3.1.1. pH

The pH of the media has a drastic influence on the MLF itself as low pH inhibits the growth of the wine LAB. Most LAB are neutrophilic [33], and the optimum pH for the growth of lactic acid bacteria is close to neutrality. Some bacteria strains of the genera of *Lactobacillus* and *Oenococcus* show more acidophilic behavior. At pH values less than 3.0, bacterial growth is very difficult or impossible [34]. *Oenococcus oeni*, which is the organism of choice to conduct MLF under acidic conditions, will generally dominate, and in wine of pH above 3.5, strains of the genera of *Lactobacillus* or *Pediococcus* can be more present. The ability of the bacteria to obtain energy from the metabolism of glucose is inhibited at the low pH of wine [28]. *L. plantarum* shows a preference for malate as an energy source at low pH [35], even in the presence of glucose, which suggests this species as a starter for malate decarboxylation in fermenting musts [36]. Prahl [8] and Bou and Krieger [9]) proposed *Lactobacillus plantarum* as most promising for use as a starter culture in higher pH wines.
