Valorization of brewer’s spent grain by furfural recovery/removal from subcritical water hydrolysates by pervaporation

This work is focused on the development of a sustainable process for the valorisation of the main by-product generated in the brewing industry, the brewer’s spent grain (BSG). A two-step process combining subcritical water treatment and pervaporation (PV) was proposed to hydrolyse the hemicelluloses fraction of this lignocellulosic biomass and further removal/recovery of some of the degradation products of sugars by using two different organophilic membranes, polydimethylsiloxane (PDMS) and polyoctilmethylsiloxane (POMS) membranes. Specifically, furfural is the dehydration product of pentoses and it is one of the top biomass-based chemicals being an important platform chemical. For synthetic binary mixtures, lower total permeation flux but higher enrichment factors for furfural were determined for POMS. When dealing with subW hydrolysates, POMS membranes yielded the highest furfural recovery, 94.1 %, with permeate concentrations as high as 40 g·L-1. Furthermore, it was assessed that PV is a suitable detoxification method that yielded a retentate nearly free of furfural allowing its use as growth media in the opposite to the subW hydrolysate with inhibitory furfural concentrations for microbial bioprocesses.