In vitro gut model fermentation. (i) Fecal sample preparation.

Ethical approval of collecting fecal samples from healthy volunteers was obtained from the University of Reading Research Ethics Committee in 2014. Fecal samples were obtained from three healthy meat-eating individuals and three healthy vegetarian volunteers between the ages of 18 and 60 (vegetarians, 26.67 ± 5.69 years old; omnivores, 28.00 ± 4.36), who had not taken antibiotics for at least 6 months prior to the experiment and had no history of gastrointestinal disorders. All volunteers were following their diet for at least 5 years.

Fecal samples were diluted 1 in 20 (wt/vol) using 1 M phosphate-buffered saline (PBS) (Oxoid, Hampshire, UK), pH 7.4. This suspension was homogenized in a stomacher (Stomacher 80 Biomaster; Seward) for 120 s at normal speed.