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Genetic modification is useful for improving the nutritional qualities of cyanobacteria. To increase the total unsaturated fatty acid content, along with the ratio of ω-3/ω-6 fatty acids, genetic engineering can be used to modify fatty acid metabolism. Synechococcus sp. PCC7002, a fast-growing cyanobacterium, does not contain a Δ6 desaturase gene and is therefore unable to synthesize γ-linolenic acid (GLA) and stearidonic acid (SDA), which are important in human health. In this work, we constructed recombinant vectors Syd6D, Syd15D and Syd6Dd15D to express the Δ15 desaturase and Δ6 desaturase genes from Synechocystis PCC6803 in Synechococcus sp. PCC7002, with the aim of expressing polyunsaturated fatty acids. Overexpression of the Δ15 desaturase gene in Synechococcus resulted in 5.4 times greater accumulation of α-linolenic acid compared with the wild-type while Δ6 desaturase gene expression produced both GLA and SDA. Co-expression of the two genes resulted in low-level accumulation of GLA but much larger amounts of SDA, accounting for as much to 11.64% of the total fatty acid content. 相似文献
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本研究采用总抗氧化能力、DPPH自由基清除能力、亚铁离子螯合能力及总还原力等抗氧化指标评价隐甲藻（Crypthecodinium cohnii）藻渣醇水提取物不同极性萃取物的抗氧化能力，采用分光光度法测定样品中总酚和总黄酮含量。结果表明隐甲藻渣不同极性萃取物均具有一定的抗氧化能力，其中乙酸乙酯相和石油醚相总抗氧化能力和亚铁离子螯合能力较高，水相和正丁醇相的DPPH自由基清除能力和总还原能力较高，且在一定质量浓度范围内存在量效关系。相关性分析结果显示，不同极性萃取物的总多酚含量与DPPH自由基清除能力和总还原能力显著正相关，而总黄酮仅与总抗氧化能力和金属离子螯合能力呈正相关关系，提示除酚类和黄酮类化合物外，可能还含有其他抗氧化成分。本研究表明隐甲藻藻渣具有较好地抗氧化活性，有待合理开发利用，其可能存在的其他抗氧化活性成分也有待于进一步明确。 相似文献
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