Compound Sodium Nitrophenolate Promotes Denitrification by Nitrifying Bacteria by Upregulating Nitrate Reductase

Abstract

Biological denitrification is an efficient and low-cost method to treat wastewater, and it has been shown that growth promoters can regulate the metabolism of microorganisms. This study aimed to investigate the effects of gibberellic acid, naphthalene acetic acid, compound sodium nitrophenolate, and diethyl aminoethyl hexanoate on the growth and denitrification process of denitrifying microorganisms and to examine the associated mechanisms. All four tested growth promoters did not affect the growth of the strain Q1; further, compound sodium nitrophenolate could significantly improve the bacterial denitrification efficiency and showed an increase in the removal rate of 13.08% in 72 h. The addition of 15 mg/L compound sodium nitrophenolate increased the removal rate of strain Q1 by 25.88% at 72 h, significantly improving the efficiency of reducing the chemical oxygen demand of the effluent. Transcriptome analysis identified 1664 differentially expressed genes (573 upregulated and 1091 downregulated genes) in the strain Q1 treated with compound sodium nitrophenolate. Nitrate reductase and nitrate transporter, which are two key enzymes related to the nitrate reduction pathway, were found to be upregulated during the denitrification process. Compound sodium nitrophenolate has promising applications in high-salt and high-nitrogen wastewater treatment.