| Single carbon source for the cultivation of microalgae usually caused some disadvantages such as low lipid productivity,high culture cost by high dosage?e.g.glucose carbon accounts for about 80%of the total cost of culture substrate?,which limited the further application of microalgae biomass.The mixed carbon source can achieve synergy through the complementarity of their respective advantages,while reducing the cost of culture and promoting the growth of microalgae and the enrichment of intracellular lipid.In this thesis,crude glycerol and glucose as single carbon source act as the control group,and crude glycerol and glucose synergistic as the experimental group,to explore the synergistic effect of crude glycerol and glucose on the growth and intracellular lipid rich.The effect of the synergistic of crude glycerol and glucose carbon source on the mechanism of synthesizing and accumulating the lipid accumulation of C.subellipsoidea was preliminarily explored.The main research results obtained were as follows:1)When the concentration of a single glucose carbon source was 25 g/L,the biomass,lipid content and lipid yield of C.subellipsoidea reached their maximum values,which were 7.04 g/L,42.46%and 2.99 g/L,respectively.When the single crude glycerin carbon source was 20 g/L,the biomass,lipid content and lipid yield of cultured algae reached the maximum,which were 3.05 g/L,46.85%and 1.43 g/L,respectively.Under the action of a single glucose carbon source,the maximum biomass of C.subellipsoidea was 1.31 times that of a single crude glycerol carbon source,and under the action of a single crude glycerol carbon source,the maximum lipid content of C.subellipsoidea increased by 10.34%,which indicated that a single glucose carbon source was more conducive to the accumulation of biomass of C.subellipsoidea,and when a single crude glycerol carbon source which accumulated more lipid;When a single crude glycerol carbon source cultivates C.subellipsoidea,the content of saturated fatty acids?54.31%?is higher than that of a single glucose carbon source?47.94%?,the content of C18:2?10.08%?and C18:3?6.15%?is lower than that of a single glucose carbon source that the content of C18:2?16.03%?and C18:3?11.39%?.It is more conducive to the preparation of high-quality microalgae biodiesel by crude glycerol cultivating C.subellipsoidea.2)Crude glycerol/glucose carbon source synergy on C.subellipsoidea?crude glycerol/glucose carbon source ratio is 5:5,and the order of addition is simultaneous addition of crude glycerol and glucose?.Compared with a single glucose carbon source?25 g/L?,The lipid content increased by 21.42%,the lipid yield increased by1.21 times,resoectively.Compared with the single crude glycerin carbon source?25g/L?,the biomass increased by 2.70 times,the lipid content increased by 14.97%,and the lipid yield increased by 3.09 times.This shows that the synergistic effect of crude glycerol/glucose carbon source was more conducive to the growth and accumulation of lipid of C.subellipsoidea;When crude glycerol/glucose carbon source synergy on C.subellipsoidea,the carbon source cost per unit biomass was 7.26×10-4$/L,and the carbon source cost per unit lipid is 1.39×10-3$/L.Compared with a single crude glycerol carbon source,the carbon source cost per unit of biomass was reduced by35.75%and 16.55%,and the carbon source cost per unit of lipid and fat was reduced by 46.74%and 27.23%,respectively.This shows that crude glycerol/glucose synergistically produces biodiesel with a cost advantage.3)The metabolomics of the crude glycerol/glucose carbon source synergistic culture of C.subellipsoidea showed that the glycolysis pathway was active in the algae cells,and the expression levels of glyceraldehyde-3-phosphate,dihydroxyacetone phosphate,glycerol-3-phosphate and pyruvate increased,which was conducive to the increase of lipid content in algal cells.Intermediate metabolites of the tricarboxylic acid cycle,such as oxaloacetic acid,fumaric acid and?-ketoglutaric acid were reduced,allowing more acetyl Co A to enter the fatty acid synthesis pathway.The significant down-regulation of the expression levels of amino acids generated by these intermediate metabolites indicates that the tricarboxylic acid cycle process provides more precursors or energy for lipid synthesis.The increased expression of phospholipid metabolites in algal cells promotes the enrichment of intracellular triglycerides.Decreased expression of metabolites such as starch,isoprenoids,lactose diglycerides,etc.,resulting in the accumulation of precursors for lipid synthesis such as acetyl Co A,malonyl Co A,1,2-diacylglycerol,thereby promoting cell lipid accumulation under the synergistic effect of crude glycerol/glucose. |
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