Microbial Conversion of Lignocellulosic Resources to Energetic Molecules: Bottlenecks and Prospects

This paper provides a comprehensive overview of microbial and thermal conversion routes for lignocellulosic feedstocks into energetic molecules. It first describes physico-chemical pretreatments and enzymatic hydrolysis steps needed to produce fermentable hydrolysates, and the fermentation by yeasts or bacteria to obtain liquids (ethanol, lipids) or gases (hydrogen). Thermochemical processes such as pyrolysis and gasification are also covered, with focus on syngas composition and downstream synthesis. The review highlights scientific and technological bottlenecks—low initial carbon concentration, inhibitor generation, gas–liquid mass transfer constraints, and poor carbon-to-product yields—and discusses ongoing developments in genetically engineered strains, novel bioprocess designs, and integrated valorization and recycling of residues to enhance economic and environmental viability.