Free fatty acids are basic oleochemicals implemented in a range of applications including surfactants, lubricants, paints, plastics, and cosmetics. Microbial fatty acid biosynthesis has gained much attention as it provides a sustainable alternative for petrol- and plant oil-derived chemicals. The yeast Starmerella bombicola is a microbial cell factory that naturally employs its powerful lipid metabolism for the production of the biodetergents sophorolipids (> 300 g/L). However, in this study we exploit the lipidic potential of S. bombicola and convert it from the glycolipid production platform into a free fatty acid cell factory. We used several metabolic engineering strategies to promote extracellular fatty acid accumulation which include blocking competing pathways (sophorolipid biosynthesis and β-oxidation) and preventing free fatty acid activation. The best producing mutant (Δcyp52m1Δfaa1Δmfe2) secreted 0.933 g/L (± 0.04) free fatty acids with a majority of C18:1 (43.8%) followed by C18:0 and C16:0 (40.0 and 13.2%, respectively). Interestingly, deletion of SbFaa1 in a strain still producing sophorolipids also resulted in 25% increased de novo sophorolipid synthesis (P = 0.0089) and when oil was supplemented to the same strain, a 50% increase in sophorolipid production was observed compared to the wild type (P = 0.03). We believe that our work is pivotal for the further development and exploration of S. bombicola as a platform for synthesis of environmentally friendly oleochemicals.

中文翻译：

---

将酵母小球菌的脂质代谢从糖脂重定向到脂肪酸生产。

游离脂肪酸是在多种应用中实施的基本油脂化学制品，包括表面活性剂，润滑剂，油漆，塑料和化妆品。微生物脂肪酸生物合成得到了广泛的关注，因为它为汽油和植物油衍生的化学品提供了可持续的替代方法。酵母菌Staremella bombicola是一家微生物细胞工厂，自然利用其强大的脂质代谢功能来生产槐糖脂（> 300 g / L）。但是，在这项研究中，我们利用了S. bombicola的脂质潜力，并将其从糖脂生产平台转化为游离脂肪酸细胞工厂。我们使用了几种代谢工程学策略来促进细胞外脂肪酸积累，包括阻断竞争途径（槐糖脂生物合成和β-氧化）和防止游离脂肪酸活化。产量最高的突变体（Δcyp52m1Δfaa1Δmfe2）分泌0.933 g / L（±0.04）游离脂肪酸，其中大部分C18：1（43.8％），其次是C18：0和C16：0（分别为40.0和13.2％）。有趣的是，在仍产生槐糖脂的菌株中SbFaa1的缺失也导致从头槐糖脂的合成增加了25％（P = 0.0089），并且当向同一菌株中补充油时，与野生型相比，槐糖脂的产量增加了50％ （P ＝ 0.03）。我们相信，我们的工作对于S的进一步发展和探索至关重要。