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Wednesday, October 04, 2006

New Gene Process Makes Low-Lactose Milk

Wow. Every once in a while a scientific discovery comes out of the blue and suggests a possibility that no one ever thought of.

Here's the science. I'll follow with the English translation.

From GM bacteria could naturally sweeten dairy, by Stephen Daniells on

By adding a novel genetically engineered bacterial strain to dairy, the fermentation process is limited to converting lactose to glucose, a technique that could remove the need to add sweeteners to dairy products.

The research, part of the EU-funded Nutra Cells project (QLK1-CT-2000-01376), also has implications for lactose intolerance because, by converting the lactose in the dairy to glucose, the final lactose content of the dairy is significantly reduced.

Lactococcus lactis is used extensively in the dairy industry in the production of fermented milk products, and has a relatively simple carbon metabolism pathway. By directly engineering this strain of Lactococcus lactis the researchers were able to delete genes that coded for glucose metabolism by the bacteria. This was achieved by disrupting the main sugar transport system, the so-called sugar phosphotransferase system (PTS).

Lactose is a disaccharide, meaning it is made up of two basic sugar molecules, a galactose molecule bonded to a glucose molecule. By deleting certain genes in the lactose-PTS, it was possible to create a bacterium (NZ9000Glc-Lac+) that selectively fermented the galactose part of the lactose, but not the glucose part. The glucose then accumulated outside of the cell, in the dairy product.

OK, here it is in English. When lactose hits the intestines, it normally is digested – split into its smallest components - by the enzyme lactase. Those smallest components are the simple sugars called glucose and galactose. We know that many beneficial bacteria can do the same thing. That's what probiotic bacteria are for. (I've had a long series of posts about this. See Probiotic Kefir Healthier Alternative to Yogurt; Prebiotics and Probiotics; and Kids and Lactose Intolerance, among others.) The bacteria can do this in the body – that's why they reduce symptoms from lactose intolerance – and they can also do it directly in the milk itself. That's what makes products like yogurt and kefir low in lactose.

What the scientists, led by Professor Oscar Kuipers from the University of Groningen for the European Union-funded Nutra Cells project, did was change one piece of the process. The modified bacteria gobbled up a lactose molecule, split it, fermented only the galactose half and released the glucose half back into the milk. This made for a sweeter, but lower-lactose milk product.

This isn't a big breakthrough all by itself. In fact, one of the problems with lactose-reduced milk is that it is often considered too sweet by many people. Oddly, both glucose and galactose individually are sweeter than they are combined as lactose. But whey and other high-lactose sweeteners made from dairy products are often added to milk in commercial food processing. If the milk itself were sweeter to begin with, then no extra sweeteners would be needed. [Lactose-free milk could be used in the first place, but it is expensive because of the lengthy period needed for the added lactase to work.]

An additional impact of this is that the process would be acceptable both to Europeans worried about genetically-modified food, since no new DNA is added. Instead one already-existing gene is stopped from working.

Prof. Kuipers said that while an industrial level process hasn't yet been developed, it isn't a big technical issue. Even so, don't expect to see this on the market for a few years.

Nonetheless, it's a startling advance and perhaps just a tease of what's coming as scientists learn more about manipulating genes. For good.

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