The objective of this project was to construct recombinant plasmids co-expressing protein disulfide isomerase (PDI) and distinct thaumatin variants (A/B/C/D). Following transformation, expression, and purification, the sweet-tasting functionality of thaumatin proteins was validated using thin-layer chromatography (TLC), 3,5-dinitrosalicylic acid assay (DNS), and electronic tongue analysis. Experimental results demonstrated that thaumatin variant A exhibited the highest sweetness intensity among single variants, while the quadruple-variant combination (A&B&C&D) achieved the highest sweetness intensity. The relevant parts are listed in Table 1.

Table 1. Part collection