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Sustainable citriculture through controlled release of antibacterial compounds from microgel-based formulations

Grant number: 21/10839-4
Support type:Research Projects - Thematic Grants
Duration: October 01, 2022 - September 30, 2027
Field of knowledge:Agronomical Sciences - Agronomy - Plant Health
Cooperation agreement: Netherlands Organisation for Scientific Research (NWO)
Principal researcher:Henrique Ferreira
Grantee:Henrique Ferreira
Principal researcher abroad: Dirk-Jan Scheffers
Institution abroad: University of Groningen, Netherlands
Home Institution: Instituto de Biociências (IB). Universidade Estadual Paulista (UNESP). Campus de Rio Claro. Rio Claro , SP, Brazil
Assoc. researchers: Andrij Pich ; Fernando Rogério Pavan ; Franklin Behlau ; Michel Brienzo ; Peter Deuss ; Yvonne van der Meer


There is a clear need for sustainable methods to combat agricultural pests. Copper salts are widely used in regular agriculture, but also in organic agriculture. One agricultural area where copper salts are used widely is citriculture, to combat citrus canker, a disease caused by the plant pathogen Xanthomonas citri subsp. citri. The disease is endemic in all major orange producing regions in the world, except Europe. Citriculture generates US$2 billion/year in export revenues in Brazil indicating the size and importance of this industry. This project is aimed at the development of a bio-based, sustainable technology for the protection of citrus trees, as an alternative to copper. Specifically, we will focus on the fabrication of stimuli-responsive microgels that are capable of 1) strong attachment to citrus leaves and 2) controlled release of antibacterial compounds. In collaboration with our societal partner in Brazil, the efficacy of the protection system will be tested in the field. Our research program is based on interdisciplinary research contributing to practical solutions for the production of biomass-derived building blocks for the bio-based plant protection systems and sustainable agriculture of the future. Within this project, the partners will combine previously developed antibacterial compounds that target Xanthomonas (gallates, dihydroxybenzoates, eugenol) with microgels, that offer binding to plant leaves and long-term stability. The microgel carriers for antimicrobial compounds will be synthesized using biopolymer (chitosan) building blocks, to ensure complete degradation under field conditions. The extraction and up-scaling of biopolymer production will be optimized for large-scale microgel synthesis. Controlled release of compounds from the microgel will be achieved through use of environmental triggers (humidity, light, enzymes, etc.) that will allow dosage-controlled, precise, and efficient deactivation of bacteria. Rain simulation within a greenhouse will be used to verify if and how well the microgels/compounds can be fixed on leaves. Thus, microgels will be optimized so that release and antibacterial efficacy is optimal at farming conditions. Also, the toxicity to honeybees and other models will be determined to establish whether the microgels are safe to use. Production of the best performing microgel/antibacterial combination will be scaled up. Subsequently, field tests at our societal partner will be done to determine the efficacy of the microgel/antibacterial to protect against citrus canker in farming conditions in comparison with copper and treatment with non-encapsulated antibacterials. In parallel with the development of the microgels, our partner Santa Clara has the expertise to test for compatibility among active compounds and adjuvants, and to prepare formulations that can be directly and easily evaluated in green-house and field trials. Formulations will be tested for effectiveness using the green-house plant protection test, and the best selected formulations will be subsequently tested in the field. To analyse environmental impact, biodegradation and ecotoxicity of the antibacterial molecules, formulations and microgels will be analyzed through soil analysis for compound retention, and metagenome sequencing to determine what the effects of the various compounds are on the soil microbiome. Life Cycle Assessment and market analysis will be performed to assess the environmental, economic, and social impact of the new technology. We plan a comparative Life Cycle Assessment of the environmental and health impact of formulated product that will be developed within this project and the currently used copper-based formulations. The market analysis will include an analysis of social impacts relevant for stakeholders like governments and farmers. (AU)

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