A Microbial Sensor for Highly Sensitive and Automatic Determination of Sulfite in Foods and Food Materials. Kinetic Study of the Sulfite Dehydrogenase-catalyzed Reaction in the Microbial State of Thiobacillus thiooxidans.

Abstract

A highly sensitive and automatic microbial sensor apparatus has been constructed with Thiobacillus thiooxidans and employed for sulfite analysis of food materials in practical fields including the starch industry, thus we tried to obtain enzymatic bases on the T. thiooxidans-catalyzed reaction. Based on the spectrophotometric observation of ferricyanide and the proportional dependency of the initial velocity on the concentration of T. thiooxidans, the sulfite oxidation was confirmed to be a microbial dehydrogenase-catalyzed reaction, of which the optimal pH is 7.5. The kinetic parameters, the Michaelis constant Km and the maximum velocity V were evaluated to be 1.0±0.1 mM and 0.065±0.032 mM/min/mg protein, respectively. The concentration of ferricyanide was proportional to the initial velocity in the range of 0 to 2 nix. These results prove that the microbial sensor apparatus developed is satisfactory to determine the enzymatic bases for sulfite oxidation.