Table 2.
Major products of amino acid fermentation by the human gut microbiota
| Amino acid | Amino acid class | Major products |
|---|---|---|
| Aspartate | Acidic | Propionate |
| Glutamate | Acidic | Acetate, Butyrate |
| Alanine | Aliphatic | Acetate, Propionate, Butyrate |
| Glycine | Aliphatic |
Acetate Methylamine |
| Isoleucine | Aliphatic | 2-Methylbutyrate or converted to Valine |
| Leucine | Aliphatic | Isovalerate |
| Proline | Aliphatic | Acetate |
| Valine | Aliphatic | Isobutyrate |
| Asparagine | Amidic | Converted to aspartate |
| Glutamine | Amidic | Converted to glutamate |
| Phenylalanine | Aromatic |
Phenolic SCFA Phenylethylamine |
| Tryptophan | Aromatic |
Indolic SCFA Tryptamine |
| Tyrosine | Aromatic |
4-Hydroxyphenolic SCFA Tyramine |
| Arginine | Basic |
Converted to other amino acids (mainly Ornithine) Agmatine |
| Histidine | Basic |
Acetate, Butyrate Histamine |
| Lysine | Basic |
Acetate, Butyrate Cadaverine |
| Serine | Hydroxylic | Butyrate |
| Threonine | Hydroxylic | Acetate, Propionate, Butyrate |
| Cysteine | Sulfur-containing | Acetate, Butyrate, Hydrogen sulfide |
| Methionine | Sulfur-containing | Propionate, Butyrate, Methanethiol |
Listed are the compounds found to be above 1 mM concentration in in vitro fermentation experiments conducted by Smith and Macfarlane [92], in addition to the biogenic amines that can be produced by decarboxylation [12, 13]. Underlined are the products indicated as most abundant as reported in a review article by Fan et al. [12]