Microbial Production of Xylitol from Oil Palm Empty Fruit Bunches Hydrolysate: The Effect of Glucose Concentration

抄録

Xylitol has beneficial health properties and can be found in nature albeit in small quantities. In commercial industries, xylitol is produced via chemical hydrogenation of xylose. This process, however, requires high purity of xylose as the raw material. Biotechnological process offers an alternative xylitol production process, using the hydrolysate of lignocellulosic material such as the agricultural waste oil palm empty fruit bunches (OPEFB) as raw material. This substances may contain glucose beside xylose. The presence of glucose as cosubstrate, in the fermentation medium is also a critical factor that regulates the xylitol production by yeasts. Glucose may repress the activity of the key xylose reductase enzyme involved in the xylose conversion into xylitol resulting in low yields of the product. The purpose of this study was to explore the ability of microorganism to produce xylitol from OPEFB hydrolysate. This paper describes the effect of glucose as the co-substrate in xylitol production by Debaryomyces hansenii ITBCC R85 and further the use of OPEFB hydrolyasate as substrate in xylitol production. This research showed that addition of co-substrate glucose affected the fermentation performance of D. hansenii in producing xylitol. Glucose concentration of 2.5 g/L or concentration ratio of glucose to xylose of 25 % gave the highest yield of xylitol. The fermentation using OPEFB hydrolysate containing glucose to xylose ratio more than 25 % gave lower xylitol yield, addressing the hydrolysis of OPEFB to be optimized further.