Summary

The RhamBO project addressed two central challenges of a sustainable bioeconomy: environmentally friendly plant protection and the scalable production of bio-based chemicals. The project focused on rhamnolipids, a class of microbial biosurfactants, as novel bioactive compounds for crop protection and as promising products for industrial biotechnology. Field trials demonstrated that rhamnolipids, as biological compounds, can provide robust biological pest control while fully maintaining yield and sugar production, highlighting their strong potential as a sustainable alternative to conventional strategies in sugar beet cultivation, for which biological solutions remain limited. Towards elucidating the underlying molecular mechanisms, defense-related genes in Arabidopsis thaliana differentially regulated upon rhamnolipid treatment were identified, and orthologs in sugar beet were determined. In parallel, the project established a scalable bioprocess for rhamnolipid production using recombinant Pseudomonas putida. A novel process strategy based on headspace aeration under elevated pressure was developed to overcome excessive foaming, a major bottleneck in biosurfactant production. This enabled stable fermentations at technical scale and the production of sufficient quantities of rhamnolipids for field applications.
Overall, RhamBO successfully bridged fundamental research and application by demonstrating both the field efficacy of rhamnolipids and the feasibility of their technical-scale production. The results provide a strong basis for further development towards industrial implementation and sustainable plant protection strategies.