A Preliminary Study On The Effect Of Several Antioxidants On Lipid Synthesis Of Heveochlorella

Due to the impact of the energy crisis that broke out in the 1970s and the increasingly severe environmental problems since the 21st century,biodiesel has received widespread attention.The biodiesel produced by microalgae has many advantages,but the high production cost of lipid raw materials restricts the large-scale industrial production,and the improvement on lipid production capacity of microalgae is a direct way to reduce the production cost.Therefore,improving the lipid production capacity of microalgae has great practical significance for the development of microalgae biodiesel.In this study,Heveochlorella sp.Yu was used as the object to study the growth,lipid synthesis and accumulation of microalgae under different media and antioxidant conditions.At the same time,pay attention to whether the relevant parameters of the fatty acid composition of the lipid meet the standards for preparing biodiesel.The genes of some key enzymes(acc D,ME and rbc L)in the lipid synthesis pathway of Heveochlorella sp.Yu were cloned.Starting with the effect of MLT on NO,the relationship between MLT,NO,expression of key enzyme genes and lipid content was discussed,which explains to a certain extent the internal mechanism of MLT to promote lipid production.This paper provides a method to improve the lipid production capacity of microalgae through the optimization of culture medium and the addition of antioxidants,studies the mechanism of MLT to promote the lipid synthesis and accumulation of microalgae,and provides a basis for antioxidants to regulate lipid synthesis of microaglae.The specific research results are as follows:(1)The growth characteristics and growth cycle of Heveochlorella sp.Yu were clarified,the lag period was 0-5 days after inoculation,the logarithmic growth period was 5-9 days,and the stable period was entered after 9 days.Four culture media BG-11,Zhu-10,MS and TAP were used to cultivate,and measure the cell concentration,biomass,lipid content and lipid productivity.It was found that the maximum cell concentration is140.13×10⁶ m L^-1 cultured with TAP,compared with other three kinds of media increased by 1.3 to 1.8 times.The maximum biomass was 4.11 g L^-1,which was increased by 2.0 to 2.5 times compared to the other three media.The highest lipid content was 40.11%,no significant change.The highest lipid productivity was 185.57 mg L^-1d^-1,which was increased by 2.0-2.6times compared to the other three media.Discovered the characteristics that TAP is more conducive to the growth of Heveochlorella sp.Yu,and selected the TAP medium that can significantly increase the biomass,which lays the foundation for reducing the cost of biodiesel production.(2)Incubate Heveochlorella sp.Yu by adding 4 kinds of antioxidants MLT,BHA,FA and BHT,and optimize the concentration of added antioxidant to investigate the effects of four antioxidants on biomass,lipid content and lipid productivity.It was found that after the induction with the addition of MLT at a concentration of 40?mol L^-1,the maximum biomass was 4.01 g L^-1,which was slightly lower than control.The highest lipid content was 54.66%,which was an increase of 36.55%compared to the control.The highest lipid productivity is 244.63 mg L^-1d^-1,which is an increase of 31.83%compared with the control.The fatty acid composition before and after MLT induction is analyzed,and the DU is 97.03 and 94.44,CFPP is-15.25?and-15.26?,which meets the standards for biodiesel production in most regions.Established to increase the lipid content and productivity of Heveochlorella sp.Yu by adding MLT,and increase the lipid production capacity,which directly reduces the cost of producing biodiesel.(3)The genes of the three key enzymes acc D,ME and rbc L in the lipid synthesis pathway of Heveochlorella sp.Yu were cloned,and the sequences were compared with corresponding genes in other species.It lays the foundation for explaining from the genetic level that MLT promotes the lipid production capacity of Heveochlorella sp.Yu.(4)The effect of NO-mediated MLT on the lipid synthesis and accumulation and the expression of some key enzymes acc D,ME and rbc L in the lipid synthesis pathway of Heveochlorella sp.Yu was investigated.It was found that under MLT induction,the NO concentration reached 4234,which was 31.37%higher than control,the expressions of acc D,ME and rbc L genes were 1.8 times,1.6 times and 1.9 times that of the control,the highest lipid content is 54.66%,which was 36.28%higher compared with the control.On this basis,by adding the NO promoter SNP and the NO inhibitor c PTIO to change the NO concentration.Under the condition of adding SNP,the highest NO concentration is 5038,which is an increase of 56.31%compared with the control,the gene expression of acc D,ME and rbc L is 2.0times,1.8 times and 2.2 times of the control,the highest lipid content is57.40%,which is an increase of 43.39%compared with the control.With the addition of c PTIO,the highest NO concentration is 2570,which is 20.26%lower than control.The expressions of acc D,ME and rbc L genes are 0.5times,0.3 times and 0.3 times that of the control.The highest lipid content is 32.78%,which is 18.11%lower than control.The relationship between MLT,endogenous NO,gene expression of key enzymes for lipid synthesis was discovered,and the mechanism by which MLT promoted the lipid production capacity of Heveochlorella sp.Yu was preliminary explored.