Miscellaneous Carbohydrates

KEY Fermenters: Oxidation or fermentation by gut bacteria producing acid; Use: Utilisation or assimilation by gut bacteria; Common: Combined use and O/F for widespread, moderate and minor gut colonisers (total bacteria: 500);

Miscellaneous carbs	Common users	All users	Common fermenters	All fermenters	Example users	Prevalence in Food	Human digestion, metabolism, interactions	Structure
Methanol	2	29	0	0	Eubacterium limosum; Methanosphaera stadtmanae;	Fruit juices and vegetables can contain free methanol up to ~640 mg/L. Methanol is a degradation product of methyl ester hydrolysis and pectin breakdown.	Methanol is rapidly absorbed into the bloodstream, and can penetrate into various tissues and organs. It is metabolised by alcohol dehydrogenase to formic acid. Small amounts are utilised as a one-carbon source, but larger amounts lead to toxicity.
Ethanol	3	87	0	13	Desulfitobacterium hafniense; Desulfovibrio desulfuricans; Desulfovibrio piger;	High ethanol concentrations are found in foods that have been fermented (yeast, kefir). Natural levels of ethanol ranging from 0.06-0.66 g/L have been measured in apple juice, 13 g/L in hamburger buns (not particularly 'natural') and 0.4 g/L in bananas.	Humans can readily clear small amounts of ethanol occurring in non-fermented foods. The alcohol is excreted through the kidneys or metabolised in the liver.
Propanol	0	24	0	0		Occurs in small amounts primarily in fermented foods.	n-Propanol exhibits low acute oral toxicity at 1-6 g/Kg level. It is rapidly absorbed and distributed throughout the body (USEPA2005) and is metabolised by alcohol dehydrogenase to propionic acid via the aldehyde and may enter the tricarboxylic acid cycle.
Butanol	0	20	0	0		Found in small quantities in fermented foods, hops, cheese and a number of other food items.	The body can absorb and metabolise n-butanol first to butyraldehyde and then to butyric acid. The acid can be utilised by cells, such as colonocytes, for energy. Butanol exhibits relatively low acute toxicity, although it is more toxic than ethanol to rats.
Ethylene-glycol	1	6	0	0	Terrisporobacter glycolicus;	Does not appear to occur naturally in foods.	Highly toxic and sweet to taste. Levels at ~0.1 g/Kg of body weight typically require medical intervention. Two toxic metabolites (oxalic acid, high levels of glycolic acid) are produced from ethylene glycol is metabolised.
Propanediol	1	10	0	0	Terrisporobacter glycolicus;	Found in corn sugar.	Propane-1,2-diol is readily absorbed by the gut and would likely be widely distributed to the organs and surrounding tissues. The diol is oxidised to lactic acid and pyruvic acid. Excessive amounts are excreted via the kidneys, but the acute oral toxicity of propane-1,2-diol is low (Aggett2018).
2,3-Butanediol	1	19	0	0	Rothia mucilaginosa;	The diol is found in fermented products, including beer, wine and some cheeses; soy sauce after the fermentation of soy beans and wheat; some breads, pickles and aged meats. Also detected in cocoa butter.	Humans oxidise 2,3-butanediol to acetyl-CoA via acetoin, and the diol has been detected in the sera of alcoholics.
Pyruvate	46	389	2	13	Acetivibrio ethanolgignens; Anaerotignum lactatifermentans; Anaerotruncus colihominis; Bacteroides caccae; Bacteroides stercoris; Bilophila wadsworthia; Blautia hydrogenotrophica;	Present in red wine, dark beer, red apples and a number of other fruits.	Readily absorbed by the gut and metabolised in the liver, forming lactate.
2-Ketogluconate	10	101	4	35	Citrobacter farmeri; Citrobacter freundii; Citrobacter koseri; Cronobacter sakazakii; Enterobacter asburiae; Enterobacter cloacae; Klebsiella grimontii;		Used for biochemical tests and not generally consumed.
5-Ketogluconate	6	54	26	135	Bacteroides ndongoniae; Citrobacter farmeri; Citrobacter freundii; Citrobacter koseri; Serratia marcescens; Turicibacter sanguinis;		Used for biochemical tests and not generally consumed.
galactono-lactone	0	3	0	0			Used for biochemical tests and not generally consumed.
Gluconate	20	257	27	123	Bacillus licheniformis; Bacteroides pectinophilus; Citrobacter farmeri; Citrobacter freundii; Citrobacter koseri; Cronobacter sakazakii; Enterobacter asburiae;	Occurs naturally in fruit, wine and honey. Added to food to produce a sour flavour.	In pigs, gluconic acid is poorly absorbed but readily fermented to acetate and lactate by gut bacteria. Serum concentrations increase in patients with chronic kidney disease (Toyohara2010).
Methyl-Glucoside	12	63	53	185	Citrobacter farmeri; Citrobacter koseri; Clostridium beijerinckii; Cronobacter sakazakii; Enterobacter asburiae; Enterobacter cloacae; Enterobacter hormaechei subsp. hormaechei;		Used for biochemical tests and not generally consumed.
Methyl-Mannoside	0	0	6	36			Used for biochemical tests and not generally consumed.
Methyl-Xyloside	0	0	2	40			Used for biochemical tests and not generally consumed.
N-Acetyl-glucosamine	18	227	75	335	Anaerotruncus colihominis; Bacteroides ovatus; Citrobacter farmeri; Citrobacter freundii; Citrobacter koseri; Cronobacter sakazakii; Enterobacter asburiae;	NAG is the monomeric unit of the polmer chitin and is found in crustaceans, insects and fungi. Also used for bacterial cell wall biosynthesis.	NAG can be incorporated into glycosaminoglycans and appears to reduce IBD and Crohn's symptoms (Salvatore2000). Indications that NAG delays biofilm formation in AIEC E. coli strains. Serum concentrations increase in patients with chronic kidney disease (Toyohara2010).
Arbutin	4	69	57	263	Anaerotruncus colihominis; Cronobacter sakazakii; Rothia aeria; Subdoligranulum variabile;	Isolated from medicinal plants such as bearberry, but can also be found in small amounts in wheat and pears.	Used to inhibit skin melanin biosynthesis. Used for biochemical tests and not generally consumed.
Salicin	24	147	128	494	Acetivibrio ethanolgignens; Agathobaculum desmolans; Anaerofustis stercorihominis; Blautia hydrogenotrophica; Butyrivibrio fibrisolvens; Clostridium baratii; Clostridium beijerinckii;	The aromatic glycoside is found in the bark of willow trees and poplars. Not seen in regular foods.	Salicin is used as a biochemical test for the presence of beta-glucosidase. High doses can damage the kidneys.