Enzymatic and alkaline treatment of hardwood dissolving pulp

Dissolving pulp was solubilized in 9% NaOH, resulting in 32% solubilization of the pulp. Most of the pulp hemicelluloses were solubilized during this treatment. During the alkaline treatment the cellulose crystalline form was converted from cellulose I to cellulose II. The alkaline insoluble residue was further treated with cellulases in order to render it more alkaline soluble (two-step process). The cellulose II was readily hydrolysed by Trichoderma reesei endoglucanases. Considerably higher hydrolysis yields and lower viscosities were obtained in the hydrolysis of the alkaline insoluble residue as compared with the original pulp.
Compared with direct enzymatic treatment with subsequent solubilization in alkali, the overall alkaline solubility of the two-step process was slightly higher at the same enzyme dosage. However, when compared at the same hydrolysis levels, slightly lower overall alkaline solubilities were obtained in the two-step method.