Recombinant sweet-tasting monellin was purified on a large scale (50 grams) from yeast strain ABI10. The purification yield was 45%, and the purity was as high as 95%, as determined by HPLC gel filtration. Since monellin was proved to be a very basic protein (Cagan, R. : Science, 181, 32-35, 1973), the basicity was utilized as an efficient purification method. Acid treatment for precipitating yeast proteins made proteins denatured except monellin.