sources.Trehalose lipids which could be used as carbon source for FF strain to grow did can promote the degradations of naphthalene and anthracene obviously.When the concentration of trehalose lipids was 100mg/L,it was the most significant for the degradations of naphthalene and anthracene by FF strain.The maximum biomasses could be increased by 145%and 51.86%within 6days,and the removal rates of naphthalene and anthracene could be increased by 23.86%and 22.69%,respectively.However,because of?-naphthol's high toxicity,FF strain could hardly grow with it as the only carbon source,even trehalose lipids addition did not significantly improve FF strain's growth situation.?3?FF strain also showed pretty degradation effects for the oil sludge of petrochemical enterprises with complex components.Pre-dispersing sludge with the trehalose lipids could increase the removal rate of petroleum hydrocarbons in 500g/L oil sludge by FF strain.The experimental results showed that when the oil sludge was predispersed with trehalose lipids of 500mg/L,after 2 days of degradation,the removal rate of petroleum hydrocarbons was 87%,which was 8.21%higher than that of unpretreatment,and the removal rate of petroleum hydrocarbons increased by 9.6%compared with that of unpretreatment after pretreatment with"sawdust+soil"and100mg/L trehalose lipids as dispersant.After the pilot scale enlargement,FF strain still had good treatment effects on oil sludge.After a 10-day degradation,the removal rate of petroleum hydrocarbons was higher than 95%.The results can provide theoretical guidances for the fermentation and application of trehalose lipids.