Screening Of High-yield DHA Microalgae, Optimization Of Algal Oil Extraction Process And Anti-obesity Activity

DHA is one of theω-3 polyunsaturated fatty acids,which has important biological and physiological functions.Therefore,DHA has been widely used in medicine,health products and other industries.In this paper,Schizochytrium limacinumATCCMYA-1381,Aurantiochytrium.spATCCPRA-276,Crypthecodinium cohnii ATCC 30334 and Crypthecodinium cohnii ATCC 30336 were evaluated by comparing with index of growth period,biomass and total lipid.And S.limacinum ATCC MYA-1381 was verified as the most optimal microalgae for the advantages of fast growth rate,short cycle,high biomass and total fat yield.Thus,the S.limacinum ATCC MYA-1381was selected as the research object in this paper.Furthermore,to improve the DHA yield,the effects of exogenous additives on the biomass and oil content were also researched.At the same time,the extraction conditions of microalgae oil were optimized,and the anti-obesity activity of microalgae oil DHA was considered.The main research results are listed as follows:1.Schizochytrium limacinum ATCC MYA-1381,Aurantiochytrium.sp ATCC PRA-276,Crypthecodinium cohnii ATCC 30334 and Crypthecodinium cohnii ATCC30336 were evaluated by surveying the index of the biomass,oil content under the same conditions.The results showed that the growth rate,biomass,oil content and total volume of fat of S.limacinum MYA-1381 were 72 h,7.27 g/L,60.34%and3.17 g/L,respectively,which were superior to other algae strains.Therefore,S.limacinum ATCC MYA-1381 is the ideal microalgae for the production of DHA.2.The extracts were fractional extracted from celery root,Cryptosporidium phytophthora,Schizophyllum demericum and Cryptosporidium phytophthora by ethyl acetate,acetone and water.The effects of exogenous extractson the biomass,oil content,unit volume and total lipid of Schizochytrium limacinum ATCC MYA-1381were investigated.The ethyl acetate fraction of ethanol extract of the Crypthecodinium cohnii has a significant effect on the accumulation of oil content and total fat content per unit volume.When the concentration of Cryptheca forgone at ethyl acetate fraction reached 250mg/L,the promotion effect of Crypthecophyta ethylacetate extract reached the maximum,with the oil content increased by 12.43%and the total volume of fat per unit volume increased by 12.03%.3.Ultrasonic assisted extraction and supercritical CO₂ extraction were used to extract algae oil.The effects of medium-to-liquid ratio,ultrasonic time,and ultrasonic powerin ultrasonic assisted method and the temperature,pressure,extraction time and extraction pressure in supercritical CO₂ extraction method were investigated taken oil content as a screening index.The optimum conditions for the extraction of Schizochytrium limacinum ATCC MYA-1381 by supercritical CO₂ fluid were chosen as the extraction time of 60 min,the extraction pressure of 29 MPa,and the extraction temperature of 35℃.Finally,the extraction rate reached 46.79%.The optimum conditions of ultrasonic-assisted extraction were selected as ultrasonic time of 30 min,solid-liquid ratio of 1:40,ultrasonic power of 350 W.And the extraction rate was53.13%4.The obesity model was induced by high fat diet,and the anti-obesity effect of DHA was discussed.The mice were weighed with different doses of algae DHA,and the body weight,adipose tissue weight and liver weight and serum lipid levels and lipid metabolism related genes（HSL）were measured after 9 weeks of treatment.The results displayed that DHA could significantly decrease the weight of adipose tissue in mice,decrease the content of triglyceride and total cholesterol in serum and increase the expression of HSL gene in mouse adipose tissue.