Lipid Production From Chitin Constituent Units By Cutaneotrichosporon Oleaginosum

With the increasing demand for oleochemicals,many researchers are devoted to the research on microbial lipids.Due to the limited area of arable land,many cheap or waste raw materials have been developed as substrates for microbial lipids production.Chitin is the second most abundant biomass resource on earth next to lignocellulose,and a potential raw material for microbial lipids production.In this thesis,researches were carried out on the conversion of chitin constituent units D-glucosamine(GlcN)and N-acetyl-D-glucosamine(GlcNAc)into lipids by Cutaneotrichosporon oleaginosum.A small-scale metabolic model of C.oleaginosum ATCC 20509 was constructed,and the main metabolic pathways and the maximum theoretical lipid yields were compared and analyzed with the substrates of conventional carbon sources(glucose,xylose and glycerol)and chitin constituent units.The results of flux balance analysis showed that the theoretical lipid yield was the highest when GlcNAc was used as substrate,which was 0.340 g/g,and the co-substrate fermentation with equal molar amount of GlcN and acetate(Ac)(GlcN & Ac)could improve the overall lipid yield,which theoretically confirmed the potential of lipid production from GlcNAc and GlcN & Ac by C.oleaginosum.With GlcNAc as the substrate,a two-stage fermentation process was adopted.The lipid yield obtained by optimizing the relevant parameters reached 0.229 g/g under nonsterile condition.With the phosphorus starvation fermentation strategy,the higher the molar ratio of carbon-to-phosphorus(C/P),the higher the lipid content,and the maximum lipid yield of 0.249 g/g was achieved when C/P was 5676.When the GlcN and Ac cosubstrate were used for fermentation,the higher Ac concentration was,the higher lipid content obtained.However,when the concentration of Ac was higher than 20 g/L,the cell growth was significantly inhibited and the resulting lipid concentration was relatively low.With the phosphorus-limitation fermentation strategy,the greater the C/P value,the higher the lipid concentration,and a lipid yield of 0.174 g/g was achieved when C/P was 5676.Overall,the fatty acid compositions of lipids produced by C.oleaginosum in this study were very similar to that of palm oil,and the total contents of oleic acid and linoleic acid of lipids produced under the phosphorus-limitation fermentation strategy exceeded 58%.This study laid a foundation for the reconstruction of C.oleaginosum 20509 genomescale metabolic model,and providing fermentation strategies conducive to lipid production for chitin constituent units GlcNAc and GlcN,affirmed the excellent lipid production fermentation performance with GlcNAc as the carbon source,which provided an important reference for the lipid production process of chitin.