Recyclable thermophilic hybrid protein-inorganic nanoflowers for the hydrolysis of milk lactose.

Thermostable β-galactosidase (TmLac) has been immobilized as hybrid inorganic-protein nanoflowers using salts of Cu2+, Mn2+, Zn2+, Co2+ and Ca2+ as the inorganic component. The incorporation efficiency of enzyme into the nanoflowers was higher than 95% for a protein concentration of 0.05 mg/mL. The structure, activity and recyclability of the nanoflowers with different chemical composition were analyzed. Ca2+, Mn2+ and Co2+ nanoflowers showed a level of lactase activity equivalent to their same content of free enzyme. Cu2+nanoflowers showed only marginal enzyme activity in agreement with the inhibitory effect of this cation on the enzyme. TmLac nanoflowers provide an efficient methodology for enzyme immobilization and recyclability. TmLac-Ca2+ nanoflowers presented the best properties for lactose hydrolysis both in buffered and in milk, and could be reused in five consecutive cycles.