The effects of six pretreatments of five agricultural wastes (corn cob, pineapple waste, bagasse, rice straw and water
hyacinth) on the chemical composition and total reducing sugar yield were investigated. Six pretreatments were: 1% NaOH
with ultrasound for 60 min; 1% NaOH with ultrasound 100% duty; 2% NaOH with ultrasound for 60 min; 2% NaOH
with ultrasound 100% duty cycle; 1% NaOH by standing in the oven at 60°C for 90 min; and 2% NaOH by standing
in the oven at 60°C for 90 min. Among them, the highest cellulose content of 55.15% was obtained from bagasse by
pretreating with 1% NaOH with ultrasound 100% duty cycle. It subsequently yielded the highest total reducing sugar of
36.21% (36.21 g reducing sugar/100 g substrate). The lignin content of all samples significantly decreased, but ultrasonic
pretreatment increased the cellulose content. However, the best pretreatment method for each sample was different. Based
on SEM analysis, the morphologies of all samples were changed after pretreatment. In addition, the increase of enzyme
loading from 250 to 550 CMC U/g biomass led to more than 20% increase in the total reducing sugar. It was found that
the higher enzyme loading (700 CMC U/g dried biomass) did not improve the total reducing sugar for all samples.