Fermentable

Fermentable is an adjective used across biology, nutrition, and food science to describe a substrate that can be metabolized by microorganisms through fermentation. In fermentation, microorganisms convert organic compounds, usually sugars, into energy and byproducts such as ethanol, organic acids, and gases.

Common fermentable substrates include simple sugars such as glucose, fructose, sucrose, and maltose, as well as more complex carbohydrates that can be hydrolyzed into fermentable units. Substances that cannot be fermented by a given organism are described as nonfermentable, at least for that organism and conditions.

In nutrition, fermentable carbohydrates are those that gut microbes can ferment. This idea is central to the FODMAP concept, which groups fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. Examples include lactose, fructans, galacto-oligosaccharides, and sorbitol. Fermentable fibers can support gut microbiota and production of short-chain fatty acids but may cause gas or osmotic effects in some individuals.

In industry and brewing, fermentable substrates are selected for how readily yeast or bacteria can convert them into desired products such as alcohol, organic acids, or enzymes. Yeast typically ferments simple sugars like glucose, sucrose, and maltose, but many dextrins and some starch-derived carbohydrates are less readily fermented.

Fermentability depends on the organism, its enzymatic capabilities, and environmental factors such as pH and temperature. A substrate may be fermentable by one organism yet nonfermentable by another.