Optimization of Nitrate and Manganese Removal by Bacterium Pseudomonas sp. H117 in Mixotrophic Condition

Abstract

Previous study has revealed that Pseudomonas sp. H117 could exhibit excellent performance on autotrophic and heterotrophic denitrification in polluted groundwater. However, a novel character of simultaneous denitrification and manganese removal by the bacteria remained to be further explored. In this study, we investigated optimum conditions of nitrate and Mn(II) removal by the strain H117 in mixotrophic condition. Different factors (temperature, initial pH, nitrate concentration, and Mn(II) concentration) were investigated and optimized by response surface methodology (RSM), demonstrating that the highest nitrate removal ratio (100%) in the mixotrophic condition occurred at the temperature of 30.20 °C, pH of 6.90, and Mn(II) concentration of 61.81 mg/l. Meanwhile, the optimal Mn(II) removal (73.34%) conditions were at the temperature of 29.33 °C, pH of 7.22, and nitrate concentration of 20.74 mg/l. Furthermore, microbial development pattern, cellular metabolites, and bioprecipitation were characterized by the excitation emission matrix (EEM), meteorological chromatography analysis, and scanning electron microscopy (SEM) methods, respectively. These results demonstrated that strain H117 can have good adaptability to the environment, thus exhibiting an efficient ability for bioremediation of groundwater polluted by nitrate and Mn(II).