Biocatalyst-adsorbant systems: a viable alternative to proteolytic processes in solution

Abstract

Proteolytic biocatalysts were adsorbed and stabilized using alumina as a support medium. Two biocatalyst-adsorbant systems were prepared with different physical characteristics of the adsorbant: alumina powder and alumina pearls. Direct adsorption onto the support medium has the main advantage, over other fixation methods, that preliminary steps are not required for a good interaction between the support and the biocatalyst. Proteases were adsorbed and stabilized without modifying or sterically hindering their active sites. Parameters affecting adsorption (pH, temperature, ionic strength) were varied so as to optimize adsorption conditions. Operational viability of the immobilized biocatalysts was demonstrated, taking into account the rate of desorption, resistance to microbial attack, and stability during storage. Desorption in water was studied in batch and continuous-flow processes, at various flow rates. The systems also proved to be resistant to microorganisms. Tests for stability during storage found the systems' activity remained constant after 60 days, and they performed better than biocatalysts in solution. Proteolysis of a solution of g per litre of azocasein was carried out in continuous-flow and batch modes, using our biocatalyst-adsorbant systems we prepared. In all cases, free amino group concentrations were around 2.5 times greater after treatment with biocatalyst-adsorbants than they were in the starting solution.