The interest towards legumes in food applications has risen over the past decades. However, the presence of antinutritional factors (ANF) and the poor technological performances still restricts their application in food fortification. In this study, four lactic acid bacteria (LAB) isolated from faba bean were applied as starter cultures for faba bean bioprocessing. None of the strains employed produced exopolysaccharides from raffinose, on the contrary, they did with sucrose as substrate. The fermented doughs were characterized and the strains were compared for their adaptation capacity and metabolic performance including the formation of dextrans, the degradation of ANF and the ability to improve antioxidant activity and in vitro protein digestibility (IVPD). A contribution to the proteolysis was given by the presence of endogenous enzymes, responsible for the increase of peptides and amino acids in dough from irradiated flour. However, the LAB strains further enhanced proteolysis. Weissella cibaria VTT E-153485 led to the highest peptide release and consequentially to the highest IVPD. In doughs fermented with Pediococcus pentosaceus VTT E-153483 and Leuconostoc kimchi VTT E-153484, phytic acid was reduced to more than half the initial concentration. Inoculated doughs had significantly lower content of oligosaccharides after 24 h of incubation compared to the controls. The most efficient raffinose consumption was found for Leuc. kimchi and W. cibaria. Doughs inoculated with weissellas contained >1% of dextrans. Weissella confusa VTT E-143403 induced a significant increment in viscosity (ca. 7 times higher than the controls). This study revealed that well-characterized, indigenous LAB provided beneficial biotechnological features in faba bean dough processing and contributed to its implementation in the food production.

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Wheat bran offers health benefits as a baking ingredient, but is detrimental to bread textural quality. Dextran production by microbial fermentation improves sourdough bread volume and freshness, but extensive acid production during fermentation may negate this effect. Enzymatic production of dextran in wheat bran was tested to determine if dextran-containing bran could be used in baking without disrupting bread texture. The Weissella confusa VTT E-90392 dextransucrase gene was sequenced and His-tagged dextransucrase Wc392-rDSR was produced in Lactococcus lactis. Purified enzyme was characterized using 14C-sucrose radioisotope and reducing value-based assays, the former yielding K m and V max values of 14.7 mM and 8.2 μmol/(mg∙min), respectively, at the pH optimum of 5.4. The structure and size of in vitro dextran product was similar to dextran produced in vivo. Dextran (8.1% dry weight) was produced in wheat bran in 6 h using Wc392-rDSR. Bran with and without dextran was used in wheat baking at 20% supplementation level. Dextran presence improved bread softness and neutralized bran-induced volume loss, clearly demonstrating the potential of using dextransucrases in bran bioprocessing for use in baking.

The consumption of fiber-rich foods such as cereal bran is highly recommended due to its beneficial health effects. Pre-fermentation of bran with lactic acid bacteria can be used to improve the otherwise impaired flavor and textural qualities of bran-rich products. These positive effects are attributed to enzymatic modification of bran components and the production of functional metabolites like organic acids and exopolysaccharides such as dextrans. The aim of this study was to investigate dextran production in wheat and rye bran by fermentation with two Weissella confusa strains. Bran raw materials were analyzed for their chemical compositions and mineral content. Microbial growth and acidification kinetics were determined from the fermentations. Both strains produced more dextran in rye bran in which the fermentation-induced acidification was slower and the acidification lag phase longer than in wheat bran. Higher dextran production in rye bran is expected to be due to the longer period of optimal pH for dextran synthesis during fermentation. The starch content of wheat bran was higher, which may promote isomaltooligosaccharide formation at the expense of dextran production. W. confusa Cab3 produced slightly higher amounts of dextran than W. confusa VTT E-90392 in all raw materials. Fermentation with W. confusa Cab3 also resulted in lower residual fructose content which has technological relevance. The results indicate that wheat and particularly rye bran are promising matrices for producing technologically significant amounts of dextran, which facilitates the use of nutritionally valuable raw bran in food applications.

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