Effect of Pretreatments on the Production of Fermentable Sugars from Rice Husk

Cheoh, Angela (2018) Effect of Pretreatments on the Production of Fermentable Sugars from Rice Husk. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

This research was carried out to investigate the effect of different pretreatment methods on the efficiency of enzymatic hydrolysis of rice husk for fermentable sugars production. Initially, the rice husk was pretreated with hydrochloric acid (HCl), citric acid (C6H8O7), sodium hydroxide (NaOH) and sodium hydrogen carbonate (NaHCO3) respectively at different concentrations [5% (w/v), 10% (w/v), 15%(w/v)] and temperatures (60ºC, 100ºC, 130ºC) for 60 minutes. Then, the pretreated rice husks were enzymatic hydrolysed and the best pretreatment was selected based on the highest glucose yield. Lastly the fermentability of rice husk hydrolysate was determined via Saccharomyces cerevisiae fermentation. According to the experimental results, 15% (w/v) NaOH and 15% (w/v) NaHCO3 at 130ºC pretreatment provided the highest glucose yield at 14.598 ± 0.168g/L and 14.325 ± 0.281g/L respectively. Among the tested methods, NaOH pretreated rice husk underwent the highest loss (86.0 ± 3.4%), followed by NaHCO3-, C6H8O7- and HCl- pretreated rice husks. High weight loss indicates better delignification. This result was verified by FTIR and SEM analysis. Lignin and hemicellulose removal after alkaline pretreatments ease the enzymes penetration during enzymatic hydrolysis, hence produced high fermentable sugars yield. Through yeast S. cerevisiae fermentation, ethanol yield from the hydrolysate of NaOH-pretreated rice husk (18.668 ± 0.026g/L) was higher than those produced from hydrolysate of NaHCO3-pretreated rice husk (17.758 ± 0.046g/L). Thus, this study proved that 15% (w/v) NaOH pretreatment at 130oC for 60 minutes is the best pretreatment for rice husk to enhance fermentable sugars production.