Engineering a Gluconate Bypass Carbon Entry Architecture for Robust Stationary Phase Biomanufacturing.

Abstract

Two-stage bioprocesses which decouple cell growth from product synthesis are an attractive approach to biomanufacturing. However high levels of production in stationary phase cultures often suffer from a progressive decline in metabolism. We demonstrate that in E. coli pyruvate accumulation, an inevitable consequence of high-flux metabolism, acts as a major inhibitor of stationary-phase glucose uptake. To address this limitation, we introduce a redesigned central metabolic architecture, the gluconate-bypass (GBP), which reroutes carbon flux around glucose-6-phosphate to sustain metabolic activity during stationary phase production. This architecture provides two key advantages: it decouples glucose uptake from pyruvate mediated inhibition, enabling prolonged stationary phase productivity, and glucose oxidation intrinsically co-generates the reducing cofactor NADPH to support biosynthetic pathways that require NADPH. We validated this architecture using the NADPH dependent production of L-alanine as a representative case study. Implementation of the GBP metabolism generated a self regulating host that achieved a record alanine titer of 197 g L-1 and extended production longevity by 1.6 fold, resulting in an improved production yield of 94%. Together, these results demonstrate that the GBP metabolism supports robust stationary phase biosynthesis and provides a versatile framework for efficient production of pyruvate derived chemicals.