Isolation and Identification of a Sulfate-Reducing Bacteria Species (Desulfovibrio Sp.) and Investigation Its Effect on Carbon Steel Corrosion

More than 100 samples were taken from various environmental and industrial places in Iran to isolate the Sulfate reducing bacteria (SRBs). These bacteria are anaerobic and sensitive to oxygen; therefore, pre-prepared emichment culture media were inoculated in situ to reduce the effect of adverse conditions. Also, we designed and constructed. a special device for preparing the culture media under anaerobic condition that allowed. us to purge dissolved. oxygen by introducing Nz gas and distribute culture medium aseptically. Enriched cultures were sub-cultured 2-5 times to eliminate sludge particles and non-SRB bacteria using two methods: ''agar shake method" and "streaked.-cuhure on Postgate E agar medium" using an anaerobic jar. The isolates were checked regularly to ensure the absence of any aerobic or anaerobic contaminant. Identification of purified strains were done by morphologica~ biochemical and physiological tests including Gram staining, hanging drop method. applying various carbon sources, fermenting of pyruvate in absence of sulfate, the desulfoviridin test, resistance to hibitan and salt tolerance (7-20 gil NaCl). The results showed. that all of 12 isolates belonged to Desulfovibrio Sp ... Preservation of the isolates was performed. by keeping them at 4°C, - 70°C with glycerol as cryoprotective agent and :freeze-drying. In addition, a method for isolation ofSRBs was developed according to the obtained. results. Weight loss corrosion experiments with these strains were performed and results showed. that corrosion rates of tested. steels in semi-continuous cultures were higher than those of batch cuhures. Extent of this increase varied between 40010 - 90% in 12 tested SRB strains, and corrosion rate of Strain 7, isolated from corrosion products of a water purification plant in Tehran, was the highest. However, the experiments showed a direct relation between extra cellular polymeric substances production and increase of corrosion in terms of pitting.

کلیدواژه ها:

Microbiologically Influenced. Corrosion ، sulfate reducing bacteria ، Isolation ، batch cuhure. semi-continuous culture