Study On The Fermentation Of Liamocin By Aureobasidium Pullulans

Liamocin is one of the new active fermentation products of Aureobasidium pullulans.It is a kind of polyol ester.The research on the production of liamocin by Aureobasidium pullulans has been widely studied abroad earlier,and it is rarely reported in China.In order to further explore the factors affecting the synthesis of liamocin and increase the yield of liamocin.In this study,the wild high-yield liamocin strain of Aureobasidium pullulans was screened,the culture conditions,extraction methods and structural analysis of liamocin produced by Aureobasidium pullulans were studied.At the same time,the biomass hydrolysate was used for microbial fermentation to produce liamocin.The main research contents and results are as follows:?1?Many plant materials?wild leaves,bark,grass leaves,peels,flowers?and soil samples were colleted.Through enrich culuturing,primary screening and rescreening,the high-yield liamocin strains of Aureobasidium pullulans were obtained,which were identified by single colony morphological characteristics and nucleic acid sequence analysis.The two strains with higher liamocin production were named as Aureobasidium pullulans ZUST-SY and ZUST-GS.The gene sequences were submitted by Banklt to NCBI,the obtained GenBank library,accession numbers were MH329613 and MH329612,respectively.?2?Liamocin was extracted from the fermentation broth by using organic solvent 2-butanone.The structure of liamocin was analyzed by infrared spectroscopy,nuclear magnetic resonance and matrix-assisted laser desorption ionization time-of-flight mass spectrometry.The structure of produced liamocin was characterized as a mannitol headgroup partially acylated with three or four 3,5-dihydroxydecanoic ester groups.?3?The strain with higher production of liamocin was selected,and the fermentation medium was optimized by single factor experiment and response surface methodology.With single factor experiment,the best carbon and nitrogen sources were determined.P-B experiment,steepest climbing test and central combination experiment were carried out to optimize the fermentation medium further.The optimal medium composition obtained was as follows:xylose 75.17 g/L,NaNO₃ 1.57 g/L,NaCl 1 g/L,K₂HPO₄ 5 g/L,MgSO₄·7H₂O 4 g/L,initial pH natural.In this condition,the yield of liamocin was 8.41 g/L,which was 52.4%higher than that of the original condition.?4?Corn cob was selected as substrate for fermentative production of liamocin.It was hydrolyzed with 1%H₂SO₄ and detoxified with activated carbon,the furfural and reducing sugar concentration in hydrolyzate after hydrolysis and detoxification were determined.The results showed that the concentration of reducing sugar in the hydrolysate after detoxification was 28.6 g/L,and the concentration of furfural was 0.05 g/L.The fermentation medium was prepared based on the hydrolyzate after detoxification,and the effect of the optimal nitrogen source and inorganic salt on the synthesis of liamocin was observed.On the basis of this,further addition of different concentrations of carbon source was studied.The results showed that the yield of liamocin reached 7.81 g/L when 5%xylose,0.157%NaNO₃,0.1%NaCl,0.5%K₂HPO₄and0.4%MgSO₄·7H₂O inorganic salts were added to the detoxified corncob hydrolysate,which was 48.4%higher than that of the original condition.