Enhancing biological conversion of NO to N2O by utilizing thermophiles instead of mesophiles.

ABSTRACT

The production of nitrous oxide (N2O) through the biological denitrification of nitric oxide (NO) from flue gases has recently been achieved. Although the temperature of flue gas after desulphurization is usually 45-70 °C, all previous studies conducted microbial denitrification of NO under mesophilic conditions (22-35 °C). This study investigated the biological conversion of NO to N2O in both mesophilic (35-45 °C) and thermophilic conditions (45-50 °C). The results showed that temperature has a great impact on N2O production, with a maximum conversion efficiency (from NO to N2O) of 82% achieved at 45 °C, which is obviously higher than the reported conversion efficiencies (24-71%) under mesophilic conditions. Additionally, high-throughput sequencing result showed that the genera Enterococcus, Clostridium, Romboutsia, and Streptococcus were closely related to NO denitrification and N2O production. Microbial communities at 40 and 45 °C had greater metabolizing capacities for polymeric carbon sources. This study suggests that thermophilic condition (45 °C) is more suitable for biological production of N2O from NO.