Resumo

LAREZ VELASQUEZ, Cristóbal; MEDINA, Dimas  e  MILLAN BARRIOS, Enrique. Viscosimetric study of the enzymatic depolymerization of chitosan. Rev. Soc. Quím. Perú [online]. 2008, vol.74, n.4, pp.252-259. ISSN 1810-634X.

Enzymatic depolymerization of chitosan (acetylation degree and average viscosimetric molecular weight (M_v) of 0,85 and 310 kDa, respectively) was studied using commercial bromelain. Decrease of the average viscosimetric polymerization degree (X_V) was followed in a buffer solution of acetic acid (0,3 M)/sodium acetate (0,2 M) at 25 ºC. Under these experimental conditions it is possible to relate the instantaneous intrinsic viscosity [η] with M_v through the Mark-Houwink-Sakurada equation. Equations of Sano, which allow to compute values of intrinsic viscosity with a single measurement of relative and/or specific viscosity, was employed to obtain instantaneous values of [η], which were also obtained for comparative purpose through an iterative process using Huggins equation. Initial velocity of depolymerization (v_o) was obtained from different concentration of chitosan solutions and a fixed bromelain concentration. Michaelis-Menten constant (k_M) and maximum velocity (V_m) were obtained using the Lineweaver-Burk representation of the Michaelis-Menten equation for each set of [η] calculated employing the procedures mentioned. Best kinetics parameters for chitosan depolymerization (k_M = 3,92x10^-7 mol.dL^-1; V_m = 9,09x10^-8 mol.dL^-1.s^-1) were obtained when Sano`s equation was employed to calculate [η] values.

Palavras-chave : bromelain; degradation studies; chitosan depolymerization; enzymatic depolymerization.

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