Application of coffee pulp-derived pectins as a novel coating spray to mitigate Paramyrothecium breviseta, an etiological agent inducing leaf spot disease in coffee

Abstract

Coffee pulp is a significant byproduct of wet processing and poses ecological risks by contributing to soil acidification and diminished fertility in local ecosystems. Despite its potential environmental impact, coffee pulp is rich in various components, including valuable polysaccharides. This study focuses on extracting pectin from coffee pulp using HCl/KCl and ammonium oxalate. The total yield achieved was approximately 11 %, encompassing distinct types of pectins: Acidic coffee pulp pectin (ACPP) and basidic coffee pulp pectin (BCPP), which represent high and low methoxylate forms, respectively. The fabrication of the pectin (1 %) coating agent was accomplished by combining it with chitosan to form a polyelectrolyte complex (1 %) in a ratio of 10:1. The coffee pulp polyphenols fraction (CPPF), was embedded in the agent at 0.5 g/mL and characterised for inhibiting Paramyrothecium breviseta, a pathogen causing leaf spot in coffee. Experimental results demonstrated that the coating spray, derived from coated ACPP and coated CPPF exhibited the highest efficacy in inhibiting P. breviseta at distances of 0.00 and 1.70 cm on day 16, respectively. This efficacy was significantly different from both the negative control (7.40 cm) and the positive control (4.30 cm). This research highlights the potential of utilising coffee pulp as a valuable resource for pectin extraction and underscores the effectiveness of a formulated coating spray in mitigating the impact of the leaf spot-causing pathogen. The findings contribute to sustainable practices in coffee waste management while presenting a promising approach for plant disease control in coffee cultivation.