Isolation and characterization of an aerobic denitrifying Bacillus sp. YX-6 from shrimp culture ponds

In the present experiment, eighteen aerobic denitrifying Bacillus strains were isolated by BTB plate technique. The Bacillus sp. strain YX-6 was selected for the aerobic denitrification studies because it is highly effective in removing nitrite compared with other strains of Bacillus sp. The results indicated that the strain YX-6 could degrade the nitrite nitrogen (nitrite-N) from 10 mg/L to zero in 14 h and the nitrite-N degradation rate was approximately to 100% at the DO concentration of 5.2–5.8 mg/L. Furthermore, the aerobic denitrification of the strain YX-6 was significantly higher than those of the positive controls under different pH, temperature, nitrite and salinity concentrations (p < 0.05). The amplification of nitrite reductase confirmed that the strain YX-6 contained the nirS gene. According to the morphological observation and 16SrRNA gene analysis, the strain YX-6 was identified as Bacillus coagulans.