Antimicrobial and Toxicological Evaluation of Food Grade Chitosan From Crab (Callinectes sapidus)

Abstract

Food grade chitosan was produced from crab (Callinectes sapidus) shell using unconventional methods of
demineralization, deproteinization and deacetylation. The antimicrobial susceptibility and toxicological evaluation of the chitosan
was invesyigated using standard procedures. Chitosan produced from Callinectes sapidus was found to contain moisture (0.75±0.00
%), nitrogen (6.94±0.13 %), and ash (0.75±0.00 %). Functional characterization revealed a degree of deacetylation (89.0±2.50 %),
viscosity (91.0±5.00 cp), solubility (96.4±0.65 %), water binding capacity (270±6.20 %), fat binding capacity (505.3±18.20 %) and
molecular weight (152±1.30 KDA) respectively. Susceptibility profile of some food-borne pathogens to crab chitosan revealed a
minimum inhibitory concentration (MIC) which ranged from 100 - 1200μg/ml. Chitosan was active against Staphylococcus aureus,
Listeria monocytogenes, Escherichia coli 0157: H7, Salmonella typhimurium, Saccharomyces cerevisceae and Penicillium expansum.
Among the bacteria isolates, Staphylococcus aureus had the least MIC of 200μg/ml with the highest zone of inhibition of 40mm at a
concentration of 1600μg/ml. Escherichia coli 0157: H7 had the highest MIC of 1200μg/ml as the most resistant of the pathogens
examined. Saccharomyces cerevisceae and Penicillium expansum were highly susceptible to crab chitosan with MIC of 100 and
200μg/ml respectively. Gram-positive organisms were more susceptible to chitosan and this was concentration dependent. Acute
toxicity of chitosan at a single dose of 5000mg/kg on male and female albino rats (Rattus norvegicus) of Wistar strain did not produce
any sign of toxicity. The reult of the sub-chronic toxicity of chitosan revealed no changes in animal behaviour. Body weights, organ
weights, haematological indices remained at normal levels. The non-toxicity of this food grade chitosan will be useful for shelf-life
extension of foods.