Alkaline Pre-treatment and Enzymatic Saccharification of Rice husks for Bioethanol Production

This work was aimed at evaluating and optimizing the production of soluble sugars from bio-fermentation of rice husk using sodium hydroxide as a pre-treatment medium. Different samples of rice husk were pre-treated with 1, 2, 3 and 4% (w/v) sodium hydroxide respectively and allowed to de-lignify at various pre-treatment times of 2, 6, 8 and 24 hours before saccharification by cellulose at 50 o C and pH 4.8 for 48 hours. The amount of reducing sugar produced was determined using spectrophotometric methods and was recorded. High reducing sugar yields recorded at 2, 3 and 4%. NaOH were observed at 2 % with a saccharification yield of 3.373 mg/ml, at 3% with a saccharification yield of 3.74 mg/ml and at 4% with a saccharification yield of 4.31mg/mL. The highest value of reducing sugar yield was obtained at a NaOH concentration of 4.0 (w/v) after a pre-treatment time of 24 hours against other NaOH concentrations. The result obtained suggests that the degree of saccharification is dependent on sodium hydroxide concentration used and time of pre-treatment. The reduction in reducing sugar yield at 1% NaOH may be due to NaOH solubilising lignin which may act as cellulose inhibitor during enzyme hydrolysis of the de-lignified rice husks.