| Schizochytrium is a kind of marine microalgae which is rich of oil,it growth fast,easy to cultivate and it has high oil content.the composition of fatty acids in Schizochytrium oil was simple,and Schizochytrium oil has high docosahexaenoic acid(DHA)content,and it was easy to purify,so it has very important economic and scientific research value.The Schizochytrium sp.used in this study were isolated and obtained by the laboratory personnel.After the cultivation of the Schizochytrium sp.,the wet algae mud was obtained by centrifugation,and collected the wet microalge mud,the Schizochytrium sp.dry algae powder was obtained by vacuum freeze drying.In this paper,the extraction process of oil and natural antioxidant on oil oxidation stability were studied.In addition,the separation and purification process of DHA from Schizochytrium sp.oil was studied.It is a reference for the development and utilization of Schizochytrium sp.oil.Main contents and results was obtained as follows:(1)We extraction the oil by two-step enzymatic method with Schizochytrium sp.dry algae powder as raw material,clear oil extraction ratio as evaluation indicator.The results showed that the optimalextraction conditions was obtained as follows: liquid/solid ratio 1:7,neutral protease addition 7%,enzymatic hydrolysis temperature 45 ℃,enzymatic hydrolysis time 3 h,enzymatic hydrolysis pH 6.5;alkaline protease addition 10%,enzymatic hydrolysis temperature 68 ℃,enzymatic hydrolysis time 6 h,enzymatic hydrolysis pH 9.4.Under these conditions,the extraction ratio of Schizochytrium sp.oil reached91.37±0.14%.Gas Chromatography-Mass Spectrometry(GC-MS)analysis showed that the content of unsaturated fatty acids was 44.13%and the DHA content was 32.06%.(2)the peroxide(POV)value and DHA content as the evaluation index of oil oxidation stability,the effects of five kinds of natural antioxidants on the oxidative stability of the oil from schizochytrium sp.were studied by using the Schaal oven method.Three kinds of natural antioxidants were selected according to that and complexd by a certain percentage,the effects of the complex natural antioxidant on the oxidation stability of the oil from schizochytrium sp.were studied.The changes of DHA content in the oil from schizochytrium sp.were studied by gas chromatography-mass spectrometry(GC-MS).The results showed that five kinds of natural antioxidants could improve the oxidative stability of the oil from schizochytrium sp..And the complex natural antioxidant of vitamin E,rosmarinic acid and tea polyphenol(2:1:2,m/m/m)was the highest to the oxidative stability of oil fromschizochytrium sp.,under these conditions,the peroxide value of the oil from schizochytrium sp was 30.25±1.37 mmol/kg.And finally the DHA content was 3.32±0.12 g/100 g.(3)Oil from Schizochytrium sp.was used to separation and purification the docosahexaenoic acid(C22:6)in two steps by high-speed countercurrent chromatography(HSCCC).Firstly,the oil from Schizochytrium sp.was saponification,The selected liquid phases were heptane-ethyl acetate-methanol-water(15:1:15:1,V/V/V/V)for the first step and heptane-methanol-water(5:6:1,V/V/V)for the second.The separation was followed by UV detection at 210 nm.the best conditions were followed: sample size 180 mg,flow velocity 3 mL/min,revolution speed 910 r/min,column temperature 13 ℃.Under these conditions,docosahexenoic acid from Schizochytrium sp.was separated and purificated by two steps high-speed countercurrent chromatography,the docosahexenoic acid purities were 90.06% and 99.61% measured by high performance liquid chromatography(HPLC)and UV detector,the recovery ratios were 95.27% and 93.81%. |
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