Substrate consumption and hydrogen production via co-fermentation of monomers derived from carbohydrates and proteins in biomass wastes

Fermentative hydrogen production from biomass wastes is a promising technology combining waste treatment and clean fuel production. Biomass wastes have various types and components, while the fundamental fermentation reactions involve monosaccharides and amino acids. In this study, typical monosaccharides (glucose and xylose) and amino acids (glutamic acid, aspartic acid, serine, glycine, arginine and alanine) were mixed and fermented by anaerobic fermentative bacteria (AFB) obtained from heat pre-treated anaerobic digestion sludge, to directly examine the substrate consumption and hydrogen production during the co-fermentation of monosaccharides and amino acids. Hydrogen was mainly produced from the fermentation of monosaccharides, but not from the fermentation of amino acids. Monosaccharide consumption generally preceded amino acid consumption. Glucose was more readily utilised by AFB than xylose. The maximum volumetric hydrogen productivity and production rate from the co-fermentation of glucose and mixed amino acids was 2.7 times and 3.1 times higher than those from the co-fermentation of xylose and mixed amino acids. Glutamic acid, serine and alanine were more readily utilised by AFB than aspartic acid, glycine and arginine. The co-fermentation of monosaccharides and amino acids showed efficient energy conversion and carbon conversion, with the maximum efficiencies of 83.3% and 93.3%, respectively.