| Hemicelluloses are the second most abundant group of polymers on Earth, after cellulose. Wood is primarily made up of cellulose and hemicelluloses, as well as lignin. While cellulose is a well marketed natural resource used in products such as paper and rayon, the same is not true for hemicelluloses, although they comprise 25-35% of wood. Recently, research has focused on the potential for marketing products derived from hemicelluloses which would greatly increase the economic viability of the pulp and paper industry. The concept of a pulp mill producing a variety of products in addition to pulp is termed an integrated forest biorefinery (IFBR).;In order for hemicelluloses to be converted to value-added chemicals, they must be extracted from the wood and then hydrolyzed into monomeric sugars. Here we compare the acid and enzymatic hydrolysis of birch xylan and extracted hardwood hemicelluloses. Our results show that xylanase from Trichoderma viride is as effective as dilute sulfuric acid at hydrolyzing birch xylan and hardwood hemicelluloses for the conditions studied. The data indicate that the optimal pH is 4.5 and temperature is 30°C. Under these conditions, there is nearly full hydrolysis of the substrate after 24 hrs. At pH 5.6, the hydrolysis time required increases to 48 hrs. Most importantly, xylanase from T. viride hydrolyzes hardwood hemicelluloses at the "near neutral" pH, approximately pH 5.6, which would be used in an IFBR. There appears to be no negative effect of lignin degradation products on the percentage of hemicelluloses that are hydrolyzed. Therefore, enzymatic hydrolysis of hemicelluloses would be as effective and efficient as the acid hydrolysis of hemicelluloses. |
