In-vitro antimicrobial activity of chitosan derived from shrimp co-products against pathogenic microorganism isolated in Vietnam

The global overuse of antibiotics and agrochemicals in Vietnam leads to antibiotic resistance, health risks, and environmental damage. This study evaluates in-vitro antifungal properties of different types of shrimp waste-derived chitosan against Vietnamese agricultural fungi as a sustainable alternative to chemical fungicides. Several pathogenic microbe strains were isolated and identified by morphological and molecular gene sequencing: Neoscytalidium dimidiatum causing brown spot on dragon fruit; Fusarium fujikuroi & Fusarium subglutinans causing banana crown rot; Fusarium oxysporum & Fusarium odoratissimum causing banana stem rot; Lasiodiplodia theobroma e causing fruit rot & Colletotrichum queenslandicum causing anthracnose on passion fruit; Fusarium equiseti & Fusarium napiforme causing swollen swim bladder on striped catfish. The antifungal properties of several chitosan types were investigated following the inhibition of fungal mycelial growth method. CTIC15 & OLIC25 demonstrated significant fungal growth inhibition from 90% to 100% at 0.328 g/L to 0.625 g/L for all isolated fungal strains. Chitooligosaccharide COSL02 exhibited antifungal effect against L. theobromae , F. oxysporum , N. dimidiatum , F. odoratissimum with inhibition rates from 53.11±2.74% to 100±0.00% at 0.438 g/L to 0.876 g/L. Low-molecular-weight LV01 displayed broad-spectrum antifungal efficacy, excluding F. subglutinans , with inhibition rates from 74.11±10.36% to 100±0.00 % at 0.2 g/L, and above 42.08±5.87% at 0.1 g/L. Medium-molecular-weight MV01 shared comparable antifungal potency to LV01, except F. equiseti and N. dimidiatum , with inhibition rates from above 74.09±7.09% to 100±0.00% at 0.2 g/L, and above 58.77±0.87% at 0.1 g/L. This study suggested chitosan (shrimp-waste) could serve as effective and sustainable alternative to chemical fungicides in controlling pathogenic microbes.