Chloroform

After centrifuging the fecal and slurry samples at 3134× g for 20 min at 20 °C, 4 mL of supernatant was collected. The supernatant was placed in a 20-mL glass vial, and then 4 mL of chloroform (Merck, Darmstadt, Germany) and 60 μL of 4 M sodium hydroxide solution (Sigma-Aldrich, St. Louis, MO, USA) were also added to the glass vial and mixed with supernatant. The mixture in the glass vial was centrifuged at 3134× g for 20 min at 20 °C, and the chloroform layer was collected and placed into a 2.0-mL gas chromatography vial (Agilent, Santa Clara, CA, USA). Phenols and indoles in the chloroform layer were determined using a gas chromatograph (6890N, Agilent, Santa Clara, CA, USA) that was equipped with a DB-1 column (30 m × 0.25 mm × 0.25 μm, Agilent, Santa Clara, CA, USA) and a flame ionization detector. A sample of 2.0 μL was injected at a 5-to-1 split ratio. The gas chromatography oven was initially set at 40 °C for 5 min, increased to 230 °C at a rate of 10 °C per min, and finally held at 230 °C for 2 min. The injection and detection ports of gas chromatography were maintained at 250 °C.

PLA granulate was supplied from Fillamentum Manufacturing Czech s.r.o., Hulín, Czech Republic. Measured polymer parameters were as follows: number-average molecular weight (M_n), 123,500 g/mol; weight-average molecular weight (MW), 235,300 g/mol; dispersity, 1.90. PHB powder was acquired from NAFIGATE Corporation a.s., Prague, Czech Republic. Measured polymer parameters were as follows: number-average molecular weight (M_n), 85,040 g/mol; weight-average molecular weight (MW), 211,400 g/mol; dispersity, 2.49. All measurements of polymer properties were measured via GPC (Agilent 1100, Santa Clara, CA, USA) in chloroform (CHCl₃) and the analysis parameters were as follows: mobile phase flow 1 mL/min; column temperature 30 °C, used column: PLgel 5 μm MIXED-C (300 × 7.5 mm). Aliphatic alcohols for depolymerization (methanol 99%, ethanol 99%) were supplied by Honeywell Research Chemicals, Charlotte, NC, USA (used alcohols were not claimed either synthetic or bio-source by the supplier). The catalyst for alcoholyses (p-toluensulphonic acid monohydrate), methacrylic anhydride (94%), potassium hydroxide (p.a.), d-chloroform (CDCl₃; 99.8%), and 2-ethylhexanoic acid (for synthesis) were all acquired from Sigma-Aldrich, Prague, Czech Republic.