裂壶藻脂肪酸合酶途径合成多不饱和脂肪酸的研究

Study on the Synthesis of Polyunsaturated Fatty Acids by Fatty Acid Synthase Pathway of Schizochytrium sp.

裂壶藻作为一种生产DHA的重要菌种,其脂肪酸合成途径除了已经被广泛了解的聚酮合酶（PKS）途径外,还残存着作为真核微生物中常见的脂肪酸合酶（FAS）途径中的功能酶和中间产物。经过前期的研究,运用基因工程手段,将载有与裂壶藻近缘藻种中已知的Δ12-desaturase表达模块和相关筛选标记构建入载体,通过电击转化导入Schizochytrium sp.ATCC20888中,以期望修复裂壶藻中FAS途径的合成能力。通过分子水平检测确定目的功能基因已稳定转化后,再由气相色谱分析转化株油脂中相关脂肪酸含量分布情况。经过长期筛选验证,最终证明获得了两株阳性转化株,其生物量初步测定分别较野生株提高11.14%和4.12%,其油脂中DHA含量分别较野生株提高了19.50%及14.65%。

As an excellent species for the production of DHA,Schizochytrium sp. has two distinct pathways for producing DHA,fatty acid synthase pathway and polyketide synthase pathway,of which fatty acid synthase pathway played limited role in the DHA synthesis process due to its low activity of one or more of the enzymes,resulted in its only responsible for some short chain fatty acid synthesis. In order to enhance the ability of fatty acid synthase pathway for producing DHA in Schizochytrium sp. to improve the DHA content of its oil,the exogenous △12-desaturase expression plasmid with screening markers for Schizochytrium sp. ATCC20888 from the brown algae was constructed,then Schizochytrium sp. were transformed through electroporation. After long-term screening,two positive transformants were obtained by DNA and RNA identification. Their initial biomass measurements were 11. 14% and 4. 12% higher than the wild strains while the DHA content in oils and fats were19. 50% and 14. 65% higher than the wild strains.