Abstract
BackgroundNew biorefinery concepts are necessary to drive industrial use of lignocellulose biomass components. Xylan recovery before enzymatic hydrolysis of the glucan component is a way to add value to the hemicellulose fraction, which can be used in papermaking, pharmaceutical, and food industries. Hemicellulose removal can also facilitate subsequent cellulolytic glucan hydrolysis.ResultsSugarcane bagasse was pretreated with an alkaline-sulfite chemithermomechanical process to facilitate subsequent extraction of xylan by enzymatic or alkaline procedures. Alkaline extraction methods yielded 53% (w/w) xylan recovery. The enzymatic approach provided a limited yield of 22% (w/w) but produced the xylan with the lowest contamination with lignin and glucan components. All extracted xylans presented arabinosyl side groups and absence of acetylation. 2D-NMR data suggested the presence of O-methyl-glucuronic acid and p-coumarates only in enzymatically extracted xylan. Xylans isolated using the enzymatic approach resulted in products with molecular weights (Mw) lower than 6 kDa. Higher Mw values were detected in the alkali-isolated xylans. Alkaline extraction of xylan provided a glucan-enriched solid readily hydrolysable with low cellulase loads, generating hydrolysates with a high glucose/xylose ratio.ConclusionsHemicellulose removal before enzymatic hydrolysis of the cellulosic fraction proved to be an efficient manner to add value to sugarcane bagasse biorefining. Xylans with varied yield, purity, and structure can be obtained according to the extraction method. Enzymatic extraction procedures produce high-purity xylans at low yield, whereas alkaline extraction methods provided higher xylan yields with more lignin and glucan contamination. When xylan extraction is performed with alkaline methods, the residual glucan-enriched solid seems suitable for glucose production employing low cellulase loadings.
Highlights
New biorefinery concepts are necessary to drive industrial use of lignocellulose biomass components
Alkaline‐sulfite pretreatment and xylan extraction Sugarcane bagasse was pretreated in a biorefinery concept designed to recover hemicellulose in polymeric form before enzymatic hydrolysis of the glucan component
Xylan removal during pretreatment was lower than usually reported for this process (25–30%) [5], confirming that unwashed solids retained more hemicelluloses
Summary
New biorefinery concepts are necessary to drive industrial use of lignocellulose biomass components. Xylan recovery before enzymatic hydrolysis of the glucan component is a way to add value to the hemicellulose fraction, which can be used in papermaking, pharmaceutical, and food industries. Sugarcane bagasse is a valuable lignocellulosic material to produce fuels and chemicals because it is site-available at the current sugar and ethanol mills [1]. Advanced chemical and material applications of sugarcane bagasse components require suitable pretreatment technologies that facilitate efficient valorization. The alkaline-sulfite chemithermomechanical treatment is considered suitable for this purpose because it is a delignification process that retains most of the cellulose and a significant fraction of hemicellulose in the pretreated solids. Efficient sugar production from alkaline-sulfite-pretreated sugarcane bagasse was obtained by simultaneous enzymatic hydrolysis of cellulose and hemicelluloses [5, 9, 11]. Yeasts currently used in industrial fermentation processes do not efficiently ferment the blend of hexoses and pentoses, resulting in carbohydrate losses in the final product [12, 13]
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