Design of β-galactosidase/silica biocatalysts: Impact of the enzyme properties and immobilization pathways on their catalytic performance

The use of heterogeneous biocatalysis in industrial applications is advantageous and the enzyme stability improvement is a continuous challenge. Therefore, we designed -galactosidase heterogeneous biocatalysts by immobilization, involving the support synthesis and enzyme selection (from Bacillus circulans, Kluyveromyces lactis, and Aspergillus oryzae). The underivatized, tailored, macro-mesoporous silica exhibited high surface area, offered high enzyme immobilization yields and activity. Its chemical activation with glyoxyl groups bound the enzyme covalently, which suppressed lixiviation and conferred higher pH and thermal stability (120-fold than for the soluble enzyme), without observable reduction of activity/stability due to the presence of silica. The best balance between the immobilization yield (68%), activity (48%), and stability was achieved for Bacillus circulans -galactosidase immobilized on glyoxyl-activated silica, without using stabilizing agents or modifying the enzyme. The enzyme stabilization after immobilization in glyoxyl-activated silica was similar to that observed in macroporous agarose-glyoxyl support, with the reported microbiological and mechanical advantages of inorganic supports. The whey lactolysis at pH 6.0 and 25 degrees C by using this catalyst (1 mg ml(-1), 290 UI g(-1)) was still 90%, even after 10 cycles of 10 min, in batch process but it could be also implemented on continuous processes at industrial level with similar results.