Feasibility assessment of bioethanol production from humic acid-assisted alkaline pretreated Kentucky bluegrass (Poa pratensis L.) followed by downstream enrichment using direct contact membrane distillation

The effective fractionation of structural components of abundantly available lignocellulosic biomass is essential to unlock its full biorefinery potential. In this study, the feasibility of humic acid on the pretreatment of Kentucky bluegrass biomass in alkaline condition was assessed to separate 70.1% lignin and hydrolyzable biocomponents. The humic acid-assisted delignification followed by enzymatic saccharification yielded 0.55 g/g of reducing sugars from 7.5% (w/v) pretreated biomass loading and 16 FPU/g of cellulase. Yeast fermentation of the biomass hydrolysate produced 76.6% (w/w) ethanol, which was subsequently separated and concentrated using direct contact membrane distillation. The hydrophobic microporous flat-sheet membrane housed in a rectangular-shaped crossflow module and counter-current mode of flow of the feed (hot) and distillate (cold) streams yielded a flux of 11.6 kg EtOH/m²/24 h. A modular, compact, flexible, and eco-friendly membrane-integrated hybrid approach is used for the first time to effectively valorize Kentucky bluegrass biomass for sustainable production of biofuel.