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This article presents the results of a comprehensive toxicity assessment of brazzein and monellin, yeast-produced recombinant sweet-tasting proteins. Excessive sugar consumption is one of the leading dietary and nutritional problems in the world, resulting in health complications such as obesity, high blood pressure, and cardiovascular disease. Although artificial small-molecule sweeteners widely replace sugar in food, their safety and long-term health effects remain debatable. Many sweet-tasting proteins, including thaumatin, miraculin, pentadin, curculin, mabinlin, brazzein, and monellin have been found in tropical plants. These proteins, such as brazzein and monellin, are thousands-fold sweeter than sucrose. Multiple reports have presented preparations of recombinant sweet-tasting proteins. A thorough and comprehensive assessment of their toxicity and safety is necessary to introduce and apply sweet-tasting proteins in the food industry. We experimentally assessed acute, subchronic, and chronic toxicity effects, as well as allergenic and mutagenic properties of recombinant brazzein and monellin. Our study was performed on three mammalian species (mice, rats, and guinea pigs). Assessment of animals' physiological, biochemical, hematological, morphological, and behavioral indices allows us to assert that monellin and brazzein are safe and nontoxic for the mammalian organism, which opens vast opportunities for their application in the food industry as sugar alternatives. [ABSTRACT FROM AUTHOR]

Sweet proteins are a class of proteins with the ability to elicit a sweet sensation in humans upon interaction with sweet taste receptor T1R2/T1R3. Single-chain Monellin, MNEI, is among the sweetest proteins known and it could replace sugar in many food and beverage recipes. Nonetheless, its use is limited by low stability and high aggregation propensity at neutral pH. To solve this inconvenience, we designed a new construct of MNEI, dubbed Mut9, which led to gains in both sweetness and stability. Mut9 showed an extraordinary stability in acidic and neutral environments, where we observed a melting temperature over 20 °C higher than that of MNEI. In addition, Mut9 resulted twice as sweet than MNEI. Both proteins were extensively characterized by biophysical and sensory analyses. Notably, Mut9 preserved its structure and function even after 10 min boiling, with the greatest differences being observed at pH 6.8, where it remained folded and sweet, whereas MNEI lost its structure and function. Finally, we performed a 6-month shelf-life assessment, and the data confirmed the greater stability of the new construct in a wide range of conditions. These data prove that Mut9 has an even greater potential for food and beverage applications than MNEI. [ABSTRACT FROM AUTHOR]