Calcium pectate gel beads for cell entrapment: a study on the stability of Kluyveromyces marxianus whole-cell lactase entrapped in hardened calcium pectate and calcium alginate gels

摘要

Calcium pectate gel (CPG) and calcium alginate gel (CAG) were tested as the carriers for entrapment by using permeabilized cells of Kluyveromyces marxianus CCY eSY2 as the source of lactase (β-galactosidase, EC 3.2.1.23). Screening experiments show that for long-term hydrolysis of lactose in the presence of phosphate ions, stabilization ('hardening') of both gels by the action of polyethyleneimine and glutaraldehyde is required. Permeabilized cells entrapped in hardened CPG hydrolysed 5% lactose more than 80% during 55 cycles in a semicontinuous process and 11 days in a continuous one, both at 35℃. The operational stability of analogue hardened CAG-cells was lower. More than 80% hydrolysis was achieved only during 25 cycles and 6 days, in the same semicontinuous and continuous processes, respectively. Activities of lactase in permeabilized cells entrapped in both hardened gels were not affected by storage at 4℃ for 2 months.