*3.7. Effect of Cd2+ Ions*

The effect of Cd2+ ions on the metabolic activity of ST11 was investigated when atrazine was used as the substrate in crystal form or dissolved in DEHP. The concentrations of Cd2+ in MSM were set to 0–1.5 mmol/L. MSM separately supplemented with different concentrations of Cd2+ and 1.85 mmol/L atrazine was cultured at 30 ◦C, with shaking at 150 rpm for 48 h. Subsequently, the cell density of ST11 was monitored, and the residual amounts of atrazine were detected at 48 h. A sterile control culture without ST11 was included to assess the abiotic loss of atrazine. All measurements were carried out in triplicate.

## *3.8. Analytical Methods*

The method for atrazine extraction was as follows: each triangular flask was added with 30 mL of ethyl acetate and shaken at 200 rpm for 1 h. Atrazine was extracted into the ethyl acetate layer. Furthermore, the aqueous and organic phases were separated using a separatory funnel. The organic phase was centrifuged at 6380× *g* for 10 min. A total of 500 µL of the supernatant was placed in a glass tube, and ethyl acetate was evaporated in an oven at 70 ◦C. The residue was extracted with 1 mL of methanol-water solution (85%, *v*/*v*). The extracts of the same sample were merged and filled into a 2 mL sample bottle after filtration through a 0.22 µm organic filter membrane, and then sealed and stored in a 4 ◦C refrigerator. Atrazine was detected using an HPLC system (Agilent 1260, Tokyo, Japan) with a UV detector. An Agilent HC-C18 (5 µm, 150 mm × 4.6 mm) column was used for the analysis of atrazine samples. Deionized water and methanol at a ratio of 85:15 were used as the mobile phase with a flow rate of 1 mL/min. The detection wavelength was 225 nm, and the retention time was 5.11 min. The detection limit of this method was 2 mg/L.

Cd2+ was determined by spectrophotometry after cloud point extraction [49]. In a 10 mL polystyrene tube, 0.2 mL of Cd2+ sample, 1 mL of NH3-NH4Cl buffer (pH 9.5), 0.53 mL of 5-Br-PADAP ethanol solution (0.2 g/L), and 0.6 mL of Triton X-114 solution (2%, *v*/*v*) were added successively. Furthermore, the liquid in the tube was diluted to 10 mL

with deionized water and mixed with a vortex agitator for 30 s. The mixed solution was heated at 45 ◦C for 15 min and then centrifuged at 1595× *g* for 5 min to accelerate the phase separation of the cloud point system. The solution after phase separation was quickly placed into an ice water mixture for quick freezing for 30 min to make the coacervate phase viscous. After the water phase was discarded, the coacervate phase was dissolved in 2 mL of absolute ethanol by shaking in a vortex agitator. Subsequently, these samples were detected at 560 nm via spectrophotometry (UV2700, Shimadzu, Tokyo, Japan). Each sample was measured at least three times.
