10-38: Thermostable enzymes for efficient liquefaction and hydrolysis of pretreated lignocelluloses

Thermostable enzymes in lignocellulose hydrolysis have several benefits. At elevated temperatures the reaction rates are higher, potentially reducing processing times and leading to lower energy input and more efficient use of equipment. Increased thermal stabilities are usually connected with higher specific activities, reducing the total amount of enzymes needed and extending the life-time of enzymes.

From the processing point of view, an additional important advantage of thermostable enzymes is the possibility to work at higher solid loadings (decreasing viscosities with increasing temperatures), which leads to substantial savings in investments. The reduced need for freshwater also improves the sustainability of the process. In particular, the distillation costs are sharply reduced as the product concentration is increased and the amount of excess process water is minimized.

In this study, novel thermostable enzymes were characterized from various aspects. The monocomponent preparations were representative examples of the various classes/families of lignocellulose degrading enzymes (three cellobiohydrolases, two endoglucanases, two xylanases, and a β‑glucosidase). The ability to liquefy high-consistency biomasses was studied with a method based on real-time monitoring of substrate viscosity, and using hydrothermally pretreated wheat straw (15 % dry matter) as the substrate. Liquefaction and saccharification efficiencies of the preparations were evaluated and compared. Long-term performance of the enzymes was also studied in tailored mixtures. The advantages of using thermostable enzymes in various process concepts are discussed.