Improved foods using enzymes from Basidiomycota

Basidiomycota are higher fungi, many of which are appreciated as tasty, low-calorie food. They have accumulated a vast variety of genes to adapt to the different substrates they are able to grow on. Depending on the substrate, the relevant genes are expressed and degradative as well as synthesising enzymes secreted. Many of these are also of interest for the food industry and some have been studied and applied in this thesis. Pleurotus sapidus, a close relative of the oyster mushroom, produces a dye-decolorising peroxidase that was able to cleave trans-anethol through oxidative cleavage of the C-C double bond in the propylene side chain to the sweet, aniseed p-anisaldehyde. The enzyme was improved through the selection of monokaryots without the use of genetic engineering. The new enzyme variants showed increased enzymatic activity due an enhanced stability. Higher expression rates in the monokaryot further raised p-anisaldehyde yields. A lipoxygenase of the same basidiomycete catalysed the generation of the vanilla-like compound piperonal from piperine through co-oxidation of linoleic or α-linolenic acid. The impact flavour compound of smoke flavour, 4-vinylguaiacol, enables a toxin-free flavouring of food in contrast to traditional smoking methods. It was synthesised with the agro-industrial side stream sugar beet fibre as substrate in a two-step process using immobilised enzymes and solid phase extraction. In addition, ten sesquiterpene cyclases were identified, heterologously produced and their product spectrum characterised. Overall, different aroma compounds of interest for the flavour and fragrances industry could be generated using basidiomycetous enzymes that were heterologously produced in either Escherichia coli or Komagataella phaffii. Food components can cause problems with the gastro-intestinal tract for certain consumers. Two examples are celiac disease, an autoimmune disorder that is induced by peptides from gluten, and chlorogenic acid, which causes stomach irritation after coffee consumption for sensitive individuals. Celiac disease-inducing peptides in different grain flours were degraded using a prolyl endopeptidase from Flammulina velutipes, which is closely related to the golden needle mushroom, a highly appreciated food in Asia. In contrast to the peptidase from Aspergillus niger, which is commercially available for this application, the basidiomycetous enzyme was shown to cleave all disease-inducing epitopes successfully. Likewise, a p-coumaryl esterase degraded chlorogenic acid in apple juice without effecting its sensory properties. Arabinoxylans can be extracted from wheat bran or sugar beet fibre and crosslinked using basidiomycetous laccases. The formed gels were comparable in firmness to gelatine gels and showed good water-holding capacities as well as storage and temperature stabilities. Gels from sugar beet fibre were successfully sweetened. Both present an alternative for the vegan market as well as for pharmaceutical and medicinal applications. Numerous heterologously produced enzymes from Basidiomycota were utilised for the generation of aroma compounds and the synthesis and degradation of food components. Following the maxim “from foods for foods”, they hold promise for technological applications in these fields, aiming towards a sustainable and bioeconomic chemistry.