Effects Of Environmental Conditions On The Growth And DHA Production Of Schizochytrium Limacinum And Study On The Effects Of Different Antioxidants Upon Dried Cells Of Schizochytrium Limacinum

Schizochytrium limacinum is a heterotrophic marine fungal containing DHA. In this study Schizochytrium limacinum was induced by UV to further enhance DHA production. And five strains were obtained which DHA production were all higher than the original strain. Schizochytrium limacinum 12 which DHA production was the highest was used as experiment material to analyse effects of nutrient sources, environmental factors, cultural time on the growth and lipids of Schizochytrium limacinum The results showed that glucose and soybean cake hydrolysate were efficient carbon and nitrogen sources for the growth and DHA production of Schizochytrium limacinum. An increasing concentration of carbon source (glucose) from 3% to 6% induced significantly the growth and DHA accumulation, however, resulted only little changes in DHA production. An increasing concentration of nitrogen source (soybean cake hydrolysate) resulted in an increase in the cell biomass in some extent. The strain grew better and lipid contents were higher at 16~30℃and salinity of 0.9 %~3.6 % (w/v). The adaptive responses of this microbe to temperature and salinity were mainly to regulate the degree of fatty acid unsaturation to maintain the ideal membrane lipid physical state. Compared with temperature and salinity, effect of pH on DHA production was lighter, and only the cell biomass showed some shift with the changed pH.In order to prevent oxidation of dried cells of Schizochytrium limacinum during production, process and transportation and prong the storage period, three antioxidants—Vitamin C, Vitamin E and TBHQ were added into dried cells of Schizochytrium limacinum at 25℃in the dark. According to the change of POV and the effects of three antioxidants on the dried cells of Schizochytrium limacinum, we chose the optimal combination of antioxdants to do the antioxidation experiment at the higher temperature. The result showed that the optimal combination of VC, VE , TBHQ on dried cells of Schizochytrium limacinum was 2.0 mg/g, 1.0 mg/g and 0.1 mg/g. We found that the dried cells of Schizochytrium limacinum were not oxidized within 8 months after VC, VE and TBHQ were added to them.