Strategies for the Discovery of Carbohydrate-Active Enzymes from Environmental Bacteria

• Main Author: Larsbrink, Johan
• Format: Doctoral Thesis
• Language: English
• Published: KTH, Glykovetenskap 2013
• Subjects: CAZyme discovery; xyloglucan; polysaccharide-utilisation locus; microbiota; α-xylosidase; GH31; transglucosidase; human gut
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-126956; http://nbn-resolving.de/urn:isbn:978-91-7501-834-8

The focus of this thesis is a comparative study of approaches in discovery of carbohydrate-active enzymes (CAZymes). CAZymes synthesise, bind to, and degrade all the multitude of carbohydrates found in nature. As such, when aiming for sustainable methods to degrade plant biomass for the generation of biofuels, for which there is a strong drive in society, CAZymes are a natural source of environmentally friendly molecular tools. In nature, microorganisms are the principal degraders of carbohydrates. Not only do they degrade plant matter in forests and aquatic habitats, but also break down the majority of carbohydrates ingested by animals. These symbiotic microorganisms, known as the microbiota, reside in animal digestive tracts in immense quantities, where one of the key nutrient sources is complex carbohydrates. Thus, microorganisms are a plentiful source of CAZymes, and strategies in the discovery of new enzymes from bacterial sources have been the basis for the work presented here, combined with biochemical characterisation of several enzymes. Novel enzymatic activities for the glycoside hydrolase family 31 have been described as a result of the initial projects of the thesis. These later evolved into projects studying bacterial multi-gene systems for the partial or complete degradation of the heterogeneous plant polysaccharide xyloglucan. These systems contain, in addition to various hydrolytic CAZymes, necessary binding-, transport-, and regulatory proteins. The results presented here show, in detail, how very complex carbohydrates can efficiently be degraded by bacterial enzymes of industrial relevance. === <p>QC 20130826</p>