Evaluation of antifungal efficacy of chitosan against Aspergillus fumigatus of stored rice (Oryza sativa)

Contamination of stored rice with fungal pathogens results in rice of poor quality and economic value, and may also have harmful effects on human and animal health. This study aimed at evaluating the antifungal efficacy of chitosan against Aspergillus fumigatus of stored rice (Oryza sativa). Four forms of chitosan were used in this study viz; Purchased Low, Medium and high molecular weight chitosan and chitosan synthesized from Crab Shell using deproteinization, demineralization, decolouration and deacetylation. Degree of deacetylation of the synthesized chitosan was determined using Fourier transform infrared (FTIR) analysis. The in vitro antifungal activity of all forms of chitosan were determined using food poisoning method against Aspergillus fumigatus isolated from stored rice seeds using agar plate methods. The percentage inhibition of mycelial radial growth Aspergillus fumigatus by the different forms of chitosan was determined. Fourier Transfrom InfraRed Spectra of synthesized chitosan showed major absorption bands from 3444.72, 2966.17, 2512.60, 2144.84, 1429.74, 1258.12, 1160.05, 1025.2, 869.92, 710.50, 608.40 to 559.36. Absorption peak at 559 was assigned to glucopyranose ring in the chitosan matrix. Degree of deacetylation of synthesized chitosan was at 98.6% degree. Highest mycelia radial growth of 8.00 cm was recorded in control, while 2.00, 0.00, 5.23, and 1.33cm were recorded in 2.0% concentration of High Molecular Weight Chitosan (HMWC), Medium Molecular Weight Chitosan (MMWC), Low Molecular Weight Chitosan (LMWC) and Chitosan synthesized from Crab shell (CSCS) treatment respectively. The result of the percentage inhibition reveals that A. fumigatus had 100% inhibition in 1.5% HMWC and 2.0% MMWC while 85% inhibition in 2.0% CSCS which were significantly different from 2.0% LMWC with 36.5% inhibitions. Results obtained from this study has shown the effectiveness of chitosan as an effective antifungal agent which can improve and maintain the quality of stored rice and ensure a safer environment due to its nontoxic and environmental friendly properties.