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Release and characterization of beta-galactosidase from lactobacillus plantarum

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2004
Kara, Fırat
The enzyme, β-galactosidase (E.C.3.2.1.23) has been used for dairy industry for removing lactose from milk and milk by-products. In this study, three strains namely L. plantarum NCIMB 1193, L. plantarum DSM 20246 and L. plantarum E081 were used for β-galactosidase release by sonication method. The peak of the total enzyme activity was found to be corresponding to late logarithmic or early stationary phase of all strains. As a disruption method sonication was used for the release of β-galactosidase. Meanwhile, the sonication time was optimized for each strain. The peak of the enzyme activity was observed between 210 seconds and 270 seconds of sonication period. It was also found that sonication did not decrease the viability of L.plantarum NCIMB 1193 significantly. Liquid nitrogen cell disruption method was also used to compare the results with those obtained by sonication method. For characterization β-galactosidase, cell-free crude extract of sonicated cell culture of L.plantanrum NCIMB 1193 was used. Optimum pH found as 7.2, and optimum temperature range was found between between 350 C to 400 C. Km and Vmax values were found as 3.47 mM and 1.721 (æmol / min per mg protein) respectively from Lineweaver-Burk plot. Km and Vmax values were found as 4.064 mM and 1.863 (æmol / min per mg cell-free crude extract) respectively from Eadie-Hofstee plot. The number of ligand binding sites (napp) on a molecule of β-galactosidase was found as 1.03 which indicates that the number of ligand binding sites on the enzyme is one.