Positive effect of glycerol on the stability of immobilized enzymes: Is it a universal fact?

In this paper, the effect of glycerol at different concentrations and pH values on the stabilities of 13 immobilized enzymes has been analyzed. Among the enzymes, we have selected 5 lipases (immobilized on octyl or amino-glutaraldehyde supports), 3 pmteases (immobilized on glyoxyl or amino-glutaraldehyde supports), 2 glycosidases, 1 laccase, 1 catalase (immobilized on glutaraldehyde matrix) and one penicillin acylase (immobilized on glyoxyl supports). The effect was completely enzyme-dependent. The results indicate that the stabilizing effect of glycerol is not universal, as in certain cases it produced even some destabilization of the immobilized enzyme (e. g., in the case of ficin extract, a protease). The glycerol effect was strongly concentration dependent (but not always the most significant results were observed at the highest glycerol concentrations), and it also strongly depends on the inactivation pH (at pH 9.0 this agent showed the strongest destabilization effects). Very interestingly, the effect of glycerol on enzyme stability was much dependent on the used immobilization protocol, which determines not only the intensity but even the sense of this effect. Thus, before using glycerol as enzyme stabilizer agent, it is necessary to confirm that the effect is positive for a specific preparation under the specific used conditions.