The use of waste streams and other renewable feedstocks in microbial biosynthesis has long been a goal for metabolic engineers. Microbes can utilize the substrate mixtures found in waste streams, though they are more technically challenging to convert to useful products compared to the single substrates of standard practice. It is difficult to achieve consistent biosynthesis in the face of the temporally changing nature of waste streams. Furthermore, the expression of all the enzymes necessary to convert mixed substrates into a product likely presents significant metabolic burden, which already plagues processes that utilize a single substrate. We developed an approach to utilize mixed feedstocks for production by activating expression of each biosynthetic pathway in the presence of its substrate. This expression control was used for two novel pathways that converted two substrates, galacturonate and gluconate, into a single product, D-glycerate. A production strain harboring both pathway plasmids produced 1.8 ± 0.3 and 1.64 ± 0.09 g L of D-glycerate from galacturonate and gluconate alone, respectively. Fermentations that were fed a mixture of the two substrates, at different ratios, resulted in product titers between 1.48 ± 0.03 and 1.8 ± 0.1 g L. All fermentations were fed a total of 10 g L substrate and there was no statistically significant difference in D-glycerate titer from the single or mixed substrate fermentations. We thus demonstrated consistent D-glycerate biosynthesis from single and mixed substrates as an example of robust conversion of complex feedstocks.

中文翻译：

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从各种混合底物中一致地生物合成 D-甘油酸

在微生物生物合成中使用废物流和其他可再生原料长期以来一直是代谢工程师的目标。微生物可以利用废物流中发现的底物混合物，尽管与标准实践的单一底物相比，将它们转化为有用的产品在技术上更具挑战性。面对废物流随时间变化的性质，很难实现一致的生物合成。此外，将混合底物转化为产物所需的所有酶的表达可能会带来显着的代谢负担，这已经困扰着利用单一底物的过程。我们开发了一种利用混合原料进行生产的方法，通过在底物存在的情况下激活每种生物合成途径的表达。该表达控制用于将两种底物（半乳糖醛酸和葡萄糖酸）转化为单一产物 D-甘油酸的两条新途径。含有两种途径质粒的生产菌株仅从半乳糖醛酸和葡萄糖酸中分别产生 1.8 ± 0.3 和 1.64 ± 0.09 g L 的 D-甘油酸。以不同比例添加两种底物混合物的发酵，产生的产物滴度在 1.48 ± 0.03 和 1.8 ± 0.1 g L 之间。所有发酵总共添加 10 g L 底物，并且 D 没有统计学上的显着差异。 -来自单一或混合底物发酵的甘油滴度。因此，我们证明了单一和混合底物一致的 D-甘油酸生物合成，作为复杂原料稳健转化的一个例子。