Table_1_Efficient Production of Pyruvate Using Metabolically Engineered Lactococcus lactis.XLSX

Microbial production of commodity chemicals has gained increasing attention and most of the focus has been on reducing the production cost. Selecting a suitable microorganism, which can grow rapidly on cheap feedstocks, is of key importance when developing an economically feasible bioprocess. We chose Lactococcus lactis, a well-characterized lactic acid bacterium, as our microbial host to produce pyruvate, which is a commodity chemical with various important applications. Here we report the engineering of Lactococcus lactis into becoming an efficient microbial platform for producing pyruvate. The strain obtained, FS1076 (MG1363 Δ3ldh Δpta ΔadhE Δals), was able to produce pyruvate as the sole product. Since all the competitive pathways had been knocked out, we achieved growth-coupled production of pyruvate with high yield. More than 80 percent of the carbon flux was directed toward pyruvate, and a final titer of 54.6 g/L was obtained using a fed-batch fermentation setup. By introducing lactose catabolism into FS1076, we obtained the strain FS1080, which was able to generate pyruvate from lactose. We then demonstrated the potential of FS1080 for valorizing lactose contained in dairy side-streams, by achieving a high titer (40.1 g/L) and high yield (78.6%) of pyruvate using residual whey permeate (RWP) as substrate. The results obtained, show that the L. lactis platform is well-suited for transforming lactose in dairy waste into food-grade pyruvate, and the yields obtained are the highest reported in the literature. These results demonstrate that it is possible to achieve sustainable bioconversion of waste products from the dairy industry (RWP) to valuable products.

微生物生产大宗化学品日益受到关注，其中大部分研究集中于降低生产成本。在开发经济可行的生物工艺过程中，选择一种能够在廉价原料上快速生长的适宜微生物至关重要。本研究选取了已充分表征的乳酸杆菌——乳酸乳杆菌（Lactococcus lactis）作为我们的微生物宿主，以生产丙酮酸，这是一种具有多种重要应用的大宗化学品。在此，我们报道了将乳酸乳杆菌工程化，使其成为高效微生物平台生产丙酮酸的工程。获得的菌株FS1076（MG1363 Δ3ldh Δpta ΔadhE Δals）能够将丙酮酸作为唯一产物进行生产。由于所有竞争途径均已敲除，我们实现了与生长耦合的丙酮酸高产量生产。超过80%的碳流被引导至丙酮酸，在分批发酵装置中，最终获得了54.6 g/L的丙酮酸浓度。通过将乳糖代谢引入FS1076，我们获得了菌株FS1080，该菌株能够从乳糖中生成丙酮酸。随后，我们通过使用残留乳清渗透液（RWP）作为底物，实现了丙酮酸的高浓度（40.1 g/L）和高产量（78.6%），从而展示了FS1080在增值乳制品副产物中的潜力。所获得的结果表明，乳酸乳杆菌平台非常适合将乳制品废物中的乳糖转化为食品级丙酮酸，且所获得的产量在文献中报道的最高。这些结果证明，将乳制品工业的废物（RWP）可持续生物转化为有价值的产物是可行的。