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Table 2 Major products of amino acid fermentation by the human gut microbiota

From: Macronutrient metabolism by the human gut microbiome: major fermentation by-products and their impact on host health

Amino acid Amino acid class Major products
Aspartate Acidic Propionate
Glutamate Acidic Acetate, Butyrate
Alanine Aliphatic Acetate, Propionate, Butyrate
Glycine Aliphatic Acetate
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
Tryptophan Aromatic Indolic SCFA
Tyrosine Aromatic 4-Hydroxyphenolic SCFA
Arginine Basic Converted to other amino acids (mainly Ornithine)
Histidine Basic Acetate, Butyrate
Lysine Basic Acetate, Butyrate
Serine Hydroxylic Butyrate
Threonine Hydroxylic Acetate, Propionate, Butyrate
Cysteine Sulfur-containing Acetate, Butyrate, Hydrogen sulfide
Methionine Sulfur-containing Propionate, Butyrate, Methanethiol
  1. 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]