Thaumatin is an amazing protein that is reported to be 3000 times more sweeter then common sugar.
The natural proteins as a group are the sweetest compounds ever discovered. The sweet taste - which depends on nearly 100 different sensory receptors on the tongue - can be detected in the presence of thaumatin at concentrations well below one part protein molecule per 100 million parts of water. On a scale in which 0 refers to no sweetness, 1 refers to table sugar or sucrose, then thaumatin is nearly off the scale at 3,000, more than 10 times sweeter than other sugar substitutes like saccharin or aspartame.
As a non-caloric sweetener, thaumatin has attracted attention as a candidate for control of obesity, oral health and diabetic management. Thaumatin already is being marketed as a nutritional supplement in blood sugar stabilizers for childhood behavioral problems and the more than 3.5 million sufferers from attention deficit disorder. Among soft drink consumers alone, nearly 20.6 million tons of chemicals are used around the world - nearly 4 kilograms per capita, with a growth of about 20% towards the end of the decade.
Now an effort is being made to express the protien in yeast, so that it could be produced in large scale industrially.
it is about 208amino acid long protien with lot of glycosilation, so it could only be expressed in eukaryotic system to have the desried sweet properties of the protein.