ABSTRACT
Lactic acid bacteria (LAB) constitutes a group of gram-positive bacteria united by certain morphological, metabolic, and physiological characteristics. The fermentation patterns of heterofermentative LAB can also be profoundly affected by the presence of organic molecules able to act as electron acceptors and shift the direction from acetyl phosphate to acetate. The fermentation of fructose by heterofermentative LAB is an example of the same compound acting both as an electron donor and the electron acceptor with mannitol as an end product. Maltose fermentation in LAB has been extensively studied in lactococci, and in the genus the permease system seems to be operational. Adenosine triphosphate-binding cassette transporters, such as the oligopeptide transport system and one of the dipeptide transport systems and transporters associated with the defense against osmotic shock and excretion of unwanted compounds, are typical examples of primary transporters. The phosphoenolpyruvate: sugar phosphotransferase system is a complex machinery that translocates a sugar across the membrane with simultaneous phosphorylation.
