A salt-tolerant denitrifying bacterial strain: screening, identification, characterization, and detection of its product ectoine

Abstract:

[Background] Petrochemical wastewater contains nitrogen and has high salt content, which inhibits microbial metabolism and makes it difficult for common denitrifying microorganisms to effectively remove nitrogen. [Objective] To screen out and characterize the strains capable of efficiently removing nitrogen under high salt conditions. [Methods] A strain of salt-tolerant denitrifying bacterium was screened out and identified based on the physiological and biochemical properties and 16S rRNA gene sequence. The growth conditions of the strain were optimized and the denitrification capacity was measured. The products of the strain under high salt conditions were analyzed qualitatively and quantitatively. [Results] The strain YA16-1 was identified as Brevibacterium epidermidis and had the ability of denitrifying nitrate-nitrogen. It showed the nitrate-nitrogen removal rates of 97% in 18 h at 3% salinity and 55 mg/L initial nitrogen and 100% in 24 h at 250 mg/L initial nitrate-nitrogen. The optimum growth conditions for this strain were 2% NaCl, corn cob meal as the carbon source, yeast powder as the nitrogen source, pH 6.0, and 30 ℃. The strain grew well in media with salinity ranging from 2% to 15%. At 15% salinity, the strain maintained osmotic equilibrium by producing ectoine with the maximum titer of 0.89 mg/mL. [Conclusion] YA16-1 has good salt tolerance and denitrifying ability, demonstrating the potential of being applied in the treatment of high-salt wastewater and the production of ectoine.