Equol is an isoflavonoid phytoestrogen produced from the soy isoflavone daidzein by gut microflora. Not all humans produce equol from daidzein, presumably due to differences in colonic bacterial populations among individuals. Previously, smaller studies reported that approximately 30% of participants excreted equol when consuming soy. The purpose of our study was to determine the prevalence of equol excreters in a larger sample and to examine what dietary components might influence the tendency to be an equol excreter. Thirty men and thirty women consumed a soy protein beverage containing 22 mg genistein and 8 mg daidzein for 4 days as a supplement to their habitual diets. The mean daily nutrient content of their habitual intakes was determined from 4-day food records. On Day 4, participants provided a 24-hour urine collection. Urinary isoflavonoid (genistein, daidzein, equol, and O-desmethylangolensin) excretion was measured by gas chromatography-mass spectrometry. Twenty-one of the 60 participants (35%) excreted equol (> 2000 nmol/day) after 3 days of consuming the soy supplement. Daily equol excretion ranged from 2,134-20,301 nmol/day in the excreters and 21-233 nmol/day in the nonexcreters. There was no difference in equol excreter prevalence between men (43%) and women (27%). Daily excretion of daidzein, genistein, and O-desmethylangolensin was similar between equol excreters and nonexcreters and between men and women. Among the women, equol excreters consumed a significantly higher percentage of energy as carbohydrate and greater amounts of plant protein and dietary fiber, both as soluble and insoluble fiber compared to nonexcreters. Such differences were not observed in the men, who overall had significantly higher fiber intakes than the women. These data suggest that, among women, dietary fiber or other components of a high-fiber diet may promote the growth and/or the activity of bacterial populations responsible for equol production in the colon.

The hyperthermophilic archaeon Pyrococcus furiosus grows optimally at 100°C by the fermentation of peptides and carbohydrates. Growth of the organism was examined in media containing either maltose, peptides (hydrolyzed casein), or both as the carbon source(s), each with and without elemental sulfur (S 0 ). Growth rates were highest on media containing peptides and S 0 , with or without maltose. Growth did not occur on the peptide medium without S 0 . S 0 had no effect on growth rates in the maltose medium in the absence of peptides. Phenylacetate production rates (from phenylalanine fermentation) from cells grown in the peptide medium containing S 0 with or without maltose were the same, suggesting that S 0 is required for peptide utilization. The activities of 14 of 21 enzymes involved in or related to the fermentation pathways of P. furiosus were shown to be regulated under the five different growth conditions studied. The presence of S 0 in the growth media resulted in decreases in specific activities of two cytoplasmic hydrogenases (I and II) and of a membrane-bound hydrogenase, each by an order of magnitude. The primary S 0 -reducing enzyme in this organism and the mechanism of the S 0 dependence of peptide metabolism are not known. This study provides the first evidence for a highly regulated fermentation-based metabolism in P. furiosus and a significant regulatory role for elemental sulfur or its metabolites.Hyperthermophiles are microorganisms that grow optimally at 80°C and above (46,47). Virtually all of them are strict anaerobes, and most are heterotrophs. All of the heterotrophs utilize peptides as a carbon source, and most use elemental sulfur (S 0 ) as a terminal electron acceptor leading to H 2 S production. The most studied of the S 0 -reducing, heterotrophic hyperthermophiles are species of Pyrococcus. Most of these organisms only utilize peptide-related substrates as a carbon source and show no significant growth in the absence of S 0 (9,12,19,36). Notable exceptions are Pyrococcus furiosus, P. woesei, and P. glycovorans, which are capable of metabolizing poly-and oligosaccharides, as well as peptides (2, 4, 10). P. furiosus and P. woesei can also grow to high cell densities in the absence of S 0 . The pathways of peptide and carbohydrate metabolism have been well studied in P. furiosus (1, 7). Glycolysis appears to occur via a modified Embden-Meyerhof pathway (Fig. 1) (22,35). This pathway is unusual in that the hexose kinase and phosphofructokinase steps are dependent on ADP rather than ATP, and a novel tungsten-containing enzyme termed glyceraldehyde-3-phosphate:ferredoxin oxidoreductase (GAPOR) replaces the expected glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoglycerate kinase. Amino acid catabolism in P. furiosus is thought to involve four distinct 2-keto acid oxidoreductases that convert transaminated amino acids into their corresponding coenzyme A (CoA) derivatives (Fig. 2) (3,15,31,32). These CoA derivatives, together with acetylCoA produced from glycolysis via pyruvate...

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