Abstract
Chitosan and its oligomers N-acetyl chitooligosaccharides and chito-oligosaccharides prepared by deacetylation and chemical hydrolysis, respectively and have a broad antimicrobial spectrum to Gram-positive (Staph.aureus and List. monocytogenes) bacteria and Gram-negative (Sal.typhimurium). Staph.aureus, List. monocytogenes and Sal. typhimurium were isolated in lower percentages (23.3, 0 and 6.67%, respectively) from talaga cheese, followed by zabadi-baladi and kariesh cheese. This study focused on antimicrobial activity of chitosan and its oligomers by inoculation it and the isolated bacteria in yoghurt. 1% of chitosan completely inhibited the Staph.aureus, List. monocytogenes at 5th and 3rd day, respectively and Chitosan exhibited a bacteriostatic effect on Sal. typhimurium. while 0.1% of N-acetyl chitooligosaccharides and chito-oligosaccharides had reduced the count of List. monocytogenes and bactericidal effect on Staph.aureus and Sal. typhimurium. The antimicrobial properties of chitosan and its oligomers also, the perception of palatability to consumers toward it were discussed.
Highlights
IntroductionA natural polymer, found in the exoskeletons of crustaceans (Rinaudo, 2006)
Chitosan is nontoxic, a natural polymer, found in the exoskeletons of crustaceans (Rinaudo, 2006)
Some authors have stated that chitosan generally showed stronger effects for Grampositive bacteria (e.g. Listeria monocytogenes, Bacillus megaterium, B. cereus, Staphylococcus aureus, Lactobacillus plantarum, L. brevis, L. bulgaris, etc.) than for Gram-negative bacteria (e.g. E. coli, Pseudomonas fluorescens, Salmonella typhimurium, Vibrio parahaemolyticus, etc.) (Goy et al, 2009)
Summary
A natural polymer, found in the exoskeletons of crustaceans (Rinaudo, 2006). Mechanism of inhibition of microbial cells by chitosan and its oligomers via its polycationic nature which electrostatically binds with the microbial surface and interferes with metabolism of bacteria or by blocking the transcription of RNA from DNA by adsorption on DNA after penetration to the cell (Liu et al, 2001). Some authors have stated that chitosan generally showed stronger effects for Grampositive bacteria (e.g. Listeria monocytogenes, Bacillus megaterium, B. cereus, Staphylococcus aureus, Lactobacillus plantarum, L. brevis, L. bulgaris, etc.) than for Gram-negative bacteria (e.g. E_coli, Pseudomonas fluorescens, Salmonella typhimurium, Vibrio parahaemolyticus, etc.) (Goy et al, 2009). It has been demonstrated that hydrophilicity in Gram-negative bacteria is significantly higher than in Gram-positive bacteria, making them most sensitive to chitosan (No et al, 2002)
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