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BIOTECHNOLOGY
Led by professor Bilal Camara at the Institute of Plant Molecular Biology in Strasbourg, France, a unit of the National Center for Scientific Research, the group hypothesized that the structural similarity between bixin and saffron meant a similar biosynthetic pathway. They used DNA probes crafted from the genes of other plants to look for similar sequences in B. orellana. They found the enzyme pathway they were looking for: a dioxygenase to convert lycopene to bixin aldehyde, then an aldehyde dehydrogenase to produce norbixin, and finally a methyltransferase to yield bixin. The researchers transferred the relevant B. orellana genes into bacteria preengineered to produce lycopene and were able to detect bixin production. "There's a lot of interest in using natural products to replace synthetic colorants," says Patrick S. Covello, adjunct professor of biochemistry at the University of Saskatchewan and research scientist at the Canadian National Research Council's Plant Biotechnology Institute. "They did well to get those three genes." Bixin is used to color dairy products, meat, fish, cosmetics, and pharmaceuticals. The extract is particularly useful because it is available commercially in both water- and oil-soluble forms to produce yellow, orange, and red hues. "The market for natural colors, including annatto, is an important market for the color industry," says Glenn Roberts, executive director for the International Association of Color Manufacturers. Peru, Brazil, and Kenya are the world's major producers of annatto seeds; the largest importers are the U.S., Japan, and Europe. But it takes two to four years to grow B. orellana and harvest the seed, Camara notes. He proposes engineering tomato plants, which yield lycopene-rich fruit in a matter of months, to produce bixin as well. Bacteria wouldn't be as useful for bixin production in industrial quantities, Camara says, because they cannot store large amounts of the chemical. However it's produced, bixin would likely be one of the first natural pigments to enter the arena of genetically modified products. Inserting three genes into tomatoes will be challenging--it will likely require inserting each gene into one tomato, then combining them through cross-breeding. Camara hopes to have bixin-producing tomatoes within two years.
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