Effect of Dilute-acid Hydrolysis Conditions on Sugar and Productions from Paragrass

Abstract

In this study, the productions of sugars as well as inhibitory compounds, e.g hydroxymethylfurfural (HMF) and furfural, from paragrass (Brachiaria mutica) were investigated using dilute acid hydrolysis. Sulphuric acid concentration of 1.0, 1.2, 1.5 and 2.0 wt% and reaction temperature of 120, 130, 140 and 150 °C for either 30 or 60 min were investigated. Xylose was found to be the major product at a maximum yield of 99±3 mg/g grass using 1.2 wt% H2SO4 and reaction temperature of 140 °C for 30 min. Analysis of variance (ANOVA) showed that for the reaction temperature between 120-140 °C, sulphuric acid concentration was the most important factor affecting the yields of hemicellulose sugars from paragrass. However, the temperature ≥ 150 °C caused the marked drop in all sugar compounds. At the optimal condition, the concentration of HMF was 0.16 g/l and furfural 0.09 g/l. The formation of HMF and furfural was almost linearly increased with increasing hydrolysis temperature between 120 and 150 °C. Furthermore, longer reaction times led to higher levels of HMF and furfural. The dilute acid hydrolysis in series with enzyme saccharification of paragrass yielded 122 mg total reducing sugar (TRS) per g grass in the enzyme hydrolysate.