Extraction and characterisation of β-galactosidase produced by Bifidobacterium animalis spp. lactis Bb12 and Lactobacillus delbrueckii spp. bulgaricus ATCC 11842 grown in whey

This study investigated the production of β-Galactosidase (β-gal) by Bifidobacterium animalis ssp. lactis Bb12 and Lactobacillus delbrueckii ssp. bulgaricus ATCC 11842 in whey and the effect of four different extraction methods i.e. sonication, acetone-toluene, SDS-chloroform and lysozyme-EDTA treatment on enzyme activity from these organisms. Both organisms were grown in deproteinised whey containing yeast extract (3.0 g/L), peptone (5.0 g/L) and glucose (10.0 g/L) for 18 h, at 37 °C for B. animalis ssp. lactis Bb12 and at 45°C for L. delbrueckii ssp. bulgaricus ATCC 11842. The optimum intracelluar β-gal activity on 15 mM o-nitrophenyl β-D-galactopyranoside (ONPG) assay was at pH 6.8 for both organisms irrespective of the method of extraction used. Also, the effect of temperature on enzyme activity was studied at various temperatures (30, 35, 40, 45, and 50°C). At 35°C and 40°C, B. animalis ssp. lactis Bb12 exhibited more intracellular β-gal activity extracted by sonication than other temperatures and methods. However, L. delbrueckii ssp. bulgaricus ATCC 11842 showed more intracellular β-gal activity at 35°C and 45°C when extracted by lysozyme-EDTA treatment. Among the four methods used for β-gal extraction, sonication gave the best result (6.80 Unit/mL) for B. animalis ssp. lactis Bb12 while lysozyme-EDTA treatment was found to be the best (7.77 Unit/mL) for L. delbrueckii ssp. bulgaricus ATCC 11842.