Influence of Different Sugars and Initial pH on β-Glucan Formation by Lactobacillus brevis TMW 1.2112

Flow field-flow fractionation coupled with multidetector: A robust approach for the separation and characterization of resistant starch

The unique properties of resistant starch (RS) have made it applicable in the formulation of a broad range of functional foods. The physicochemical properties of RS play a crucial role in its applications. Recently, flow field-flow fractionation (FlFFF) has attracted increasing interest in the separation and characterization of different categories of RS. In this review, an overview of the theory behind FlFFF is introduced, and the controllable factors, including FlFFF channel design, sample separation conditions, and the choice of detector, are discussed in detail. Furthermore, the applications of FlFFF for the separation and characterization of RS at both the granule and molecule levels are critically reviewed. The aim of this review is to equip readers with a fundamental understanding of the theoretical principle of FlFFF and to highlight the potential for expanding the application of RS through the valuable insights gained from FlFFF coupled with multidetector analysis.

Improvement of the Lyophilization Survival Rate of Lactobacillus casei via Regulation of Its Surface Substances

The influence of surface substance production on the freeze-drying survival of Lactobacillus casei and methods to control the surface substances during fermentation were studied. The bacteria were treated with hypertonicity combined with ultrasound, and the survival rate was determined. The optimal conditions for removing surface substance without harming the bacteria were 81 w/18 min. The surface substances provided a protective effect on the lyophilization of the bacteria without protectants. However, in the presence of protectants, excessive surface substances reduced the protective effect of the optimum protectant alginate to 39.69 ± 1.27%. Finally, the amount of surface substances and lyophilized survival rate of collected bacteria were determined by adding EDTA during fermentation and regulating fermentation conditions, such as the carbon source, carbon-to-nitrogen ratio, and pH. The highest survival rate was 85.79 ± 3.29%, which was achieved when the amount of surface substances was (2.82 ± 0.55) × 10−11 mg/CFU. Therefore, the production of surface substances by the bacteria could be reduced by modifying the fermentation stage, which has significance in the improvement of the lyophilization survival rate of L. casei and the number of live bacteria per unit mass of L. casei in the lyophilized preparation.

Characterisation of recombinant GH 3 β-glucosidase from β-glucan producing Levilactobacillus brevis TMW 1.2112

Levilactobacillus (L.) brevis TMW 1.2112 is an isolate from wheat beer that produces O2-substituted (1,3)-β-D-glucan, a capsular exopolysaccharide (EPS) from activated sugar nucleotide precursors by use of a glycosyltransferase. Within the genome sequence of L. brevis TMW 1.2112 enzymes of the glycoside hydrolases families were identified. Glycoside hydrolases (GH) are carbohydrate-active enzymes, able to hydrolyse glycosidic bonds. The enzyme β-glucosidase BglB (AZI09_02170) was heterologous expressed in Escherichia coli BL21. BglB has a monomeric structure of 83.5 kDa and is a member of the glycoside hydrolase family 3 (GH 3) which strongly favoured substrates with β-glycosidic bonds. Km was 0.22 mM for pNP β-D-glucopyranoside demonstrating a high affinity of the recombinant enzyme for the substrate. Enzymes able to degrade the (1,3)-β-D-glucan of L. brevis TMW 1.2112 have not yet been described. However, BglB showed only a low hydrolytic activity towards the EPS, which was measured by means of the D-glucose releases. Besides, characterised GH 3 β-glucosidases from various lactic acid bacteria (LAB) were phylogenetically analysed to identify connections in terms of enzymatic activity and β-glucan formation. This revealed that the family of GH 3 β-glucosidases of LABs comprises most likely exo-active enzymes which are not directly associated with the ability of these LAB to produce EPS.

Proteomic Analysis Reveals Enzymes for β-D-Glucan Formation and Degradation in Levilactobacillus brevis TMW 1.2112

Bacterial exopolysaccharide (EPS) formation is crucial for biofilm formation, for protection against environmental factors, or as storage compounds. EPSs produced by lactic acid bacteria (LAB) are appropriate for applications in food fermentation or the pharmaceutical industry, yet the dynamics of formation and degradation thereof are poorly described. This study focuses on carbohydrate active enzymes, including glycosyl transferases (GT) and glycoside hydrolases (GH), and their roles in the formation and potential degradation of O2-substituted (1,3)-β-D-glucan of Levilactobacillus (L.) brevis TMW 1.2112. The fermentation broth of L. brevis TMW 1.2112 was analyzed for changes in viscosity, β-glucan, and D-glucose concentrations during the exponential, stationary, and early death phases. While the viscosity reached its maximum during the stationary phase and subsequently decreased, the β-glucan concentration only increased to a plateau. Results were correlated with secretome and proteome data to identify involved enzymes and pathways. The suggested pathway for β-glucan biosynthesis involved a β-1,3 glucan synthase (GT2) and enzymes from maltose phosphorylase (MP) operons. The decreased viscosity appeared to be associated with cell lysis as the β-glucan concentration did not decrease, most likely due to missing extracellular carbohydrate active enzymes. In addition, an operon was discovered containing known moonlighting genes, all of which were detected in both proteome and secretome samples.

β-Glucan Production by Levilactobacillus brevis and Pediococcus claussenii for In Situ Enriched Rye and Wheat Sourdough Breads

Sourdough fermentation is a common practice spread across the globe due to quality and shelf life improvement of baked goods. Above the widely studied exopolysaccharide (EPS) formation, which is exploited for structural improvements of foods including baked goods, β-glucan formation, by using lactic acid bacteria (LAB), offers additional values. Through renunciation of sucrose addition for bacterial β-d-glucan formation, which is required for the production of other homopolysaccharides, residual sweetness of baked goods can be avoided, and predicted prebiotic properties can be exploited. As promising starter cultures Levilactobacillus (L.) brevis TMW (Technische Mikrobiologie Weihenstephan) 1.2112 and Pediococcus (P.) claussenii TMW 2.340 produce O2-substituted (1,3)-β-d-glucan upon fermenting wheat and rye doughs. In this study, we have evaluated methods for bacterial β-glucan quantification, identified parameters influencing the β-glucan yield in fermented sourdoughs, and evaluated the sourdough breads by an untrained sensory panel. An immunological method for the specific detection of β-glucan proved to be suitable for its quantification, and changes in the fermentation temperature were related to higher β-glucan yields in sourdoughs. The sensory analysis resulted in an overall acceptance of the wheat and rye sourdough breads fermented by L.brevis and P.claussenii with a preference of the L. brevis fermented wheat sourdough bread and tart-flavored rye sourdough bread.

β-glucan formation is a selective advantage for beer-spoiling Levilactobacillus brevis TMW 1.2112 during planktonic growth

Some lactic acid bacteria (LAB) isolated from beer or wine produce capsular β-glucans from UDP-glucose via the membrane-anchored glycosyltransferase GTF-2. This phenomenon is feared in breweries, because the viscosity of the affected liquids drastically increases due to the β-glucan and concomitant pellicle formation of these LAB. Currently it is unknown if this type of polysaccharide formation provides any advantage for the producing LAB during the colonization of (ethanol-containing) liquids. We thus used the β-glucan producer Levilactobacillus (L.) brevis TMW 1.2112 and its β-glucan-deficient transposon mutant (Δ gtf-2), and compared their growth at different ethanol concentrations and their competitiveness during co-cultivation. No significant inhibition in growth and differences in acidification were observed for both strains up to ethanol concentrations of 8% (v/v). At 10 % ethanol, the β-glucan forming wildtype increased its cell number and produced more acid in comparison to the mutant strain, which settled at the bottom of the fermentation tubes at any tested condition. At higher ethanol concentrations (12-18 % v/v) both strains failed to grow, while a higher viability of the wildtype strain was observed. After co-cultivation of both strains for up to 72 h in liquid nutrient medium (without ethanol), significantly more ropy wildtype colonies were detected, if the wildtype had been initially applied in similar cell counts or in excess. By contrast, the number of smooth mutant colonies was solely significantly higher after 24 h of growth, if the mutant strain had been initially inoculated in excess. These results indicate that the β-glucan-mediated pellicle formation by L. brevis TMW 1.2112 is its dominant phenotype and a selective advantage during colonization of liquids.

Applications of asymmetrical flow field-flow fractionation for separation and characterization of polysaccharides: A review

Polysaccharides are the most abundant natural biopolymers on the earth and are widely used in food, medicine, materials, cosmetics, and other fields. The physicochemical properties of polysaccharides such as particle size and molecular weight often affect their practical applications. In recent years, asymmetrical flow field-flow fractionation (AF4) has been widely used in the separation and characterization of polysaccharides because it has no stationary phases or packing materials, which reduces the risk of shear degradation of polysaccharides. In this review, the principle of AF4 was introduced briefly. The operation conditions of AF4 for the analysis of polysaccharides were discussed. The applications of AF4 for the separation and characterization of polysaccharides from different sources (plants, animals, and microorganisms) over the last decade were critically reviewed.

Vaginal microbiota and the potential of Lactobacillus derivatives in maintaining vaginal health

Human vagina is colonised by a diverse array of microorganisms that make up the normal microbiota and mycobiota. Lactobacillus is the most frequently isolated microorganism from the healthy human vagina, this includes Lactobacillus crispatus, Lactobacillus gasseri, Lactobacillus iners, and Lactobacillus jensenii. These vaginal lactobacilli have been touted to prevent invasion of pathogens by keeping their population in check. However, the disruption of vaginal ecosystem contributes to the overgrowth of pathogens which causes complicated vaginal infections such as bacterial vaginosis (BV), sexually transmitted infections (STIs), and vulvovaginal candidiasis (VVC). Predisposing factors such as menses, pregnancy, sexual practice, uncontrolled usage of antibiotics, and vaginal douching can alter the microbial community. Therefore, the composition of vaginal microbiota serves an important role in determining vagina health. Owing to their Generally Recognised as Safe (GRAS) status, lactobacilli have been widely utilised as one of the alternatives besides conventional antimicrobial treatment against vaginal pathogens for the prevention of chronic vaginitis and the restoration of vaginal ecosystem. In addition, the effectiveness of Lactobacillus as prophylaxis has also been well-founded in long-term administration. This review aimed to highlight the beneficial effects of lactobacilli derivatives (i.e. surface-active molecules) with anti-biofilm, antioxidant, pathogen-inhibition, and immunomodulation activities in developing remedies for vaginal infections. We also discuss the current challenges in the implementation of the use of lactobacilli derivatives in promotion of human health. In the current review, we intend to provide insights for the development of lactobacilli derivatives as a complementary or alternative medicine to conventional probiotic therapy in vaginal health.

Surface properties associated with the production of polysaccharides in the food bacteria Propionibacterium freudenreichii

This study explores the production of polysaccharides (PS) in the strain Pf2289 of the food species Propionibacterium freudenreichii. Pf2289 presents characteristics atypical of the species: a molar-shaped morphotype upon plating, and cells strongly aggregative in liquid medium. When plating Pf2289, another morphotype was observed with a 4% frequency of appearance: round-shaped colonies, typical of the species. A clone was isolated, designated Pf456. No reversibility of Pf456 towards the molar-shaped morphotype was observed. Pf2289 was shown to produce a surface polysaccharide (PS) bound to the cell wall, mainly during the stationary growth phase. Meanwhile, Pf456 had lost the ability to produce the PS. AFM images of Pf2289 showed that entangled filaments spread over the whole surface of the bacteria, whereas Pf456 exhibited a smooth surface. Adhesion force maps, performed with concanavalin-A grafted probes, revealed twice as much adhesion of Pf2289 to concanavalin-A compared to Pf456. Furthermore, the length of PS molecules surrounding Pf2289 measured at least 7 μm, whereas it only reached 1 μm in Pf456. Finally, the presence of PS had a strong impact on adhesion properties: Pf2289 did not adhere to hydrophobic surfaces, whereas Pf456 showed strong adhesion.

Polysaccharides from Cordyceps miltaris cultured at different pH: Sugar composition and antioxidant activity

In the study, the β-glucan content, the primary structure and the antioxidant capacity of polysaccharides in Cordyceps militaris cultivated with different initial growth pH were evaluated. Meanwhile, the mechanism of β-glucan biosynthesis was investigated by RNA-Seq. Based on the results, C. militaris growing at an initial growth pH of 5-7 (CMsA) was distinguished from C. militaris growing at an initial growth pH of 8-9 (CMsB) and their unigenes showed the comparable expression. The mean of β-glucan content of CMsB group was 32.7% (w/w), 10% higher than that of CMsA. The results of RNA-seq showed 1088 differentially expressed genes between CMsA and CMsB groups. Furthermore, oxidative phosphorylation-related Gene ontology terms were up-regulated in CMsB groups. In addition, the results of structural analysis (FTIR spectrum, monosaccharide composition, periodate oxidation) and bioactivity evaluation speculated that C. militaris polysaccharides possessed higher β-(1 → 6)-glucan content and antioxidant activities in CMsB groups.