Screening of a halotolerant desulfurizing and denitrifying bacterium Stutzerimonas stuzeri with control effect on sulfide and nitrate pollution

Abstract:

Objective To better control the pollution of nitrate and sulfide in mariculture tailwater and reduce the ecological risks caused by the discharge of the tailwater, this study screened a halotolerant desulfurizing and denitrifying bacterial strain and studied its growth characteristics.Methods A dilution coating-repeat dish sandwish culture method was used to isolate and screen halotolerant desulfurizing and denitrifying bacterial strains, which were identified by morphological observation and 16S rRNA gene sequence comparison. Based on single factor experiments, the key factors affecting desulfurizing and denitrifying effects, including carbon source, temperature, salinity, pH, and inoculation amount, were optimized, and the strain tolerance threshold to sulfide (S^2-) was explored.Results A strain Stutzerimonas stutzeri D1-2 was isolated from sulfur-based mixotrophic denitrifying sludge. This strain was able to simultaneously remove sulfide and nitrate from the environment with organic carbon sources. With sodium lactate as the optimal carbon source, strain D1-2 showed the best performance at an inoculation amount of 1.5%. The strain showed the removal rates of S₂O₃^2- and NO₃^--N both greater than 80% at 15-35 ℃, salinities of 10‰-50‰, and initial pH 6.0-8.0. It demonstrated significant tolerance at an initial S^2- concentration of 50 mg/L, with the removal rates of S^2- and NO₃^--N reaching 97.91% and 94.67%, respectively.Conclusion This study reports the heterotrophic sulfur-oxidizing capacity of S. stutzeri. The halotolerant strain S. stutzeri D1-2 capable of simultaneously desulfurizing and denitrifying has a potential application value in the control of sulfide and nitrate pollution in mariculture tailwater.