The Research Of Producing DHA Functional Lipid By Fermentation

Docosahexaenoic acid (DHA) has a wide range of beneficial effect on people’s healthy,such as anticarcinogenic, antiatherogenic, and antidiabetic. At present, DHA mainly comesfrom sea fish and algal metabolin, but people pay much attention to fungal synthesis of DHA,due to several disadvantages during DHA extracting and strict conditions in alga cultivating.To isolate DHA-producing microorganisms, natural materials were collected. By platecultivation, streaking and fermentation, it used dyeing of Sudan black and has screened fourstrains producing lipids including one red yeast, two white yeasts and one mould. It extractedlipids from these strains by methanol-chloroform method, processed lipids by methyl esterand analyzed lipids’ components. At last, it screened a strain producing DHA. Refering to"Handbook of characteristic and identification of yeast", it identified producing DHA strainwith cell morphology and physiological and biochemical identification. After identification, itcalled Rhodothece glutinis (RG).Furthermore, it did induction experiments by physical, chemical and composite inductionfor RG and selected15high producing DHA strains. After genetic stability experiment, itobtained3strains stably producing DHA.It selected one of the three strains to determine72h growth curve and optimizefermentation conditions. The optimum condition is100g/L glucose,10g/L peptone,1g/L zincsulfate,10g/L safflower oil, the initial pH6.0,25℃fermentation temperature, fermentationtime of5days,4%inoculum. By optimization and orthogonal experiment, DHA productionof the mutant strain reached0.465g/L.