Evaluation of critical formulation parameters influencing the bioactivity of β-lactamases entrapped in pectin beads

The bioactivity of beta-lactamases upon entrapment in calcium-pectinate beads was evaluated. Non-amidated (NAP) and amidated pectin (AP) beads were prepared according to the ionotropic gelation method using calcium chloride (CaCl2) as gelling agent, washed and dried at 37 degrees C in an oven for 2 h. Both enzyme activity and protein content were determined as well as bead calcium content. NAP allowed a better encapsulation of the protein than AP. Increasing both CaCl2 concentration and bead residence time in the gelation medium led to a significant loss of beta-lactamase activity. The drying process of beads also lowered the enzyme activity. Moreover, bead calcium content increased as the CaCl2 concentration augmented. Being very hygroscopic, the excess of CaCl2 correlates with an increase of moisture content in beads that affects enzyme activity. After elimination of free calcium from beads, it was shown that a small amount is needed to form the Ca-pectinate network and that the activity of beta-lactamases is preserved in these conditions. Therefore, the bioactivity of encapsulated beta-lactamases in pectin beads mainly depends on formulation parameters such as pectin type, CaCl2 concentration, washing and drying processes. (c) 2006 Elsevier B.V. All rights reserved.