Enzyme Co-Immobilization on Precipitated Silica for Sustainable Lactobionic Acid Production

Lactobionic acid (LBA) is a compound that, in the last decade, has become critically important due to its potential applications in the food, chemical, pharmaceutical, and cosmetic industries. Enzymatic biosynthesis in the presence of a redox mediator is one method of producing LBA biologically. Cellobiose dehydrogenase (CDH) oxidizes the lactose to lactobionic acid, while laccase (LAC) enables the regeneration of the redox mediator (ABTS), which acts as an electron acceptor for CDH. The aim of this study was to develop an effective immobilized enzymatic system for the production of LBA. Two enzymes were used in the experiment: CDH from Phanerodontia chrysosporium (PchCDH) and LAC from Cerrena unicolor (CuLAC), which were immobilized on precipitated silica (Sipernat 22) activated by APTES and PEI. The immobilization process increased enzyme stability, improved the efficiency of LBA synthesis, and reduced costs, particularly in the context of using Sipernat 22 silica, which is inexpensive and widely used across various industries. The co-immobilization of both enzymes on the carrier proved to be the most effective approach, achieving a 90% conversion of lactose to lactobionic acid after ten cycles of synthesis. Comprehensive biochemical characterization, including protein loading, catalytic activity, and optimal pH, is provided in the main text.