Production of Xylitol From Sago Lignocellulosic Waste

Destarched sago fibre which contained lignocellulosic material can be exploited for the production of value-added product such as xylitol. Microbial xylitol production has received much attention because of its flexibility in term of adaptation, ease of operation and eco-friendliness. The aim of this study is to produce xylitol from sago lignocellulosic waste by focusing on the pre-treatment technique and fermentation parameters. Pre-treatment parameters such as dilute sulphuric acid concentration (0% (v/v) - 6% (v/v), solid to liquid ratio of hydrolysis system (5:100 – 40:100), hydrolysis process reaction time (30 – 90 minutes) using high-pressure steam pre-treatment, mild hydrothermal pre-treatment, and microwave pre-treatment were studied. The hydrolysate obtained from the selected pre-treatment was characterised and selected for fermentation. In order to obtained the highest xylitol production, fermentation parameters such as inoculum age (9, 18, 27 hours), inoculum concentration (10 – 30%), and effects of yeast extract and peptone were studied. The result revealed that pre-treatment using high pressure steam produced the highest xylose concentration with acid concentration of 2% v/v, reaction time of 30 minutes and solid to liquid ratio 30:100. The acid hydrolysis which was integrated with high pressure steam pre-treatment exhibits highest xylose (11.56 g/L) and glucose (22.51 g/L) production in which the temperature was set at 121℃ and solid to liquid ratio of 30:100. The leftover hydrolysate from pre-treatment of high-pressure steam were then used for xylitol fermentation using C. tropicalis. The inoculum age of 28 hour with inoculum level of 20% was chosen as it consumes glucose and xylose efficiently in the hydrolysate without any supplementation and produces highest xylitol concentration of 0.86 ± 0.11 g/L compared with the control experiments containing commercial xylose and glucose which produced xylitol concentration of 2.56 ± 0.11 g/L. The fermentation of destarched sago fibre hydrolysate with addition of yeast extract significantly increases the consumption of glucose and xylose and produces maximum xylitol production which was 11.75 ± 0.09 g/L which was higher than the control experiment which produced 7.07 ± 0.06 g/L after 60 h of batch fermentation process. This work indicates that the optimal pre-treatment of destarched sago fibre and selected parameter of fermentation of C. tropicalis can influences xylitol production. The studies suggests that destarched sago fibre can be potentially served as an alternative raw material for xylitol production