Spontaneous fermentation mitigates the frequency of genes encoding antimicrobial resistance spreading from the phyllosphere reservoir to the diet

The phyllosphere microbiome of vegetable products constitutes an important reservoir for multidrug resistant bacteria and Antibiotic Resistance Genes (ARG). Vegetable products including fermented products such as Paocai therefore may serve as a shuttle for extrinsic microorganisms with ARGs into the gut of consumers. Here we study the effect of fermentation on Paocai ARG dissemination by metagenomic analysis. Microbial abundance and diversity of the Paocai microbiome were diminished during fermentation, which correlated with the reduction of abundance in ARGs. Specifically, as fermentation progressed, Enterobacterales overtook Pseudomonadales as the predominant ARG carriers, and Lactobacillales and Enterobacteriales became the determinants of Paocai resistome variation. Moreover, the dual effect of microbes and metal resistance genes (MRGs) was the major contributor driving Paocai resistome dynamics. We recovered several metagenome-assembled genomes (MAGs) carrying acquired ARGs in the phyllosphere microbiome. ARGs of potential clinical and epidemiological relevance such as tet M and emrB-qacA, were mainly hosted by non-dominant bacterial genera. Overall, our study provides evidence that changes in microbial community composition by fermentation aid in constraining ARG dispersal from raw ingredients to the human microbiome but does not eliminate them.

Association between traditional Korean fermented vegetables (kimchi) intake and serum lipid profile: using the Korean Genome and Epidemiology Study (KoGES) cohort

PURPOSE

Dyslipidemia is a major health issue worldwide. There is growing interest in understanding the potential role of kimchi consumption on serum lipid profiles. However, there are limited epidemiological studies available on this topic. Therefore, this study aims to investigate the association between kimchi intake and serum lipid profiles.

METHODS

We conducted an epidemiological study on participants (aged 40-69 years old) selected from the Health Examinees (HEXA) cohort study (n = 61,761). Four types of kimchi, including Baechu kimchi (cabbage kimchi), Kkakdugi (radish kimchi), Nabak kimchi/Dongchimi (a type of water kimchi made with fermented vegetables), and other kimchi, were assessed by a 106-food item semi-quantitative validated food frequency questionnaire (FFQ). Each kimchi intake is the average value calculated from the FFQ of the baseline and follow-up surveys. Fasting blood data were obtained at baseline and follow-up visits. Linear regression was used to examine the relationship between the intake of kimchi and the change in serum lipid profiles.

RESULTS

The mean years between the baseline survey and a follow-up survey was 4.97 years. In this study, compared to the lowest category (< 1 serving/day), Baechu kimchi intake (2- < 3 servings/day) had more negative correlations with the change in values of total cholesterol (β: -1.600, 95% confidence interval [CI, -2.744, -0.456]), triglycerides (β: -3.372, 95% CI [-5.414, -1.330]), and low-density lipoprotein cholesterol (β: -1.155, 95% CI [-2.214, -0.095]) in women. In men, Baechu kimchi intake (2- < 3 servings/day) had a more positive correlation associated with the changes in values of high-density lipoprotein cholesterol (β: 0.049, 95% CI [0.031, 0.907]) compared to the lowest intake category (< 1 serving/day).

CONCLUSIONS

Among Korean adults, consumption of kimchi, particularly Baechu kimchi, was found to be associated with improvements in serum lipid profiles. Further studies are required to conduct additional interventions to confirm the association between kimchi and serum lipid profiles.

Effect of Rhodotorula mucilaginosa inoculation on the aroma development of a fermented vegetables simulated system

Fermented vegetables are known for their unique flavors and aromas, which are influenced by the complex microbial processes that occur during fermentation. Rhodotorula mucilaginosa is a red yeast strain that is frequently isolated from fermented vegetables. However, the specific mechanisms underlying their effects on aroma production remain unclear. In this study, a simulated system of vegetables fermented using vegetable juices was used to investigate the effects of R. mucilaginosa inoculation on aroma development. The results demonstrated that this red yeast strain could utilize the nutrients present in the vegetable juices to support its growth and reproduction. Moreover, the inoculation of fermented vegetable juices with this yeast strain led to an increase in the levels of umami amino acids and sweet amino acids. Furthermore, this yeast strain was found able to significantly reduce the content of sulfur-containing compounds, which may decrease the unpleasant odor of fermented vegetables. Additionally, the yeast strain was capable of producing high concentrations of aromatic compounds such as phenylethyl alcohol, methyl 2-methylbutyrate, methyl butyrate, and nonanoic acid in a minimum medium. However, only phenylethyl alcohol has been identified as a core aromatic compound in fermented vegetable juice. The three fermented vegetable juices exhibited significantly different flavor profiles according to comparative analysis. Therefore, the core flavor compounds found in fermented vegetables are primarily derived from the release and modification of endogenous flavors naturally present in the vegetables, facilitated by the yeast during fermentation.

Meta-analysis of microbiomes reveals metagenomic features of fermented vegetables

An insightful exploration of the fermented vegetable microbiome is the key to improving food quality and sustainability. Based on 57 fermented vegetable samples from China, Ireland, the UK, and Germany retrieved from public genome databases, we conducted a high-resolution meta-analysis of the fermented vegetable microbiomes. There were significant differences in the microbiota composition and functional pathway diversity of the tested samples, as reflected by the differences in their geographical origins. Metagenomic analysis also revealed the metagenomic features of carbohydrate-active enzymes and antibiotic resistance genes in the fermented vegetable metagenomes. Five putative new species were detected by recovering 221 metagenome-assembled genomes belonging to the genera Rubrobacteraceae, Bifidobacteriaceae, and Ruminococcaceae. Our results provide new ecological insights into the implications of fermented vegetable microbiota composition and functional potential and highlight the importance of high-resolution metagenomic analysis to further investigate the fermented food microbiome.

Bacteriocin and Antioxidant Production, a Beneficial Properties of Lactic Acid Bacteria Isolated from Fermented Vegetables of Northwest Bulgaria

Lactiplantibacillus plantarum ST01BG, ST07BG, ST10BG, and ST15BG; Latilactobacillus curvatus ST02BG; Lacticaseibacillus paracasei ST04BG; Pediococcus pentosaceus ST05BG; Leuconostoc mesenteroides ST06BG; and Enterococcus faecium ST11BG were isolated from home-made fermented vegetables from Northwest Bulgaria and identified by biochemical, physiological, and biomolecular analyses, including partial 16S rRNA sequencing. The strains were designated as bacteriocin producers and the expressed antimicrobials partially characterized with a focus on their proteinaceous nature, stability to different pH and temperatures. The bacteriocins were effective in inhibiting different strains of Listeria spp., Enterococcus spp. (including vancomycin resistant enterococci) and Staphylococcus spp. These strains can be considered safe, based on the evaluation of hemolytic activity, production of biogenic amines, mucin degradation, antibiotic susceptibility/resistance, and gelatinase enzyme production. Moreover, the strains can be considered potentially beneficial based on their stability and survival under simulated gastrointestinal tract conditions (stomach and duodenum), the production of diacetyl, and specific levels of hydrophobicity. Special attention was given to antioxidant properties (DPPH radical, hydroxyl radical, superoxide anion radical scavenging activity, Fe+2 ion chelating activity, and anti-lipid peroxidation) of the strains. Antioxidant properties were found to be strain specific. The beneficial attributes (antimicrobial and antioxidant) of these cultures to fermented food products may enable the reduction of chemical additives in line with consumers' demand for more natural and chemical-free food commodities.

Properties investigations of rape stalks fermented by different salt concentration: Effect of volatile compounds and physicochemical indexes

In order to find out the effect of salt concentration on fermented rape stalks, the physicochemical quality and volatile components was investigated using high performance liquid chromatography (HPLC) and headspace solid phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that there were abundant kinds of free amino acids (FAAs) in all samples, mainly presenting sweet, umami and bitter taste. Through taste activity value (TAV), His, Glu, and Ala contributed significantly to the taste of the sample. 51 volatile components were identified, of which the relative contents of ketones and alcohols were high. By the relative odor activity value (ROAV) analysis, the main components that had a great impact on the flavor were phenylacetaldehyde, β-Ionone, ethyl palmitate and furanone. Adjusting the appropriate salt concentration for fermentation could improve the comprehensive quality of fermented rape stalks and promote the development and utilization of rape products.

Consumer's acceptability and health consciousness of probiotic and prebiotic of non-dairy products

Human gut microbiota is a protective agent of intestinal and systemic health, and its modulation is of great interest for human wellbeing. In the world of biotics, besides probiotics, prebiotics, and synbiotics, also appears the denomination of "postbiotics" and "psychobiotics". Fermented dairy products are, traditionally, the major source of probiotics. Nevertheless, due to the increasing number of lactose-intolerant individuals and strict vegetarians, there is a need for innovative non-dairy products. Non-dairy biotics are being included in the normal diet and due to technological advances, many products are created using non-conventional food matrices like kombucha tea, herbal tea, baking mix, and cereal-based products. The microorganisms most used as probiotics in many of the non-dairy products are strains belonging to the genera Bifidobacterium, Enterococcus, Lactobacillus, Lactococcus, Streptococcus, and Bacillus, and some yeast strains namely Saccharomyces cerevisiae var. boulardii. Recently, several other yeasts have been described as having probiotic properties. This review describes gut-derived effects in humans of possible microorganisms, such as yeasts, and bacteria, isolated from non-dairy fermented and non-fermented foods and beverages. The microorganisms responsible for the processing of these non-dairy fermented products, together with the prebiotics, form a class of nutrients that have been proven to be beneficial for our gut health.

Metaproteomics insights into fermented fish and vegetable products and associated microbes

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Increasing global population means higher demand for healthy food.

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Fish and vegetables are healthy foods, but overproduction leads to spoilage.

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Fermentation of fish/vegetables elongate their shelf lives, improved flavour and functions.

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Microbes associated with Fish/vegetable fermentation produce health conferring peptides.

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There is little review on peptides elicited during fish/vegetable fermentations.

The interest in proteomic studies of fermented food is increasing; the role of proteins derived from fermentation extends beyond preservation, they also improve the organoleptic, anti-pathogenic, anti-cancer, anti-obesogenic properties, and other health conferring properties of fermented food. Traditional fermentation processes are still in use in certain cultures, but recently, the controlled process is gaining wider acceptance due to consistency and predictability. Scientists use modern biotechnological approaches to evaluate reactions and component yields from fermentation processes. Pieces of literature on fermented fish and vegetable end-products are scanty (compared to milk and meat), even though fish and vegetables are considered health conferring diets with high nutritional contents. Evaluations of peptides from fermented fish and vegetables show they have anti-obesity, anti-oxidative, anti-inflammatory, anti-pathogenic, anti-anti-nutrient, improves digestibility, taste, nutrient content, texture, aroma properties, etc. Despite challenges impeding the wider applications of the metaproteomic analysis of fermented fish and vegetables, their potential benefits cannot be underestimated.

Spices to Control COVID-19 Symptoms: Yes, but Not Only…

There are large country variations in COVID-19 death rates that may be partly explained by diet. Many countries with low COVID-19 death rates have a common feature of eating large quantities of fermented vegetables such as cabbage and, in some continents, various spices. Fermented vegetables and spices are agonists of the antioxidant transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2), and spices are transient receptor potential ankyrin 1 and vanillin 1 (TRPA1/V1) agonists. These mechanisms may explain many COVID-19 symptoms and severity. It appears that there is a synergy between Nrf2 and TRPA1/V1 foods that may explain the role of diet in COVID-19. One of the mechanisms of COVID-19 appears to be an oxygen species (ROS)-mediated process in synergy with TRP channels, modulated by Nrf2 pathways. Spicy foods are likely to desensitize TRP channels and act in synergy with exogenous antioxidants that activate the Nrf2 pathway.

Microbial Ecology of Fermented Vegetables and Non-Alcoholic Drinks and Current Knowledge on Their Impact on Human Health

Fermented foods are currently experiencing a re-discovery, largely driven by numerous health benefits claims. While fermented dairy, beer, and wine (and other alcoholic fermented beverages) have been the subject of intensive research, other plant-based fermented foods that are in some case widely consumed (kimchi/sauerkraut, pickles, kombucha) have received less scientific attention. In this chapter, the current knowledge on the microbiology and potential health benefits of such plant-based fermented foods are presented. Kimchi is the most studied, characterized by primarily acidic fermentation by lactic acid bacteria. Anti-obesity and anti-hypertension properties have been reported for kimchi and other pickled vegetables. Kombucha is the most popular non-alcoholic fermented drink. Kombucha's microbiology is remarkable as it involves all fermenters described in known fermented foods: lactic acid bacteria, acetic acid bacteria, fungi, and yeasts. While kombucha is often hyped as a "super-food," only antioxidant and antimicrobial properties toward foodborne pathogens are well established; and it is unknown if these properties incur beneficial impact, even in vitro or in animal models. The mode of action that has been studied and demonstrated the most is the probiotic one. However, it can be expected that fermentation metabolites may be prebiotic, or influence host health directly. To conclude, plant-based fermented foods and drinks are usually safe products; few negative reports can be found, but more research, especially human dietary intervention studies, are warranted to substantiate any health claim.

Microbioligical Hazard Contamination in Fermented Vegetables Sold in Local Markets in Cambodia

　Fermented vegetables are common part of Cambodian diet. The food safety status for these foods has not been investigated. This study was conducted to evaluate the microbiological hazards that contaminated fermented vegetables. A total of 68 samples of fermented vegetables were purchased randomly from five wet markets in Phnom Penh. The conventional culture methods for microbiological analysis were used. Coliform bacteria (Escherichia coli, Cronobactersakazakii, and Enterobacter spp.), opportunistic non-Entrobacteriaceae, Enterococcus spp., Staphylococcus spp., and Listeria spp. were found in these fermented foods. The highest contamination rate of Enterococcus spp. was 34% of total fermented vegetable samples, followed by Bacillus spp. coliform bacteria and E. coli (31%, 24% and 10%, respectively). The potential foodborne pathogen, C. sakazakii, was identified in one sample. Fermented mixed vegetables showed higher contamination rate of coliform bacteria (50%) than fermented single-type vegetables (13%). The results showed that fermented vegetables sold in wet market are poor in hygiene. The stage in the processing chain where contamination occurred should be identified and basic sanitary practice should be enforced to improve the food safety of fermented vegetables in Cambodia.

Suitability of various DNA extraction methods for a traditional Chinese paocai system

Traditional paocai brine (PB), which is continuously propagated by back-slopping and contains various species of lactic acid bacteria (LAB), is critical for the flavor of paocai. Culture-independent approaches are commonly used to investigate the microbial communities of fermented food. To evaluate the influence of different DNA (DNA) extraction methods on estimates of bacterial community profiles from 4 PBs, the lysis efficiency, DNA yield, purity and denaturing gradient gel electrophoresis (DGGE) profiles of V3 region of a 16S ribosomal ribonucleic acid gene were acquired. The cell lysis pattern of SDS + beads and Lysing matrix E+ beads (methods 3 and 4) showed higher cell lysis efficiency than SDS and SDS + Lysozyme (methods 1 and 2) in all PBs. SDS + beads obtained the largest DNA yield of the 4 methods. Moreover, methods 3 and 4 resulted in higher H' values and generated more global bacteria profiles than other methods. Overall, our results demonstrate that the properties of PB significantly affect the efficiency of DNA extraction methods. Methods 3 and 4 were both suitable for DNA extraction from PB. Method 3 is more economic, simple and rapid than method 4 for large-scale studies of the bacterial profiles of PB.

The effect of bacteriophages on the acidification of a vegetable juice medium by microencapsulated Lactobacillus plantarum

Starter cultures are increasingly being used for the production of sauerkraut, kimchi and other fermented vegetables. The goal of this study was to determine whether the microencapsulation of a bacterial culture can prevent phage infection during vegetable fermentation. Lactobacillus plantarum HER1325 was microencapsulated in alginate beads. Some beads were used without further processing, while others were freeze-dried prior to testing. Fresh beads (diameter of 2 mm) and dried cultures of the lactobacilli (particle size of 53-1000 μm) were added to a vegetable juice medium (VJM) at 1 × 10⁷ CFU/mL. The virulent phage HER325 was added at an initial titer of 1 × 10⁴ PFU/mL. In the absence of phages, the pH of the vegetable juice dropped to 4.2 after 40 h of fermentation at 19 °C. In the presence of phage HER325, acidification by both the non-microencapsulated and microencapsulated starter cultures stopped after 24 h. In all assays, the alginate particles dissolved during the 40 h of VJM fermentation. When 15 g/L of calcium chloride was added to the VJM, the alginate beads did not dissolve and significant phage protection was observed. The results suggest that phage-protected microencapsulated starter cultures can be used for vegetable fermentation if means are taken to prevent them from dissolving during acidification.

Characterization of the microbial diversity in yacon spontaneous fermentation at 20 °C

The prebiotic fructooligosaccharide content of yacon makes this root an attractive alternative for the supplementation of a variety of food products. The preservation of yacon by fermentation has been proposed as an alternative to increase the probiotic content of the root concomitantly with its shelf life. Thus the fermented yacon could have significant functional content. The objective of this research was to characterize the biochemistry and microbiology of spontaneous yacon fermentation with 2% NaCl and define the viability of the proposed process. The biochemical analysis of spontaneous heterolactic fermentation of yacon showed a progressive drop in pH with increased lactic and acetic acids, and the production of mannitol during fermentation. The microbial ecology of yacon fermentation was investigated using culture-dependent and culture-independent methods. Bacterial cell counts revealed a dominance of lactic acid bacteria (LAB) over yeasts, which were also present during the first 2 days of the fermentation. Results showed that the heterofermentative LAB were primarily Leuconostoc species, thus it presents a viable method to achieve long term preservation of this root.

Preparation and evaluation of sauces from lactic acid fermented vegetables

Different combinations of fermented vegetables like carrot, radish and cucumber with pear and mango pulps were made separately and were processed. All the sauces prepared were having a constant TSS of 18°B using different combinations of fermented pulp viz., 25, 50, 75 and 100% with fruit pulps of mango and pear. The titratable acidity of carrot, radish and cucumber based sauces ranged from 1.22 to 1.39%. The blending ratio influenced the titratable acidity, Brix-acid ratio, pH and colour of the various sauces. In general, physico-chemical and sensory characteristics of all sauces prepared met the FPO specifications. Carrot with pear pulp based sauce had the highest overall acceptability. Product prepared with 25% radish + 75% pear and sauce with blend of 50% cucumber + 50% pear were preferred to others. Fermented carrot based sauce having blend of 75% fermented carrot + 25% pear was adjudged sensorily as the best. The cost of production of fermented vegetable based sauces (200 ml bottle) ranged between Rs 15.54 and 24.14 and the lowest (Rs 15.54) cost was for radish based fermented sauce.