Immobilization and stabilization of pullulanase from Klebsiella pneumoniae by a multipoint attachment method using activated agar gel supports

The immobilization and stabilization of pullulanase from Klebsiella pneumoniae were investigated. Pullulanases immobilized on activated agar gel (glyoxyl-agar gel) via multipoint attachment between amino groups of pullulanase and aldehyde groups on the gel surface were significantly stable compared with free pullulanase and pullulanase adsorbed on chitosan beads. The immobilization yield, thermal stability and activity of immobilized pullulanase greatly depended on the surface density of aldehyde groups on the support gel. The optimum temperature and pH of immobilized pullulanases prepared by the multipoint attachment method using activated agar gels were 50 °C and 6.0, respectively. These values were the same as those of free pullulanase. Pullulanase immobilized on agar gel activated with 4.8 M glycidol retained 60% of its initial activity after a 250-h incubation at 45 °C, while free pullulanase completely lost its activity after a 72-h incubation at the same temperature.