Sugars relevant for sourdough fermentation stimulate growth of and bacteriocin production by Lactobacillus amylovorus...

The effects of sugars relevant for sourdough fermentation (i.e. glucose, fructose, maltose, and sucrose) on the kinetics of the bacteriocin-producing Lactobacillus amylovorus DCE 471 strain were assessed. The sugars were applied solely or in combination in a sourdough simulation medium during batch fermentations at temperature and pH conditions encountered during the production of type II sourdoughs. When growing on a single energy source, glucose was preferentially consumed by L. amylovorus DCE 471, followed by maltose and fructose. The strain was unable to grow on sucrose. In glucose-containing mixtures, glucose was always consumed most rapidly by L. amylovorus DCE 471 and seemed to steer its growth during the early growth phase, mainly because of the delaying effect on maltose consumption. Maltose consumption started only when low glucose levels were reached. In all cases, fructose was used as an energy source and not as a terminal electron acceptor, since no acetic acid or mannitol were produced. Increased bacteriocin titres were observed with binary or ternary sugar combinations compared to single energy sources. Thus, the diversity of the energy source seemed to stimulate the production of amylovorin L. Cell growth of and production of amylovorin L by L. amylovorus DCE 471 paralleled for all sugar combinations tested.