产琥珀酸重组解脂酵母发酵副产物乙酸的代谢控制

Control of acetic acid metabolism of recombinant Yarrowia lipolytica for efficient succinic acid production

摘要:

琥珀酸是一种高附加值的有机酸，广泛用于食品、化工和农药领域。解脂酵母Yarrowia lipolytica作为新型强健的非传统酵母，近年来逐渐吸引了研究者的注意。前期通过基因敲除琥珀酸脱氢酶基因构建了一株产琥珀酸的重组解脂酵母PGC01003。由于糖酵解和TCA循环流量不协调，PGC01003分泌大量副产物乙酸，限制了琥珀酸产量的进一步提高。为降低乙酸的溢出，实现自然低pH值发酵生产琥珀酸，首先干扰旁路代谢，异源表达来自鼠沙门氏菌的乙酰辅酶A合酶，乙酸的产量下降至4.6 g/L，比对照降低了24.6%。而基因敲除乙酰辅酶A水解酶基因得到的重组菌PGC11505，发酵96 h乙酸分泌量只有0.4 g/L，琥珀酸产量提高到7.0 g/L，琥珀酸的转化率为0.30 g/g，为进一步构建高产琥珀酸的细胞工厂奠定基础。

Abstract:

Succinic acid is a high value-added organic acid widely used in food, chemical and pesticide industries. As a new robust non-conventional yeast, Yarrowia lipolytica attracts more and more attention due to its potential for industrial applications. Previously, we obtained a succinic acid-producing strain through gene deletion of succinic acid dehydrogenase subunit encoding gene Ylsdh5, resulting in the strain of PGC01003. However, the recombinant strain produced large amount of acetic acid due to imbalance between glycolysis and TCA cycle which hindered the efficient production of succinic acid. PDH bypass was interfered to decrease the overflow of acetic acid and produce succinic acid under natural pH. Acetic acid was reduced to 4.6 g/L through heterologous expression of acetyl coenzyme A synthase from Salmonella enteric, which was 75.4% of the control strain. Deletion of CoA-transferase gene Ylach1 eliminated acetate formation and improved succinic acid production, and the resulting strain produced as high as 7.0 g/L succinic acid. Our study provides foundation for further construction of efficient cell factory of succinic acid production.