Kimchi bacteriophages of lactic acid bacteria: population, characteristics, and their role in watery kimchi

The effects of fermented vegetables on the gut microbiota for prevention of cardiovascular disease

This study investigated the impact of regular consumption of fermented vegetables (FVs) on inflammation and the composition of the gut microbiota in adults at increased risk for cardiovascular disease. Eighty-seven adults ages 35-64 were randomized into an FV group, who consumed 100 g FVs daily at least five times per week for eight weeks, or a usual diet (UD) group. Blood and stool samples were obtained before and after the intervention. Dependent samples t tests and adjusted linear models were used for within- and between-group comparisons. The mean age and body mass index of participants were 45 years and 30 kg/m2, and 80% were female. Bloating or gas was the most common side effect reported (19.3% FV group vs. 9.4% UD group). There were no changes in C-reactive protein, oxidized low-density lipoprotein-receptor 1, angiopoietin-like protein 4, trimethylamine oxide, and lipopolysaccharide-binding protein or bacterial alpha diversity between groups. Our findings indicate that consuming 100 g of FVs for at least five days per week for eight weeks does not change inflammatory biomarkers or microbial alpha diversity as measured by the Shannon index. It is possible that higher doses of FVs are necessary to elicit a significant response by gut bacteria.

The bacteriome-coupled phage communities continuously contract and shift to orchestrate the traditional rice vinegar fermentation

Amounts of microbiome studies have uncovered the microbial communities of traditional food fermentations, while in which the phageome development with time is poorly understood. Here, we conducted a study to decipher both phageome and bacteriome of the traditional rice vinegar fermentation. The vinegar phageomes showed significant differences in the alpha diversity, network density and clustering coefficient over time. Peduoviridae had the highest relative abundance. Moreover, the phageome negatively correlated to the cognate bacteriome in alpha diversity, and undergone constantly contracting and shifting across the temporal scale. Nevertheless, 257 core virial clusters (VCs) persistently occurred with time whatever the significant impacts imposed by the varied physiochemical properties. Glycoside hydrolase (GH) and glycosyltransferase (GT) families genes displayed the higher abundances across all samples. Intriguingly, diversely structuring of toxin-antitoxin systems (TAs) and CRISPR-Cas arrays were frequently harbored by phage genomes. Their divergent organization and encoding attributes underlie the multiple biological roles in modulation of network and/or contest of phage community as well as bacterial host community. This phageome-wide mapping will fuel the current insights of phage community ecology in other traditional fermented ecosystems that are challenging to decipher.

Pediococcus inopinatus with a well-developed CRISPR-Cas system dominates in long-term fermented kimchi, Mukeunji

Kimchi is produced through a low-temperature fermentation without pre-sterilization, resulting in a heterogeneous microbial community. As fermentation progresses, dominant lactic acid bacteria (LAB) species emerge and undergo a transition process. In this study, LAB were isolated from Mukeunji, a long-term fermented kimchi that is in the final stage of kimchi fermentation process. It was confirmed, through culture-dependent and independent analysis, as well as metagenome analysis, that Pediococcus inopinatus are generally dominant in long-term fermented kimchi. Comparative analysis of the de novo assembled whole genome of P. inopinatus with other kimchi LAB revealed that this species has a well-developed clustered regularly interspaced short palindromic repeats (CRISPR) system. The CRISPR system of P. inopinatus has an additional copy of the csa3 gene, a transcription factor for cas genes. Indeed, this species not only highly expresses cas1 and cas2, which induce spacer acquisition, but also has many diverse spacers that are actively expressed. These findings indicate that the well-developed CRISPR-Cas system is enabling P. inopinatus to dominate in long-fermented kimchi. Overall, this study revealed that LAB with a robust defense system dominate in the final stage of kimchi fermentation and presented a model for the succession mechanism of kimchi LAB.

Association between kimchi consumption and obesity based on BMI and abdominal obesity in Korean adults: a cross-sectional analysis of the Health Examinees study

OBJECTIVE

Previous animal studies have shown the anti-obesity effect of kimchi-derived probiotic lactic acid bacteria. However, only a few epidemiological studies have investigated the association between kimchi consumption and obesity. Therefore, we aim to assess this relationship in Korean adults.

DESIGN

Cross-sectional study.

SETTING

The Health Examinees study was conducted from 2004 to 2013.

PARTICIPANTS

This study analysed 115 726 participants aged 40-69 years enrolled in the Health Examinees study in Korea.

PRIMARY AND SECONDARY OUTCOME MEASURES

Obesity was defined as body mass index ≥25 kg/m2, and abdominal obesity was defined as waist circumference ≥90 cm in men and ≥85 cm in women. Kimchi consumption was assessed by the validated food frequency questionnaire.

RESULTS

In men, total kimchi consumption of 1-3 servings/day was related to a lower prevalence of obesity (OR: 0.875 in 1-2 servings/day and OR: 0.893 in 2-3 servings/day) compared with total kimchi consumption of <1 serving/day. Also, men with the highest baechu kimchi (cabbage kimchi) consumption had 10% lower odds of obesity and abdominal obesity. Participants who consumed kkakdugi (radish kimchi) ≥median were inversely associated with 8% in men and 11% in women with lower odds of abdominal obesity compared with non-consumers, respectively.

CONCLUSIONS AND RELEVANCE

Consumption of 1-3 servings/day of total kimchi was associated with a lower risk of obesity in men. Baechu kimchi was associated with a lower prevalence of obesity in men, and kkakdugi was associated with a lower prevalence of abdominal obesity in both men and women. However, since all results showed a 'J-shaped' association, it is recommended to limit excessive kimchi intake.

Isolation of Aroma-Producing Wickerhamomyces anomalus Yeast and Analysis of Its Typical Flavoring Metabolites

In this study, 21 strains of aroma-producing yeast were isolated from Sichuan paocai juice of farmers in western, eastern and southern Sichuan. One strain, Y3, with the best aroma-producing characteristics, was screened using an olfactory method and a total ester titration method, and was identified as Wickerhamomyces anomalus. The total ester content of Y3 fermentation broth was as high as 1.22 g/L, and there was no white colonies or film on the surface. Meanwhile, the Y3 strain could tolerate 14% salt concentration conditions and grow well in a pH range of 3-4. Through sensory analysis, the fermented mustard with a ratio of Lactiplantibacillus plantarum to Y3 of 1:1 showed the highest overall acceptability. Ethyl acetate with its fruit and wine flavor was also detected in the fermented Sichuan paocai juice with a mixed bacteria ratio of 1:1, analyzed with SPME-GC-MS technology, as well as phenylethyl alcohol, isobutyl alcohol, isothiocyanate eaters, myrcene and dimethyl disulfide. These contributed greatly to the unique flavor of Sichuan paocai. In general, Wickerhamomyces anomalus Y3 enhanced the aroma of the fermented Sichuan paocai.

Characterization of Prophages in Leuconostoc Derived from Kimchi and Genomic Analysis of the Induced Prophage in Leuconostoc lactis

Leuconostoc has been used as a principal starter in natural kimchi fermentation, but limited research has been conducted on its phages. In this study, prophage distribution and characterization in kimchi-derived Leuconostoc strains were investigated, and phage induction was performed. Except for one strain, 16 Leuconostoc strains had at least one prophage region with questionable and incomplete regions, which comprised 0.5-6.0% of the bacterial genome. Based on major capsid protein analysis, ten intact prophages and an induced incomplete prophage of Leu. lactis CBA3626 belonged to the Siphoviridae family and were similar to Lc-Nu-like, sha1-like, phiMH1-like, and TPA_asm groups. Bacterial immunology genes, such as superinfection exclusion proteins and methylase, were found on several prophages. One prophage of Leu. lactis CBA3626 was induced using mitomycin C and was confirmed as belonging to the Siphoviridae family. Homology of the induced prophage with 21 reported prophages was not high (< 4%), and 47% identity was confirmed only with TPA_asm from Siphoviridae sp. isolate ct3pk4. Therefore, it is suggested that Leuconostoc from kimchi had diverse prophages with less than 6% genome proportion and some immunological genes. Interestingly, the induced prophage was very different from the reported prophages of other Leuconostoc species.