Enhancing Enzyme-Mediated Hydrolysis of Mechanical\nPulps by Deacetylation and Delignification

Alkaline\ninduced deacetylation of the hemicellulose combined with\nsubsequent mechanical refining enhanced the enzyme-mediated hydrolysis\nof pretreated corn stover. The addition of either NaOH (80 °C)\nor mild KOH (25 °C) to corn stover prior to mechanical refining\nled to greater than 80% deacetylation with the NaOH treatment also\nsolubilizing low-molecular-weight lignin that was enriched in β-O-4\nlinkages with more than 25% and 13% of the total and surface lignin\nremoved, respectively. The influence of deacetylation and delignification\nwere further enhanced when NaOH was supplemented with 3% Na₂SO₃, resulting in 100% deacetylation, 34% delignification,\nand a >20% increase in the hydrolysis yield of the substrate xylan.\nA milder KOH treatment resulted in the retention of more than 95%\nof the lignin within the cellulose rich, water-insoluble fraction\nwith no apparent change in the surface lignin. However, both methods\nresulted in enhanced xylan hydrolysis when treated with xylanases,\nsuggesting that deacetylation had enhanced accessibility to the xylan\npresent in the pretreated of corn stover. It was apparent that cellulose\naccessibility was also enhanced by partial delignification, as NaOH\ntreatment resulted in a 65% and 43% increase in the Water Retention\nValue and Directed Orange dye adsorption, respectively.