Vine shoots pre-treatment strategies for improved hydrogen production and metabolites redistribution in Clostridium butyricum

Abstract

This work deals with the use of vine shoots, a renewable, largely available, lacking of alternatives lignocellulosic material as a feedstock for hydrogen production. Physical pre-treatments by steam explosion (SE), chemical by organosolv (OS) and biological by laccase (LAC) were carried out in vine shoots to disrupt the cell fiber and increase the biomass hydrolysis and fermentation into hydrogen (H2). After SE, there was a slight decrease in cellulose and hemicellulose contents in biomass fibers, while a decrease in lignin content occurred after OS pre-treatment. There were no quantifiable changes after laccase pre-treatment, however the enzyme-substrate oxidative reactions were favorable for hydrolysis and fermentation since an increase in soluble sugars and H2 production was observed with LAC vine shoots as substrate. 300.1 mL H2/L were obtained from raw material vine shoots, while 649.4, 399.8 and 749.7 mL H2/L were obtained from biomass pre-treated by SE, OS and LAC, respectively. Furthermore, the hydrolysis of pre-treated biomass by addition of cellulase was evaluated to improve H2 production. Higher amounts of H2 were obtained from hydrolyzed biomass in relation to non-hydrolyzed ones (154.2%, 602.0% and 167.1% more with SE, OS and LAC hydrolyzed, respectively). In all cases, the mixed acid pathway was carried out by Clostridium butyricum, since acetic and butyric acids were produced.