Why does milk bother me?

1. Why does milk bother me? And other lactose-related fables Scott MacLean CHEE 450 – January 23,2004

2. Lactose Intolerance • Inability to digest milk protein lactose • Symptoms include nausea, cramps, bloating, gas, and diarrhea • 30-50 million Americans are lactose intolerant • 75% of African Americans, 90% of Asian Americans are lactose intolerant

3. What’s the Deal? • Lactose is broken down by lactase into glucose and galactose • If a patient is deficient in the enzyme lactase and demonstrate symptoms, they are considered lactose intolerant

4. Treatment • Dietary control • Lactase tablets/liquid (Aspergillus oryzae-produced lactase is functional in GI-Tract) • Lactose-reduced products

5. Lactose-Reduced Milk • Addition of lactase enzyme before pasteurization • 70-100% Lactose reduction, available in skim, 1%, 2%, whole, and chocolate, as well as calcium fortified! • (May be UHT pasteurized)

6. The Microorganism • Kluyveromyces lactis • Yeast • Has also been GM to produce rennin

7. The Enzyme • Lactase, a.k.a. β-galactosidase • Optimum pH=7, T=3-25oC (K. lactis) • Competitively inhibited by galactose

8. The Process • Growth (Submerged liquid, solid-state) • Harvesting Cells • Extraction of Enzyme (Lysis, mechanical disintegration, electric field pulses) • Purification (Chromatography) • Ready for use!

9. The Process • Liquid lactase is commercially available • Added to milk, 25mL/100L milk • 99% lactose reduction in 24h at 4oC

10. The Economics • Problem: Milk Spoils! • UHT Pasteurization helps extend shelf life • Enzyme available commercially, 7mL for $7US • Lacteeze: $3.49, 2L, Food Basics

11. Summary • Enzyme selection dependent on type of process, administration and use • Different organisms produce similar enzymes, active under different conditions! • Lactose Intolerance is a big problem, but with the help of a little bug, can be helped!

12. Reference • National Centre for Biotechnology Education, http://www.ncbe.reading.ac.uk