Ics 3000

The fecal samples were thawed at 4°C and mixed homogeneously. Approximately 0.5 g of the sample was placed in a 10 ml polypropylene tube and 8 ml of ultrapure water was added, then centrifuged at 12,000 g for 10 min at 4°C after sonication for 30 min in an ice-water bath (mixing per 10 min). The supernatant was extracted and diluted 50 times with ultrapure water, filtered through a 0.22 mm membrane, and added to the injection vial. The analysis was carried out using ICS-3000 ion chromatography (ICS-3000, Thermo Scientific, USA), the external standard solution containing eight organic acids was obtained from Sigma-Aldrich (Saint Louis, USA). A variety of organic acids were separated by an AS11 analytical column (250 × 4 mm) and an AG11 guard column (50 × 2 mm) under the mobile phase elution conditions: potassium hydroxide gradient, 0–5 min, 0.8–1.5 mM; 5–10 min, 1.5–2.5 mM; 10–15 min, 2.5 mM, 1 ml/min flow rate.

Samples were melted in a class 100 clean room at LGGE-CNRS laboratory (Grenoble, France). They were then transferred into Dionex glass vials previously rinsed with ultra-pure Millipore water (conductivity > 18.2 mΩ, TOC < 10 ng/g) and analyzed less than 24 h after melting. Analyses were performed by conductivity-suppressed ion chromatography using a Dionex ICS 3000© apparatus and a Dionex AS40© autosampler placed in the clean room facilities. Different chemical parameters were measured during this study (e.g., major/minor ions, organic acids, and pH). Soluble anions (methyl sulfonic acid (MSA), SO₄, NO₃, Cl) and cations (Na, NH₄, K, Mg, Ca) and organic acids were analyzed by ionic chromatography (IC, Dionex ICS3000). AS/AG 11HC and CS/CG 12A columns were used for anions and cations analyses, respectively. All chemical analyses were carried out at on the airOsol platform of the IGE laboratory in Grenoble, France. This data set can be found in Supplementary Table S1. The following parameters were used for statistical analyses [Organic acids (oxalate, lactate, glutarate, propionate, succinate, formate, acetate), NO₃^–, NH₄⁺, SO₄^2–, mercury, fluoride, calcium, magnesium, bromide, strontium, lithium, sodium, chloride, potassium, number of particles, methyl sulfonic acid (MSA)] and pH. For values below the detection limit, we used the detection limit divided by 2.

The polysaccharide sample (10 mg) was hydrolyzed with 4 mol/L trifluoroacetic acid at 120 °C in a sealed tube for 4 h, and the hydrolysate was dried with nitrogen to remove excess trifluoroacetic acid. The polysaccharide hydrolysate was dissolved with 10 mL distilled water and then passed through a 0.2 μm microporous filter. Chromatographic separation conditions of fucose (Fuc), rhamnose (Rha), arabinose (Ara), galactose (Gal), glucose (Glc), fructose (Fru), glucuronic acid (GlcA) and galacturonic acid (Gala): Ion Chromatography (IC, DIONEX ICS-3000, California, USA), CarboPacTMPA10 (4 × 250 mm) analytical column, using sodium acetate (1 mol/L), sodium hydroxide (200 mmol/L) and water as the mobile phase at a flow rate of 1 mL/min. Chromatographic separation conditions of xylose (Xyl) and mannose (Man): IC (DIONEX ICS-3000, California, USA), CarboPacTMPA20 (3 × 150 mm) analytical column, using sodium hydroxide (250 mmol/L) and water as the mobile phase at a flow rate of 0.5 mL/min. The column temperature was 35 °C, and a 10 μL sample was injected.