Lactase (ß-Galactosidase) - 25ml. Please note that none of our enzymes are to be considered as being of Food Grade Standard. They are only suitable for use in education. Working Concentration: 1 - 2 %. pH range: 6.5 - 8. Temperature range: 35 - 50°C. Substrate: 5% Lactose. Product: Glucose & Galactose. Source: Yeast. It's good practice to store enzymes in a refrigerator (5°C approx.). This should give a shelf life of 12 months without significant loss of activity. All enzymes, as supplied, should be considered as 100% (unless otherwise specified) for example: Cellulase is supplied as 2g powder - 1g in 100ml gives a 1% working solution. Pectinase supplied as 100ml - 1ml diluted to 100ml gives a 1% solution. Glossary: pH - Recommended range for maximum activity. Temperature - recommended range for maximum activity. Working Concentration - dilution of the Enzyme (as supplied) to this level should give an acceptable reaction time. Substrate - substance to be reacted with the Enzyme, and appropriate concentration. Product - substance produced by breakdown of the substrate. Source - origin of the Enzyme.