Bioaffinity based immobilization of almond (Amygdalus communis) β-galactosidase on Con A-layered calcium alginate-cellulose beads: Its application in lactose hydrolysis in batch and continuous mode

Abstract

In this study, immobilization of partially purified almond (Amygdalus communis) β-galactosidase on Con A layered calcium alginate-cellulose beads was investigated. Immobilized β-galactosidase retained 72% of the<br />initial activity after crosslinking by glutaraldehyde. Both soluble and immobilized enzyme exhibited the same<br />pH and temperature optima at pH 5.5 and 50ºC, respectively. However, the immobilized enzyme<br />showed a remarkable broadening in pH and temperature-activity profiles as compared to the native<br />enzyme. Immobilized enzyme was significantly more stable against thermal denaturation at 60ºC.<br />Immobilized β-galactosidase exhibited 67% residual activity in the presence of 5% D-galactose while its soluble counterpart retained only 35% activity under identical conditions. Soluble enzyme showed 69% residual<br />activity after exposure to pepsin (0.15 mg/ml) for 1 h whereas the immobilized β-galactosidase was more<br />stable and retained nearly 84% activity under identical experimental conditions. The activity of immobilized<br />enzyme was enhanced to 156% whereas soluble β-galactosidase showed an enhancement upto 134%<br />when exposed to trypsin (0.1 mg/ml) for 1 h. Moreover, immobilized β-galactosidase exhibited greater<br />enhancement in enzyme activity against exposure to various ions present in milk such as Na+, K+, Ca+2,<br />Mg+2 and citrate ions. The higher concentration of lactose was hydrolyzed from whey as compared to the<br />hydrolysis from milk by immobilized enzyme at 50ºC and 60ºC in batch processes. Lactose was hydrolyzed<br />to 86% and 78% after 20 days continuous operation of reactors at the flow rates of 20 ml/h and 30 ml/h,<br />respectively. In view of its stability and utility in batch and continuous processes, such preparation could be<br />exploited for the hydrolysis of lactose from milk and whey in a more convenient and cheaper way in dairy<br />industries.<br /><br />