How is beta-galactosidase activity affected by pH and temperature?

Beta galactosidase activity is influenced by pH and temperature in different ways, depending on where the molecule is being isolated from. Beta-galactosidase derived from Bacillus circulans has an optimal pH of 6 and an optimal temperature of 50 °C. Beta galactosidases derived from Drosophila have an optimal pH of either 6 or 7. Another example is beta glucosidases isolated from Aspergillus niger have an optimal pH between 3-5 and temperature between 55–60°C. 

Alterations in pH and temperature affect beta galactosidase activity when outside the optimal ranges and can reduce activity. For example, in beta glucosidases isolated from Aspergillus niger, low acid environments can denature the enzyme.