Biohydrogen production from hemicellulose rich softwood hydrolysate

Abstract

Woody biomass is a significant resource but is rarely considered as a fermentation feedstock due to its recalcitrance to biological attack. For the first time, the softwood hydrolysate rich in galactoglucomannan hemicelluloses was evaluated as a feedstock for biohydrogen and then biomethane production using an integrated dark fermentation and anaerobic digestion approach. A biohydrogen production rate of 497  mL/L/d was obtained under steady state continuous dark fermentation. The volatile fatty acid rich fermentate produced an additional 426 mL/L/d of biomethane with complete mineralisation of most of the hemicellulose sugars present in softwood hydrolysate. The fermentation inhibitors were 75 % to 85 % metabolised in a mixed culture of organisms acclimatised to biohydrogen production conditions. Genome sequencing revealed 34 % of genome abundance from known H₂ producers and 46 % of identified CAZy enzyme abundance are glycosyltransferases that catalyse sugar residues to saccharides. The study demonstrates the future potential of using woody biomass hydrolysates as a fermentation feedstock.