Isolation of a thermophilic aerobic denitrifier and characterization for its denitrification performance

At present, no Chelatococcus daeguensis strain has been reported to be an aerobic denitrifier. In this study, an aerobic denitrifier was isolated from the biofilm of a field biotrickling filter and its aerobic denitrification activity was evaluated under various conditions in batch reactor experiments at 50°C. Based on biochemical studies and 16S rRNA sequencing analysis, the isolate was identified as C. daeguensis strain TAD1. The strain TAD1 was examined to determine the effects of different carbon sources, C/N ratios, and dissolved oxygen concentration on aerobic denitrification activity at 50°C. C. daeguensis TAD1 efficiently removed nitrate using disodium succinate as the sole carbon source. Nitrate was hardly reduced when glucose was used at 50°C. The optimal C/N ratio was 9, giving a denitrification efficiency of 96.1% and higher carbon concentrations did not inhibit cell growth and denitrification activity. C. daeguensis TAD1 tolerated oxygen levels about 5.1 mg/L. The denitrification efficiency of C. daeguensis TAD1 was higher than that of mesophilic bacteria.