In vivo biotinylation of recombinant beta-glucosidase enables simultaneous purification and immobilization on streptavidin coated magnetic particles

Beta-glucosidase from Bacillus licheniformis was in vivo biotinylated in Escherichia coli and subsequently immobilized directly from cell lysate on streptavidin coated magnetic particles. In vivo biotinylation was mediated by fusing the Biotin Acceptor Peptide to the C-terminal of beta-glucosidase and co-expressing the BirA biotin ligase. The approach enabled simultaneous purification and immobilization of the enzyme from crude cell lysate on magnetic particles because of the high affinity and strong interaction between biotin and streptavidin. After immobilization of the biotinylated beta-glucosidase the specific activity (using p-nitrophenyl-β-d-glucopyranoside as substrate) was increased 6.5 fold (compared to cell lysate). Immobilization of the enzyme resulted in improved thermal stability compared to free enzyme; after 2 h of incubation (at 50 °C) the residual enzyme activity of immobilized and free beta-glucosidase was 67 and 13%, respectively. The recyclability of immobilized beta-glucosidase was examined and it was observed that the enzyme could be recycled at least 9 times and retain 89% of its initial activity.