In this study,cellulose and xylan were in vitro fermented by pig fecal bacteria.Rapid fermentation(40 h) and extended fermentation(eight weeks)were performed.The properties and ultra-structure changes of post-fermented solid residues were studied.In the end effluent,acetic acid,propionic acid,and butyric acid were observed to be the principal short-chain fatty acids(SCFAs) produced by anaerobic fermentation.Xylan was more accessible to bacteria than cellulose,leading to higher SCFA and lactic acid production.In addition,the crystalline structure of cellulose changed,leading to 16.3% and42.1% increases in crystallinity index for rapid and extended fermentation,respectively.Through this research,a systematic and advanced method to study the degradation chemistry of cellulose and xylan during fermentation was developed.
A significant amount of lignin and hemicellulose are dissolved in the hydrothermal treatment of biomass.The hemicellulose can be recovered and utilized for value-added products.The dissolved lignin can undergo depolymerization and condensation reactions,and interferes with the separation and purification process for hemicellulose recovery.This paper investigated the behavior of the lignin extracted from the hydrothermal pretreatment of bamboo and its contributions to the physical characteristics of the hydrolysate.It was found that the turbidity of the hydrolysate was strongly associated with the lignin fragments and suspended long chain hemicelluloses.As the lignin depolymerization and condensation reactions occurred simultaneously,the dissolved lignin fractions in the hydrolysate increased first and then decreased.The molecular weight(MW)of the dissolved lignin fragments ranged from 3342~5611 g/mol,with mainly guaiacyl(G)and syringyl(S)unit in the structure.
