Performance of <Emphasis Type="Italic">Lactobacillus sanfranciscensis</Emphasis> TMW 1.392 and its levansucrase deletion mutant in wheat dough and comparison of their impact on bread quality

The performance of Lactobacillus sanfranciscensis TMW 1.392 and its levansucrase deletion mutant TMW 1.392 Δlev in wheat dough was compared. The effects of both strains on dough and bread characteristics were determined in order to find benchmarks for in situ production of exopolysaccharides (EPS). Growth and acidification were lower in doughs prepared with the Δlev mutant than in those employing the wild type. Extensogram resistance of the dough was reduced and extensibility increased with the addition of L. sanfranciscensis levan. Added EPS positively influenced water absorption, bread volume and firming of the crumb. In situ production of EPS was not sufficient to achieve the same positive effects of EPS, as they partially overlapped with effects resulting from enhanced acidification. Control doughs were made to separate effects of predough, EPS and different metabolism/acidification. High acetic acid levels decreased extensibility and volume. High lactic acid levels negatively influenced crumb hardness and firming kinetics. The use of knock out mutants proved helpful to judge overall performance of a strain, although the interpretation of specific effects must consider all changes in its metabolism.