Hemp hurds biorefining for chemicals productions. Chemical characterization, organosolv fractionation and enzymatic depredation for sugars exploitation

Lignocellulosic biomass has been highlighted to be a sustainable and renewable feedstock for fossil source replacement. As in the petroleum refinery, the challenges are in making the cellulose fraction accessible to enzymes during enzymatic hydrolysis and maximizing the utilization of all the constituents within the feedstock. In a biorefinery facility the fermentation of the saccharidic fraction to liquid fuels or chemicals provide the gross value, whereas the valorization of the others constituents help to make the process economically viable. In this work the effective fractionation of hemp hurds (HH) into its three main components, cellulose, hemicellulose, and lignin, has been obtained by means of an organosolv pretreatment step followed by enzymatic hydrolysis of the pretreated HH. The effect of different process variables and the kinetic of enzymatic hydrolysis have been studied; the two steps were optimized to yield the highest amounts of fermentable monomeric xylose (from hemicellulose, C5) and glucose (from cellulose, C6). The aptness of C5 and C6 streams has been evaluated, in a fermentation process, by producing butanol and lactic acid, two of the most valuable platform chemicals for biorefinery. In particular, 42 g of polymer-grade lactic acid has been obtained from 100 g of raw HH. These results can be considered promising for HH valorization through the biorefinery concept