Antimicrobial Activity of Chitosan with Different Degrees of Acetylation and Molecular Weights

A review of the antimicrobial activity of chitosan

“…Both parameters affect the antimicrobial activity of chitosan independently, though it has been suggested that the influence of the MW on the antimicrobial activity is greater then the influence of the DA [41] . To cite recent examples, studies carried out on Bacillus cereus, E. coli, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella enterica, B. subtilis, Listeria monocytogenes and Klebsiella pneumoniae [42][43][44][45][46][47] , proved that for lower chitosan MW (LMW), greater is the observed effect on the reducing of microorganism growth and multiplication. The size and conformation appears to be fundamental to understand the effectiveness of LMW chitosan.…”

“…Pseudomonas fluorescens 250 500 ~1000 [19] [7] [31] Enterobacter aerogenes 250 [19] Gram positive Bacillus cereus <1000 1000 [31] [ 7,50] Bacillus megaterium 800 [44] Staphylococcus aureus 20 100 >800 700 >1250 [7] [19] [44] [61] [49] Listeria monocytogenes 150 250 800 [50] [19]…”

Antibacterial activity of chitosan and the interpolyelectrolyte complexes of poly(acrylic acid)-chitosan

“…Chitosan has been demonstrated to induce an increase in germination percentage and yield of cereal plants and tomato (Hadwiger, 1984;Hidalgo et al 1989). Omura et al (2002) measured the antimicrobial activity (Minimum Inhibitory Concentration, MIC) of chitosan and chitooligosaccharides with different molecular weights but without acetylated groups. They observed that chitosan with high molecular weight showed strong antimicrobial activity against Gram positive bacteria, whereas chitosans of 11 kDa and 20-30 kDa molecular weight were most effective against Gram negative bacteria.…”

Synthesis and screening of N-acyl thiolated chitosans for antibacterial applications

“…Concerning the structure-activity relationship (SAR) of chitosan, manifold studies indicate that the molecular weight (MW) and the degree of deacetylation (DD) are among the most influential parameters (Omura et al, 2003;Younes, Sellimi, Rinaudo, Jellouli, & Nasri, 2014). However, the impact of MW on the antimicrobial activity appears to be different for gram-negative and grampositive bacteria Seo, Mitsuhashi, & Tanibe, 1992).…”

“…While low MW (LMW)-chitosan has been reported as superior for eliminating gram-negative-bacteria, higher MWs exert 4 stronger effects against gram-positive bacteria (Omura et al, 2003;Younes et al, 2014;Zheng & Zhu, 2003), probably due to the different cell wall types. Chitosans with high DD values display higher positive charge density of the protonated amine group in acidic media, which enhances their antimicrobial efficiency (Fernandes et al, 2010;Omura et al, 2003;Zheng & Zhu, 2003) mainly against gram-negative strains, and to a lower extent vs. gram-positive strains (Younes et al, 2014). Generally, pH is another key factor for antimicrobial chitosan activity, which is higher against many microorganisms at low pH Park, Nah, & Park, 2011).…”