The fermentation medium used previously was prepared as a mixture of 450 mL of distilled water, 2.25 g of tryptone, 2.25 g of glucose, 1.125 g of maltose, 2.25 g of yeast extract, 50.7 μL of vitamin K1 (0.5 mg L -1 ) and 5.07 mg haemin (5 mg L -1 ), 112.5 μL of a micromineral solution The sodium phosphate buffer for preparation of the fecal slurries was made up of 70 mM KH2PO4 and 70 mM Na2HPO4 (pH 7 at 20 °C). The reducing solution consisted of 312.5 mg of cysteine hydrochloride, 2 mL of 1 M NaOH, 101.5 mg of Na2S and 50 mL of distilled water.