Pretreatment and enzymic saccharification of water hyacinth cellulose

Abstract

► Water hyacinth was pretreated, for removal of lignin under variable conditions. ► Combined pretreatment with 0.1% NaClO 2 and peracetic resulted in removal of 99.3% of lignin. ► Under these conditions, the recovered cellulose content was 96%. ► Cellulase hydrolysis using 20 FPU/g substrate this sample showed 90% saccharification with 80.8% cellulose conversion. ► Addition of cellobiase to the reaction mixture increased cellulose conversion and saccharification by 10%. Water hyacinth was pretreated, under variable conditions, with NaOH, alkaline H 2 O 2 , peracetic acid and sodium chlorite. Combined pretreatments included sodium chlorite with each of NaOH, alkaline H 2 O 2 and peracetic acid. Combined pretreatment with 0.1% NaClO 2 for 1 h at 100 °C and peracetic acid at 100 °C for 15 min afforded the most promising sample. The recovered lignin, cellulose and hemicellulose of this sample was 2.56%, 96.69%, and 81.38%, respectively. The same sample, by cellulase hydrolysis showed the highest cellulose conversion (80.8%) and 90% saccharification using 200 FPU/g substrate. Some ambient factors affecting saccharification of pretreated water hyacinth were investigated. Enzymic saccharification after 6 h was about 50% of that at 48 h, indicating a slow hydrolysis rate by time. Addition of 8% glucose at the beginning of the enzymic hydrolysis decreased the saccharification to about its half while addition of 8% ethanol brought about complete inhibition of the enzyme. Addition of cellobiase to the reaction mixture increased cellulose conversion and saccharification by 10%.