Comparison of different polysaccharides in combination with chitosan in the preparation of biogel for controlled release of antibacterials in citrus growing

Abstract

Citrus farming is an economic activity of great importance worldwide, especially in tropical and subtropical countries. Brazil stands out as a leader in the production of sweet oranges, however, it faces challenges related to diseases such as citrus canker, caused by the bacterium Xanthomonas citri. Conventional control of this disease uses copper-based compounds, which can be harmful to the environment. More sustainable alternatives, such as organic compounds and bioactive agents such as essential oils, emerge as potential defensive agents due to their antimicrobial properties. However, its direct application to plants can be challenging due to the lack of adhesion to the substrate. In this sense, chitosan can be used as a matrix for controlling essential oils release. In addition, X. citri produces enzymes such as cellulases, xylanases, and pectinases, involved in plant cell wall degradation. Polysaccharides such as cellulose (micro/nanofibrils), xylan, and pectin, added to the chitosan matrix, can serve as triggers for the controlled release of the essential oil. The hydrolysis of these polysaccharides by the enzymes produced by X. citri would release the essential oil, providing an effect aimed at combating citrus canker. On the other hand, chitosan can have a high cost, therefore, it is necessary to evaluate other polysaccharides for emulsion with eugenol. This research project aims to evaluate the use of chitosan in combination with cellulose, xylan and pectin for the production of a biogel for the controlled release of essential oil in the fight against citrus canker. Polysaccharides such as starch gel, xanthan gum, acacia gum, and alginate will be compared with chitosan for controlled release of eugenol. This project is part of a broader context of a Fapesp Thematic Project (2021/10839-4), which aims to use a biogel as a vehicle for eugenol in the fight against citrus canker. The present study will contribute to the biogel formulation step, being an important step for subsequent scaling and field application.