Value addition to sugarcane bagasse: Xylan extraction and its process optimization for xylooligosaccharides production

The effect of alkali viz., sodium hydroxide and potassium hydroxide, on the recovery of xylan from sugarcane bagasse under two different conditions namely overnight incubation at room temperature and autoclaving was investigated. Conditions for the enzymatic cleavage of the extracted xylan leading to the best yields of xylooligosaccharides was investigated using a fixed substrate concentration (2%, w/v) and varied inputs of other critical factors like pH, temperature, enzyme dose and reaction time. The sugarcane bagasse constituted of 98.99 +/- 0.01% organic matter, 35.67 +/- 0.15% cellulose, 23.22 +/- 0.05% hemicellulose, 6.04 +/- 0.06% lignin and 2.3 +/- 0.01% protein. The highest xylan recovery of 85% was attained using 12% sodium hydroxide combined with steam application. Analyses of the enzymatic hydrolyzate showed the presence of XOS of varying degree of polymerization falling in the range of 2-3. The maximum conversion to XOS was observed at temperature of 40 degrees C, pH of 4 with an enzyme dose of 2.65 U and a reaction time of 8 h. The response surface analysis predicted ideal condition viz., temperature 40.99 degrees C, pH 4.92, enzyme dose 3.13 U and reaction time 19.19 h for maximizing xylobiose yield, while for maximum xylotriose yields the ideal variables were 40.37 degrees C, pH 4.13, enzyme dose 5.89 U and an incubation time of 18.14 h. The findings established the suitability of sugarcane bagasse as a raw material for extraction of xylan vis a vis its conversion into XOS. (C) 2012 Elsevier B.V. All rights reserved.