中文摘要：

培养温度对裂殖壶菌产油脂中二十二碳六烯酸（Docosahexaenoic acid，DHA）含量以及超氧化物歧化酶（Superoxide dismutase，SOD）表达水平均有重大影响。细胞干重测定和气相质谱联用法检测了不同温度下裂殖壶菌Schizochytrium sp．FJU-512的生长和脂肪酸组成，荧光定量PCR法比较各温度下SOD mRNA表达量。结果表明，低温有利于DHA的合成，低温胁迫下SOD mRNA表达量最高。探讨裂殖壶菌耐低温胁迫的机制可能是低温增加培养基中溶解氧水平，氧化应激造成SOD的高表达，加快活性氧自由基的清除，促进DHA等不饱和脂肪酸的积累，增强膜的流动性以适应低温环境。其次，从DHA高产菌株裂殖壶菌Schizochytrium sp．FJU-512 EST文库筛选出SOD基因，并应用生物信息学分析该氨基酸序列。

英文摘要：

The cultural temperatures had much effect on docosahexaenoic acid （DHA） content in total lipid extracted from dried cell with different superoxide dismutase （SOD） expression levels. The growth and fatty acid composition of Schizochytrium sp. FJU- 512 at different cultural temperatures were determined by dried cell and GC-MS. The expression level of SOD mRNA at different temperatures was compared by fluorescence quantitative.PCR. The results showed that low temperature was beneficial to DHA biosynthesis in marine Schizochytrium and the SOD mRNA increased to maximum at low temperature. The mechanism of Schizochytrium adapting to low temperature stress may be that the low temperature made oxygen easy to dissolve in cul- tural medium enhancing SOD expression that could improve the removal of reactive oxygen species. Unsaturated fatty acids were accumulated to maintain the mobility of membrane under the condition of low temperature. SOD gene was screened in FAST library based on cDNAs extracted from cells of strains Schizochytriurn sp. FJU-512 highly produces DHA. The amino sequence of SOD was analyzed by bioinformatics.