Production of medium-sized chitosan oligomers using molecular sieves and their antibacterial activity.

Chitosan, derived from the natural polysaccharide chitin, was fragmented in very dilute acetic acid solutions using zeolites and molecular sieves, a type of zeolites, under variable reaction conditions of temperature, acid concentration, duration of reaction, and zeolites of variable pore sizes. Fragmentation resulted in the formation of appreciable amounts of chitosan oligomers comprised of 4-8 units, which were studied by using LC-MS, MS, as well as IR spectroscopy. The prepared fragments were tested for their biological activity and some of them showed antibacterial activity against Gram-positive bacteria.

Preparation of Chito-Oligomers by Hydrolysis of Chitosan in the Presence of Zeolite as Adsorbent.

An increasing interest has recently been shown to use chitin/chitosan oligomers (chito-oligomers) in medicine and food fields because they are not only water-soluble, nontoxic, and biocompatible materials, but they also exhibit numerous biological properties, including antibacterial, antifungal, and antitumor activities, as well as immuno-enhancing effects on animals. Conventional depolymerization methods of chitosan to chito-oligomers are either chemical by acid-hydrolysis under harsh conditions or by enzymatic degradation. In this work, hydrolysis of chitosan to chito-oligomers has been achieved by applying adsorption-separation technique using diluted HCl in the presence of different types of zeolite as adsorbents. The chito-oligomers were retrieved from adsorbents and characterized by differential scanning calorimetry (DSC), liquid chromatography/mass spectroscopy (LC/MS), and ninhydrin test.