外源油脂的添加促进卷枝毛霉脂肪酸的积累

卷枝毛霉（Mucor circinelloides）可利用多种碳源实现脂质积累，不同的碳源对其脂质积累的影响不同。在不改变其它发酵培养条件和碳氮比的情况下，以100%葡萄糖为对照，添加不同比例的外源油脂（大豆油）作为另一种碳源，对其细胞生长和脂质生成的影响进行了研究。采用氯仿-甲醇法提取脂质，通过气相色谱技术（gas chromatography,GC）测定其脂肪酸组成及含量。同时，采用实时荧光定量PCR法检测了与脂肪酸合成相关的脱饱和酶基因在菌株中的表达情况。结果表明：碳氮比不变的情况下，最佳碳源混合比例为葡萄糖35 g/L，大豆油24.3 g/L，该培养基中生长的卷枝毛霉的生物量、脂质含量和脂质产量在发酵前期迅速增长，在发酵后期的增长趋势逐渐平缓，在发酵72 h之后略有下降，其最高生物量、脂质含量和产量分别为19.60 g/L、42.62%和8.35 g/L，而对照组（以葡萄糖为单一碳源）仅为14.72 g/L、34.41%和5.06 g/L。与对照组相比，经混合碳源培养的卷枝毛霉的生物量、脂质含量和产量分别提高了33.15%、23.8%和65.10%，且可以将大豆油中的α-亚麻酸...

Enhanced Fatty Acid Production by Addition of Exogenous Oil in Mucor circinelloides

Mucor circinelloides has the ability to use a wide range of carbon sources to accumulate lipids. The different carbon sources have significantly influenced the total lipids through different metabolic pathways in oleaginous organisms. In the present study, the effects of exogenous oil (soybean oil) at different concentrations as an alternative carbon source on its fungal growth and lipid accumulation were investigated without changing fermentation culture conditions and the original C/N ratio, while using 100% glucose as a control. Total lipids and their fatty acid composition were determined by gas chromatography (GC). Moreover, the expression levels of desaturases genes involved in fatty acid biosynthesis were investigated in the studied strains using real-time fluorescence quantitative PCR. The results showed that a concentration of 35 g/L of glucose mixed with 24.3 g/L of soybean oil were the optimal carbon sources with constant carbon to nitrogen ratio. The biomass, lipid content and lipid yield of M. circinelloides grown in this medium increased rapidly in the early stage of fermentation, and the growth trend gradually slowed down in the late stage of fermentation, decreasing slightly after 72 h of fermentation. It was found that the highest biomass, total lipids, and lipid yields were significantly increased at 19.60 g/L, 42.62%, and 8.35 g/L (33.15%, 23.8%, and 65.10%), respectively. In contrast, the control group (those cultured on glucose as a single carbon source) was only 14.72 g/L, 34.41%, and 5.06 g/L, respectively. The critical step was in which α-linolenic acid (ALA) was stored from the exogenous oil in fungal cells supplying enough soybean oil with mixed substrates for fatty acids synthesis. The overexpression of the △12-desaturase gene in WJ11 significantly (P<0.05) increased, while the overexpression of △9- and △6-desaturases genes was significantly (P<0.05) decreased. This study could provide important insights for further investigation of the effect of other exogenous oils on lipid production by M. circinelloide and other oleaginous fungi.