The potential of steam pretreatment to produce good levels of prebiotic xylo-oligosaccharides from sugarcane bagasse

Agro-industrial residues such as sugarcane bagasse could be used as renewable sources to produce nutraceuticals, chemicals and biofuels. The hemicellulose extracted from these residues can be used to produce xylo-oligosaccharides (XOS) which have been shown to have prebiotic effects and can be used as soluble dietary fiber due to their low caloric value. In the work that will be described various acid catalysed steam explosion conditions were assessed, including cooking time, temperature, dried or wet substrate, type of acid, etc., to result in high XOS yields in the waters soluble component.  The total amount of monomers and oligomers obtained after pre- and post-hydrolysis of the water soluble fraction was assessed as well as the total mass balance. It appeared that the steam pretreatment conditions that resulted in high production of XOS_2-6 (two to six units of xylose) were about 190°C, 0.5% H₂SO₄, 5 min, and of XOS_>6 (XOS with more than six units of xylose) were 150°C, 0.5% H₂SO₄ in 30 min. These conditions also resulted in the selective solubilization of hemicellulose in oligomeric form as more than 35% of the hemicellulosic sugars in the liquid streams was in oligomeric form. Typically, the total carbohydrate recovery (hemicellulose and cellulose) was higher than 90% for most pretreatment conditions. In summary, these results show that steam explosion pretreatment is a potential method for the selective production of XOS from sugarcane bagasse.