Exploring the Health Benefits of Yeast Isolated from Traditional Fermented Foods in Korea: Anti-Inflammatory and Functional Properties of Saccharomyces and Non-Saccharomyces Strains.

Traditional yeast (Saccharomyces cerevisiae) has been used for its benefits in various fermentation processes; the benefits of non-Saccharomyces yeast as a material for food, feed, and pharmaceuticals have been studied recently. This study evaluated the anti-inflammatory activity and extracellular functional characteristics of wild-type yeasts isolated from traditional fermented foods (doenjang (common name: soybean paste) and nuruk) in Korea. The viability of the yeast and lipopolysaccharide (LPS)-stimulated RAWBlue™ cells was improved, similar to unstimulated RAWBlue™ cells, and the isolates demonstrated NF-κB inhibitory activity. Yeast suppressed the nitric oxide production in LPS-stimulated RAWBlue™ cells, which was attributed to the inhibition of iNOS or COX-2 mRNA expression depending on the strain. Although there were differences depending on the strain, the production of anti-inflammatory cytokines was reduced in the yeast and LPS-stimulated RAWBlue™ cells, some of which were demonstrated at the mRNA level. In addition, the isolates exhibited high antioxidant and antihypertensive activities (similar to the positive control), which varied depending on the strain. This suggests that yeast can be used for fermentation with enhanced antioxidant and antihypertensive activities. Furthermore, the isolates inhibited the growth of pathogenic Gram-negative bacteria, indicating that yeast can inhibit food spoilage and the growth of pathogenic bacteria during fermentation. Consequently, utilizing raw materials to cultivate yeast strains could be a promising avenue for developing functional foods to prevent and treat inflammatory reactions; such foods may exhibit antioxidant, antihypertensive, and antibacterial properties.

Microbiome Analysis of Traditional Grain Vinegar Produced under Different Fermentation Conditions in Various Regions in Korea.

The fermentation of traditional vinegar is a spontaneous and complex process that involves interactions among various microorganisms. Here, we used a microbiome approach to determine the effects of networks, such as fermentation temperature, location, physicochemical and sensory characteristics, and bacterial profile, within traditional grain vinegar samples collected from various regions of Korea. Acetic acid and lactic acid were identified as the major metabolites of grain vinegar, and sourness and umami were determined as taste fingerprints that could distinguish between vinegar samples. Acetobacter ghanensis and Lactobacillus acetotolerans were the predominant bacterial species, and the functional composition of the microbiota revealed that the nucleotide biosynthesis pathway was the most enriched. These results reveal that vinegar samples fermented outdoors are more similar to each other than vinegar samples fermented at 30 °C, when comparing the distance matrix for comprehending bacterial networks among samples. This study may help obtain high-quality vinegar through optimized fermentation conditions by suggesting differences in sensory characteristics according to the fermentation environment.

Safety Evaluation of Weissella cibaria JW15 by Phenotypic and Genotypic Property Analysis.

Weissella cibaria is one of the bacteria in charge of the initial fermentation of kimchi and has beneficial effects such as immune-modulating, antagonistic, and antioxidant activities. In our study, we aimed to estimate the safety of W. cibaria JW15 for the use of probiotics according to international standards based on phenotypic (antibiotic resistance, hemolysis, and toxic metabolite production) and genotypic analysis (virulence genes including antibiotic resistance genes). The results of the safety assessment on W. cibaria JW15 were as follows; (1) antibiotic resistance genes (ARGs) (kanamycin and vancomycin etc.) were intrinsic characteristics; (2) There were no acquired virulence genes including Cytolysin (cylA), aggregation substance (asa1), Hyaluronidase (hyl), and Gelatinase (gelE); (3) this strain also lacked ß-hemolysis and the production of toxic metabolites (D-lactate and bile salt deconjugation). Consequently, W. cibaria JW15 is expected to be applied as a functional food ingredient in the food market.

Comparative Evaluation of Quality and Metabolite Profiles in Meju Using Starter Cultures of Bacillus velezensis and Aspergillus oryzae.

The production of good Meju soybean paste primarily depends on the selection of raw materials and fermenting microorganisms, which together influence its characteristic metabolites, taste, and aroma. In this study, we analyzed the relationship between properties and metabolites in Meju samples fermented by Aspergillus oryzae alone or with Bacillus velezensis. We developed fast-stable processing techniques to obtain Meju from A. oryzae and B. velezensis using the inoculation method, thereby ensuring safety in the production of soybean paste. The amino-type nitrogen content increased from an initial 180-228 mg% to a final 226-776 mg% during fermentation and was higher in Meju inoculated separately with the fungi and bacteria (C group) than in Meju co-inoculated with both the starters concurrently (D group). The levels of metabolites such as glucose, myo-inositol, glycerol, and fatty acids (palmitic, stearic, oleic, and linoleic acids) in Meju fermented by A. oryzae with B. velezensis were higher than those in Meju fermented by A. oryzae alone. Fungal growth was affected by the inoculated bacteria, which often occurs during the fermentation of co-inoculated Meju.

Carboxy-Terminal Region of a Thermostable CITase from Thermoanaerobacter thermocopriae Has the Ability to Produce Long Isomaltooligosaccharides.

Isomaltooligosaccharides (IMOs) have good prebiotic effects, and long IMOs (LIMOs) with a degree of polymerization (DP) of 7 or above show improved effects. However, they are not yet commercially available, and require costly enzymes and processes for production. The Nterminal region of the thermostable Thermoanaerobacter thermocopriae cycloisomaltooligosaccharide glucanotransferase (TtCITase) shows cyclic isomaltooligosaccharide (CI)-producing activity owing to a catalytic domain of glycoside hydrolase (GH) family 66 and carbohydrate-binding module (CBM) 35. In the present study, we elucidated the activity of the C-terminal region of TtCITase (TtCITase-C; Met740-Phe1,559), including a CBM35-like region and the GH family 15 domain. The domain was successfully cloned, expressed, and purified as a single protein with a molecular mass of 115 kDa. TtCITase-C exhibited optimal activity at 40°C and pH 5.5, and retained 100% activity at pH 5.5 after 18-h incubation. TtCITase-C synthesized α-1,6 glucosyl products with over seven degrees of polymerization (DP) by an α-1,6 glucosyl transfer reaction from maltopentaose, isomaltopentaose, or commercialized maltodextrins as substrates. These results indicate that TtCITase-C could be used for the production of α-1,6 glucosyl oligosaccharides with over DP7 (LIMOs) in a more cost-effective manner, without requiring cyclodextran.

Characterization of divergent pseudo-sucrose isomerase from Azotobacter vinelandii: Deciphering the absence of sucrose isomerase activity.

Among members of the glycoside hydrolase (GH) family, sucrose isomerase (SIase) and oligo-1,6-glucosidase (O16G) are evolutionarily closely related even though their activities show different specificities. A gene (Avin_08330) encoding a putative SIase (AZOG: Azotobacterglucocosidase) from the nitrogen-fixing bacterium Azotobacter vinelandii is a type of pseudo-SIase harboring the "RLDRD" motif, a SIase-specific region in 329-333. However, neither sucrose isomerization nor hydrolysis activities were observed in recombinant AZOG (rAZOG). The rAZOG showed similar substrate specificity to Bacillus O16G as it catalyzes the hydrolysis of isomaltulose and isomaltose, which contain α-1,6-glycosidic linkages. Interestingly, rAZOG could generate isomaltose from the small substrate methyl-α-glucoside (MαG) via intermolecular transglycosylation. In addition, sucrose isomers isomaltulose and trehalulose were produced when 250 mM fructose was added to the MαG reaction mixture. The conserved regions I and II of AZOG are shared with many O16Gs, while regions III and IV are very similar to those of SIases. Strikingly, a shuffled AZOG, in which the N-terminal region of SIase containing conserved regions I and II was exchanged with the original enzyme, exhibited a production of sucrose isomers. This study demonstrates an evolutionary relationship between SIase and O16G and suggests some of the main regions that determine the specificity of SIase and O16G.

Enzymatic Characteristics of a Highly Thermostable ß-(1-4)-Glucanase from Fervidobacterium islandicum AW-1 (KCTC 4680).

A highly thermostable ß-(1-4)-glucanase (NA23_08975) gene (fig) from Fervidobacterium islandicum AW-1, a native-feather degrading thermophilic eubacterium, was cloned and expressed in Escherichia coli. The recombinant FiG (rFiG) protein showed strong activity toward ß-D-glucan from barley (367.0 IU/mg), galactomannan (174.0 IU/mg), and 4-nitrophenyl-cellobioside (66.1 IU/mg), but relatively weak activity was observed with hydroxyethyl cellulose (5.3 IU/mg), carboxymethyl cellulose (2.4 IU/mg), and xylan from oat spelt (1.4 IU/mg). rFiG exhibited optimal activity at 90°C and pH 5.0. In addition, this enzyme was extremely thermostable, showing a half-life of 113 h at 85°C. These results indicate that rFiG could be used for hydrolysis of cellulosic and hemicellulosic biomass substrates for biofuel production.