Evaluation of Secondary Acid and Enzymatic Hydrolysis of Hemicellulose in Hot Water Pre-Pulping Extract of Mixed Hardwoods

Abstract

Pre-pulping extracts were found to contain a dilute amount of xylo-oligosaccharides and acetic acid as the major components, and many minor components including other organic acids, lignin-derived phenolics, and sugar degradation products. Once separated from the pulp, a secondary hydrolysis step was required to hydrolyze oligomeric hemicellulose sugars into monomeric sugars before fermentation. The following study detailed the extent of hemicellulose recovery by pre-pulping using hot water extraction and characterized the hydrolysis of the extract with respect to comparing acid and enzymatic hydrolysis. The secondaryhydrolysis of hot water extracts made at an H-Factor of 800 was tested for a variety of acid and enzyme loading levels using the sulfuric acid and xylanases. The maximum fermentable sugar yield from acid and enzyme hydrolysis of the extract was 18.7 g/<TEX>${\ell}$</TEX> and 17.7 g/<TEX>${\ell}$</TEX> representing 84.6% and 80.1% of the maximum possible yield, respectively.