Green production of short-chain diols through microbial fermentation and bioconversion: Current advances, challenges, and future perspectives

Short-chain diols (C2-C5) are important platform chemicals used in polymers, textiles, pharmaceuticals, cosmetics, and specialty chemicals. Their conventional petrochemical production is associated with fossil-resource dependence and substantial energy requirements, motivating the development of bio-based alternatives. However, existing knowledge remains fragmented across individual diols, microbial hosts, metabolic pathways, and production technologies, limiting systematic assessment of their relative performance and industrial feasibility. This review addresses these gaps through a product-oriented comparative analysis of microbial production of ethylene glycol, propanediols, butanediols, and pentanediols. It examines metabolic pathway design, host engineering, renewable feedstock utilization, and fermentation strategies, highlighting how precursor availability, intermediate toxicity, redox balance, and cofactor requirements influence product yield, titer, and productivity. The review further evaluates downstream recovery options and their implications for purification costs, alongside reported techno-economic and life-cycle assessment findings. Particular attention is given to the challenges of comparing studies with different process conditions, economic assumptions, and environmental system boundaries. Finally, the review distinguishes comparatively mature bio-based production platforms from emerging pathways and identifies priorities for improving process integration, economic competitiveness, and environmental performance. This integrated perspective provides a basis for evaluating research progress and guiding the development of commercially viable and environmentally sustainable short-chain diol production systems.