This technology involves transgenic tomatoes and a method for their production that achieves high expression of the sweet protein brazzein in fruit by introducing a recombinant expression vector into tomatoes. This vector incorporates the CaMV 35S promoter, alfalfa mosaic virus RNA4 enhancer, ER signal sequence, brazzein gene, and terminator, supplemented with the tobacco etch virus untranslated leader sequence and the KEDL ER retention signal sequence.
Brazzein is about 2,000 times sweeter than sugar, nearly calorie-free, and stable under heat and pH, making it an ideal sugar substitute. However, its natural source, the oubli fruit, grows only in tropical West Africa, making cultivation difficult and commercial supply virtually impossible. While attempts have been made to produce recombinant brazzein using E. coli, yeast, and transgenic plants, none have reached commercialization, and artificial sweeteners have faced ongoing controversy regarding side effects.
This technology utilizes the ETP-BZ1 vector, which attaches TEV leader sequences to both ends of the brazzein gene to enhance translation efficiency and adds a KEDL sequence to the rear to ensure protein retention and accumulation in the endoplasmic reticulum. By using tomatoes as a host—where the introduced gene remains stable across generations—brazzein with intact sweet activity is reliably obtained from the fruit. This can be applied to natural sweetener ingredients for low-calorie beverages and confectionery, foods for diabetics, and the development of functional tomato varieties containing sweet proteins. It allows for the low-cost production of brazzein with activity identical to the wild type by cultivating tomatoes, a temperate crop, without relying on tropical plant cultivation.
This invention was developed with support from the Ministry of Education for research on the interaction between human GPCR sweet taste receptors and sweet substances, and for the development of new sweet materials.
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