Response surface methodology (RSM) has been used to optimize the extraction conditions of antioxidants with relatively low caffeine content from green tea by using ultrasonic extraction. The predicted optimal conditions for the highest antioxidant activity and minimum caffeine level were found at 19.7% ethanol, 26.4 min extraction time, and 24.0 °C extraction temperature. In the predicted optimal conditions, the experimental values were very close to the predicted values. Moreover, the ratio of (EGCg + ECg)/EGC was identified a major factor contributing to the antioxidant activity of green tea extracts. In this study, ultrasonic extraction showed that the ethanol concentration and extraction time used for antioxidant extraction could be remarkably reduced without a decrease in antioxidant activity compared to the conventional extraction conditions.

Weissella cibaria CMU and CMS1 are known to exert beneficial effects on the oral cavity but have not yet been determined to be generally recognized as safe (GRAS), although they are used as commercial strains in Korea. We aimed to verify the safety of W. cibaria CMU and CMS1 strains through phenotypic and genotypic analyses. Their safety was evaluated by a minimum inhibitory concentration assay for 14 antibiotics, DNA analysis for 28 antibiotic resistance genes (ARGs) and one conjugative element, antibiotic resistance gene transferability, virulence gene analysis, hemolysis, mucin degradation, toxic metabolite production, and platelet aggregation reaction. W. cibaria CMU showed higher kanamycin resistance than the European Food Safety Authority (EFSA) cut-off, but this resistance was not transferred to the recipient strain. W. cibaria CMU and CMS1 lacked ARGs in chromosomes and plasmids, and genetic analysis confirmed that antibiotic resistance of kanamycin was an intrinsic characteristic of W. cibaria. Additionally, these strains did not harbor virulence genes associated with pathogenic bacteria and lacked toxic metabolite production, β-hemolysis, mucin degradation, bile salt deconjugation, β-glucuronidase, nitroreductase activity, gelatin liquefaction, phenylalanine degradation, and platelet aggregation. Our findings demonstrate that W. cibaria CMU and CMS1 can achieve the GRAS status in future.

Probiotics have been demonstrated as a new paradigm to substitute antibiotic treatment for dental caries, gingivitis, and chronic periodontitis. The present work was conducted to compare the characteristics of oral care probiotics: Weissella cibaria CMU (Chonnam Medical University) and four commercial probiotic strains. Survival rates under poor oral conditions, acid production, hydrogen peroxide production, as well as inhibition of biofilm formation, coaggregation, antibacterial activity, and inhibition of volatile sulfur compounds were evaluated. The viability of W. cibaria CMU was not affected by treatment of 100 mg/L lysozyme for 90 min and 1 mM hydrogen peroxide for 6 h. Interestingly, W. cibaria produced less acid and more hydrogen peroxide than the other four probiotics. W. cibaria inhibited biofilm formation by Streptococcus mutans at lower concentrations (S. mutans/CMU = 8) and efficiently coaggregated with Fusobacterium nucleatum. W. cibaria CMU and two commercial probiotics, including Lactobacillus salivarius and Lactobacillus reuteri, showed high antibacterial activities (>97%) against cariogens (S. mutans and Streptococcus sobrinus), and against periodontopathogens (F. nucleatum and Porphyromonas gingivalis). All of the lactic acid bacterial strains in this study significantly reduced levels of hydrogen sulfide and methyl mercaptan produced by F. nucleatum and P. gingivalis (p < 0.05). These results suggest that W. cibaria CMU is applicable as an oral care probiotic.

Recently, studies have explored the use of probiotics like the Weissella cibaria strain, CMU (oraCMU), for use as preventive dental medicine instead of chemical oral care methods. The present study was conducted to investigate the antibacterial properties of the cell-free supernatant (CFS) from this bacterium. Cell morphology using the scanning electron microscope, and the antibacterial effect of CFS under various growth conditions were evaluated. The production of hydrogen peroxide, organic acids, fatty acids, and secretory proteins was also studied. Most of the antibacterial effects of oraCMU against periodontal pathogens were found to be acid- and hydrogen peroxide-dose-dependent effects. Lactic acid, acetic acid, and citric acid were the most common organic acids. Among the 37 fatty acids, only 0.02% of oleic acid (C18:1n-9, cis) was detected. Proteomic analysis of the oraCMU secretome identified a total of 19 secreted proteins, including N-acetylmuramidase. This protein may be a potential anti-microbial agent effective against Porphyromonas gingivalis.

Doenjang is a traditional Korean fermented soybean-based food that is now produced industrially as traditional Doenjang and modernized Doenjang, depending on the conditions of the manufacturing process. In this study, the effect of the production process on Doenjang metabolites was analyzed using untargeted capillary electrophoresis time-of-flight mass spectrometry (CE-TOF/MS). Of the 247 metabolites detected in 19 traditional and three modernized Doenjang samples, the level of 55 metabolites were significantly different between the two production groups. The S-plot of the orthogonal projection to latent structures-discriminant analysis (OPLS-DA) revealed that nine compounds (tryptamine, 2-phenylethylamine, citrulline, gamma-aminobutyric acid, putrescine, tyramine, 2-aminoisobutyric acid, stachydrine, and N⁵-ethylglutamine) were highly distributed in the traditional group, and six compounds (arginine, citric acid, choline, cytidine, hypoxanthine, and glucaric acid) were considered distinguishable metabolites of the modernized group. Microbial community analysis indicated that the levels of these metabolites were significantly altered by the presence of Bacillus spp., Enterococcus faecium, Tetragenococcus halophilus, Aspergillus oryzae, Penicillium spp., and Saccharomyces cerevisiae. These findings will give better understanding of the influence of the manufacturing process on Doenjang production in terms of both microbial activity and metabolite profiles.

To identify and analyze the characteristics of the microorganisms involved in the formation of the desirable flavor of Doenjang, a total of 179 strains were isolated from ninety-four Doenjang collected from six regions in South Korea, and fourteen strains were selected through a sensory evaluation of the aroma of each culture. The enzyme activities of amylase, protease and lipase was shown in the various strains. Bacillus sp.-K3, Bacillus sp.-K4 and Bacillus amyloliquefaciens-J2 showed relatively high protease activity, at 317.1 U, 317.3 U and 319.5 U, respectively. The Bacillus sp.-K1 showed the highest lipase activity at 2453.6 U. In the case of amylase, Bacillus subtilis-H6 showed the highest activity at 4105.5 U. The results of the PCA showed that Bacillus subtilis-H2, Bacillus subtilis-H3, and Bacillus sp.-K2 were closely related to the production of 3-hydroxy-2-butanone (23.51%~43.37%), and that Bacillus subtilis-H5 and Bacillus amyloliquefaciens-J2 were significantly associated with the production of phenethyl alcohol (0.39% and 0.37%). The production of peptides was observed to vary among the Bacillus cultures such as Val-Val-Pro-Pro-Phe-Leu and Pro-Ala-Glu-Val-Leu-Asp-Ile. These peptides are precursors of related volatile flavor compounds created in Doenjang via the enzymatic or non-enzymatic route; it is expected that these strains could be used to enhance the flavor of Doenjang.