Enzymatic hydrolysis of loblolly pine: effects of cellulose crystallinity and delignification

摘要

Hydrolysis experiments with commercial cellu-lases have been performed to understand the effects of cell wall crystallinity and lignin on the process. In the focus of the paper are loblolly pine wood samples, which were systematically delignified and partly ball-milled, and, for comparison, Whatman CC31 cellulose samples with different crystallinities. In pure cellulose samples, the percentage of cellulose hydrolysis was inversely proportional to the degree of crystallinity. For the loblolly pine samples, the extent of hydrolysis was low for the fraction with 74-to 149-um particle size, but the ball-milled fraction was hydrolyzed easily. The impact of lignin removal was also influential as demonstrated on progressively delignified wood, i.e., the degree of saccharification increased with lignin removal. On the basis of data of 72 h hydrolysis time on materials with similar crystallinity, the cell wall was found to be eight times less hydrolyzable than Whatman CC31 cellulose. Taken together, cellulose crystallinity and composition are not as important as the ultrastructural changes caused by the disruption of the tightly packed regions of the cell wall that ensued upon acid chlorite delignification.