From the biocatalyst point of view carrier-free immobilized enzymes, such as CLECs (Cross-linked Enzyme Crystals) or CLEAs (Cross-linked Enzyme Aggregates), present numerous advantages versus carrier-bound or free enzyme: 10 to 1000 higher volumetric activities (U/g) and higher stability against unnatural conditions (high temperature, organic solvents, etc.) and, in some cases, higher selectivity. Although both CLECs and CLEAs are obtained through the precipitation of the enzyme (as crystalline or aggregate forms), the intrinsic difficulties and lack of knowledge on how to control nucleation and growth of the enzyme crystals has favour the focus of the research on the aggregates.
Crystallization is identified as the limiting step for the production of CLECs. Therefore our main objective is to develop methodologies for the production of protein (enzyme) crystals in gel media (reinforced protein crystals) that can be in situ cross-linked and recovered for different biotechnological applications. On the other hand, stability, size and quality of biomacromolecule crystals are important factors that make difficult the exploration of their optical, mechanical, electrical or magnetic properties, and restrict their use in technological applications. These limitations could be overcome by the production of RCLPCs of appropriate size, quality and composition.
Equilibrium morphology of lysozyme and thaumatin crystals as a function of silica gel concentration (Gavira et al., 2013).