高濃度亜硫酸を含むブドウ果汁からの亜硫酸の除去

Abstract

Microbial desulfurization of Koshu grape juice containing high concentration of sulfite (1, 000 ppm) was investigated using Thiobacillus thiooxidans JCM 7814, which is one of the chemoautotrophic sulfur-oxidizing bacteria. The bacterial cells proved to oxidize both types of sulfite, i. e., free-sulfite (f-SO2) and bound-sulfite (b-SO2). The oxidizing activity on b-SO2 was observed over the pH range from 3.5 to 5.5, and the maximum activity was at pH 4.5. As for f-SO2, the activity was observed over the pH range from 4.5 to 6.5; the maximum was at pH 5.5. The activity of sulfite oxidation was little affected by sugars and organic acids (citric, tartaric, and malic acids), which were major components of grape juice. Microbial desulfurization was also possible in the grape juice adjusted at pH from 4.5 to 5.5, in which the color was not changed. In grape juice adjusted at pH 4.5, 1, 000 ppm of sulfite was almost completely removed within 3.5 hours at 30 °C. The desulfurization was not accompanied by the decrease in reducing sugar, citric acid, tartaric acid, and malic acids, indicating that T. thiooxidans removed sulfite from grape juice containing high concentration of sulfite without changing major components.