Biotechnological valorization of levulinic acid as a non-sugar feedstock: New paradigm in biorefineries

Due to the severe climate crisis, biorefineries have been highlighted as replacements for fossil fuel-derived refineries. In traditional sugar-based biorefineries, levulinic acid (LA) is a byproduct. Nonetheless, in 2002, the US Department of Energy noted that LA is a significant building block obtained from biomass, and the biorefinery paradigm has shifted from being sugar-based to non-sugar-based. Accordingly, LA is of interest in this review since it can be converted into useful precursors and ultimately can broaden the product spectrum toward more valuable products (e.g., fuels, plastics, and pharmaceuticals), thereby enabling the construction of economically viable biorefineries. This study comprehensively reviews LA production techniques utilizing various bioresources. Recent progress in enzymatic and microbial routes for LA valorization and the LA-derived product spectrum and its versatility are discussed. Finally, challenges and future outlooks for LA-based non-sugar biorefineries are suggested.