Pilot Study On Sulphate Reducing Bacteria-Sulfite Reductase

A key step in the assimilation of sulfate by plants and microorganisms is the six-electron reduction of SO32- to S2-, catalyzed by sulfite reductase. The fermentation conditions of sulphate reducing bacteria producing sulfite reductase, purification and characterization were reported, in order to provide basis for industrialization of sulfite reductase.The fermentation conditions include carbon sources, nitrogen sources, temperature, pH, the loading amount and so on. Through the single factor experiments, it was indicated the culture for sulfite reductase production consisted of soluble starch, urea, the C:N rate of 1:3. After fermentation at pH 7.0, 5 percent of inoculating amount, with loading amount of 1:3(v/v) and fermented at 35℃for 42 hours. The enzyme activity was about 16.2U/mL.The sulfite reductase was purified to electrophoretic homogeneity by ammonium sulfate fractionation, dialysis, Sephadex G-100 and DEAE-52 chromatography. A 115.30-fold-purification was achieved. The specific activity and recovery were 69.18U/mg and 18.36%.With sodium sulfite as the substrate, the characterization was reported. The optimal temperature and pH for the activity were 30℃and 7.7, respectively. The purified reductase was very stable. At 80℃, there was still about 55% activity left.