Inhibitory effects of nitrogen oxides on a mixed methanogenic culture

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

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 214 KB
• Volume: 96
• Category: Article
• ISSN: 0006-3592
• DOI: 10.1002/bit.21105

✦ Synopsis

Abstract

The effect of nitrate, nitrite, nitric oxide (NO), and nitrous oxide on a mixed, mesophilic (35°C) methanogenic culture was investigated. Short‐term inhibition assays were conducted at a concentration range of 10–350 mg N/L nitrate, 17–500 mg N/L nitrite, 0.02–0.8 mg N/L aqueous NO, and 19–191 mg N/L aqueous nitrous oxide. Simultaneous methane production and N‐oxide reduction was observed in 10 and 30 mg N/L nitrate and 0.02 mg N/L aqueous NO‐amended cultures. However, addition of N‐oxide resulted in immediate cessation of methanogenesis in all other cultures. Methanogenesis completely recovered subsequent to the complete reduction of N‐oxides to nitrogen gas in all N‐oxide‐amended cultures, with the exception of the 500 mg N/L nitrite‐ and 0.8 mg N/L aqueous NO‐amended cultures. Partial recovery of methanogenesis was observed in the 500 mg N/L nitrite‐amended culture in contrast to complete inhibition of methanogenesis in the 0.8 mg N/L aqueous NO‐amended culture. Accumulation of volatile fatty acids was observed in both cultures at the end of the incubation period. Among all N‐oxides, NO exerted the most and nitrate exerted the least inhibitory effect on the fermentative/methanogenic consortia. The effect of multiple additions of nitrate (300 mg N/L) on the same methanogenic culture was also investigated. Long‐term exposure of the methanogenic culture to nitrate resulted in an increase of N‐oxide reduction rates and decrease of methane production rates, which was attributed to changes in the microbial community structure due to nitrate addition. Biotechnol. Bioeng. 2007;96: 444–455. © 2006 Wiley Periodicals, Inc.