Reprogramming yeast metabolism for customized starch-rich micro-grain through low-carbon microbial manufacturing

Abstract

Starch is a primary food ingredient and industrial feedstock. Low-carbon microbial manufacturing offers a carbon-neutral/negative arable land-independent strategy for starch production. Here, we reconfigure the oleaginous yeast as a starch-rich micro-grain producer by rewiring the starch biosynthesis and gluconeogenesis pathways and regulating cell morphology. With the CO₂ electro-synthesized acetate as the substrate, the strain accumulates starch 47.18% of dry cell weight. The optimized system renders spatial-temporal starch productivity (243.7 g/m²/d) approximately 50-fold higher than crop cultivation and volumetric productivity (160.83 mg/L/h) over other microbial systems by an order of magnitude. We demonstrate tunable starch composition and starch-protein ratios via strain and process engineering. The engineered artificial strains adopt a cellular resources reallocation strategy to ensure high-level starch production in micro-grain and could facilitate a highly efficient straw/cellulose-to-starch conversion. This work elucidates starch biosynthesis machinery and establishes a superior-to-nature platform for customizable starch synthesis, advancing low-carbon nutritional manufacturing.