Effect of electron donor on methanol production by ammonia-oxidizing bacterium Nitrosomonas europaea

Abstract

Nitrosomonas europaea, an autotrophic bacteria, can catalyze both the oxidation of ammonia to nitrite and methane to methanol by ammonia monooxygenase (AMO). N. europaea obtains electrons for the AMO reaction by oxidation of ammonia and hydroxylamine. Therefore, the effects of ammonia and hydroxylamine on AMO activity and methanol production by the whole cells of N. europaea were investigated. The addition of electron donors increased both AMO activity and methanol production. The optimal methanol production was achieved by either the repeated addition of 100 μM (1 M = 1 mol·dm-3) ammonium chloride every 30 min, or 200 μM ammonium chloride every 1 h during reaction to the final concentration of 1 mM. During 6 h reaction, 440 μM methanol was accumulated, 47% higher compared with no addition of electron donor or 30% higher compared with the one time addition of 1 mM ammonium chloride before reaction.