The influence of oxygen concentration in liquid medium on elemental sulphur oxidation by Thiobacillus thiooxidans

Abstract

Rate of elemental sulphur biooxidation byThiobacillus thiooxidans bacteria in continuous culture with nutrient circulation was determined for oxygen concentration in liquid in the range 1±17 mg/dm 3 for temperature range 19±40°C, pH from 1.5 to 4.5 and for CO 2 concentration above 110 mg/dm 3 . Equation describing the in¯uence of above mentioned parameters on the rate of sulphur oxidation was presented. List of symbolsC AB alive bacteria protein concentration, [lg/ml] C B total bacteria protein concentration, [lg/ml] C O 2 oxygen concentration in liquid medium, [lg/dm 3 ] C 1 total protein concentration in liquid, [lg/ml] C 2 protein concentration in supernatant, [lg/ml] R RBES rate of biooxidation of elemental sulphur, [mg S 0 / m 2 * h)] T temperature, [°C] X B alive bacteria fraction 1 IntroductionThe Thiobacillus thiooxidans bacteria are commonly known as strictly aerobic however there doesn't exist any quantitative data showing the in¯uence of oxygen concentration both in liquid nutrient and in gas over the nutrient on the rate of elemental sulphur oxidation caused by this bacteria. There are only few qualitative data according to which the rate increases with the increase of oxygen concentration in gas contacting with liquid nutrient in which elemental sulphur was suspended [1]. Positive effects of shaking the culture against the stationary cultures [2] as well as the increase of sulphur biooxidation rate caused by aeration of both stationary and shaking culture [3,4] con®rm the very important in¯uence of oxygen transportation on the rate. The aim of this work was to determine quantitatively the in¯uence of oxygen concentration in liquid medium on sulphur oxidation rate and Thiobacillus thiooxidans bacteria concentration. Materials and methods Bacterial strainStudies were performed using Thiobacillus thiooxidans strain originally isolated from the surface waters of sulphur ore mine Macho Âw near Tarnobrzeg (Poland). As an inoculum eight days old stationary culture containing 10 6 ±10 7 cells/ml was used. Culture mediumModi®ed Waksman mineral salts medium was used for cultivation. It consisted of: 2.0 g of (NH 4 )SO 4 , 0.5 g of KCl, 0.5 g of KH 2 PO 4 , 1.02 g of MgSO 4 á 7H2O, 0.02 g of FeSO 4 7H 2 O, 1 dm 3 of distilled water. pH of the medium was 4.5. Neutralizing solutionTo stabilize the pH of culture medium during the experiments the culture medium as in 2.2 was applied, but (NH 4 ) 2 SO 4 was replaced with 2.39 g NH 4 HCO 3 . pH of the neutralizing solution was 8.5. Procedure of determination of sulphur biooxidation rateThe rate of biooxidation of elemental sulphur (R RBES ) was de®ned as the amount of elemental sulphur oxidized per unit of time by the bacteria operating on a unit of elemental sulphur surface exposed to their action. Rate can be determined according to the method proposed earlier [5].In this method RRBES is based on the sulphate ions' production rate. The rate of sulphate ions production was determined on the basis of SO 2À 4 ions balance which were produced by the bacteria, introduce...

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“…The dissolved oxygen concentration directly influences the growth of At. thiooxidans and its capacity to oxidize S 0 (Jaworska and Urbanek, 1998). Thus, a lack of dissolved oxygen also may have negative effects on biofilm growth and structures of Acidianus sp.…”

Development of advanced biofiltration process for hydrogen sulphide control

“…it grows well at pH 2 as shown in Table 2.6). Jaworska and Urbanek (1998) reported that the optimum temperature for Acidithiobacillus thiooxidans was 33 o C. The shape of Acidithiobacillus thiooxidans is short rod, 0.5 by 1~2 μm, occurring singly, in pairs or in short chains. Colonies on thiosulfate agar are minute (<1.0 mm), transparent or whitish or yellow (Bergey and Holt, 1994), and usually appear after 2~3 days since inoculation.…”