Analytical Sciences

Study on Degradation Characteristics of Chitosan by Pepsin with Piezoelectric Quartz Crystal Impedance Analysis Technique

Han TAO, Wanzhi WEI, Youan MAO, Shufen ZHANG, and Jianjun XIA

State Key Laboratory of Chemo/Biological Sensing & Chemometrics, Hunan University, Hunan Changsha, 410082, P. R. China

Piezoelectric quartz crystal impedance analysis technique was applied to study the chitosanolytic activity of pepsin. The method is based on the viscosity-density reduction of chitosan solution during the enzymatic degradation process. Experiments examined the time courses of the variations of motional resistance (ΔR₁) for a quartz crystal. By comparing the ΔR₁ response curves under different degradation conditions, the effects of pH, temperature, enzyme and substrate concentration on the chitosanolytic activity of pepsin was investigated in detail. The results suggest that the optimum pH and temperature were 4.6 and 55°C, respectively. Increasing aptly the enzyme or substrate concentration was in favor of the degradation of chitosan. Moreover, the influence of the degree of deacetylation (DD) on the enzymatic degradation was studied. The result indicates that chitosan with a lower DD was easier to be degrade compared with chitosan with a higher DD. Also, it was found that there was a good linear relationship between the ΔR₁ response and the DD value. The regression equation was ΔR₁ = 0.058 × DD - 6.795 and the correlation coefficient was 0.987.

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