heterofermentativ

Heterofermentativ, or heterofermentative metabolism, describes a fermentation pattern in which microorganisms convert carbohydrates into more than one major end product. In lactic acid bacteria that are heterofermentativ, glucose is processed via the phosphoketolase pathway, yielding lactic acid, carbon dioxide, and an additional product such as ethanol or acetate. This contrasts with homofermentativ metabolism, which produces primarily lactic acid from hexoses.

The phosphoketolase pathway cleaves xylulose-5-phosphate into glyceraldehyde-3-phosphate and acetyl phosphate. Glyceraldehyde-3-phosphate is further reduced to lactate, while acetyl phosphate is converted to ethanol or to acetate, with CO2 released in the process. The exact end products depend on redox balance and substrate availability; many heterofermentativ lactic acid bacteria can ferment both hexoses and pentoses, producing a characteristic mix of metabolites.

Classical heterofermentativ lactic acid bacteria include the genera Leuconostoc, Weissella, and Oenococcus; some Lactobacillus species, notably L. brevis and L. buchneri, are also heterofermentativ. These organisms are encountered in a range of fermented foods and environments, including dairy products, vegetables such as sauerkraut and pickles, and sourdough, where they contribute to acidity, aroma, and, in some cases, gas production.

Significance and applications arise from their distinct end-product profiles. Heterofermentativ metabolism influences flavor and texture in fermented foods, contributes to carbon dioxide production in doughs, and shapes microbial ecology in food processing and the gut. It is commonly contrasted with homofermentativ pathways in studies of carbohydrate metabolism.