Enhancing enzymatic saccharification of water hyacinth through microwave heating with dilute acid pretreatment for biomass energy utilization

Abstract

Water hyacinth, as waste biomass, can potentially replace fossil fuels and address pressing issues of energy shortage and serious environmental pollution. In this study, microwave-assisted dilute acid pretreatment was proposed to enhance the enzymatic saccharification of water hyacinth for biomass energy utilization. After the pretreatment, a large amount of hemicellulose in the pretreated water hyacinth was hydrolyzed into xylose, galactose, and arabinose, whereas only a small amount of cellulose and lignin was hydrolyzed into glucose and propiolic acid, respectively. Increased pretreatment temperature, reaction time, and H2SO4 concentration generated more hemicellulose, cellulose, and lignin degradation products, including monosaccharides and other hydrolyzates, which were further degraded into smaller acids and aldehydes. In the enzymatic hydrolysis step following the pretreatment, a large amount of cellulose was hydrolyzed into glucose and cellobiose, whereas hemicellulose was completely degraded. When 20 g/l of water hyacinth feedstock was subjected to microwave pretreatment with 1% H2SO4 at 140 °C for 15 min and then enzymatically hydrolyzed using cellulase, a maximum reducing sugar yield of 48.3 g/100 g hyacinth was obtained. This value was 94.6% of the theoretical reducing sugar yield.