The antifungal agent amphotericin B (AmB) is a polyketide produced by Streptomyces nodosus. The synthetic precursors of the amphotericin macrolactone skeleton are acetyl-CoA, malonyl-CoA and methylmalonyl-CoA. The genome sequence of the wild type S. nodosus ATCC14899 revealed a type II polyketide synthase (PKS) competing for malonyl-CoA. The same competitive branch was sequenced and verified in a mutant named S. nodosus ZJB2016050 (S. nodosus N3) screened in our lab. The transcriptome of the secondary metabolic synthetic gene cluster comparisons suggested that type II PKS (PKS5) competition is a factor in low production. The deletion of the PKS5 gene led to the titer of AmB improved from 5.01 g/L to 6.32 g/L while the by-product amphotericin A (AmA) reduced from 0.51 g/L to 0.12 g/L. A sequence of genes including PKS amphA, acc1, mme and mcm were overexpressed in a ΔPKS5 mutant, resulting in improved production AmB from 5.01 g/L to 7.06 g/L in shake flasks at 96 h. The yield of AmB and AmA in a 5 L bioreactor at 144 h was 15.6 g/L and 0.36 g/L, respectively. The intracellular reducibility of the wild type, mutagenesis type and genetically engineered type were detected, which was first found to be related to the by-product AmA. The increment of skeleton biosynthesis may consume more NADPH and reduces AmphC ER5 domain reduction. This study can be implemented for other polyketides in industrial production.

抗真菌剂两性霉素B（AmB）是结节链霉菌生产的聚酮化合物。两性霉素大内酯骨架的合成前体是乙酰辅酶A，丙二酰辅酶A和甲基丙二酰辅酶A。野生S. nodosus ATCC14899的基因组序列揭示了竞争丙二酰辅酶A的II型聚酮化合物合酶（PKS）。在一个名为S. nodosus ZJB2016050（S. nodosus的突变体）中对同一竞争分支进行了测序和验证N3）在我们的实验室中筛选。次级代谢合成基因簇的转录组比较表明II型PKS（PKS5）竞争是产量低的一个因素。PKS5基因的缺失导致AmB的效价从5.01 g / L提高到6.32 g / L，而副产物两性霉素A（AmA）从0.51 g / L降低到0.12 g / L。包括PKS amphA，acc 1，mme和mcm的基因序列ΔPKS5突变体中的过表达量在96 h摇瓶中从5.01 g / L提高到7.06 g / L。在144 h，5 L生物反应器中AmB和AmA的产量分别为15.6 g / L和0.36 g / L。检测到野生型，诱变型和基因工程型的细胞内还原性，这首先发现与副产物AmA有关。骨架生物合成的增加可能会消耗更多的NADPH，并减少AmphC ER5结构域的减少。这项研究可用于工业生产中的其他聚酮化合物。