P001 EVALUATION OF FRESHWATER LOBSTER (Cherax quadricarinatus) SHELLS AS A GREEN BIO-FUNGICIDE AGAINST Fusarium sp.

Abstract

Fusarium spp. is a highly destructive soil-borne pathogen responsible for vascular wilt in major economic crops globally. Currently, the mitigation of this pathogen relies heavily on hazardous synthetic fungicides, which pose severe risks to environmental and public health. Concurrently, the rapidly expanding aquaculture industry generates massive quantities of underutilized crustacean shell waste. This study aimed at extracting chitosan from freshwater lobster (Cherax quadricarinatus) shells and thoroughly evaluate its potential as a sustainable bio-fungicide against Fusarium sp. The chitosan was synthesized via a sequential chemical process of demineralization, deproteinization, and deacetylation. Comprehensive characterization involved solubility testing and acid-base titration. Antifungal efficacy was subsequently assessed in vitro utilizing Poisoned Food (direct contact) and Well Diffusion at formulated concentrations ranging from 0.5% to 2.0%, compared against both negative and positive (Mancozeb) controls. Results indicated the highly successful extraction of quality chitosan, featuring an exceptional Degree of Deacetylation (DD) of 96.6%, confirming a dense presence of active amino groups. In the Poisoned Food assay, the 2.0% chitosan treatment exhibited profound, dose-dependent growth inhibition, drastically reducing the fungal radial diameter to 16.00 ± 1.73 mm (a 74.6% inhibition rate) compared to the control (63.00 ± 2.65 mm). Statistical analysis (ANOVA, p < 0.05) confirmed there was no significant difference in efficacy between the 2.0% bio-fungicide and the commercial synthetic standard. While its activity in diffusion assays was constrained by the polymer’s high molecular weight, the overarching findings establish Cherax quadricarinatus shells as a highly viable, sustainable source of potent antifungal chitosan.