Traditionally engineered to produce novel bioactive molecules, Type I modular polyketide synthases (PKSs) could be engineered as a new biosynthetic platform for the production of de novo fuels, commodity chemicals, and specialty chemicals. Previously, our investigations manipulated the first module of the lipomycin PKS to produce short chain ketones, 3-hydroxy acids, and saturated, branched carboxylic acids. Building upon this work, we have expanded to multi-modular systems by engineering the first two modules of lipomycin to generate unnatural polyketides as potential biofuels and specialty chemicals in Streptomyces albus. First, we produce 20.6 mg/L of the ethyl ketone, 4,6 dimethylheptanone through a reductive loop exchange in LipPKS1 and a ketoreductase knockouts in LipPKS2. We then show that an AT swap in LipPKS1 and a reductive loop exchange in LipPKS2 can produce the potential fragrance 3-isopropyl-6-methyltetrahydropyranone. Highlighting the challenge of maintaining product fidelity, in both bimodular systems we observed side products from premature hydrolysis in the engineered first module and stalled dehydration in reductive loop exchanges. Collectively, our work expands the biological design space and moves the field closer to the production of “designer” biomolecules.

传统上设计用于生产新型生物活性分子的 I 型模块化聚酮化合物合酶 (PKS) 可以设计为新的生物合成平台，用于生产从头燃料、商品化学品和特种化学品。以前，我们的研究操纵脂霉素 PKS 的第一个模块来生产短链酮、3-羟基酸和饱和的支链羧酸。在这项工作的基础上，我们通过设计脂霉素的前两个模块来生成非天然聚酮化合物作为潜在的生物燃料和白色链霉菌中的特殊化学品，从而扩展到多模块系统. 首先，我们通过 LipPKS1 中的还原环交换和 LipPKS2 中的酮还原酶敲除产生 20.6 mg/L 的乙基酮、4,6 二甲基庚酮。然后，我们表明 LipPKS1 中的 AT 交换和 LipPKS2 中的还原环交换可以产生潜在的香味 3-异丙基-6-甲基四氢吡喃酮。强调保持产品保真度的挑战，在两个双模块系统中，我们观察到来自设计的第一个模块中过早水解的副产物和还原循环交换中的停滞脱水。总的来说，我们的工作扩展了生物设计空间，并使该领域更接近于“设计”生物分子的生产。