greenDegradation - Degradation of Pectin- and Chitosan-Microgels by the Soil Microbiome  

Fabian Kolodzy, Functional and Interactive polymers, RWTH Aachen
Anna Wendel, INRES - Molecular Biology of the Rhizosphere, University of Bonn

Funding period: 15.03.-14.09.2024

Controlled release of fertilizers and pesticides is used in agriculture to increase crop yield while minimizing environmental impact from agrochemicals. Microgels are swellable polymer networks whose stimuli-responsive swelling behavior, for example, in response to pH or temperature changes, makes them suitable for controlled release. The successful application of microgel-based plant protection formulations has already been confirmed in laboratory and field trials. However, the use of microgels poses a risk to soil health, as their biodegradability has not yet been adequately studied. Therefore, the aim of this mini-project was to investigate the microbial degradation of chitosan- and pectin-based microgels, with a particular focus on comparing chemical and ionic crosslinking mechanisms. 
Within this mini-project, two chitosan- and two pectin-based microgels could be produced at larger scale. The synthesis of ionically crosslinked microgels can be achieved without the use of organic solvents, making it more sustainable than the emulsion-based synthesis of chemically crosslinked microgels. Subsequently, the biodegradation of the microgels in solution by enzymes and in soil by microorganisms was demonstrated, whereby the ionically crosslinked microgels degrade faster than the chemically crosslinked ones. Further, significant differences in degradation behavior were observed between chemically crosslinked chitosan and pectin microgels. These differences correlate with the microgel’s swelling behavior and suggests that the degree of swelling plays a crucial role in their biodegradability, which should be investigated further. 
Our findings demonstrate biological degradability of chitosan- and pectin-based microgels. Since chitosan and pectin are bio-based polysaccharides, plant protection formulations based on these microgels are well-suited for establishing a circular bioeconomy that ensures both, regulatory goals for global food security and environmental safety. Consequently, the project results will contribute to increasing acceptance of this technology among regulatory institutions as well as users and consumers in the future. 

CyPrACoL – Efficiency of Cyanobacterial Production with Artificially Composed Lights

Tobias Pfennig, Computational Life Science, RWTH Aachen
Andreas Nakielski, Yasemin Baran, Synthetic Mikrobiology, HHU Düsseldorf

Funding period: 01.01.-30.06.2024

The project CyPrACoL aimed to determine the best option to light and grow cyanobacteria. Cyanobacteria grow using light and draw carbon dioxide from the air, which makes them very interesting for biotechnology. Various products, from food to high-value chemicals, can be produced. However, there are many available light sources for growing the cyanobacteria. The two most important aspects of bioeconomy are 1) how power efficient the light is and 2) how well cyanobacteria can grow with the light. Cyanobacteria absorb some colors of light better than others. This has a considerable influence on how well their photosynthesis functions. Importantly, different light sources produce different amounts of each light color, which may make them better or worse for fueling the cyanobacteria.
To test this hypothesis, we first grew cyanobacteria using either LED or fluorescent light with a fixed intensity. The power consumption of the LEDs was 80 times lower because old and over-sized fluorescent lights were used. However, there was only a slight difference in growth which could not be clearly attributed to an effect of the different lights. Therefore, we also simulated the growth computationally using a mathematical model to support our analysis. In the simulation, the LED light allowed the cyanobacteria to grow 14 % faster. 
Additionally, we simulated the cyanobacteria's growth under many different lights reported on the internet and divided them by their reported power consumption. We found that some, but not all, of the LED lights could be used to grow the cyanobacteria using overall less power. In a second simulation, we optimized how much red and blue LED light is given into the model to get the highest cyanobacterial growth. We found that using pure red light is the most power-efficient, but adding blue light may improve the growth while sacrificing power efficiency. Therefore, LED lighting could be a good option to make biotechnology with cyanobacteria more eco-friendly and less costly compared to traditional fluorescent lights when taking the time and searching for the right lights for one cause.