Microwave‐assisted degradation of chitosan with hydrogen peroxide treatment using Box‐Behnken design for enhanced antibacterial activity

Abstract

SummaryLow molecular mass (MM) chitosan with high degree of deacetylation (DDA) has excellent bioactivity including antioxidant, antibacterial and encapsulation properties. In this work, to reduce the MM of chitosan, microwave‐assisted heating treatment (MAHT) conditions were investigated using three factors at three levels Box‐Behnken design (BBD). Microwave heating (MH) time, H2O2 concentration and solid‐to‐liquid ratio significantly affected the DDA and MM of chitosan. The antibacterial activities of chitosan before and after degradation were investigated based on minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The results showed that a second‐order polynomial equation fitted the observed values using multiple regression analysis and had a high coefficient of determination (R2 = 0.9591 and 0.9161 for the DDA and MM of chitosan, respectively). An optimisation study was performed using Derringer's desirability function methodology, and the optimal conditions were 80‐s MH time, 1.5% H2O2 concentration and 1:40 solid‐to‐liquid ratio. The MIC and MBC of chitosan before and after degradation against Escherichia coli and Salmonella typhimurium were 0.031 and 0.063 mg mL−1, and 0.25 and 0.125 mg mL−1, respectively. The optimised DDA and MM of chitosan were 90.58 ± 2.04% and 124.25 ± 14.36 kDa, respectively, which significantly reduces the use of oxidant reagent.