Bifunctional immobilization of a hyperthermostable endo ß 1,3 glucanase

Laminarinase A (LamA) from Pyrococcus furiosus is a hyperthermostable endo-ß-1,3-glucanase (EC 3.2.1.39) belonging to the glycosyl hydrolase family GH16. Here, we report the two-step immobilization of LamA on macroporous acrylic epoxy beads, extra-functionalized with disulfide groups. To facilitate initial immobilization via thiol–disulfide exchange, we introduced, by site-directed mutagenesis, a superficial cysteine residue near the protein C-terminal end. The thus-obtained S296C variant showed similar catalytic properties as native LamA. The activity of immobilized S296C displayed an inverse relationship with particle size. Use of conventional beads (150–300 µm in diameter) obstructed the catalytic efficiency due to pore diffusion limitation of the polysaccharide substrate. Bifunctional attachment to milled beads (20–40 µm) resulted in high enzyme load and outstanding catalytic features. Bifunctional immobilized S296C showed extreme pH stability and could be repeatedly used at 60 °C without significant activity loss.