Carbon dioxide stimulates the production of amylovorin L by Lactobacillus amylovorus DCE 471, while enhanced aeration causes biphasic kinetics of growth and bacteriocin production.

The effects of both oxygen and carbon dioxide on growth of and product formation by Lactobacillus amylovorus DCE 471, a promising new sourdough starter culture, were assessed through controlled, in vitro fermentation experiments, using a temperature of 37 degrees C and a constant pH of 5.4. It was seen that aeration affected both cell growth and amylovorin L production. At aeration rates of 1 l min(-1) and more, the bacterial population was subjected to oxidative stress as reflected by biphasic growth patterns. During the first growth phase, the maximum specific growth rate increased with increasing aeration rates stabilizing at the highest oxygen concentrations. The maximum obtainable cell yields decreased. During the second growth phase, the amylovorin L production was stimulated at the highest aeration. However, amylovorin titers were never higher in the presence of oxygen compared with the anaerobic fermentations. Carbon dioxide did not influence cell growth of L. amylovorus DCE 471. The maximum specific growth rate and the biomass concentrations were merely affected. On the other hand, the maximum soluble bacteriocin titers coincided with the highest carbon dioxide flow rates. These results indicate that mild aeration of type II sourdoughs might enhance both cell yield and amylovorin L production by L. amylovorus DCE 471, thereby contributing to the competitiveness of the strain. Growth in an ecosystem together with yeasts producing carbon dioxide might exert a positive effect on the production of amylovorin L as well.