An effective method for enhancing metabolic activity of anammox bacteria: Accelerating heme biosynthesis by glutamate

Enhancing and maintaining anammox bacteria (AnAOB) activity is a major challenge for application of anammox process, which could be achieved by accelerating heme biosynthesis. Heme is crucial for electron transport and redox reaction and its biosynthesis may be promoted by glutamate. To explore the effect of glutamate on AnAOB activity, four parallel anammox systems (named R0, R1, R2, and R3) with different concentrations of glutamate (0, 0.125, 0.25, and 0.5 mM) were set up. The results showed that AnAOB activities and nitrogen removal efficiencies of R1 and R2 were about 58.3 % and 48.8 %, and 80.5 % and 64.1 % higher than that of R0, respectively, whereas excessive glutamate (0.5 mM) deteriorated the system performance. Moreover, heme content, activities of hydrazine synthase and hydrazine dehydrogenase, and sludge particle size in R1 and R2 were significantly higher than R0. Metagenomic sequencing analysis further revealed that the moderate amount of glutamate (0.125 mM, 0.25 mM) could effectively improve AnAOB activity by enhancing heme biosynthesis, accelerating electron transport and energy synthesis, and promoting the aggregation of microorganisms. This study provides an effective method for enhancing AnAOB metabolic activity and clarifies the underlying mechanism.