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Production and Characterization of β‐Galactosidase from Streptococcus thermophilus
Author(s) -
GREENBERG N. A.,
MAHONEY R. R.
Publication year - 1982
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1982.tb12891.x
Subject(s) - streptococcus thermophilus , chemistry , lactose , size exclusion chromatography , hydrolysis , divalent , ammonium sulfate precipitation , chromatography , ammonium sulfate , lysis , galactose , ion chromatography , ion exchange , enzyme , yield (engineering) , salting out , biochemistry , fermentation , lactobacillus , ion , organic chemistry , materials science , aqueous solution , metallurgy
Crude β‐galatosidase was produced by lysis of cells of Streptococcus thermophilus grown on deproteinized whey. The enzyme was partially purified by ammonium sulfate precipitation and ion‐exchange chromatography to yield a preparation free of protease activity. Highest activity was observed at pH 7.1, in the presence of potassium and manganese ions. Both monovalent and divalent cations were required for maximum activity but not for stability. The K m for o ‐nitrophenyl‐β‐galactopyranoside and lactose was 0.98 mM and 6.9 mM, respectively. Galactose was a competitive inhibitor with K i of 60 mM. Gel‐filtration indicated a molecular weight of 530,000. The enzyme seems well suited to hydrolysis of lactose in milk.