Alexander Fuchs1, Enrico Hupfeld1, Volker Sieber1,2,3,4
1 Chair of Chemistry of Biogenic Resources, Technical University of Munich, Campus Straubing for Biotechnology and Sustainability, Schulgasse 16, 94315 Straubing, Germany, 2 Catalysis Research Center, Technical University of Munich, Ernst-Otto-Fischer-Strasse 1, 85748 Garching, Germany, 3 SynBiofoundry@TUM, Technical University of Munich, Schulgasse 16, 94315 Straubing, Germany, 4 School of Chemistry and Molecular Biosciences, The University of Queensland, 68 Copper Road, St. Lucia 4072, Australia
Correspondence: Volker Sieber, sieber@tum.de
Carrageenans are a group of sulfated biopolymers that represent the commercially most relevant products obtained from red algae that are highly appreciated for their gelling behaviour or as thickeners and stabilizers in the food and cosmetic industry. The degree and position of sulfation has a decisive influence on their rheological properties and thus defines their commercial use. By the targeted cleavage of sulfate groups, e. g. by the use of sulfatases, carrageenan variants with new physico-chemical properties can be generated. To tackle this issue, we screened several putative carrageenolytic polysaccharide utilization loci of heterotrophic bacteria for sulfatases active on different types of carrageenans. Two carrageenan-active sulfatases were found in this approach, which were produced in an active form. They catalyze the specific desulfation of both ι- and κ- carrageenan as well as the hybrid carrageenan furcellaran. Spectroscopic analysis and desulfation experiments revealed the production of hybrid ι-α- & κ-β-carrageenan as well as highly pure α- & β- carrageenan, respectively. The enzymes were used for the biotransformation of ι- & κ-carrageenan in a preparative scale and the rheological analysis of the products uncovered the structure-function relationship of the sulfation architecture on their viscoelastic properties. These discoveries lay the groundwork for enzymatically modified carrageenans and their utilization in new application fields.