Producing food for a growing population involves a massive consumption of resources, chemical pesticides and fertilisers leading to pollution and soil depletion.^[1,2] The crop yield is significantly influenced by seed quality, making seed coatings an interesting enhancement tool.^[1,3] Seed coatings improve seed performance by adding protective layers that may contain pesticides, nutrients, or biostimulants. This can boost germination, plant growth or protects against pathogens and abiotic stresses while ensuring precise application, and minimising active ingredient usage per plant.^[1,3] As a more versatile, environmentally friendly and potentially long-lasting alternative to synthetic agents, bacteria can be incorporated.^[4] They can promote plant growth via direct mechanisms in phytohormone production, as biofertilisers enabling e.g. nitrogen fixation or indirect mechanisms as biological control agents producing antibiotics or lytic enzymes.^[5] Current limitations of available seed coatings include low shelf-life and low loading capacity for biostimulants and microorganisms.^[6] Additionally, incorporation of synthetic polymers that can persist in the environment as microplastics poses potential health risks.^.[7]

We focus on creating biopolymer-based, biodegradable bulk hydrogels and microgels combined with adhesion-promoting peptides to encapsulate beneficial bacteria, such as Bacillus subtilis. The aim is to develop hydrogels with programmable rehydration mechanisms to support seeds and bacteria under different environmental conditions and drought. Mechanical properties are modulated by varying the molecular weight of the biopolymers, their concentration and crosslinking, which is studied by rheology and nanoindentation. Crosslinks in the hydrogel layer will control spore germination, bacterial mobility and viability of many bacterial populations, as well as nutrient release ensuring long-term adaptability. By advancing biomaterial-based technology, this project aims to provide a sustainable alternative to traditional seed coatings, contributing to more resilient and eco-friendly agricultural practices.

[1] M. Cardarelli, S. L. Woo, Y. Rouphael, G. Colla, Plants 2022, 11.

[2] A. Balla, A. Silini, H. Cherif-Silini, A. Chenari Bouket, F. N. Alenezi, L. Belbahri, Appl. Sci. 2022, 12, 9020.

[3] I. Afzal, T. Javed, M. Amirkhani, A. G. Taylor, Agriculture 2020, 10, 526.

[4] A. Paravar, R. Piri, H. Balouchi, Y. Ma, Biotechnology reports (Amsterdam, Netherlands) 2023, 37, e00781.

[5] a) A. Fanai, B. Bohia, F. Lalremruati, N. Lalhriatpuii, Lalrokimi, R. Lalmuanpuii, P. K. Singh, Zothanpuia, PeerJ 2024, 12, e17882; b) L. J. Gómez-Godínez, J. L. Aguirre-Noyola, E. Martínez-Romero, R. I. Arteaga-Garibay, J. Ireta-Moreno, J. M. Ruvalcaba-Gómez, Plants 2023, 12.

[6] I. Rocha, Y. Ma, P. Souza-Alonso, M. Vosátka, H. Freitas, R. S. Oliveira, Front. Plant Sci. 2019, 10, 1357.

[7] a) M. Sohail, T. Pirzada, C. H. Opperman, S. A. Khan, Green Chem. 2022, 24, 6052; b) R. Langlet, R. Valentin, M. Morard, C. D. Raynaud, Polymers 2024, 16.