In our work one focus lies on the polysaccharide degrading potential due to hydrolytic enzymes. Therefore different metagenomic libraries were functionally screened for cellulolytic activity. Among 14 hydrolytic hits, three promising cellulases were discovered, two derived from elephant feces and another from a biogas plant. All three enzymes showed remarkable tolerance for salt and ionic liquids [1].
Another focus of our group is the enzymatic glycoside transfer, especially glycosyltransferases to modify flavonoids. Flavonoids are small plant-derived polyphenols that have beneficial effects on the human health. The glycosylation of flavonoids has decisive impact on their solubility, stability, bioavailability, and is capable of altering their physiological effects. To identify flavonoid modifying enzymes we established a new functional screening method using high performance thin layer chromatography (HPTLC) [2]. This setup led to the identification of the novel glycosyltransferase GtfC from the Elbe river sediment metagenome. This recombinant enzyme is able to transfer dTDP-activated sugar residues to various flavonoids [2].
Further, the screen enabled the discovery of a metagenomic hydrolase. This novel α-L-rhamnosidase RhaB from elephant feces possesses a novel domain architecture and opened a new subclass of rhamnosidases. Recombinantly expressed, RhaB was active on glycosylated flavonoids, rutinoses as well as hesperidoses, and was biochemically and kinetically characterized [3].
[1] N. Ilmberger et al. Appl Microbiol Biotechnol 95:135-146.
[2] U. Rabausch et al. Appl Environ Microbiol 79:4551-63.
[3] U. Rabausch et al. J Biotechnol 191:38-45.