Alkaline pretreatment for practicable production of ethanol and xylooligosaccharides

Abstract

AbstractThe economics for production of secondgeneration (2G) ethanol from sugarcane bagasse in large scale, competing with the cogeneration of electric energy, is still not consolidated. In this scenario, the key for feasibility may be the biorefinery concept, a multiproduct industry using biomass fractions to produce energy, chemicals and by-products. Xylooligosaccharides (XOS) are oligomers of xylose often used as additives in food, animal feeds, and drugs. The effect of NaOH pretreatment on the recovery of xylan for XOS production from sugarcane bagasse under different conditions, namely 121°C, 4-7% NaOH loading, was investigated. The best condition was 4% NaOH and 60 min of reaction, achieving 55% of xylan extraction, without monomer production. In order to produce XOS, soluble and immobilized xylanases were used to hydrolyze commercial birchwood xylan (as control) and the sugarcane bagasse xylan. The immobilized endoxylanase produced XOS with 37% of xylobiose and 20% of xylotriose (w/w). The small production of xylose clearly indicated the purity of the xylan extracted from sugarcane bagasse. The biocatalyst had more than 90% of its activity preserved after 5 reaction cycles. The results showed the suitability of sugarcane bagasse as a raw material for production of ethanol and of XOS using immobilized xylanase.