Effective Diffusivity Coefficients for Degradation of Pectin in Guava (Psidium guajava L.) Pulps Using Immobilized Pectinase

Background and objective: Recently, use of immobilization technology through cell entrapment to entrap biocatalysts has been shown as an economical method since it offers several advantages over suspension cultures such as reusability, high cell concentrations over a period of time, elimination of costly processes of cell recovery and cell recycling and simplifying the downstream processing. Understanding diffusion and permeability coefficients is necessary for the creation of optimized encapsulation systems. The major objectives of the present study included degradation studies on pectin using batch systems using soluble and immobilized pectinase enzymes. Materials and methods: Commercial pectinase enzymes were immobilized using entrapment method for liquefaction of Guava (Psidium guajava L.) pulps with a wide range of applications in food industries. Guava fruit pulps were liquefied using free and immobilized pectinase enzymes to assess the intra-particle mass transfer resistance. Results and conclusion: In the current study, effects of mass transfer on liquefaction process were revealed. Effectiveness factors for the various sizes of immobilized beads included less than 1.0, which indicated that the pectin degradation was a diffusion-controlled process. Effectiveness factors included 0.520 and 0.268 for beads having smallest and largest diameters, respectively. Intra-particle mass transfer resistance was assessed by calculating Thiele modulus (ф) using effectiveness factors calculated for various bead sizes. These results were further used to calculate the effective diffusivity coefficients (De) of guava pulps into the pores. Thiele modulus values (ф) were much higher than 1, which showed that the reaction was very fast and the system was mass transfer controlled. Beads with lower diameters included higher diffusivity coefficients showing a better rate of diffusion of substrates from bulk solutions.