A novel coating formulated with sodium alginate loaded with a mixed lactic acid bacteria culture to control anthracnose in guava and mango

Guava and mango are tropical fruits widely consumed due to their pleasant flavor and nutritional composition. Anthracnose caused by Colletotrichum spp. Is considered a primary post-harvest disease affecting these fruits. Applying biocontrol agents, such as lactic acid bacteria (LAB), combined with coating materials is an innovative fruit biopreservation method. This study investigated the effects of a novel sodium alginate coating loaded with a mixed culture of LAB in controlling anthracnose caused by different pathogenic Colletotrichum isolates in guava (cv.) Paluma and mango (cv.) Palmer during 15 days of room temperature storage (25 ± 0.5 °C). A mixed culture formed by three different LAB species strains (Levilactobacillus brevis 59, Lactiplantibacillus pentosus 129, and Limosilactobacillus fermentum 263) was tested against ten target Colletotrichum isolates. The mixed culture inhibited the mycelial growth of all target Colletotrichum isolates in vitro, with up to 100 % inhibition. In the nutrient competition method, the mixed LAB culture survived and caused mycelial growth inhibition even at low nutrient concentrations. The coatings showed sizes of LAB cell subpopulations with non-permeabilized membrane (viable cells, PI-CFDA+) of >31 % at the end of refrigerated storage and viable cell counts of >7 log CFU/g. Applying coatings with sodium alginate loaded with mixed LAB culture delayed the development and decreased the severity of anthracnose lesions in guava and mango artificially contaminated with either of the tested Colletotrichum isolates. The coating formulated with sodium alginate and mixed LAB culture can be effective for postharvest anthracnose biocontrol in guava and mango.