Electron donor effect on nitrate reduction pathway and kinetics in a mixed methanogenic culture

✍ Scribed by A. Evren Tugtas; Spyros G. Pavlostathis

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 160 KB
• Volume: 98
• Category: Article
• ISSN: 0006-3592
• DOI: 10.1002/bit.21487

✦ Synopsis

Abstract

The effect of different electron donors on the pathway and kinetics of nitrate reduction in a sulfide‐acclimated mixed, mesophilic (35°C) methanogenic culture was investigated. A mixture of dextrin and peptone, glucose, propionate, acetate, and H~2~/CO~2~ were used as substrates at an initial chemical oxygen demand of 1,500 mg/L and the initial nitrate concentration ranged between 0 and 300 mg N/L. The fastest nitrate reduction was observed in the H~2~/CO~2~ and acetate‐fed cultures. In the case of propionate, nitrate reduction was the slowest followed by partial recovery of methanogenesis and accumulation of volatile fatty acids due to inhibition as a result of accumulation of denitrification intermediates. Similarly, accumulation of nitrite and nitric oxide and partial or complete inhibition of methanogenesis was observed in the H~2~/CO~2~‐fed cultures. Methanogenesis completely recovered in the dextrin/peptone‐, glucose‐, and acetate‐fed cultures at all nitrate levels. Denitrification was the dominant pathway of nitrate reduction in the propionate‐, acetate‐, and H~2~/CO~2~‐fed cultures regardless of the COD/N value. However, both denitrification and dissimilatory nitrate reduction to ammonia (DNRA) were observed in the dextrin/peptone‐ and glucose‐fed cultures and the degree of predominance of either of the two pathways was a function of the COD/N value. Therefore, the type of electron donor used affected both the nitrate reduction pathway and kinetics, as well as the recovery of fermentation and/or methanogenesis in the mixed methanogenic culture. Biotechnol. Biotechnol. Bioeng. 2007;98: 756–763. © 2007 Wiley Periodicals, Inc.