Denitrification performance and mechanism of a novel isolated Acinetobacter sp. FYF8 in oligotrophic ecosystem.

• A novel isolated oligotrophic strain FYF8 was identified as Acinetobacter sp. • The highest denitrification (97.90%) was predicted via RSM method. • Nitrogen balance texts elucidate the fate of nitrogen by strain FYF8. • The C/N ratio affects the content of fluorescent substances and EPS. • The biofilm substances increased the ability to capture organic matter. The main purpose of this study is to isolate and purify oligotrophic denitrifying bacteria, Acinetobacter sp. FYF8, so as to study the denitrification capacity and characteristics in response to oligotrophic ecosystem. The RSM showed that the best denitrification efficiency was 97.90% under 7.58 pH, 20.69 °C temperature, and 2.83 C/N ratio. Nitrogen balance experiments showed that the nitrogen gas conversion ratio was 39.88, 68.85, and 78.79% at 2.0, 2.5, and 3.0 C/N ratio, respectively. According to 3D-EEM, tyrosine, tryptophan and aromatic protein were the metabolites produced by strain FYF8. The concentration of polysaccharide (PS) and proteins (PN) in different types of extracellular polymeric substances (EPS) and the variation trend were quantitatively studied. Different functional groups such as CH 2 , C = O, and C-O-C was characterized by FTIR. These findings indicated that the denitrification strategy of strain FYF8 was related to EPS, which might be a reserve carbon storage in carbon scarcity. [ABSTRACT FROM AUTHOR]