Sweet proteins designed with increased thermostability
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Published on: February 11, 2019
Verónica Ramos-Viana1, Teemu K E Rönkkö2, Gonzalo Nahuel Bidart1
1The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kemitorvet Building 220, 2800 Kongens Lyngby, Denmark.
Abstract:
Sweet proteins represent a healthy alternative to refined sugar and non-nutritive sweeteners, but their thermostability limits several industrial food applications. We rationally designed 20 variants of Q-brazzein and thaumatin-II to enhance thermostability, expressing and testing 16 in vitro. Variants of both sweet proteins were identified with increased thermostability. Across all designed sweet protein variants, we found a significant inverse correlation between predicted ΔΔG and experimental Tm and a positive correlation between Tm and charge density. For thaumatin-II we identified a variant, Thau69, with 10 °C higher melting temperature. For Q-Brazzein we identified a variant, Braz110, that exhibited a melting point above 110 °C. Structural modelling of Braz110 indicated no interference with key amino acids important for sweetness or the interaction with the T1R2/T1R3 sweet taste receptor, which is supported by human consumer sensory evaluations. This study highlights the potential to design sweet protein variants with improved functionality for food applications.
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