Genetic engineers create sugar that is not fattening

THE NEWS for slimmers just gets better and better. First there was Olestra, the fat that didn't make you fat; and now Dutch scientists have produced a sugar beet whose sugar tastes sweet but which the body cannot digest.

The result is a plant that efficiently makes a calorie-free sweetener known as a fructan, using genes taken from the Jerusalem artichoke. The first crop from a field trial of these transgenic plants will be harvested later this month.

The sugar industry is keenly interested in the new plants, but the companies involved have already put Dr Andries Koops, of the Centre for Plant Breeding and Reproduction Research in Wageningen, under a contractual gag on their names.

"I can't name them. But there are a number of patents being filed for this," he told The Independent. If commercially successful, such plants could revolutionise dieting and farming.

The sugar beet crop provides half of the UK's sugar, amounting to hundreds of thousands of tons annually, and biotechnology companies are already spending millions of pounds to develop herbicide-resistant transgenic forms of the plant, to improve crop yields.

Early results from the Dutch field trial suggest that the genetically modified plants are as healthy as normal sugar beet plants, which store sucrose in an underground root to help them survive the winter,

However, they might be infertile, because the normal sugar beet plant uses its stored sucrose to make seeds. The transgenic plant may lack the ability to turn its fructan store back into sugar, meaning the seeds are not viable.

That, though, could be an advantage in a commercial transgenic plant, since it would lower the chances of the gene crossing into wild species.

The modified plants contain a gene taken from the Jerusalem artichoke, which naturally turns the sucrose into fructans - indigestible forms of the fruit sugar fructose. Fructans taste sweet to the human palate. "We all have the enzymes to digest sucrose, which chemically is a disaccharide," said Professor Koops. "But fructans are trisaccharides" - consisting of three sugar molecules linked together - "and we can't digest those. Only some of the bacteria in our colons might be able to, and the results would be converted to fatty acids that would be dealt with by the liver."

The Dutch group's work, which has taken nine years, is reported this month in the science journal Nature Biotechnology.

"The system holds great promise for commercial exploitation," commented Professor Sjef Smeekens of the University of Utrecht, who said that for "those with a sweet tooth, but a mind for their waistline" the work should be a cause for celebration.

However, Dr Koops is less interested by this breakthrough than by future possibilities from transgenic sugar beet. "This is just testing the concept," he said. "What we are really looking at is the possibilities of using plants to produce chemicals such as polymers to order."