The industrially relevant biopolymer poly-γ-glutamic acid (γ-PGA) is commonly synthesized using glycerol, citrate, and glutamic acid as carbon sources. In this study, two strains capable of utilizing glucose as sole carbon source for γ-PGA synthesis were constructed. Efficient γ-PGA production was achieved with derivatives of the well-investigated laboratory strain Bacillus subtilis 168, by replacing the native promoter of the PGA synthetase operon with the strong constitutive promoter P_veg or with the xylose-inducible promoter P_xyl. The carbon yield for γ-PGA increased by 129% to 0.131 C-mol C-mol⁻¹ when using glucose as the sole substrate compared to the conventional carbon source mixture glycerol, citrate, and glutamic acid. The characterization of the produced γ-PGA demonstrated a time-dependent molecular weight of 1180–1850 kDa and a d-glutamic acid monomer content of 49–62%. To elucidate the consequences of γ-PGA production, we characterized the engineered strain by metabolomics. While the metabolite concentrations in the TCA cycle leading up to 2-oxoglutarate decreased in γ-PGA producer strains, the glutamic acid concentration was constant, despite the drastic increase in glutamic acid demand. The results are discussed in the context of metabolic regulation and future metabolic engineering strategies to enhance precursor supply for γ-PGA synthesis from glucose.

工业上相关的生物聚合物聚-γ-谷氨酸（γ-PGA）通常使用甘油，柠檬酸盐和谷氨酸作为碳源来合成。在这项研究中，构建了两个能够利用葡萄糖作为γ-PGA合成唯一碳源的菌株。通过用强组成型启动子P _veg或木糖诱导型启动子P _xyl代替PGA合成酶操纵子的天然启动子，用经过充分研究的实验室枯草芽孢杆菌168的衍生物实现了高效的γ-PGA生产。γ-PGA的碳收率增加129％至0.131 C-mol C-mol ^-1与传统的碳源混合物（甘油，柠檬酸盐和谷氨酸）相比，当使用葡萄糖作为唯一底物时。所产生的γ-PGA的表征显示出随时间变化的分子量为1180–1850 kDa，d-谷氨酸单体的含量为49–62％。为了阐明γ-PGA生产的后果，我们通过代谢组学对工程菌株进行了表征。尽管在γ-PGA生产菌株中，TCA循环中导致2-氧代戊二酸的代谢物浓度降低，但尽管谷氨酸需求量急剧增加，但谷氨酸浓度却是恒定的。在代谢调节和未来代谢工程策略的背景下讨论了结果，以增强从葡萄糖合成γ-PGA的前体供应。