| Docosahexaenoic acid is the longest chain of long-chain polyunsaturated fatty acids omega-3 PUFA found by now,and is a kind of essential fatty acids which can not be synthesized oneself and must be supplemented in the diet.DHA,mainly distributed in the cerebral cortex,retina,myocardium,breast milk,etc,has many important physiological functions in the human body.For example,intaking of DHA can greatly reduce the probability of suffering from cardiovascular disease,arthritis,arrhythmia and asthma and other chronic disease,and also can improve intelligence and alleviate some mental illness,and so on.Traditionally,DHA is derived from marine fish.As DHA's physiological functions are continuously discovered and the quality of people's of life continues to improve,the demand for DHA is markedly increased.However,the traditional source is far from being able to meet the needs of the market.Previuos study showed that fish DHA derived from the intake of food at the bottom of the food chain,that is,some marine microorganism.Therefore,DHA from marine microbial fermentation production has attracted researcher's attention.Currently,there are only few DHA-rich marine microalgae which is found and applied to the production of DHA.Schizochytrium sp.is the ideal algae which can be used for the industrial production of DHA.Schizochytrium sp.is a marine microalgae with spherical single cell which has and belongs to eukaryotic organism.It grows and reproduces speedly with strong vitality and can be cultured heterotrophically or autotrophically,mainly relys on organic carbon source,organic nitrogen source and inorganic salt to grow.It was demonstrated that the algae powder and microalgal DHA from Schizochytrium sp.are safe and non-toxic side effects on the human body.However,there are still many problems to be solved in the industrial fermentation production.In this paper,we finished the purification and preservation of the Schizochytrium limacinum MYA-1381,and preliminary studied the basic growth characteristics and culture condition of the schizochytrium limacinum,including the pH,temperature,seed age and inoculum concentration,etc.In order to improve the biomass and DHA production,the concentration of glucose,yeast powder,corn steep liquor and sea salt in the culture medium by single factor method were optimized,and the best optimum concentration and culture time was abtained.Then,the medium formulation by Box-Behnken Design in the response surface method was used to optimized the culture medium.Finally,the optimum culture conditions are as follows:initial pH:6.5;inoculation amount:10%;culture temperature:25?;rotational speed of the shaker:170 rpm/min;the media component is glucose 52.68 g/L,yeast powder 8.78 g/L,corn steep 5.48 g/L,sea salt 18.40 g/L.When the culture time is 96 h,the biomass reaches to 14.25 g/L and DHA content is 133.60 mg/g highly.At the same time,the anti-obesity effect of the microalgal DHA from Schizochytrium limacinum on mice feeding with high fat diet was investigated.In this study,C57BL/6J mice were used as the study object,and the microalgal oil which contains different purity of DHA was used as material.The low fat diet group was used as a normal control and the fish oil diet group was taken as reference.The differences of the weight of mice and related tissue weight,serum lipid indicators,liver morphological changes and genes related to lipid metabolism were detected.The results shwed that microalgal oil DHA could prevent weight gain from the early stage,while fish oil showed better results in the later stage of treatment.Both algae and fish oil could effectively prevent weight gain and abdominal fat accumulation induced by high fat diet,and alsosignificantly decrease the level of serum TG and TC and improve the liver morphology.The anti-obesity mechanism might be partially related to the regulation of lipogenesis-,lipolysis-and thermogenesis-associated genes in liver.Moreover,although SMO2 was purified,SMO1 had a similar effect as SMO2,and also equivalent to FO under the dosage of 100 mg/kg ?-3 PUFAs.In conclusion,the result of this study suggests that DHA-enriched microalgal oil derived from Schizochytrium sp.can be used to prevent or treat obesity and is a kind of potential functional food for anti-obesity. |
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