16S rRNA-Based Identification of a Glucan-Hyperproducing Weissella confusa

A gram-positive, nonmotile, irregular, short, rod-shaped new strain of Weissella confusa bacterium was isolated from fermented cabbage. The isolate was physiologically and biochemically characterised. The 16S rDNA was amplified by polymerase chain reaction (PCR). The isolate was identified as Weissella confusa (GenBank accession number: GU138518.1) based on nucleotide homology and phylogenetic analysis. The isolate produces glucansucrase when grown in sucrose-supplemented culture medium which catalyses glucan formation. This novel isolate possesses high capacity of industrial use due to its high productivity of glucan (34 mg/mL) as compared to other strains reported. The optimum temperature for glucansucrase production was 25°C. The shaking condition gave an enzyme activity of 6.1 U/mL which was 1.5 times higher than that given by static condition (4.1 U/mL). The temperature 35°C, pH 5.4, and ionic strength 10–20 mM were optimum for enzyme assay. This investigation unraveled the abundance of industrially valuable microflora of the north east India

Olutmäskin maitohappobakteerikäyminen : in situ dekstraanisynteesin arviointi

Ravintorikas mäski on oluentuotannon suurin sivutuote. Olutmäskin hyödyntäminen elintarviketuotannossa on haastavaa sen kehnojen teknologisten ominaisuuksien vuoksi. Bakteerien tuottamat eksopolysakkaridit voisivat mahdollisesti parantaa mäskin ominaisuuksia, sillä ne pystyvät pidättämään kosteutta ja toimimaan vuorovaikutuksessa materiaalin komponenttien kanssa, vaikuttaen siten rakenteen muodostumiseen. Erilaisista viljaraaka-aineista valmistettujen tuotteiden teknologisia ja aistittavia ominaisuuksia onkin pystytty parantamaan esimerkiksi maitohappobakteerien in situ -tuottamalla dekstraanilla. Tämän tutkimuksen tavoitteena oli tarkastella maitohappobakteerien dekstraanisynteesiä mäskissä. 16 dekstraania tuottavaa maitohappobakteerikantaa seulottiin viskositeetin muodostamisen perusteella, ja lupaavimpien kantojen käymisprosessia tarkasteltiin lähemmin kahdessa eri lämpötilassa. Maitohappobakteerien lisääntymistä, materiaalin happamoitumista ja viskositeetin muodostumista verrattiin 20 °C:n ja 25 °C:n lämpötiloissa, joista suotuisampi valittiin korkeamman viskositeetin perusteella. Dekstraani ja oligosakkaridit määritettiin näistä näytteistä. Sakkaroosin, glukoosin, maltoosin sekä fruktoosin määrä analysoitiin sokerinkulutuksen sekä dekstraanin ja oligosakkaridien muodostumisen tutkimiseksi. Suurimmat viskositeetit saavutettiin Weissella confusa -kannoilla A16 ja 2LABPTO5, sekä Leuconostoc pseudomesenteroides -kannalla DSM20193, ja ne vaikuttivat siten lupaavilta dekstraanintuottajilta tässä materiaalissa. 25 °C:n käymislämpötilassa viskositeettia muodostui enemmän kuin 20 °C:ssa, joten se arvioitiin suotuisammaksi käymislämpötilaksi halutunlaisen dekstraanin muodostamiselle. Muodostuneen dekstraanin määrä vaihteli 1.1 ja 1.7 % w/w (koko näytteen märkäpainosta) välillä. Olutmäskin muodostui dekstraania, ja sen reologiset ominaisuudet muuttuivat, ja siten sen soveltuvuus elintarvikekäyttöön mahdollisesti parani.Brewers’ spent grains (BSG) are by-products of the brewing industry. Utilization of BSG in food applications is challenging, due to its poor technological characteristics. Because of their water retaining properties, interactions with matrix components and impact on texture formation, bacterial exopolysaccharides (EPS) represent a promising tool for improvement of BSG properties. Among bacterial exopolysaccharides, dextran produced in situ by lactic acid bacteria (LAB) during fermentation has shown major improvements in technological and sensorial features of products prepared from various types of plant materials. The nutritious composition of BSG may support the growth of LAB and enable in situ dextran production. The aim of this study was to establish and examine the synthesis of dextran by LAB in BSG. Sixteen dextran producing LAB strains were screened for viscosity formation in BSG fermentation. The strains showing the highest viscosity formation were further assessed for fermentation performance. The more suitable fermentation temperature was traced by comparing the viscosifying performance of selected starters at 20 and 25 °C. Dextran amount was determined semi-quantitatively from selected fermented samples showing optimal results, and the presence of oligosaccharides was assessed. Sucrose, glucose, maltose and fructose amounts were analyzed to observe the relation between sugar consumption and dextran and oligosaccharides formation. Weissella confusa strains A16 and 2LABPTO5 and Leuconostoc pseudomesenteroides strain DSM20193 appeared the most promising starters for viscosity formation and thus dextran synthesis in this matrix. From the examined fermentation temperatures, strains showed the highest potential for dextran synthesis at 25 °C. The amount of synthesized dextran ranged from 1.1 to 1.7 % w/w (of the wet weight of the whole sample matrix). The rheological properties of BSG were modified via LAB fermentation and dextran synthesis, resulting in more viscous texture, and its applicability in food systems was thus potentially enhanced

The role of dextran and maltosyl-isomalto-oligosaccharides on the structure of bread enriched with surplus bread

Occurrence of surplus bread (SB) is common in the baking industry. Edible surplus bread can be utilized as a new bread dough ingredient; however, it creates technological challenges that affect the quality of the new bread. In this study, the interactions of SB with dough macromolecules were studied in a gluten-starch model dough system and subsequent model bread. Moreover, dextran or maltosyl-isomalto-oligosaccharides (MIMO) were produced by dextransucrase preparation, incorporated into the dough containing SB, and their individual in-fluence on dough rheology and bread structure was investigated. Compared to control model dough/bread, the addition of SB at 10% level significantly decreased extensibility of the dough, dough level, and specific volume (SV) of bread, despite standardized gluten content and optimized water absorption (WA). This confirms that SB constituents (especially gelatinized starch) deteriorate the dough structure-forming by interactions with gluten network. Dextran addition at appropriate level (0.7%) with optimized WA, shielded the gluten network from the interactions of SB, thus, increasing dough extensibility and softness. Furthermore, dextran-enrichment signifi-cantly reduced the hardness and staling of breads and increased the SV to the control model bread level. MIMOs, especially at low concentration, induced stronger interactions with gluten proteins than dextran. However, the addition of MIMOs reduced the SV of breads containing SB and did not reduce the overall crumb hardness despite partially preventing starch retrogradation in the early phase of storage. The protective interactions of dextran with dough macromolecules showed that in vitro dextran could be utilized to enable recycling of edible SB.Peer reviewe

Synthesis and structural characterization of glucooligosaccharides and dextran from Weissella confusa dextransucrases

Many lactic acid bacteria are able to synthesize dextrans from sucrose by dextransucrases. Weissella confusa strains have attracted increasing attention due to their production of texture-modifying dextrans during food fermentation. Potential prebiotic oligosaccharides have also been produced by dextransucrases in the presence of sucrose and acceptor sugars. However, only few W. confusa dextransucrases have been previously studied, and the reactions of Weissella dextransucrases to synthesize oligosaccharides have not been investigated. In this thesis, two W. confusa dextransucrases from efficient dextran-producers were studied, and their products were structurally characterized because this information is essential for a better usability of these enzymes and corresponding bacteria in food and health applications. The biochemical and kinetic properties of one of the W. confusa dextransucrases were studied. Two activity assays were compared to determine the kinetic parameters. A sucrose radioisotope assay gave a KM of 14.7 mM and a Vmax of 8.2 µmol/(mg∙min), whereas a Nelson-Somogyi assay gave values of 13.0 mM and 19.9 µmol/(mg∙min), respectively. The dextrans from the two W. confusa dextransucrases were found by, e.g., NMR analysis to consist of mainly α-(1→6) linkages and 3% α-(1→3) branches, of which some were elongated. A high-performance size-exclusion chromatography analysis of the dextrans revealed high molar masses of 107‒108 g/mol. Weissella dextransucrases were also studied with acceptor sugars for the synthesis of glucooligosaccharides. The most efficient acceptor was maltose, followed by isomaltose, maltotriose, and nigerose, which formed series of glucooligosaccharides by the further elongation of intermediate acceptor products. The products derived from maltose formed two homologous series, with one series being predominant and the other being minor. The major maltose product series were linear isomaltooligosaccharides (IMOs) with reducing-end maltose units, as identified by multistage mass spectrometry (MSn) analysis. The minor maltose series were revealed by an NMR analysis of the isolated minor trisaccharide product to bear a novel branched structure. These products contained an α-(1→2)-linked glucosyl residue on the reducing residue of the linear IMOs. These structures have not been previously obtained by a dextransucrase. They probably formed by the attachment of a single-unit branch to linear IMOs. For the acceptor analogs lactose and cellobiose, their main acceptor products were identified by NMR analysis to be branched trisaccharides, with a glucosyl residue α-(1→2) linked to the acceptor s reducing end. Surprisingly, a side product, isomelezitose (6Fru-α-Glcp-sucrose), was produced when using lactose as an acceptor. The synthesis of this nonreducing trisaccharide by a dextransucrase was reported here for the first time. Linear IMOs with a degree of polymerization ≥3.3 serve as prebiotics for their resistance to digestion. However, industrial IMO production often leads to a high portion of unwanted digestible sugars. The dextransucrase reaction in the presence of the efficient acceptor maltose was demonstrated here as a promising alternative synthesis process to control IMO size distribution by varying the sucrose/maltose ratio. The effects of substrate concentrations (0.15 1 M) and dextransucrase dosage (1 10 U/g sucrose) on the IMO yield and profile were modeled. High sucrose (1 M) and medium maltose (0.5 M) concentrations were found to be optimal for the synthesis of long-chain IMOs, with 366 g/L of total IMOs attained.

Challenges and opportunities for wheat alternative grains in breadmaking : Ex-situ- versus in-situ-produced dextran

Background: The use of grains as an alternative to wheat in breadmaking has rapidly grown in the last few years, driven by the Sustainable Development Goals toward improving food security and promoting sustainable agriculture. Flours from legumes, pseudo-cereals, minor cereals and milling by-products, such as bran, are of particular interest. The production of partially substituted or wheat-free bread is, however, a challenging task in terms of texture and flavour attributes. Scope and approach: The present review covers recent advances in the application of dextrans in improving dough rheology, baking performance and bread flavour characteristics. Emphasis has been given to in situ application of dextran via sourdough technology as a & lsquo;clean label & rsquo; alternative to commercial hydrocolloid additives. Key findings and conclusions: In-situ dextran production leads to bread with higher specific volume, softer crumbs and increased moisture content. Dextran also provides an anti-staling effect attributable to its ability to reduce water mobility and retard starch retrogradation. A structure & ndash;function relationship has suggested that dextran with high molecular weight and less branching is superior in enhancing bread quality. Furthermore, mild acidification favours the functionality of dextran in dough and bread systems, while intensive acidification results in adverse effects. Lactic acid bacterial strains belonging to the genus Weissella exhibiting mild acidification are therefore appreciated in regard to the utilisation of in-situ produced dextran. This review highlights the novel application of dextran as a flavour masking agent to minimise off-flavours (e.g. beany flavour, bitter taste, and aftertaste) originating from non-wheat grains, consequently improving the acceptability of the final products.Peer reviewe

Fermentation Conditions Affect the Synthesis of Volatile Compounds, Dextran, and Organic Acids by Weissella confusa A16 in Faba Bean Protein Concentrate

Fermentation with Weissella confusa A16 could improve the flavor of various plant-based sources. However, less is known about the influence of fermentation conditions on the profile of volatile compounds, dextran synthesis and acidity. The present work investigates the synthesis of potential flavor-active volatile compounds, dextran, acetic acid, and lactic acid, as well as the changes in viscosity, pH, and total titratable acidity, during fermentation of faba bean protein concentrate with W. confusa A16. A Response Surface Methodology was applied to study the effect of time, temperature, dough yield, and inoculum ratio on the aforementioned responses. Twenty-nine fermentations were carried out using a Central Composite Face design. A total of 39 volatile organic compounds were identified: 2 organic acids, 7 alcohols, 8 aldehydes, 2 alkanes, 12 esters, 3 ketones, 2 aromatic compounds, and 3 terpenes. Long fermentation time and high temperature caused the formation of ethanol and ethyl acetate and the reduction of hexanal, among other compounds linked to the beany flavor. Levels of dextran, acetic acid, and lactic acid increased with increasing temperature, time, and dough yield. Optimal points set for increased dextran and reduced acidity were found at low temperatures and high dough yield. Such conditions would result in hexanal, ethyl acetate and ethanol having a relative peak area of 35.9%, 7.4%, and 4.9%, respectively

In vitro synthesis and structural analysis of selected acceptor products of Weissella confusa VTT E-90392 dextransucrase

Non-digestible oligosaccharides possess important physicochemical and physiological properties. They have gained great attention because of their potential prebiotic properties. The oligosaccharides have wide food industrial applications as dietary fibers, sweeteners, humectants, and possible weight controlling agents. In this thesis, cloned Weissella confusa VTT E-90392 dextransucrase was used to catalyze the synthesis of oligosaccharides (acceptor products) by acceptor reaction, when sucrose was the glucosyl unit donor. Maltose acceptor reaction was selected to analyze the effects of the concentrations of sucrose and maltose, as well as the dosages of dextransucrase on maltose acceptor products. Other acceptor reactions were also evaluated, with primary lactose and cellobiose acceptor products being purified and partially characterized by MS/MS. Concentrations of sucrose and maltose, as well as their interactions were the most important factors regarding isomalto-oligosaccharides production. The production of overall oligosaccharides could be increased by increasing sucrose and maltose concentrations. Lactose, cellobiose, other disaccharides and trisaccharides could be acceptors for W. consufa dextransucrase. In combination with the structures from previous publications, 2-a-Dglucopyranosyl-cellobiose and 2-a-D-glucopyranosyl-lactose were probably the primary products for cellobiose and lactose, although one trisaccharide synthesized by lactose acceptor reaction remains unknown. In order to verify the characterization, NMR spectroscopic analysis is needed for further study. In conclusion, W. consufa dextransucrase is capable of catalyzing oligosaccharides synthesis, and acceptor reactions would be promising methods in producing prebiotic oligosaccharides

Dextran of Diverse Molecular-Configurations Used as a Blood-Plasma Substitute, Drug-Delivery Vehicle and Food Additive Biosynthesized by Leuconostoc, Lactobacillus and Weissella

Dextran, a microbial metabolite of diverse molecular configurations, can be biosynthesized employing selected strains of characterized species of bacteria. Dextran molecules are secreted as an extracellular polysaccharide in the culture medium of the bacterial fermentation system. This microbially produced polymer of glucose possesses multi-faceted characteristics such as its solubility in different solvents and formation of dextran solutions of needed viscosity. Several preparations can be formulated for the desired thermal and rheological properties. Due to such multifunctional characteristics, dextran with different structural specifications is a desired polysaccharide for clinical, pharmaceutical, and food industry commercial applications. Dextran and its derivative products with various molecular weights, in a range of high and low, have established their uses in drug delivery and in analytical devices using columns packed with polysaccharide gel. Therefore, being a neutral raw material, the resourcefulness of dextran preparations of different molecular weights and linkages in their polymer configuration is important. For this purpose, several studies have been performed to produce this commercially important polysaccharide under optimized bacterial cultivation processes. This article aims to overview recently published research reports on some significant applications of dextran in the pharmaceutical and food industries. Studies conducted under optimized conditions in fermentation processes for the biosynthesis of dextran of diverse molecular configurations, which are responsible for its multifunctional properties, have been summarized. Concise information has been presented in three separate tables for each group of specific bacterial species employed to obtain this extracellular microbial polysaccharide.Keywords: polysaccharide; dextran; clinical; drug delivery; dextranase; food; pharmaceutical; sucrose; Leuconostoc; Lactobacillus; bacteri

Structures, physico-chemical properties, production and (potential) applications of sucrose-derived α-d-glucans synthesized by glucansucrases

Glycoside hydrolase family 70 (GH70) glucansucrases produce α-d-glucan polysaccharides (e.g. dextran), which have different linkage composition, branching degree and size distribution, and hold potential applications in food, cosmetic and medicine industry. In addition, GH70 branching sucrases add single α-(1→2) or α-(1→3) branches onto dextran, resulting in highly branched polysaccharides with "comb-like" structure. The physico-chemical properties of these α-d-glucans are highly influenced by their linkage compositions, branching degrees and sizes. Among these α-d-glucans, dextran is commercially applied as plasma expander and separation matrix based on extensive studies of its structure and physico-chemical properties. However, such detailed information is lacking for the other type of α-d-glucans. Aiming to stimulate the application of α-d-glucans produced by glucansucrases, we present an overview of the structures, production, physico-chemical properties and (potential) applications of these sucrose-derived α-d-glucan polysaccharides. We also discuss bottlenecks and future perspectives for the application of these α-d-glucan polysaccharides