Effects Of Carbon And Nitrate On Biochemical Components,Sedimentation And Metabolism Of Oocystis Borgei

The Directional Cultivation of microalgae is an important measure of ecological health cultivation,and the application of concentrated microalgae as an ecological agent in aquaculture ponds can accelerate the Directional Cultivation of microalgae in ponds.Microalgae ecological preparation is an active microalgae product with specific ecological functions that can be used immediately.It can be produced by large-scale cultivation of microalgae and concentration of living microalgae.However,the development and utilization of microalgae ecological preparation has been faced with the problems of low efficiency and high cost of living algae concentration.Oocystis borgei is a kind of microalgae ecological preparation which has been developed and has remarkable effect on the water quality control of shrimp culture.It plays an important role in improving the quality of shrimp culture products and accelerating the green and healthy culture of shrimp.The self settling characteristics of O.borgei are of great significance to the concentration of algae in vivo,but the factors that affect the self settling recovery and the mechanism of self settling have not been reported.Therefore,this paper studies the effects of different nitrogen and carbon concentrations on the growth,biochemical component content and sedimentation change of O.borgei,analyzes the relationship between sedimentation and growth and biochemical component,and uses metabonomics analysis method to understand the internal regulation of response nitrogen concentration of O.borgei,and preliminarily explores the biological mechanism of self sedimentation of O.borgei.The main results are as follows:1.Effect of nitrogen concentration on the sedimentation of O.borgeiNitrogen concentration had a significant effect on the sedimentation rate of O.borgei(P < 0.05).The sedimentation rate of O.borgei had a significant effect on growth and biochemical components,among which the most significant correlation was lipid content and biomass,followed by total sugar content.There was a positive correlation between the biomass and sedimentation rate,Pearson coefficient r = 0.785.The more biomass was,the higher the sedimentation rate was.There was a negative correlation between lipid and total sugar and sedimentation rate,Pearson coefficient r was-0.788 and-0.731,respectively.The lower the content of lipid and total sugar,the higher the sedimentation rate.There wasno significant correlation between protein and sedimentation rate.When the concentration of nitrate was 12.32 mg/L,the growth state of O.borgei was the best,the content of lipid and total sugar was the least,the sedimentation rate was significantly better than other concentration groups,and the sedimentation effect of short time(6 hour)was the best at75%.2.The effect of carbon concentration on the deposition of O.borgeiCarbon concentration had a significant effect on the sedimentation rate of O.borgei(P < 0.05).The sedimentation rate of O.borgei had a significant effect on growth and biochemical components,among which the most significant correlation was lipid content and biomass,followed by protein content.There was a positive correlation between the biomass and sedimentation rate,Pearson coefficient r = 0.884.The better the cell growth,the more biomass,the higher the sedimentation rate.There was a negative correlation between lipid and protein and sedimentation rate,Pearson's coefficient r was-0.748 and-0.582,respectively.There was no significant correlation between total sugar and sedimentation rate.When the carbon concentration is 49.57 mg/L,the growth state of the algae is the best,the lipid content is the least,the sedimentation rate is significantly better than other concentration groups,and the sedimentation effect of short time(10 hour)was the best at 69%.3.Metabonomics of O.borgei at different nitrogen concentrationsUPLC-QE-MS technology was used to detect and analyze the non targeted metabolism of 30 samples from 5 groups: nitrate-deprived stress(NS,0 mg / L),low nitrate(LN,6.16 mg / L),Control(12.32 mg / L),high nitrate(HN,492.8 mg / L)and high-nitrate stress(HS,862.4 mg / L).17392 and 10948 ion peaks were detected in the positive and negative ion mode respectively,695 and 157 metabolites were identified.With the increase of nitrate concentration,the increase of metabolites was the most in the HN and HS groups,the second in the Control group,the least in the LN and NS groups,and the high nitrate condition played a major role in the accumulation of metabolites.In the Control group,lipid accumulation was less,protein began to accumulate,and cell density increased,so the sedimentation rate was higher;in the NS and LN group,algal cells synthesized carbohydrate and lipid substances through protein degradation,and the cell density was smaller,so the cell sedimentation rate decreased;in the HN and HS group,lipid accumulation,more substances synthesized vesicle structure,leading to lower cell sedimentation rate.Differential metabolites such as amino acids,lipids and sugars at different nitrate concentrations lead to the accumulation of a series of substances,changes in cell structure,composition and cell density in algal cells,thus affecting cellsedimentation rate.To sum up,the concentration of carbon and nitrate changes the sedimentation rate of algae cells by affecting the growth and biochemical components of O.borgei.The biomass and sedimentation rate of O.borgei have a positive correlation,while the lipid content and sedimentation rate have a negative correlation.Under certain conditions,the protein and total sugar content of O.borgei have a correlation with sedimentation rate,which depends on whether its gravity can counteract the cells Buoyancy.The results of physiological and metabome showed that when the concentration of nitrate was 12.32 mg/L,the growth rate of O.borgei was fast,the cell density was increased,the accumulation of lipid and carbohydrate was less,and the accumulation of protein was the highest,which could reach75% in 6 hours.By optimizing the distribution of carbon and nitrate in cells,the carbon flow can flow to the direction of biomass and protein synthesis as much as possible,reducing the synthesis of sugar and lipid,and increasing the sedimentation rate of O.borgei.