Thaumatin II - a palatability protein

Thaumatin is a sweet-tasting protein produced by the plant Thaumatococcus danielli in the gelatinous arils of the fruit, and has recently been developed as a non-nutritive sweetener for the food industry. The composition and properties of thaumatin are discussed. The thaumatins are a family of 5 proteins, the most predominant are thaumatin I and thaumatin II. In man, thaumatin tastes sweet and at low concentrations can enhance many other flavours. Thaumatin does not cause tooth decay and can be used by diabetics. Thaumatin only tastes sweet to old-world monkeys and apes (including man), but rats experience the flavour enhancement, and weight gain in pigs is increased if thaumatin is added to the feed. T. danielli grown away from the tropics does not produce normal fruit, so to enable thaumatin to be produced in greater quantities and more cheaply, thaumatin genes have been introduced and expressed in microorganisms under the control of heterologous promoters. These micro organisms include Escherichia coli, Bacillus subtilis, Streptomyces lividans and yeasts, but results so far have been disappointing. More promising results were achieved when the thaumatin gene was introduced into the temperate crop plant solanum tuberosum cv. Iwa using the hairy root transformation technique. It is suggested that other crop plants for human or animal consumption, such as strawberry, melon, cucumber and apple, may be suitable for thaumatin production which would improve flavour and produce sweeter cultivars. Thaumatin may also be used to improve palatability of animal feeds, and rather than using purified thaumatin as a feed additive, the thaumatin gene could be introduced into fodder crops.