Mutation Breeding Of The Chlorella Vulgaris And Interactions Between Microalgae And Bacteria

Microalgae have been considered to be one of the most promising candidates for biodiesel production because of their explicit advantages,including high growth rate,high lipid content,and no competition with agricultural food.In order to solve the mutually incongruous nature of lipid accumulation and biomass production pattern,Chlorella vulgaris was irradiated by lowtemperature plasma to select the algae with high growth rate and lipid content,and then Chlorella vulgaris were co-cultured with bacteria at different initial ratio under nitrogen limitation,to investigate the characteristics of the co-culture system on the growth and lipid accumulation of algae.And also high-throughput sequencing was used to analyze the symbiotic microbial diversity in microalgae culture water.Low-temperature plasma could cause microalgal cell mutation in a short time,resulting in obvious mutagenic effect.The lipid content,neutral lipid content,lipid productivity and neutral lipid productivity of the mutant M1 was 37.28%,19.12%,8.20 mg/(L·d)and 4.21 mg/(L·d),respectively,which increased by 103.5%,133.5%,163.7% and 202.2% compared with the wild type.The biomass and protein content of M1 were increased significantly.The proportion of MUFA and PUFA in M1 were 44.0% and 19.8%,which increased by 23.6% and 32.9% of the parental strain,respectively.Methyl ester(C18:1),which was the properties of biodiesel,increased by 64.9%.The co-cultivation of algae-bacteria system can effectively contribute to the quality and quantity of microalgal oil,and had great potential for production of biodiesel.The biomass and lipid content of algae were significantly higher than that of the pure culture of axenic C.vulgaris when C.vulgaris and B2.3 strains were inoculated at the ratio of 70:1.The biomass,lipid content,lipid productivity,neutral lipid content and neutral lipid productivity of algae in the cocultures were 1.68 g/L,45.2%,75.94 mg/(L·d),23.0% and 38.65 mg/(L·d),respectively.And the biomass concentration and lipid content in the co-culture system were 66.3% and 47.7%higher than that of the axenic pure algal cultures,respectively.Furthermore,the consortium system significantly increased the proportion of unsaturated fatty acids and C18:1 fatty acids.The microbial diversity in the microalgal culture system indicated that the microbial richness in HL was the largest(OUT = 1315),and the microbial richness in NLD was the least(OUT = 900).The microbial diversity in the microalgae culture waters in the north and the south were divided into 26 phylum,78 class,134 order,230 family,and 433 genus.The main microbial diversity at the phylum level had greater similarity.Actinobacteria,Proteobacteria and Bacteroidetes were the main phylum.The relative abundance of Actinobacteria was the highest phylum,the relative abundances in NL,NLD,HX and HL were 82.5%,67.5%,74.2%and 62.4%,respectively.The most dominant microbial group in HX was Actinobacteria,with a relative abundance of 67.0%,and its relative abundance in HL was only 21.8%.The most dominant microbial group in NL was Nitriliruptoria,with a relative abundance of 54.6%,and its relative abundance in HL was only 11.2%.The most dominant microbial groups in NL and NLD were all Nitriliruptoria,with relative abundances of 54.6% and 45.7%,respectively.