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Research project (§ 26 & § 27)
Duration : 2020-09-01 - 2022-08-31

The introduction of microalgae into food products is still limited but has a large potential for future developments of sutainable foods. Algae production efficiency but also consumer acceptance need to be increased. With regard to consumer acceptance, the sensory profile of algae and algae based products is still a limiting factor. Currently, mainly drying is applied to stabilize the algae biomass and algae powder is used as the main intermediate product and ingredient. However, alternative processing options may contribute to better sensory characteristics as well as to a larger variation of possible application options. Especially preservation technologies for the stabilization of wet, concentrated algae biomass are required to allow a shelf life extension while maintaining nutritional characteristics and avoiding a negative sensory impact. Processing concepts including non-thermal preservation technologies as well as packaging solutions will be investigated in order to provide optimized algae products to be used as ingredients in different types of food applications.
Research project (§ 26 & § 27)
Duration : 2020-06-01 - 2023-11-30

Wider research context / theoretical framework. The glucose-methanol-choline (GMC) superfamily of FAD-dependent oxidoreductases comprises a range of oxidases and dehydrogenases acting on various electron donor substrates such as sugars or alcohols. This large superfamily of oxidoreductases is defined by a common fold and by a close phylogenetic relationship, and includes industrially relevant enzymes such as aryl-alcohol oxidases (AAO) and pyranose dehydrogenases (PDH), forming one clade of this superfamily, or glucose oxidases (GOx) glucose dehydrogenases (GDH) constituting another GMC clade. Hypotheses / research questions / objectives. We hypothesis that the AAO/PDH as well as the GOx/GDH clades of GMC oxidoreductases have a common ancestor each, which most probably was a generalist biocatalyst, and that the substrate specificities of these individual enzymes were introduced slowly during evolution. AAOs are mainly active on aromatic alcohols and show pronounced activity with oxygen, while PDHs oxidize various sugars and show negligible activity with oxygen. Both GOx and GDH oxidize glucose, and while the reactivity with oxygen has been tuned up significantly for the former enzyme compared to free FAD, it is almost abolished in GDH. We are interested in structure/function relationships of these enzymes, i.e., how amino acid residues in the direct vicinity of the FAD modulate the reactivity with oxygen (increase or decrease it compared to free FAD), and how the transition from an alcohol-oxidizing to a sugar-oxidizing enzyme proceeded during evolution. Approach / methods. We will use ancestral sequence reconstruction (ASR) to recreate common ancestors at different internal nodes of the AAO/PDH as well as the GOx/GDH phylogenetic trees using GRASP (Graphic Representation of Ancestral Sequence Predictions), which had been developed by our partners from the University of Queensland, Brisbane. We will then study the biochemical and biophysical properties of these ancestral enzymes. Level of originality / innovation. Oxygen reactivity of flavin-dependent enzymes is still poorly understood. It is not clear at present how the polypeptide environment of the isoalloxazine modulates this activity. Several studies have focused on this topic, yet none aimed at understand how oxygen reactivity was introduced into oxidoreductases during evolution. Hence using ASR is a novel approach to study this important topic in flavin enzymology.
Research project (§ 26 & § 27)
Duration : 2020-04-01 - 2022-09-30

Lactate biosensors are very interesting for different applications and are already commercially available. The currently available sensors are very well suited for single measurements, but not suitable for long-term measurements due to their lack of stability. The project deals with the stabilization of the lactate oxidase used in these sensors by means of a new method, the reconstruction of anestral sequences. Enzyme ancestors of lactate oxidase obtained in this way will be characterised in detail biochemically, biophysically and bioelectrochemically. In addition, new alpha-hydroxy acid oxidases will be investigated and adapted for application in sensors by means of Directed Evolution.

Supervised Theses and Dissertations