Research

The work of the group focuses on investigating a range of functional oligo- and polysaccharides from microorganisms and seaweeds, as well as glycoproteins from various sources. These highly diverse carbohydrate-based biomolecules can be used in foods as additives or ingredients, but they can also be formed directly in foods by the use of suitable enzymes or fermentation. In these products, the respective compounds have a major influence on technofunctional and nutritional properties.

The functionality of oligomeric and polymeric carbohydrate-based biomolecules is strongly dependent on their molecular structure; therefore, the structural characterization and analysis of these compounds is an important part of our work. Various established methods of carbohydrate analysis are used for this purpose. Particularly noteworthy are the determination of monosaccharide composition after acid hydrolysis by HPAEC-PAD, the determination of glycosidic linkages after methylation analysis by GC-MS/FID, and one- and two-dimensional NMR spectroscopy. In addition, the enzymatic release, isolation, and characterization of oligomers also play a major role, as this approach can often provide additional information about the structural elements present. Because the enzymes required are frequently not commercially available, we produce them using various biochemical techniques involving cloning and recombinant expression in E. coli. Chromatographic analysis of the oligosaccharide profiles obtained after enzymatic treatment is also highly suitable for the rapid and detailed analysis of various samples. The development of such analytical methods is therefore an enduringly important aspect of our research.

Our focus is not limited to commercially available carbohydrates and glycoproteins, but also enzymatic synthesis and modification of complex carbohydrates. Recombinant carbohydrate-active enzymes also play an important role here, as they enable the targeted cleavage of polymers and the selective removal or incorporation of specific monosaccharide units. Enzymes can also facilitate the de novo formation of oligo- and polymeric carbohydrates from simple sugars such as sucrose, enabling, for example, the use of by-products from the food industry such as molasses and sugar reduction in foods. Microorganisms are also used to produce polymeric carbohydrates, which also allows for the production of polysaccharides composed of several different monosaccharide units (heteropolysaccharides).

Following the synthesis, modification, and detailed characterization of the various carbohydrates, structure–function relationships are of particular interest. The focus here includes, for example, stability during heat treatment or storage in acidic food matrices, which can be investigated effectively using suitable analytical methods. Interactions with other polysaccharides, proteins, and food constituents are another relevant aspect. The functional properties of individual carbohydrates in foods and relationships between molecular structure and nutritional properties are likewise investigated, often through interdisciplinary collaborations.

For both established and novel carbohydrates, their occurrence and formation in foods are also relevant. Analytical methods for many polysaccharides are often still lacking. Approaches based on partial hydrolysis can offer considerable added value for detecting or quantifying the relevant carbohydrates in food matrices. The targeted microbial or enzymatic formation of prebiotic carbohydrates in foods is also of interest which can be used to improve nutritional properties of the respective products.