CONICET | Buscador de Institutos y Recursos Humanos

Currently several important industrial processes apply immobilized enzymes. Basically, the immobilization process converts a homogeneous catalyst into an active enzyme staked in a solid support. Novelties in immobilization procedures tend to reduce toxicity (generally associated to the support), increase commercial availability at low cost, to ease the handling, improve high catalytic activity and allow reusability. In our laboratory we produce and isolate β-Gal inclusion bodies (IBβ-Gal). This is a singular immobilized enzyme because of the biological nature of its immobilization process and the self-supported condition which makes it environmentally friendly. In a previous work, we have demonstrated that in the IBβ-Gal format the enzyme was more active with respect to the soluble version. In this work we study the reusability of IBβ-Gal to hydrolyze lactose and analyze the effect of the storage temperature (ST) without cryoprotectant. We demonstrate that the ST modulates the recovery of IBβ-Gal catalytic activity. At ST=4ºC the activity decrease, but in frozen conditions the activity grows up vs the conservation time. At ST=-20ºC we measured the lowest activities. Surprisingly at a ST≤-80ºC the highest IBβ-Gal activities were obtained. In full hydrated conditions (4ºC) the enzyme desorbed from IBs. In contrast, the non-hydrated (frozen) conditions prevents the desorption process and consequently the activity lost. Moreover, the freezing rate (dehydration rate) seems to determine the enzyme integrity. At ST=-20ºC the lower dehydration rate allows the unfolding of a protein population within IBs, Conversely, the fast dehydration (ST≤-80ºC) preserved a high-quality conformation concomitant with a IBβ-gal restructuration in each dehydration process, We propose that the best storage condition is at -80ºC where the microorganism contamination is prevented and the speedy of freezing would improve -Gal catalytic activity.