α-Amyrin is a plant-originated high-valued triterpene that is highly effective against several pathological ailments. α-Amyrin production by engineered Saccharomyces cerevisiae has been achieved by introducing α-amyrin synthase (αAS). However, the low yield of α-amyrin highly limits its industrial application; the low catalytic activity of αAS and the toxic effect of α-amyrin have been considered key elements. In this study, the highest yield of α-amyrin was obtained in engineered S. cerevisiae by remodeling α-amyrin synthase MdOSC1 and expanding the storage pool. The yield of α-amyrin was increased to 11-fold higher than that of the control by the triple mutant MdOSC1^{N11T/P250H/P373A} obtained based on the modeling analysis. Furthermore, key genes of MVA pathway were overexpressed to provide sufficient precursors, and DGA1 (Diacylglycerol acyltransferase) was overexpressed to expand the intracellular storage capacity. Finally, the as-constructed aAM12 strain produced 213.7 ± 12.4 mg/L α-amyrin in the shake flask and 1107.9 ± 76.8 mg/L in fed-batch fermentation; the fermentation yield was 106-fold higher than that of the original aAM1 strain under the same conditions, representing the highest α-amyrin yield in yeast reported to date. Microbial production of α-amyrin with over 1 g/L will be suitable for commercialization and can accelerate the industrial production of α-amyrin in yeast.

α-香树脂素是一种植物来源的高价值三萜，对多种病理疾病非常有效。通过引入 α-香树脂醇合酶 (αAS)，已经实现了由工程酿酒酵母生产α-香树脂醇。然而，α-香树脂精的低收率极大地限制了其工业应用；αAS 的低催化活性和 α-香树脂醇的毒性作用被认为是关键因素。在这项研究中，通过改造 α-香树脂醇合酶 MdOSC1 并扩大储存池，在工程酿酒酵母中获得了最高的 α-香树脂醇产量。通过三重突变体 MdOSC1 ^{N11T/P250H/P373A}，α-香树脂醇的产量比对照高 11 倍根据建模分析得到。此外，过表达MVA途径的关键基因以提供足够的前体，并过表达DGA1（二酰基甘油酰基转移酶）以扩大细胞内储存容量。最后，构建的 aAM12 菌株在摇瓶中产生 213.7 ± 12.4 mg/L α-香树脂醇，在补料分批发酵中产生 1107.9 ± 76.8 mg/L；在相同条件下，发酵产量比原始 aAM1 菌株高 106 倍，是迄今为止报道的酵母中最高的 α-香树脂素产量。微生物生产 1 g/L 以上的 α-香树脂醇将适合商业化，并可以加速酵母中 α-香树脂醇的工业化生产。