Isolation and Purification of β-Galactosidase Enzyme from Local Lactic Acid Bacteria Isolates to Overcome the Phenomenon of Non-Degradation of Milk Lactose

Abstract

This study aim is to purify β-galactosidase from a local isolate of yogurt in Salah al-Din Governorate to overcome the phenomenon of lactose in decomposition. The bacteria were grown on MRS medium supplemented with 1%CaCo3. Twenty isolates of lactic acid bacteria were obtained and conducting culture tests and microscopic examinations were on these isolates. In order to classify them to the level of species, it was found that there were four types, namely: Lactobacilluse acidophilus,LactobacilluseCasei,Lactobacilluse delubrici subsp.bulgaricus,Streptococcus thermophilus, The cultivation and activation steps of the different isolates were carried out forobtaining the most productive and active isolate, which is Lactobacilluse acidophiluse. Beta-galactosidase activation processes were carried out for the enzyme and cell breakdown by lysozyme. Purification and sedimentation processes were carried out using ammonium sulfate and membrane sorting, followed by gel filtration using Lactobacillus G-150. The best extraction rate (L.acidophiluse 70%) was achieved by enzyme precipitation (4,375) units/mol, and the activity increased in the membrane sorting step to (5,900) units/mol, and in gel filtration we obtained activity of the enzyme (15.591) units/mol.