Ph-switchable brazzein oligomers for enhanced sweetener stability and purification
A protein engineering approach that fuses brazzein (a natural sweetener 500-2000x sweeter than sugar) with computationally designed oligomerization domains stable at low pH. This switchable assembly enhances shelf-life in acidic beverages, simplifies purification, and rapidly disassembles in the neutral pH of the mouth to deliver full sweetness.
Overview
Brazzein is a small natural protein (54 amino acids) that is 500-2000 times sweeter than sugar and is already targeted for commercialization. This project aims to enhance brazzein's commercial viability by engineering pH-switchable oligomers using computational protein design. The oligomerization domains are stabilized through hydrogen bonds between protonated acidic residues at low pH, enabling brazzein to remain stable and assembled in acidic beverages during storage. Once consumed, the neutral pH of the mouth triggers rapid disassembly, releasing monomeric brazzein for optimal sweetness perception. This switchable assembly strategy offers three key advantages: enhanced thermal and acid stability for longer shelf-life, reduced effective protein concentration to combat aggregation, and dramatically simplified purification through pH-triggered assembly and disassembly cycles.
Technical specifications
- Sweet protein base: Brazzein (54 amino acids), 500-2000 times sweeter than sugar, with four disulfide bonds providing natural thermal and acid stability
- Computational design tools: RFdiffusion for backbone generation, ProteinMPNN for sequence design, and AlphaFold2 for structure prediction and ranking
- Oligomerization mechanism: Designed domains stabilized by hydrogen bonds between protonated aspartic and glutamic acid residues at low pH
- Switchable behavior: Stable oligomers at pH 3 (beverage conditions); rapid disassembly at pH 7 (mouth conditions)
- Expression system: Cell-free expression (His-Pure) enabling rapid prototyping of 20 candidate designs
- Stability benefit: Tetramerization reduces effective storage concentration 4-fold, directly combating aggregation
- Purification advantage: pH-switchable assembly enables simple purification cycles, addressing a key bottleneck in food-grade protein production
- Validation methods: Analytical size exclusion chromatography, dynamic light scattering, differential scanning fluorimetry, and sweetness evaluation
Technology readiness level
This research is at an early-to-mid stage of development. Natural brazzein has already been validated through ongoing commercialization efforts, and the biophysical principles supporting protein oligomer stability are well-established in the literature. However, no pH-switchable brazzein oligomers have been designed or tested to date. The proposed work spans computational design, experimental validation of 20 candidate oligomers, and sweetness evaluation with industry partners or mouse trials over a one-year timeline. Successful completion would yield a panel of characterized switchable brazzein variants ready for further development toward beverage applications.
About Colorado State University
Colorado State University is a comprehensive public land‑grant research university with an applied, partnership‑driven culture. Multiple research campuses—including the Fort Collins main campus, a public‑facing Denver site, and a foothills research complex with shared core facilities and pilot‑scale testbeds—enable companies to co‑locate, access instrumentation, and run validation studies. A statewide Extension network and proximity to the Front Range innovation corridor provide streamlined engagement with regional and national industry, while an integrated veterinary teaching hospital supports translational studies. Research is supported by competitive federal funding from agencies such as NSF, NIH, USDA, DOE, and DoD. A dedicated technology transfer office streamlines IP, contracting, and startup formation, with incubator and collaboration space for industry partners.
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