Integrated Process of Arabinose Biopurification and Xylitol Fermentation Based on the Diverse Action of Candida boidinii

Agricultural and agro-industrial residues (agro-residues) containing high amounts of carbohydrates, such as cellulose and hemicellulose, are produced in large amounts annually worldwide.1,2 Agro-residues are attractive raw materials of biorefinery processes producing value-added products due to their relatively low commercial value, renewability and abundant availability.3 Biorefining of agro-residues for biofuel and bioproducts does not compete with food production and is considered to be advantageous from the environmental point of view, as it contributes to waste management, and its products can replace fossil-derived ones.4,5 One of the most important steps in lignocellulose-based biorefining technologies is the fractionation of the lignocellulosic biomass into its core constituent (hemicellulose, cellulose and lignin). Several studies proved the applicability of dilute acid-catalysed hydrolysis to selectively solubilise the hemicellulose fraction, therefore it is widely used as part of lignocellulose fractionation.2,3 Hemicellulosic hydrolysates containing high amounts of xylose have great potential as a raw material for microbial xylitol production1, while hemicellulosic hydrolysates with considerable amounts of arabinose might be suitable for arabinose production.6 L-Arabinose can be used as a non-caloric sweetener in the food industry; moreover, it strongly inhibits intestinal sucrase uncompetitively and consequently inhibits the absorption of sucrose in the small intestine, which makes it a promising sugar substitute in treatment of diabetes.6,7 L-Arabinose can be utilized for bacterial diagnostics,8 as a starting material in the synthesis of non-ionic surfactants9 and as intermediate for antiviral drug synthesis.10 Commercial production of L-arabinose is a complex process consisting of acid hydrolysis of gum arabic, followed by multiple procedures of purification.6 The relatively high cost of gum arabic and the expensive purification steps result in the high cost of pure arabinose,11 which has evoked an increasing research effort to develop new cost-effective methods of arabinose production from agro-residues rich in hemicellulose or pectin, for example from sugar beet pulp,11 corn hull,12 xylose-mother liquor,6 wheat bran13 and corn fibre.14 Biopurification of hemicellulosic hydrolysate is an interesting and inexpensive strategy to produce a pure arabinose solution through the depletion of other sugars (e.g. glucose, xylose, galactose) using Integrated Process of Arabinose Biopurification and Xylitol Fermentation Based on the Diverse Action of Candida boidinii