A comparative study on immobilization of Jack Bean urease on different matrices

Abstract

Biotechnological applications of urease enzyme prevalently involve biosensor development, wastewater treatment systems, artificial kidney machines, restoration of cultural heritages, beverage industries, bioregenerative long-distance space travel systems and rehabilitation of agricultural fields. However, the integration of free urease to industrial, medical, or agricultural applications results in considerable drawbacks, such as activity loss in process conditions and high cost of isolation and purification for reuse. To overcome these mentioned restrictions and develop new biotechnological products, in this thesis study, we immobilized soluble urease onto the eggshell membrane and inner epidermis of the onion bulb scale. Natural supports for the immobilization of Jack Bean urease are already available as waste products of the food sector, with materials that are biocompatible, biodegradable, non-toxic and low-cost. Further, considering sustainability and feasibility issues, the eggshell and onion membranes were chosen for this approach. The eggshell membrane is essentially made of cross-linked collagens as a flexible protein fiber. Additionally, the inner epidermis of the onion bulb scale is predominantly composed of microfibrillar cellulose. The surface morphology of these natural membranes, as displayed by SEM imaging, provided a suitable support for the adsorption technique. This method is the simplest, undemanding, and economically attractive enzyme immobilization approach, relying on weak electrostatic interactions or physical bonding. For the immobilization of Jack Bean urease, each supportive membrane was initially washed with water, air-dried, and cut into 1 cm2 pieces. Subsequently they were treated with branched polyethyleneimine to generate polycationic surfaces. This adsorbent is generally recognized as an FDA-approved safe substance. The urease activity was detected by measuring the amount of released ammonia, as an indicator of residual urease activity.