Synthesis and antimicrobial activity of high molecular weight diethylaminoethyl chitosan biopolymer films

Author(s)

Otávio da Mata Cunha

• Document type: Master's Dissertation
• Press: São José do Rio Preto. 2019-03-28.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências Letras e Ciências Exatas. São José do Rio Preto
• Defense date: 2019-03-08
• Advisor: Vera Aparecida de Oliveira Tiera

Abstract

Chitosan (CH) derivatives substituted with diethylaminoethyl (CH-DEAE) and DODECIL (CH-DEAE-DD) groups show excellent inhibition activity against fungi Aspergillus flavus and Aspergillus parasiticus and antimicrobial activity is related to the degree of modification structural, concentration and molecular mass of the polymers. Based on this assumption, the present study had the objective to obtain films processed from these derivatives with potential application as edible coating in the post-harvest conservation of fruits and vegetables. The antimicrobial activity of the films was evaluated against the fungi Alternaria solani, Alternaria alternata and Penicillium expansum that impact the production and conservation of foods. To obtain the films, the structure of the high molecular weight chitosan (Mw), 282 KDa, was first modified by the substitution reaction by DEAE groups followed by the reaction with dodecyl aldehyde and subsequent reduction with sodium borohydride. Chitosan and its derivatives were characterized by ¹H NMR, obtaining degrees of substitution (DS) of 40% of DEAE groups and 3% of DD. The biopolymer films were obtained by casting and characterized by Infrared Spectroscopy with Fourier Transform (FTIR). The thermogravimetric (TG) analyzes indicated that the addition of plasticizers, glycerol and sorbitol, results in the formation of a polymer blender and the results of the mechanical properties corroborated with this analysis, since the chemical modifications carried out in the chitosan structure provided better malleability in biopolymer films. The images obtained by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) showed a smooth surface with no porosity and cracking. X-ray diffraction (XRD) showed that the synthesized chitosan derivatives have a more amorphous structure than the commercial chitosan one. The cytotoxicity of the polymers was assessed using 3T3 cells and showed cell viability above 90% for all polymers, indicating that this material can be used as a coating of fruits and seeds. The results of the in vitro antimicrobial activity showed that the biopolymer films of amphiphilic chitosan derivatives are more effective than CH films against the fungi Alternaria and Penicillium. For the coating of fruits, the results showed that the CH-DEAE-DD film showed a better efficiency in food preservation. (AU)

• FAPESP's process: 17/13762-7 - Synthesis and antimicrobial activity of biopolimer film of high molecular mass dietilaminoetil chitosan
• Grantee: Otávio da Mata Cunha
• Support type: Scholarships in Brazil - Master