Diluted Sulphuric Acid Hydrolysis of Destarched Sago Fibre assisted with Selected Pre-treatments for Glucose and Xylose Production

Abstract

In Sarawak, Malaysia, approximately 7 t of sago fibre waste is produced daily from a single sago starch processing mill and it is currently disposed of either directly into a river nearby or in open spaces. On a dry basis, sago fibre contains 58% starch, 23% cellulose, 9.2% hemicellulose and 4% lignin. Our previous study used the trapped starch of sago fibre as a substrate for producing glucose through an enzymatic hydrolysis process in which the destarched fibre (DSF) remained unused. This study represents an attempt to utilise destarched sago fibre (DSF) as a raw material for glucose and xylose production. The DSF initially underwent a pre-treatment process via dilute sulphuric acid hydrolysis to liberate xylose for which four parameters were studied: the solid-to-liquid ratio (5:100-40:100), the dilute sulphuric acid concentration (0% (v/v) - 9% (v/v)), reaction time (30, 60 and 90 minutes) and the effects of steaming and microwave pre-treatment. Steaming pre-treatment led to the highest xylose (28.19 ± 0.78 g/L) and glucose (78.63 g/L ± 0.22 g/L) production, for which the dilute sulphuric acid concentration was set at 2% (v/v), reaction time was set at 60 minutes. The solid-to-liquid ratio was 30:100. Overall, this work indicates that the optimal pre-treatment of DSF can yield glucose and xylose which can be used to produce bioethanol and xylitol. The study also suggests that DSF can be an alternative raw material for xylitol production.