Enhancing the fermentability of brewer’s spent grains to short- and medium-chain carboxylates through dilute alkaline pretreatment

The substitution of fossil resources with renewable carbon requires the development of cost-efficient treatments and conversion processes for biomass. Brewer’s spent grains (BSG) are low-cost organic residues from the agroindustry. The valorization of BSG has been investigated to produce carboxylates through acidogenic fermentation. However, the high lignocellulose content of BSG limits their fermentability. This study examines moderate-temperature dilute alkaline pretreatments of BSG to improve their fermentability and their conversion to short- and medium-chain carboxylates (SCC and MCC) using mixed microbial fermentation. Room temperature and 80 °C pretreatments for 40 or 120 min with a KOH concentration of 0.25 M or 0.5 M were tested. The KOH added for pretreatment was then successfully neutralized by sparging CO2 to adjust the pH to 6 prior the fermentation. The alkaline pretreatment increased the BSG to carboxylate conversion yield from 15 to 21