Open Access

Das Projekt Nutrient+CtrlIVF der Hochschule Osnabrück verfolgt das Ziel, eine bedarfsgenaue und ressourcenschonende Nährstoffversorgung in rezirkulierenden, hydroponischen Indoor Vertical Farms (IVF) zu realisieren. Im Mittelpunkt steht die Entwicklung eines innovativen Steuerungssystems, das mithilfe ionensensitiver Feldeffekttransistoren (ISFET) die Konzentrationen einzelner Pflanzennährstoffe wie Nitrat, Ammonium und Kalium in Echtzeit überwacht und reguliert. Dadurch wird die bisher übliche Steuerung über den unspezifischen EC-Wert deutlich präzisiert. Das System ermöglicht eine adaptive, pflanzenartspezifische Nährstoffversorgung und trägt zur Optimierung von Ertrag, Qualität und Ressourceneffizienz bei. Pilotversuche mit Wasserlinsen und Süßkartoffeln belegen die Praxistauglichkeit und das Potenzial für den Einsatz in nachhaltigen Agrarsystemen der Zukunft.

The cell wall of filamentous fungi is essential for growth and development, both of which are crucial for fermentations that play a vital role in the bioeconomy. It typically has an inner rigid core composed of chitin and beta-1,3-/beta-1,6-glucans and a rather gel-like outer layer containing other polysaccharides and glycoproteins varying between and within species. Only a fraction of filamentous fungal species is used for the biotechnological production of enzymes, organic acids, and bioactive compounds such as antibiotics in large amounts on a yearly basis by precision fermentation. Most of these products are secreted into the production medium and must therefore pass through fungal cell walls at high transfer rates. Thus, cell wall mutants have gained interest for industrial enzyme production, although the causal relationship between cell walls and productivity requires further elucidation. Additionally, the extraction of valuable biopolymers like chitin and chitosan from spent fungal biomass, which is predominantly composed of cell walls, represents an underexplored opportunity for circular bioeconomy. Questions persist regarding the effective extraction of these biopolymers from the cell wall and their repurposing in valorization processes. This review aims to address these issues and promote further research on understanding the cell walls in filamentous fungi to optimize their biotechnological use. Key points • The highly complex cell walls of filamentous fungi are important for biotechnology. • Cell wall mutants show promising potential to improve industrial enzyme secretion. • Recent studies revealed enhanced avenues for chitin/chitosan from fungal biomass.

Aspergillus niger is a filamentous fungus extensively utilized in industrial biotechnology for the production of enzymes, organic acids, and other metabolites. The increasing demand for enhanced protein production and efficient secretion pathways necessitates the development of novel screening methods. Although luciferase technology has been employed in mammalian cells and bacteria for an extended period, only recent advancements have expanded its applicability in fungal biology to investigate gene expression, signal transduction, and metabolic processes. The research landscape is shaped not only by optimization efforts and persistent challenges, but high-throughput methods are currently a primary focus, particularly for the screening of traits pertinent to industrial enzyme production. In this study, we report successful heterologous expression and secretion of extracellular luciferases in A. niger. Using a luciferase-based high-throughput screening assay in 96-well plates, a sensitive method for evaluating the differences in secretion or production efficiency was introduced. This will be highly valuable for screening genetic modifications, for example, across mutant libraries of secretion signals, in future applications. Moreover, fusion of luciferases with homologous or heterologous proteins offers a straightforward approach for determining the secretion and production efficiencies of proteins, both without any enzymatic activity and with activity that is challenging to measure. The findings of this study indicate that this novel assay addresses the limitations of conventional screening methodologies and may significantly enhance the application of luciferase technology in filamentous fungi. Moreover, the results demonstrate the potential for subsequent research to expand this approach, facilitating improved production systems for A. niger.