When immobilization of enzymes results in user-unfriendly biocatalysts: Secondary immobilization and other solutions to overcome handling shortcomings

One recent trend in enzyme immobilization is the use of relatively simple immobilization techniques that produce ex novo solids containing the enzymes. Many of them may present some problems in the handling or during operation (by size and/or mechanical resistance), while bringing forth great improvements in the enzyme features. Other methods use metals, that can lead to unexpected effects. To solve this handling problems may be critical for the implementation of these biocatalysts. This is exemplified using different biocatalysts (enzymes immobilized on pre-existing macroporous supports or nanoparticles, crosslinking enzyme aggregates or enzyme-nanoflowers). After presenting the different immobilization techniques, and discussing the possible role of the metals, we shall discuss how the recovery and mechanical fragility issues can be solved. Recovering can be simplified just by using magnetic materials, while trapping in alginate or polyvinyl alcohol polymeric beads or immobilization in larger particles may solve both problems. Some additional advantages of this strategy are the improvement of enzyme stability, generation of enzyme nanoenvironments, which can permit the promotion of partition effects and produce enzyme stabilization in the presence of hydrophobic organic solvents or improve thermodynamic yields.