The role of rye bran acidification and in situ dextran formation on structure and texture of high fibre extrudates.

High insoluble dietary fibre content causes challenges with structure and texture in extrusion. This paper focused on studying the structure of extrudate enriched with rye bran modified in different ways. Fermentation of rye bran with dextran-producing Weissella confusa (with 10 g/100 g, 5 g/100 g and 0 g/100 g added sucrose as substrate for dextran production), in situ enzymatic production of dextran in the bran and chemical acidification of bran with lactic acid were compared in extrusion trials. Endosperm rye flour was the base in extrusion, of which 32 g/100 g was substituted for rye bran. Fermentation with dextran production showed similar improvement in extrudate expansion as chemically acidified bran samples (489 and 493%), in comparison with native bran (420%). Similarly, these treatments decreased extrudate hardness and increased crispiness index (CI) (16 N, 0.06 and 14 N, 0.071 respectively) compared to the control (39 N, 0.008). Enzymatically produced dextran did not affect expansion, although it decreased hardness (26 N) and increased CI compared to the control (0.023). Chemical changes in the fermented and acidified rye bran included reduction in insoluble dietary fibre (DF) (19 g/100 g â†’ 17 g/100 g) and increase in soluble DF (5.17 g/100 g â†’ 5.51-7.19 g/100 g), as well as soluble protein (8 g/100 g â†’ 11 g/100 g) content. Lactic acid bacteria fermentation or acidification is therefore a promising method to increase the functionality of rye bran in extrusion.

Characterization of indigenous Pediococcus pentosaceus, Leuconostoc kimchii, Weissella cibaria and Weissella confusa for faba bean bioprocessing.

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.

Lactobacillus backii and Pediococcus damnosus isolated from 170-year-old beer recovered from a shipwreck lack the metabolic activities required to grow in modern lager beer.

In 2010, bottles of beer containing viable bacteria of the common beer-spoilage species Lactobacillus backii and Pediococcus damnosus were recovered from a shipwreck near the Åland Islands, Finland. The 170-year quiescent state maintained by the shipwreck bacteria presented a unique opportunity to study lactic acid bacteria (LAB) evolution vis-a-vis growth and survival in the beer environment. Three shipwreck bacteria (one L. backii strain and two P. damnosus strains) and modern-day beer-spoilage isolates of the same two species were genome sequenced, characterized for hop iso-α-acid tolerance, and growth in degassed lager and wheat beer. In addition, plasmid variants of the modern-day P. damnosus strain were analyzed for the effect of plasmid-encoded genes on growth in lager beer. Coding content on two plasmids was identified as essential for LAB growth in modern lager beer. Three chromosomal regions containing genes related to sugar transport and cell wall polysaccharides were shared by pediococci able to grow in beer. Our results show that the three shipwreck bacteria lack the necessary plasmid-located genetic content to grow in modern lager beer, but carry additional genes related to acid tolerance and biofilm formation compared to their modern counterparts.

Next-generation sequencing approaches for improvement of lactic acid bacteria-fermented plant-based beverages.

Plant-based beverages and milk alternatives produced from cereals and legumes have grown in popularity in recent years due to a range of consumer concerns over dairy products. These plant-based products can often have undesirable physiochemical properties related to flavour, texture, and nutrient availability and/or deficiencies. Lactic acid bacteria (LAB) fermentation offers potential remediation for many of these issues, and allows consumers to retain their perception of the resultant products as natural and additive-free. Using next-generation sequencing (NGS) or omics approaches to characterize LAB isolates to find those that will improve properties of plant-based beverages is the most direct way to product improvement. Although NGS/omics approaches have been extensively used for selection of LAB for use in the dairy industry, a comparable effort has not occurred for selecting LAB for fermenting plant raw substrates, save those used in producing wine and certain types of beer. Here we review the few and recent applications of NGS/omics to profile and improve LAB fermentation of various plant-based substrates for beverage production. We also identify specific issues in the production of various LAB fermented plant-based beverages that such NGS/omics applications have the power to resolve.

Optimization of Isomaltooligosaccharide Size Distribution by Acceptor Reaction of Weissella confusa Dextransucrase and Characterization of Novel α-(1→2)-Branched Isomaltooligosaccharides.

Long-chain isomaltooligosaccharides (IMOs) are promising prebiotics. IMOs were produced by a Weissella confusa dextransucrase via maltose acceptor reaction. The inputs of substrates (i.e., sucrose and maltose, 0.15-1 M) and dextransucrase (1-10 U/g sucrose) were used to control IMO yield and profile. According to response surface modeling, 1 M sucrose and 0.5 M maltose were optimal for the synthesis of longer IMOs, whereas the dextransucrase dosage showed no significant effect. In addition to the principal linear IMOs, a homologous series of minor IMOs were also produced from maltose. As identified by MS(n) and NMR spectroscopy, the minor trisaccharide contained an α-(1→2)-linked glucosyl residue on the reducing residue of maltose and thus was α-d-glucopyranosyl-(1→2)-[α-d-glucopyranosyl-(1→4)]-d-glucopyranose (centose). The higher members of the series were probably formed by the attachment of a single unit branch to linear IMOs. This is the first report of such α-(1→2)-branched IMOs produced from maltose by a dextransucrase.

Structure modeling and functional analysis of recombinant dextransucrase from Weissella confusa Cab3 expressed in Lactococcus lactis.

The dextransucrase gene from Weissella confusa Cab3, having an open reading frame of 4.2 kb coding for 1,402 amino acids, was amplified, cloned, and expressed in Lactococcus lactis. The recombinant dextransucrase, WcCab3-rDSR was expressed as extracellular enzyme in M17 medium with a specific activity of 1.5 U/mg which after purification by PEG-400 fractionation gave 6.1 U/mg resulting in 4-fold purification. WcCab3-rDSR was expressed as soluble and homogeneous protein of molecular mass, approximately, 180 kDa as analyzed by SDS-PAGE. It displayed maximum enzyme activity at 35°C at pH 5.0 in 50 mM sodium acetate buffer. WcCab3-rDSR gave Km of 6.2 mM and Vm of 6.3 µmol/min/mg. The characterization of dextran synthesized by WcCab3-rDSR by Fourier transform infrared and nuclear magnetic resonance spectroscopic analyses revealed the structural similarities with the dextran produced by the native dextransucrase. The modeled structure of WcCab3-rDSR using the crystal structures of dextransucrase from Lactobacillus reuteri (protein data bank, PDB id: 3HZ3) and Streptococcus mutans (PDB id: 3AIB) as templates depicted the presence of different domains such as A, B, C, IV, and V. The domains A and B are circularly permuted in nature having (ß/α)8 triose phosphate isomerase-barrel fold making the catalytic core of WcCab3-rDSR. The structure superposition and multiple sequence alignment analyses of WcCab3-rDSR with available structures of enzymes from family 70 GH suggested that the amino acid residue Asp510 acts as a nucleophile, Glu548 acts as a catalytic acid/base, whereas Asp621 acts as a transition-state stabilizer and these residues are found to be conserved within the family.

Rye bran as fermentation matrix boosts in situ dextran production by Weissella confusa compared to wheat bran.

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.

Lactose- and cellobiose-derived branched trisaccharides and a sucrose-containing trisaccharide produced by acceptor reactions of Weissella confusa dextransucrase.

Dextran-producing Weissella have received significant attention. However, except for maltose, the acceptor reactions of Weissella dextransucrases with different sugars have not been investigated. The action of recombinant Weissella confusa VTT E-90392 dextransucrase was tested with several potential acceptors, particularly, analogs lactose and cellobiose. The major acceptor products of both disaccharides were identified as branched trisaccharides, with a glucosyl residue α-(1 → 2)-linked to the acceptor's reducing end. An additional product, isomelezitose (6(Fru)-α-Glcp-sucrose), was also produced when using lactose as an acceptor. This is the first report of the synthesis of isomelezitose by a dextransucrase. The NMR spectra of the three trisaccharides were fully assigned, and their structures were confirmed by selective enzymatic hydrolysis. The trisaccharides prepared from (13)C6(glc) sucrose and lactose were analyzed by ESI-MS(n), and the fragmentation patterns of these compounds were characterized.

Cloning and characterization of a Weissella confusa dextransucrase and its application in high fibre baking.

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 (14)C-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.