Extracellular Metabolites Produced by a Novel Strain, Bacillus alvei NRC-14: 4. Antimicrobial Activity of Chitosan Oligosaccharides

Degradation of chitosan by specific and/or non-specific enzymes resulted in the production of chitosan oligosaccharides (COSs) which effectively confirmed to be inhibitor agents. These bioactive chitosan oligosaccharidesare used mainly for medical applications due to their specific biological activities. In the present study, flaked chitosan was used along with sugarcane bagasse as carbon sources for production of COSs by a novel bacterial strain, Bacillus alvei NRC-14.Thisstrain is,constitutively, able to producecarbohydrate-active enzymes.The enzymes activity increased from 1.7 U/ml, in a minimal chitosan medium, to 4.6 U/ml by optimizing the culture conditions using sugarcane bagasse as carbon source. The crude culture was found to contain a variety of enzymes,i.e. chitosanase, glucanase, cellulase as well as chitobiase and high amounts of cellobiase. These enzymes efficiently degraded flaked chitosan to COSs. Three chitosan oligosaccharides with different molecular weights were obtained; signed CH-76, CH-25, and CH-10. Antimicrobial activity of native chitosan and these COSs against bacteria and fungi was shown to be closely dependent on the molecular weight, degree of deacetylation as well as the pH and the strain tested. Recently, COSs are extensively demonstrated to be