Part A: Young scientist`s project

In the ASHtoCASH project, we investigated whether currently underutilized side streams from the bioeconomy could serve as a source of novel, natural active ingredients for crop protection. The central idea was to view biological residues not as the end point of a production chain, but as the starting point for new value creation: identifying compounds that either directly protect plants against pathogens or activate their own defence and stress responses.

To this end, different side streams were sourced, suitable extraction methods were developed, and the resulting extracts were evaluated in various biological test systems. Several materials showed promising activities. Certain yeast and fermentation-derived fractions, for example, were able to stimulate plant defence responses. Particularly interesting results were obtained with side streams from edible mushroom production. Extracts derived from fungal mycelium and mycelium-colonized cultivation substrates showed direct antifungal activity against several phytopathogenic fungi. This opens up an attractive circular-economy perspective: edible mushrooms can be cultivated on agricultural residues, while the spent, mycelium-containing substrates remaining after harvest could in turn serve as raw materials for new crop protection solutions. The identified extracts were therefore also evaluated in more application-oriented systems, including against Cercospora beticola in sugar beet and Botrytis cinerea in strawberry. Pathogens such as these cause substantial crop losses and often require repeated crop protection measures. At the same time, these experiments highlighted a key challenge for further development: strong antifungal activity under laboratory conditions does not automatically translate into equally robust protection in whole plants. Extraction procedures, active ingredient concentrations, formulation, and application therefore need to be further optimized.

ASHtoCASH thus demonstrates the potential hidden in what are currently considered low-value side streams of the bioeconomy. At the same time, the project showed that biological efficacy, raw-material availability, reproducible production, and regulatory requirements must be considered together when moving towards practical applications. Particularly promising approaches based on side streams from edible mushroom production will therefore be pursued in further research. In the long term, such circular concepts could contribute to the development of new bio-based crop protection solutions and help reduce the use of conventional crop protection products.

Part B: Mentoring Tandem Project

The cross-generational and interdisciplinary collaboration within the mentoring tandem complemented the plant science focus of ASHtoCASH with regulatory and application-oriented perspectives. A key benefit was the early consideration of potential pathways towards practical utilization. This allowed scientific decisions to be assessed in terms of their practical implications and potential development hurdles to be identified at an early stage.

This was particularly relevant when selecting suitable side streams. In addition to availability and biological potential, the origin and composition of the materials as well as potential regulatory requirements were considered. For example, the project focused on well-defined substrates from specialty mushroom cultivation, even though these are available in considerably smaller quantities than substrates from conventional button mushroom production. The latter often contain animal-derived components such as poultry manure, which may introduce additional regulatory challenges. The mentoring therefore helped focus the search on side streams that combined scientific potential with a realistic perspective for future application. Similar considerations were incorporated into the development of extraction procedures. Since the choice of extraction solvent can also affect the technical and regulatory feasibility of subsequent applications, potentially critical solvents and complex procedures were questioned early on. Where scientifically appropriate, simpler and more application-oriented approaches were preferred. The mentoring also supported the identification and assessment of potential cooperation and commercialization partners. The exchange highlighted that biological activity alone is not sufficient when selecting promising candidates. Long-term availability and reproducibility of the raw material, scalable processing methods, and realistic regulatory and economic development pathways are equally important. Expanding the network through relevant conferences and trade fairs further helped to broaden the potential routes for future exploitation and commercialization.

Overall, the interdisciplinary and cross-generational collaboration helped connect scientific questions with the requirements of future practical implementation at an early stage, identify potential dead ends, and focus development resources on the most promising approaches.