UPLC-QTOF-MS/MS and GC-MS Characterization of Phytochemicals in Vegetable Juice Fermented Using Lactic Acid Bacteria from Kimchi and Their Antioxidant Potential

Exploring the Biogenic Transformation Mechanism of Polyphenols by Lactobacillus plantarum NCU137 Fermentation and Its Enhancement of Antioxidant Properties in Wolfberry Juice

This study investigated the transformation of polyphenols, including free and bound polyphenols during the fermentation of wolfberry juice by Lactobacillus plantarum NCU137. Results indicated that fermentation significantly increased the free polyphenols content and released bound polyphenols, enhancing the antioxidant activity. Analysis showed that there were 19 free polyphenols, mainly scopoletin, pyrogallol, and dihydroferulic acid, and 16 bound polyphenols, especially p-coumaric acid, feruloyl hexoside, and caffeic acid. A significant correlation was observed between the generation and degradation of polyphenols, and specific bound polyphenols peaked during the 24-48 h fermentation. Furthermore, reduced surface roughness and galacturonic acid content in wolfberry residue, along with increased pectinase activity, suggested substantial pectin degradation in the cell wall, which may be associated with the release of polyphenols, due to pectin serving as carriers for bound polyphenols. The fermentation also increased polyphenol oxidase and peroxidase activity, contributing to polyphenol breakdown. These findings provide insights for improving wolfberry juice production.

Widely targeted metabolomics-based analysis of the impact of L. plantarum and L. paracasei fermentation on rosa roxburghii Tratt juice

Rosa roxburghii Tratt fruits (RRT) exhibit extremely high nutritional and medicinal properties due to its unique phytochemical composition. Probiotic fermentation is a common method of processing fruits. Variations in the non-volatile metabolites and bioactivities of RRT juice caused by different lactobacilli are not well understood. Therefore, we aimed to profile the non-volatile components and investigate the impact of L. plantarum fermentation (LP) and L. paracasei fermentation (LC) on RRT juice (the control, CG). There were both similarities and differences in the effects of LP and LC on RRT juice. Both of the two strains significantly increased the content of total phenolic, total flavonoid, and some bioactive compounds such as 2-hydroxyisocaproic acid, hydroxytyrosol and indole-3-lactic acid in RRT juice. Interestingly, compared with L. paracasei, L. plantarum showed better ability to increase the content of total phenolic and these valuable compounds, as well as certain bioactivities. The antioxidant capacity and α-glucosidase inhibitory activity of RRT juice were notably enhanced after the fermentations, whereas its cholesterol esterase inhibitory activity was reduced significantly. Moreover, a total of 1466 metabolites were identified in the unfermented and fermented RRT juices. There were 278, 251 and 134 differential metabolites in LP vs CG, LC vs CG, LC vs LP, respectively, most of which were upregulated. The key differential metabolites were classified into amino acids and their derivatives, organic acids, nucleotides and their analogues, phenolic acids and alkaloids, which can serve as potential markers for authentication and discrimination between the unfermented and lactobacilli fermented RRT juice samples. The KEGG enrichment analysis uncovered that metabolic pathways, purine metabolism, nucleotide metabolism and ABC transporters contributed mainly to the formation of unique composition of fermented RRT juice. These results provide good coverage of the metabolome of RRT juice in both unfermented and fermented forms and also provide a reference for future research on the processing of RRT or other fruits.

Effect of mixed fermentation of Lactiplantibacillus plantarum and Lactiplantibacillus pentosus on phytochemical and flavor characteristics of Wallace melon juice

BACKGROUND

Melons (Cucumis melo L.) are among the most commonly consumed fruits but they are highly susceptible to mechanical damage and rot during storage and transportation. New processed products are needed to avoid postharvest fruit loss and to increase health benefits. Fermentation is an effective means of utilizing the nutrients and improving flavor.

RESULTS

Fermented melon juice (MJ) was prepared using three potential probiotics Lactiplantibacillus plantarum CICC21824 (LP), Lactiplantibacillus plantarum GB3-2 (LG), and Lactiplantibacillus pentosus XZ-34 (LX). The nutrition, flavor characteristics, and digestive properties of different fermented MJs were compared. The results demonstrated that, in comparison with mono-fermentation, mixed fermentation by LG and LX could increase the level of organic acids and phenolic acids. Correspondingly, antioxidant capacity was improved significantly and positively correlated with p-coumaric acid and cinnamic acid content. The production of alcohols and acids was more strongly enhanced by mixed culture fermentation, whereas mono-fermentation reduced the content of esters, especially ethyl acetate and isopropyl acetate. Aldehydes and ketones increased significantly in fermented MJ, and damascenone and heptanal could be the characteristic aroma compounds.

CONCLUSION

Mixed fermented MJ provides more beneficial phytochemicals, better flavor, and stronger antioxidant properties than mono-fermentation. © 2024 Society of Chemical Industry.

Metabolites of Kimchi Lactic Acid Bacteria, Indole-3-Lactic Acid, Phenyllactic Acid, and Leucic Acid, Inhibit Obesity-Related Inflammation in Human Mesenchymal Stem Cells

Given the diversity of vegetables utilized in food fermentation and various lactic acid bacteria (LAB) populations in these materials, comprehensive studies on LAB from vegetable foods, including kimchi, are imperative. Therefore, this study aimed to investigate the obesity-related inflammation response of three metabolites-phenyllactic acid (PLA), indole-3-lactic acid (ILA), and leucic acid (LA)-produced by LAB (Companilactobacillus allii WiKim39 and Lactococcus lactis WiKim0124) isolated from kimchi. Their effects on tumor necrosis factor-α-induced changes in adipokines and inflammatory response in adipose-derived human mesenchymal stem cells were examined. The study results showed that PLA, ILA, and LA, particularly PLA, effectively reduced lipid accumulation and triglyceride, glycerol, free fatty acid, and adiponectin levels. Furthermore, the identified metabolites were found to modulate the expression of signaling proteins involved in adipogenesis and inflammation. Specifically, these metabolites were associated with enriched expression in the chemokine signaling pathway and cytokine-cytokine receptor interaction, which are critical pathways involved in regulating immune responses and inflammation. PLA, ILA, and LA also suppressed the secretion of pro-inflammatory cytokines and several inflammatory markers, with the PLA-treated group exhibiting the lowest levels. These results suggest that PLA, ILA, and LA are potential therapeutic agents for treating obesity and inflammation by regulating adipokine secretion and suppressing pro-inflammatory cytokine production.

Effect of lactic acid bacteria co-fermentation on antioxidant activity and metabolomic profiles of a juice made from wolfberry and longan

Lactic acid bacteria (LAB) fermentation is frequently employed to improve the nutritional, functional, and sensory characteristics of foods. Our study explored the effects of co-fermentation with Lacticaseibacillus paracasei ZH8 and Lactococcus lactis subsp. lactis YM313 on the physicochemical properties, antioxidant activity, and metabolomic profiles of wolfberry-longan juice (WLJ). Fermentation was carried out at 35 °C for 15 h. The results suggest that WLJ is a favorable substrate for LAB growth, reaching a total viable count exceeding 8 log CFU/mL after fermentation. LAB fermentation increased acidity, reduced the sugar content, and significantly impacted the juice color. The total phenolic and flavonoid contents of the WLJ and the antioxidant capacities based on 2,2-diphenyl-1-picrylhydrazyl (DPPH), ABTS radical scavenging abilities and FRAP were significantly improved by LAB fermentation. Nontargeted metabolomics analysis suggested that the contents of small molecule substances in WLJ were considerably affected by LAB fermentation. A total of 374 differential metabolites were identified in the juice before and after fermentation, with 193 significantly upregulated metabolites and 181 siginificantly downregulated metabolites. The regulation of metabolites is important for improving the flavor and functions of juices, such as L-eucylproline, Isovitexin, Netivudine, 3-Phenyllactic acid, vanillin, and ethyl maltol, ect. This study provides a theoretical foundation for developing plant-based foods fermented with LAB.

Advancing Insights into Probiotics during Vegetable Fermentation

Fermented vegetables have a long history and are enjoyed worldwide for their unique flavors and health benefits. The process of fermentation improves the nutritional value, taste, and shelf life of foods. Microorganisms play a crucial role in this process through the production of metabolites. The flavors of fermented vegetables are closely related to the evaluation and succession of microbiota. Lactic acid bacteria (LABs) are typically the dominant bacteria in fermented vegetables, and they help inhibit the growth of spoilage bacteria and maintain a healthy gut microbiota in humans. However, homemade and small-scale artisanal products rely on spontaneous fermentation using bacteria naturally present on fresh vegetables or from aged brine, which may introduce external microorganisms and lead to spoilage and substandard products. Hence, understanding the role of LABs and other probiotics in maintaining the quality and safety of fermented vegetables is essential. Additionally, selecting probiotic fermentation microbiota and isolating beneficial probiotics from fermented vegetables can facilitate the use of safe and healthy starter cultures for large-scale industrial production. This review provides insights into the traditional fermentation process of making fermented vegetables, explains the mechanisms involved, and discusses the use of modern microbiome technologies to regulate fermentation microorganisms and create probiotic fermentation microbiota for the production of highly effective, wholesome, safe, and healthy fermented vegetable foods.

Effect of Thermal Inactivation on Antioxidant, Anti-Inflammatory Activities and Chemical Profile of Postbiotics

Inactivation is a crucial step in the production of postbiotics, with thermal inactivation being the prevailing method employed. Nevertheless, the impact of thermal treatment on bioactivity and chemical composition remains unexplored. The objective of this study was to assess the influence of heating temperature on the antioxidant, anti-inflammatory properties and the chemical composition of ET-22 and BL-99 postbiotics. The findings revealed that subjecting ET-22 and BL-99 to thermal treatment ranging from 70 °C to 121 °C for a duration of 10 min effectively deactivated them, leading to the disruption of cellular structure and release of intracellular contents. The antioxidant and anti-inflammatory activity of ET-22 and BL-99 postbiotics remained unaffected by mild heating temperatures (below 100 °C). However, excessive heating at 121 °C diminished the antioxidant activity of the postbiotic. To further investigate the impact of thermal treatments on chemical composition, non-targeted metabolomics was conducted to analyze the cell-free supernatants derived from ET-22 and BL-99. The results revealed that compared to mild inactivation at temperatures below 100 °C, the excessive temperature of 121 °C significantly altered the chemical profile of the postbiotic. Several bioactive components with antioxidant and anti-inflammatory properties, including zomepirac, flumethasone, 6-hydroxyhexanoic acid, and phenyllactic acid, exhibited a significant reduction in their levels following exposure to a temperature of 121 °C. This decline in their abundance may be associated with a corresponding decrease in their antioxidant and anti-inflammatory activities. The cumulative evidence gathered strongly indicates that heating temperatures exert a discernible influence on the properties of postbiotics, whereby excessive heating leads to the degradation of heat-sensitive active constituents and subsequent diminishment of their biological efficacy.

Chemically Defined Lactobacillus plantarum Cell-Free Metabolites Demonstrate Cytoprotection in HepG2 Cells through Nrf2-Dependent Mechanism

Centering around the concept that metabolites from the gut commensals can exert metabolic health benefits along the gut-liver axis, we tested whether the cell-free global metabolome of probiotic bacteria can exert hepatoprotective benefits against H₂O₂-induced oxidative stress. Cell-free global metabolites of Lactobacillus plantarum (LPM) were isolated and untargeted metabolomics was performed. The free radical scavenging potentials of LPM were measured. The cytoprotective effects of LPM were tested on HepG2 cells. A total of 66 diverse metabolites were identified in LPM, among which saturated fatty acids, amino acids and dicarboxylic acids were highly enriched. LPM attenuated cell damage, lipid peroxidation and the levels of intracellular cytoprotective enzymes in H₂O₂-treated cells. LPM also attenuated H₂O₂-induced increased expressions of TNF-α and IL-6. However, the cytoprotective effects of LPM were diminished in cells that were pretreated with a pharmacological inhibitor of Nrf2. Our data collectively indicate that LPM can significantly attenuate oxidative damage to HepG2 cells. However, the cytoprotective effects of LPM likely depend on an Nrf2-dependent mechanism.

Unraveling multifunction of low-temperature Daqu in simultaneous saccharification and fermentation of Chinese light aroma type liquor

Chinese liquor is produced by a representative simultaneous saccharification and fermentation process. Daqu, as a starter of Chinese liquor fermentation, affects both saccharification and fermentation. However, it is still unclear how Daqu contributed to the simultaneous saccharification and fermentation process. Here, using Chinese light aroma type liquor as a case, we identified low-temperature Daqu-originated enzymes and microorganisms that contributed to the simultaneous saccharification and fermentation using metaproteomic analysis combined with amplicon sequencing analysis. α-Amylase and glucoamylase accounted for 95 % of total saccharifying enzymes and were identified as key saccharifying enzymes. Lichtheimia was the key producer of these two enzymes (> 90 %) in low-temperature Daqu. Daqu contributed 90 % α-amylase and 99 % glucoamylase to the initial liquor fermentation. These two enzymes decreased by 35 % and 49 % until day 15 in liquor fermentation. In addition, Daqu contributed key microbial genera (91 % Saccharomyces, 6.5 % Companilactobacillus) and key enzymes (37 % alcohol dehydrogenase, 40 % lactic acid dehydrogenase, 56 % aldehyde dehydrogenase) related with formations of ethanol, lactic acid and flavour compounds to the initial liquor fermentation. The average relative abundances of these fermentation-related key microorganisms and enzymes increased by 2.78 times and 1.29 times till day 15 in liquor fermentation, respectively. It indicated that Daqu provided saccharifying enzymes for starch hydrolysis, and provided both enzymes and microorganisms associated with formations of ethanol, lactic acid and flavour compounds for liquor fermentation. This work illustrated the multifunction of low-temperature Daqu in the simultaneous saccharification and fermentation of Chinese light aroma type liquor. It would facilitate improving liquor fermentation by producing high-quality Daqu.

Anti-obesity effect of vegetable juice fermented with lactic acid bacteria isolated from kimchi in C57BL/6J mice and human mesenchymal stem cells

This study aimed to investigate the effect of fermented vegetable juice (VJ) obtained from a blend of four crops (Brassica oleracea var. capitata, B. oleracea var. italica, Daucus carota L., and Beta vulgaris) on adipogenesis along with the identification of active compounds. Two lactic acid bacteria (LAB) (Companilactobacillus allii WiKim39 and Lactococcus lactis WiKim0124), isolated from kimchi, were used to ferment the VJ and their effectiveness was evaluated in differentiated human mesenchymal stem cells and obese mice. In vitro antibody array analysis was done to understand signaling proteins in adipogenesis. Gene Ontology enrichment analysis showed that differentially expressed proteins are related to biological processes including immunological processes. These were effectively regulated by LAB and fermented VJ. Supplementation of fermented VJ reduced the weight gain, blood biochemical indicators, and liver fat accumulation in mice. Oil Red O staining indicated that the fermentation metabolites of VJ (indole-3-lactic acid, leucic acid, and phenyllactic acid) had an inhibitory effect on lipid accumulation in vitro. Therefore, it can be concluded that LAB-fermented VJ and its metabolites have the potential to counter obesity, and thus can be therapeutically effective.

Correlation between microbial communities and key odourants in fermented capsicum inoculated with Pediococcus pentosaceus and Cyberlindnera rhodanensis

BACKGROUND

Fermented capsicum (i.e. pickled pepper) is one of the most popular fermented vegetables. However, the effect of inoculated microbial fermentation on pickled pepper is not yet fully understood.

RESULTS

Cyberlindnera rhodanensis J52 with a rich ester flavour and Pediococcus pentosaceus AL with a strong inhibitory effect on foodborne pathogenic bacteria were selected to prepare single- and double-strain fermented capsicum under low salt (< 10 g L^-1 sodium chloride) conditions. The inhibition zone of P. pentosaceus AL against Escherichia coli was up to 44 mm in diameter. Biochemical indicator analyses found that co-fermentation of P. pentosaceus AL and C. rhodanensis J52 changed the contents of vitamin C and short-chain fatty acids. Analysis of microbial diversity and volatile metabolome showed that 125 microbial species and 72 volatile compounds were detected, and P. pentosaceus was the dominant bacterium that inhibited the growth of other bacteria, while C. rhodanensis was the fungus that contributed the most to flavour. Correlation analysis between microorganisms and flavour compounds showed 725 correlations, and 124 microbial species may have participated in the formation of 69 compounds. Furthermore, 10 and 29 correlations were detected between P. pentosaceus AL or C. rhodanensis J52 and flavour compounds, respectively. Among them, 3-methyl-1-butanol acetate is speculated to be the main substance affecting the flavour of fermented capsicum by inoculation with C. rhodanensis J52.

CONCLUSION

The inoculation of P. pentosaceus and C. rhodanensis had a significant impact on the microbial community and volatile compounds of fermented capsicum and helped to improve its organoleptic qualities. © 2022 Society of Chemical Industry.

Lactic Acid Bacteria Strains Used as Starters for Kimchi Fermentation Protect the Disruption of Tight Junctions in the Caco-2 Cell Monolayer Model

In this study, we investigated the effect of lactic acid bacteria (LAB) strains used as starters for kimchi fermentation, namely Lactococcus lactis WiKim0124, Companilactobacillus allii WiKim39, Leuconostoc mesenteroides WiKim0121 Leuconostoc mesenteroides WiKim33, and Leuconostoc mesenteroides WiKim32, on the intestinal epithelial tight junctions (TJs). These LAB strains were not cytotoxic to Caco-2 cells at 500 μg/ml concentration. In addition, hydrogen peroxide (H₂O₂) decreased Caco-2 viability, but the LAB strains protected the cells against H₂O₂-induced cytotoxicity. We also found that lipopolysaccharide (LPS) promoted Caco-2 proliferation; however, no specific changes were observed upon treatment with LAB strains and LPS. Our evaluation of the permeability in the Caco-2 monolayer model confirmed its increase by both LPS and H₂O₂. The LAB strains inhibited the increase in permeability by protecting TJs, which we evaluated by measuring TJ proteins such as zonula occludens-1 and occludin, and analyzing them by western blotting and immunofluorescence staining. Our findings show that LAB strains used for kimchi fermentation can suppress the increase in intestinal permeability due to LPS and H₂O₂ by protecting TJs. Therefore, these results suggest the possibility of enhancing the functionality of kimchi through its fermentation using functional LAB strains.

Probiotic fermentation of polyphenols: potential sources of novel functional foods

Fermented functional food products are among the major segments of food processing industry. Fermentation imparts several characteristic effects on foods including the enhancement of organoleptic characteristics, increased shelf-life, and production of novel health beneficial compounds. However, in addition to macronutrients present in the food, secondary metabolites such as polyphenols are also emerging as suitable fermentable substrates. Despite the traditional antimicrobial view of polyphenols, accumulating research shows that polyphenols exert differential effects on bacterial communities by suppressing the growth of pathogenic microbes while concomitantly promoting the proliferation and survival of probiotic bacteria. Conversely, probiotic bacteria not only survive among polyphenols but also induce their fermentation which often leads to improved bioavailability of polyphenols, production of novel metabolic intermediates, increased polyphenolic content, and thus enhanced functional capacity of the fermented food. In addition, selective fermentation of combinations of polyphenol-rich foods or fortification with polyphenols can result in novel functional foods. The present narrative review specifically explores the potential of polyphenols as fermentable substrates in functional foods. We discuss the emerging bidirectional relationship between polyphenols and probiotic bacteria with an aim at promoting the development of novel functional foods based on the amalgamation of probiotic bacteria and polyphenols.

Graphical abstract

Effects of the Probiotic, Lactobacillus delbrueckii subsp. bulgaricus, as a Substitute for Antibiotics on the Gastrointestinal Tract Microbiota and Metabolomics Profile of Female Growing-Finishing Pigs

Lactobacillus delbrueckii subsp. bulgaricus (LDB) is an approved feed additive on the Chinese ‘Approved Feed Additives’ list. However, the possibility of LDB as an antibiotic replacement remains unclear. Particularly, the effect of LDB on microbiota and metabolites in the gastrointestinal tract (GIT) requires further explanation. This study aimed to identify the microbiota and metabolites present in fecal samples and investigate the relationship between the microbiota and metabolites to evaluate the potential of LDB as an antibiotic replacement in pig production. A total of 42 female growing-finishing pigs were randomly allocated into the antibiotic group (basal diet + 75 mg/kg aureomycin) and LDB (basal diet + 3.0 × 109 cfu/kg LDB) groups. Fecal samples were collected on days 0 and 30. Growth performance was recorded and assessed. 16S rRNA sequencing and liquid chromatography-mass spectrometry-based non-targeted metabolomics approaches were used to analyze the differences in microbiota and metabolites. Associations between the differences were calculated using Spearman correlations with the Benjamini−Hochberg adjustment. The LDB diet had no adverse effect on feed efficiency but slightly enhanced the average daily weight gain and average daily feed intake (p > 0.05). The diet supplemented with LDB increased Lactobacillus abundance and decreased that of Prevotellaceae_NK3B31_group spp. Dietary-supplemented LDB enhanced the concentrations of pyridoxine, tyramine, D-(+)-pyroglutamic acid, hypoxanthine, putrescine and 5-hydroxyindole-3-acetic acid and decreased the lithocholic acid concentration. The Lactobacillus networks (Lactobacillus, Peptococcus, Ruminococcaceae_UCG-004, Escherichia-Shigella, acetophenone, tyramine, putrescine, N-methylisopelletierine, N1-acetylspermine) and Prevotellaceae_NK3B31_group networks (Prevotellaceae_NK3B31_group, Treponema_2, monolaurin, penciclovir, N-(5-acetamidopentyl)acetamide, glycerol 3-phosphate) were the most important in the LDB effect on pig GIT health in our study. These findings indicate that LDB may regulate GIT function through the Lactobacillus and Prevotellaceae_NK3B31_group networks. However, our results were restrained to fecal samples of female growing-finishing pigs; gender, growth stages, breeds and other factors should be considered to comprehensively assess LDB as an antibiotic replacement in pig production.

Use of Lactiplantibacillus plantarum ZJ316 as a starter culture for nitrite degradation, foodborne pathogens inhibition and microbial community modulation in pickled mustard fermentation

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L. plantarum ZJ316 (ZJ316) was used as a starter for pickled mustard fermentation.

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ZJ316 inoculation could reduce the nitrite content of pickled mustard.

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The pickled mustard inoculated with ZJ316 exhibited more volatile components.

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ZJ316 could modulate the microbial community during pickled mustard fermentation

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ZJ316 as a starter could inhibit the growth of pathogenic bacteria.

The potential of Lactiplantibacillus plantarum ZJ316 (ZJ316) as a starter culture for quality improvement and microbial community regulation in pickled mustard fermentation was elucidated in this study. Our results show that ZJ316 can deter the occurrence of nitrite peaks and maintain the nitrite content of pickled mustard at a low level (0.34 mg/kg). The headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry results indicate that ZJ316 gives a good flavor to pickled mustard. According to the 16S rDNA results, Firmicutes were the predominant microbiota after inoculation with ZJ316, and the abundances of Citrobacter, Enterobacter, and Proteus decreased simultaneously. In addition, antibacterial activity analysis showed that the supernatant of pickled mustard inoculated with ZJ316 had a significant inhibitory effect on Staphylococcus aureus D48, Escherichia coli DH5α, and Listeria monocytogenes LM1. In conclusion, L. plantarum ZJ316 has potential for use as an ideal starter in the process of vegetable fermentation.