Metabolic coupling of acetate promotes xylose utilization in Kluyveromyces marxianus

Abstract

Lignocellulosic biomass is a typical agriculture waste and a potential feedstock for the green biomanufacturing. However, insufficient utilization of carbon sources caused by inhibitors, especially acetic acid, hinders the economic bioconversion. Here, we demonstrated the acetate metabolic pathway via glyoxylate shunt in nonconventional yeast Kluyveromyces marxianus. Acetate metabolism increased to 122.7 % at 40 °C after overexpressing ICL1 and MLS1, key genes of glyoxylate shunt revealed by transcriptomic data. Strengthening GPD2 and FDH1 further enhanced the robustness of the K. marxianus, acetate metabolism was significantly increased. Finally, the modified K. marxianus 1727–5-ICL1-MLS1-GPD2-FDH1 boosted the efficiency for xylose uptake up to 1.3 folds in non-detoxified lignocellulosic hydrolysate, benefiting from a 3.9-fold increase in acetate consumption. Our results propose a novel strategy for xylose assimilation by coupling acetate metabolism, contributing the bioconversion of sustainable lignocellulosic biomass. It also provides a new scheme for the total carbon utilization of lignocellulosic biomass, including carbon dioxide (CO2) released from the biofuel production to achieve a circular economy.