Michelle Teune

• This thesis is structured around five studies that contribute to the understanding of marine polysaccharide degradation and the potential application of bacterial enzymes for the biotechnological utilization of marine xylans. The first article (Article I) addresses the identification of carbohydrate transport proteins in the marine Gammaproteobacterium Pseudoalteromonas distincta, which were so far exclusively found in the Bacteroidota phylum. In three further articles, we investigated enzymes from Flavimarina sp. deriving from two distinct polysaccharide utilization loci (PULs) of the same strain. We could show that both xylan PULs differ in their substrate specificity (Article II), targeting xylans with variable side chains. The esterases of both PULs were further investigated. While the characterization of the multimodular esterases Fl6, Fll1 and Fll4 revealed unique features and potential affiliation to new carbohydrate esterase (CE) families (Article III), the enzyme Fl8CE20_II could be identified as a member of the CE20 family which has not been described in detail so far. We elucidated the crystal structure of two members of the CE20 family and identified a novel active site architecture, which we termed the “water-mediated” triad (Article IV). Finally, two glycoside hydrolases (GH) from Formosa sp. Hel3_A1_48 were characterized and utilized to degrade xylan from the red algae Palmaria palmata. We could show that a one-step enzymatic hydrolysis of raw biomass enables the production of large amounts of xylooligosaccharides (XOS), the exact structure of which we could solve using NMR spectroscopy and MS/MS analyses (Article V).