Response Surface Methodology for Optimizing Cd Removal by Mineralizing Bacterial Strains

Highly efficient cadmium (Cd)-tolerant mineralizing bacterial strains were isolated and screened from farmland soil around abandoned mining areas via isolation and culture methods of mineralizing bacteria. Taxonomic identification of the strains was conducted through morphological observation and 16S rRNA gene sequence analysis, and their adsorption characteristics and mechanisms for Cd 2 + were investigated. Single-factor experiments were performed to analyze the effects of pH, temperature, urea addition amount, and bacterial solution addition amount on the Cd 2 + removal rate, and the adsorption conditions were optimized using the response surface methodology (RSM). The results showed that a Cd-tolerant mineralizing bacterial strain, designated as FG43, was isolated and screened, and it was identified as Priestia sp. (GenBank accession number: PX121665). This strain grew well at a Cd 2 + concentration of 100 mg/L, and its adsorption of Cd 2 + was mainly extracellular adsorption. The maximum adsorption capacity for Cd 2 + at 100 mg/L was 21.48 mg/g. Response surface optimization indicated that the order of significance of the factors affecting the Cd 2 + removal rate was: pH > urea addition amount > temperature > bacterial solution addition amount. Under the optimal conditions (pH = 9, temperature = 30℃, urea addition amount = 22.3 g/L, bacterial solution addition amount = 20.4%), the actual measured value of Cd 2 + removal rate reached 86.83%. This study provides technical references for the adsorption and immobilization of Cd 2 + by the mineralizing bacterium Priestia sp. in contaminated water bodies and soils.