A Comprehensive Review on Xylitol Production: Experimental and Theoretical Insights, Research Gaps, and Future Perspectives

Abstract

This review presents an integrated upstream-to-downstream assessment of xylitol production via chemical and biological pathways, with a focus on mechanistic understanding, process limitations, and sustainability. Distinct from previous reviews, this work first provides a comparative evaluation of lignocellulosic feedstocks for xylose extraction, emphasizing the role of hemicellulose content and its direct impact on xylose concentration and hydrolysate quality. Chemical and biological conversions are then critically examined. For chemical pathways, catalytic hydrogenation mechanisms, catalyst systems, reactor configurations, and operating conditions are systematically elucidated. For biological routes, microbial strains, enzymatic pathways, metabolic regulation, and fermentation strategies influencing xylitol yield and productivity are comprehensively discussed. Notably, this is the first review to integrate density functional theory-based investigations into the discussion of xylitol production, providing molecular-level insights to xylose adsorption, ring-opening, and hydrogenation mechanisms. Importantly, unresolved research gaps are systematically identified across all reviewed sections, enabling researchers to readily build upon the presented knowledge and accelerate future experimental and theoretical developments. Finally, recent life cycle assessment and techno-economic studies are reviewed to evaluate the environmental and economic feasibility of renewable xylitol production and to outline future research directions toward sustainable lignocellulosic processes.