Effects of Lignin Contents and Delignification Methods on Enzymatic Saccharification of Loblolly Pine

Softwood pulp is more recalcitrant toward enzymatic hydrolysis than hardwood or nonwood pulps. Pulps of various kappa numbers were prepared from loblolly pine chips by kraft cooking, which was followed by delignifying with oxygen/NaOH, chlorine dioxide, or ozone to lower lignin levels. These pulps were subject to enzymatic saccharification to investigate the effects of lignin content and delignification methods. Kappa number is not a good indication of lignin content of chlorine dioxide- and oxygen-delignified pulps. Both the lignin content of the pulp and the method of delignification affect enzymatic saccharification. Decreasing lignin content of a given pulp improves saccharification efficiency. The delignification methods have a profound influence on enzymatic hydrolysis efficiency, with chlorine dioxide- and oxygen-delignified pulps being more efficient than ozone-delignified and kraft pulps. X-ray photoelectric spectroscopy analysis shows that the surface lignin content of the pulp may account for the difference between the three methods of oxidative delignification.