[Growth inhibition of Pseudomonas aeroginosa by degree of deacetylation values of chitosan]

ABSTRACT

Chitin, which entails the most abundant biopolymer in nature after cellulose, having found numerous applications in food processing, cosmetics, agriculture, medical and environment. Natural sources of this polymer are component of exoskeletons of crustaceans and insects as well as cell walls from some bacteria and fungi. Chitosan is a partially deacetylated polymer of chitin, which is more soluble than chitin. The goal of this research is to investigate the diversity of antimicrobial effects of deacetylated chitosan extracted from a certain Persian Gulf shrimp waste [Penaeus semisculcatus], against clinical Pseudomonas aeroginosa. At first, chitin and chitosan were extracted from Penaeus semisulcatus waste by chemical and microbial methods at optimum situation. Deacetylation process of chitin was carried out in alkaline solution at 85°C for 15, 20, 45 minutes and 10 hours respectively and subsequently washed with anhydrous EtOH to remove the residual water. Degree of deacetylation of chitosan samples and its structure were measured by FTIR and Scanning electronic microscopy respectively. Antimicrobial activity was tested against clinical Pseudomonas aeroginosa by agar disc diffusion method. Finally, wound band was made by these compounds and antimicrobial activity was studied invitro. The result of present study confirmed the degree of deacetylation of chitosan samples up to 65% by FTIR method. There was no indication of shift on increasing acetylation degree by heating duration from 15 minutes to 10 hours. Pore diameter was decreased from 0.5-1 micro to 0.065-0.25 micro by the increasing of heating duration. Increased clinical Pseudomonas aeroginosa growth inhibitory up to 50% was obtained by usage of more effective materials up to 3 times on disc. The result of our study showed that there was no relationship between increased heating duration and deacetylation degree. Membrane pores were smaller and antimicrobial activity was more effective by increasing of deacetylation and Ca[+2] presences. The method which was used in this research to prepare porous chitosan membranes with different pore diameter, is suitable and cost effective. Because chitin and chitosan are not toxic, better antimicrobial activity results can be obtained by using more concentrated versions of these components