K2hpo4 kh2po4

2-[(2,6-dichlorophenyl)amino]benzeneacetic acid sodium salt (DF, Sigma-Aldrich, Saint Louis, USA) was dissolved in deionized water to prepare a 0.01 mol L⁻¹ stock solution of DF. This solution was diluted as required in individual experiments using deionized water. The effects of the type and the pH of the supporting electrolyte on the DF signal were examined using 0.1 mol L⁻¹ solutions of H₂SO₄, CH₃COOH, CH₃COONa + CH₃COOH (NaAc–HAc) with pH values of 3.5 ± 0.1, 4.0 ± 0.1, 4.2 ± 0.1, 4.5 ± 0.1, 5.0 ± 0.1 and 5.6 ± 0.1, K₂HPO₄ + KH₂PO₄ with a pH value of 7.0 ± 0.1, (NH₄)₂SO₄ + NH₄OH with a pH value of 8.3 ± 0.1, NH₄Cl + NH₄OH with a pH value of 10.0 ± 0.1, and NaOH with a pH value of 13.0 ± 0.1 prepared from Sigma-Aldrich reagents. Interferences were tested with the use of standard solutions of Ni²⁺, Fe³⁺, Zn²⁺, Pb²⁺, Sb³⁺, Cu²⁺, Cd²⁺, V⁵⁺, and Mo⁶⁺ (Merck). The influences of organic substances were investigated based on a reagent obtained from Sigma-Aldrich (ibuprofen, caffeine, paracetamol, and humic acid) and Fluka (Triton X-100, sodium dodecyl sulphate (SDS), and cetyltrimethylamonnium bromide (CTAB)). HPLC-grade acetonitrile and trifluoroacetic acids (TFA) were purchased from Merck (Darmstadt, Germany). The solutions were prepared using ultrapurified water (>18 MΩ cm, Milli-Q system, Millipore, UK).

The auto-aggregation assay was performed following the protocol described by Rastogi, Mittal & Singh (2020) (link) with some modifications. L. paracasei_6714, L. fermentum_6702 and L. casei ATCC 393 (control) were grown in MRS broth at 35 ± 2 °C for 24 h and were later harvested through centrifugation (10.000×g for 15 min, 4 °C), washed twice with phosphate buffer solution (PBS) (50 mM KH2PO4/K2HPO4, pH 6.8) (Sigma-Aldrich, San Luis, Missouri, USA) and resuspended in PBS to obtain an absorbance of around 0.8 at 600 nm. three mL of bacterial suspension was vortexed and incubated at room temperature for 4 h. Every hour, 0.1 mL of upper suspension was transferred to 3.9 mL of PBS and the OD₆₀₀ was measured. PBS was used as blank.
The auto-aggregation percentage was then calculated using the equation: ${\displaystyle \frac{\left[Ao-At\right]}{Ao}\ast 100=\text{\%}CellularAuto-aggregation}$
where A_t is the OD₆₀₀ at time t (t = 1, 2, 3, 4) and A_o is the OD₆₀₀ at t = 0.

The electrochemical measurements were controlled with EC-Lab SP-200 Potentiostat. Resistance between reference electrode and working electrode was measured with Potential Electrochemical Impedance Spectroscopy (PEIS). 50% of the resistance was corrected by the software and the rest was manually corrected. CO₂ electrolysis was carried out in a custom-made two-compartment cell, in which the working electrode was separated from the counter electrode by Nafion membrane to hinder the re-oxidation of the products on the counter electrode. The glassware was cleaned in nochromix mixed sulfuric acid bath and afterwards in concentrated HNO₃ for 1 h, respectively, rinsed and sonicated with 80 °C ultrapure water several times, and dried at 60 °C in an oven. Each compartment of the cell was filled with 40 mL CO₂ (Air liquid 4.5, flow from button, rate: 30 mL min⁻¹) purged electrolyte. A Pt mesh 100 (Sigma-Aldrich 99.9%) was used as counter electrode (CE) and a leak-free Ag/AgCl electrode (Hugo Sachs Elektronik Harvard apparatus GmbH) was used as the reference electrode. The CO₂ free measurements were carried out in N₂-saturated 0.1 M KH₂PO₄/K₂HPO₄ (Sigma-Aldrich, pH of 6.9), while the CO₂ electrolysis in presence of CO₂ was done in 0.1 M KHCO₃ (Sigma-Aldrich, pH of 6.8).