<h4>Background</h4>Based on prior evidence that red ginseng pectin GPS-1 ameliorates T2DM in rats and modulates gut microbiota, we report for the first time that GPS-1 interacts with the gut microbiota of T2DM rats, as demonstrated through an <i>in vitro</i> digestion-fermentation model. The gene discussed is GPS1; the disease is type 2 diabetes mellitus.