Investigation of enzyme mechanisms for total hydrolysis of cellulosic materials for recycling purposes

This project will elucidate the mechanism of cellulose degrading enzymes for total hydrolysis of cellulose moieties contained in process side streams and wastes. Cellulose is the most abundant biodegradable and renewable polymer with an annual production of approximately 1.5 · 1011 tons. Besides the use of cellulose as construction material, cellulose fibers are the raw material for the paper and pulp industry and are also widely used in the textile industry as natural textile fibers. There are basically four enzyme types that act synergistically in the degradation of cellulose: Endoglucanases, cellobiohydrolases, cellobiases and polysaccharide monooxygenases (LPMOs). Endoglucanases are able to cleave cellulose fibers randomly and preferably at amorphous regions. Cellobiohydrolases are exoglucanases and split glyosidic bonds from the ends of cellulose fibers, releasing the disaccharide Cellobiose. Cellobiose is then hydrolyzed by cellobiases ({beta}-glucosidases) to glucose. Polysaccharide monooxygenases introduce carboxyl groups in crystalline areas of cellulose, which enables cellulases to attack these areas. The addition of LPMOs makes the degradation of cellulose much faster. All these enzymes carry so-called binding modules to target the enzymes to cellulose, which, however, can also lead to non-target adsorption of other components in blended materials The generated glucose is an excellent carbon source and can be used for the biotechnological production of new products in a biorefinery, e.g. for the fermentation of biopharmaceuticals, chemicals or the production of bioethanol. In this project commercial enzyme cocktails will be investigated for the recovery of glucose from blended materials. The mechanisms of the enzymes included in this cocktails are still poorly understood. A detailed investigation is essential for controlling such enzyme degradation processes and for making the recycling and the production of biofuels or bulk chemicals cost-effective. In the end, a fully integrated biorefinery should be established which means no waste streams exist any longer. This makes this PhD project very interdisciplinary with many contact points between university research and industrial applicationcarbon source and can be used for the biotechnological production of new products in a biorefinery, e.g. for the fermentation of biopharmaceuticals, chemicals or the production of bioethanol.