Biopreservative effect of lactic and acetic acids

According to Hammes and Vogel (1995), LAB are classified in three different metabolic groups, as reported in Table 13.1. By considering the species of LAB naturally related to fermented foods, or deliberately added to them as starter cultures, all three of the metabolic categories are represented, with prevalence/combination of species as imposed by the intrinsic and extrinsic parameters acting during the process for the production of a specific food. 

LAB belonging to the genera Lactococcus, Enterococcus, Streptococcus, and Lactobacillus are the main representatives responsible for the biopreservation effect in fermented milks and cheeses as based on their homofermentative metabolism of carbohydrate, releasing 2 mol of lactic acid for each mole of glucose consumed. 

Obligately homofermentative Exclusively ferment hexoses and produce lactic acid by the BMP (Embden-Meyerhof-Pamas) pathway 

Obligately heterofeimentative Ferment both hexoses and pentoses by the 6-PG/PK (6-phosphogluconate/phosphoketolase pathway) and produce lactic acid, ethanol/acetic acid, and CO2 (this latter only from hexoses) in the ratio 1 1 1 

Facultatively heterofermentative Ferment hexoses by the EMP pathway and pentoses (besides gluconate), by the 6-PG/PK pathway 

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