Zhang, Yutong2025-01-172025-01-172025-01-17http://hdl.handle.net/10393/50105https://doi.org/10.20381/ruor-30868Fungal carbohydrate oxidoreductases catalyze redox reactions related to the synthesis, degradation and modification of carbohydrates. Pyranose dehydrogenase from Agaricus bisporus (AbPDH1) oxidizes xylooligosaccharides (XOS) from the hemicellulose of lignocellulosic biomass (LCB). Galactose oxidase from Fusarium graminearum (GalOX) can oxidize lactose. Both of these oxidoreductases can be produced at large scale by recombinant production from the low-cost Pichia pastoris expression system. At the same time, it is hypothesized that oxidized sugars can be used to crosslink chitosan polysaccharide, extracted from the shells of sea crustaceans, producing a chitosan-based hydrogel. The goal of this study was to evaluate whether AbPDH1 and GalOX could be used to make oxidized sugar-based crosslinkers that would contribute to hydrogel formation when mixed with chitosan. Toward this, mid-scale production of the enzymes were completed, followed by their purification by affinity chromatography and characterization of their yields and functionalities by spectrophotometric-based assays and SDS-PAGE. The obtained enzymes were used to produce two oxidized-sugar products (oxidized-XOS and oxidized-lactose), where catalysis was confirmed by High-Performance Anion-Exchange Chromatography with Pulsed Amperometry Detector (HPAEC-PAD) and Fourier-transform Infrared (FTIR) spectroscopy. Subsequently, chitosan gels produced by the obtained crosslinkers were prepared at different pH values. The quality and stiffness of the gels was evaluated visually and by rheometric analysis. Results showed that oxidized-XOS can form gels faster than oxidized-lactose and that hydrogels formed fastest at neutral. In conclusion, it is demonstrated that AbPDH1 and GalOX can be used to make oxidized sugar-based crosslinkers that can contribute to hydrogel formation when mixed with chitosan. Due to their non-toxic characteristic for humans and the environment, such hydrogels have the potential to be developed as new water-retaining materials for applications in agriculture and medicine. At the same time, such hydrogels enable recycling of the biomass-based waste streams, increasing the value of agricultural and marine resources.enFungal carbohydrate oxidoreductasesChitosan hydrogel using in agriculturalBiomassThesis