Spud smashes starch barrier

September 19, 1997

Biotechnology breakthroughs: starch and evening primrose oil yields and the use of holograms

A breakthrough in genetic engineering by Oxford University scientists should dramatically increase starch production from crops such as potato, rice and maize. Starch is the largest single energy source in the human diet.

The advance stems from work by the plant sciences department into how plants breathe. Led by Steven Hill and Chris Leaver, the research team's objective was to see if genetic modification of the potato plant could alter its rate of respiration - the production of energy from the oxidation of carbo- hydrates.

The study, backed by the Biotechnology and Biological Research Council, focused on a gene which carries the inherited blueprint for one particular enzyme in the potato called the NAD-malic enzyme.

"We found that although reducing the activity of the enzyme had little effect on respiration, it did seem to influence the amount of starch formed in the tuber," said Dr Hill.

Cutting down the activity of the enzyme was made possible by turning the gene "off" using genetic engineering technology called "anti-sense".

In the laboratory, the researchers have already demonstrated a 100 per cent improvement in starch yield from potatoes in which NAD-malic enzyme activity has been cut down. The work has attracted the attention of major biotechnology firms including Zeneca, which is making a "very significant" investment in the work with a view to commercialising the findings.

Finding a way of increasing the starch content of crop plants has been the holy grail of a host of research groups around the world for many years, with much of their effort being directed at enzymes well known to play a direct role in the production of starch. "It was the most obvious and logical route," said Professor Leaver.

But the advance by the Oxford team owes much more to "serendipity".

"We knew NAD-malic existed but we did not know what its purpose was. We thought it might play a role in respiration. It was a complete surprise when we found that lowering its activity resulted in an increase in starch yield."

The team is keen to continue its basic research into the biochemistry and genetics of plant metabolism in the hope that even greater starch yields may be shown in potatoes and other crop plants.

The impact of the advance could be enormous. Professor Leaver says that in addition to the direct nutritional benefits, there could be important economic implications for the starch syrup industry. The sector produces much of the glucose for the food and drink industry and biofuels for industrial use. The fuels can be made from syrups by fermentation. Other applications of starch, such as adhesives and textile sizes, could also benefit, further boosting the value of the team's work.

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