Agroindustrial waste streams such as sugar beet pulp (SBP) are rich in underutilized uronic acids, representing an abundant yet valuable source of renewable carbon. Here, we report a modular biocatalytic system using cellulose-immobilized enzyme cascades under continuous flow to produce polymer precursors at the gram scale from waste-derived feedstocks. Key to this process is the fusion of uronate dehydrogenase and ene reductase enzymes with engineered cellulose-binding domains (CBDs), allowing efficient co-immobilization on cellulose supports. These enzymes achieved >95% conversion of uronic acids and retained activity over eight continuous flow cycles. The system operates under mild aqueous conditions and integrates in-line cofactor recycling and product extraction, enabling the production of building blocks in up to 97% isolated yields. The resulting diacid and lactone products were further transformed into (poly)esters and (poly)amides with potential applications in bioplastics, surfactants, and functional materials. This modular, flow-compatible biocatalytic strategy provides a generalizable route for valorizing uronic acid-rich waste streams, advancing strategies for biomanufacturing.
Wang et al. (Tue,) studied this question.