Kimchi probiotic bacteria contribute to reduced amounts of N-nitrosodimethylamine in lactic acid bacteria-fortified kimchi

Biodegradation of chemical contamination by lactic acid bacteria: A biological tool for food safety

Chemical pollutants such as mycotoxins and pesticides exert harmful effects on human health such as inflammation, oxidative stress, and cancer. Several strategies were applied for food decontamination, including physicochemical and biological strategies. The present review comprehensively discussed the recent efforts related to the biodegradation of eight food chemical contaminants, including mycotoxins, acrylamide, biogenic amines, N-nitrosamines, polycyclic aromatic hydrocarbons, bisphenol A, pesticides, and heavy metals by lactic acid bacteria (LAB). Biological detoxification by LAB such as Lactobacillus is a promising approach to remove the risks related to the presence of chemical and environmental pollutants in foodstuffs. It is a safe, efficient, environmentally friendly, and low-cost strategy to remove hazardous compounds. LAB can directly decrease these chemical pollutants by degradation or adsorption. Also, it can indirectly reduce the content of these pollutants by reducing their precursors. Hence, LAB can contribute to reducing chemical pollutants in contaminated foods and enhance food safety.

Effects of Inoculating Autochthonous Starter Cultures on Changes of N-Nitrosamines and Their Precursors in Chinese Traditional Fermented Fish during In Vitro Human Digestion

The objective of this research was to investigate the impact of inoculating autochthonous starter cultures on the alterations in microorganisms, biogenic amines, nitrite, and N-nitrosamines in Chinese traditional fermented fish products (CTFPs) during in vitro human digestion. The results revealed that gastric digestion significantly (p < 0.05) inhibited the proliferation of lactic acid bacteria, yeast, Staphylococcus, and Enterobacteriaceae, whereas various microorganisms proliferated extensively during small intestine digestion. Meanwhile, small intestine digestion could significantly increase (p < 0.05) levels of putrescine, cadaverine, and tyramine. The reduced content observed in inoculated fermentation groups suggests that starter cultures may have the ability to deplete biogenic amines in this digestion stage. Gastric digestion significantly (p < 0.05) inhibited nitrite accumulation in all CTFPs samples. Conversely, the nitrite content increased significantly (p < 0.05) in all groups during subsequent small intestine digestion. However, the rise in the inoculated fermentation groups was smaller than that observed in the spontaneous fermentation group, indicating a potentially positive role of inoculated fermentation in inhibiting nitrite accumulation during this phase. Additionally, gastric digestion significantly (p < 0.05) elevated the levels of N-nitrosodimethylamine (NDMA) and N-nitrosopiperidine in CTFPs. Inoculation with L. plantarum 120, S. cerevisiae 2018, and mixed starter cultures (L. plantarum 120, S. cerevisiae 2018, and S. xylosus 135 [1:1:1]) effectively increased the degree of depletion of NDMA during this digestion process.

Anti-Inflammatory Effects of Barley Sprout Fermented by Lactic Acid Bacteria in RAW264.7 Macrophages and Caco-2 Cells

The anti-inflammatory effects of supernatants produced from sprouted barley inoculated with Lactiplantibacillus plantarum KCTC3104 (Lp), Leuconostoc mesenteroides KCTC3530 (Lm), Latilactobacillus curvatus KCTC3767 (Lc), or a mixture of these lactic acid bacteria were investigated using RAW264.7 macrophages. BLp and BLc, the lyophilized supernatants of fermented sprouted barley inoculated with Lp and Lc, respectively, effectively reduced the nitric oxide (NO) levels hypersecreted by lipopolysaccharide (LPS)-stimulated RAW264.7 and LPS-stimulated Caco-2 cells. BLp and BLc effectively reduced the NO levels in LPS-stimulated RAW264.7 macrophages, and these effects tended to be concentration-dependent. BLc and BLp also exhibited strong DPPH radical scavenging activity and immunostimulatory effects. BLp and BLc significantly suppressed the levels of NO and pro-inflammatory cytokines such as TNF-α, IL-1β, and IL-6 in LPS-stimulated RAW264.7 macrophages and LPS-stimulated Caco-2 cells, indicating their anti-inflammatory effects. These effects were greater than those of unfermented barley sprout (Bs). The functional components of Bs, BLp, and BLc were analyzed by HPLC, and it was found that lutonarin and saponarin were significantly increased in the fermented sprouted barley sample inoculated with Lp and Lc (BLp and BLc).

Lactiplantibacillus sp. G6 isolated from goose intestine as starter culture for degrading nitrite and improving quality in Chinese pickle fermentation

Animal intestines is considered as a source of lactic acid bacteria (LAB) that have potential to decrease the nitrite level during fermentation of food such as pickles. It was hypothesized that optimized level of LAB has a high capacity to degrade nitrite during Chinese pickle fermentation and benefit a higher acceptability of the Chinese pickle product. This study aims to investigate the performance of a goose intestine-isolated LAB strain G6 under the species Lactiplantibacillus plantarum as a starter culture of Chinese pickles. The results showed that Lactiplantibacillus sp. G6 had a nitrite degradation rate close to 100% under the MRS broth condition of 25 °C, 2% inoculum volume and pH at 5. As a starter culture for Chinese pickle, this strain was able to achieve a higher LABs amount, lower nitrite residue after fermentation, compared with the group without the starter, which implicates its feasibility of applying on fermented food for reducing nitrite level.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01433-8.

Discrimination between Korean and Chinese Kimchi using inductively coupled plasma-optical emission spectroscopy and mass spectrometry: A multivariate analysis of Kimchi

Kimchi has been designated as one of the world's five healthiest foods, and it is a traditional Korean fermented food. The purpose of this study was to investigate whether the origin of Kimchi can be discriminated against by using inorganic elements to develop a more accurate method. The OPLS-DA showed that the R² and Q² values were 0.908 and 0.81, a high-quality model. We selected 24 elements (¹³³Cs, ²³⁸U, ⁸⁸Sr, K, ¹⁵⁷Gd, Na, Mg, ¹³⁹La, P, ¹⁴¹Pr, ⁷²Ge, ¹⁴⁶Nd, ¹⁴⁷Sm, ¹⁵³Eu, ⁵⁵Mn, ¹⁶⁵Ho, ¹⁶³Dy, ¹⁶⁶Er, Fe, ¹⁷²Yb, ¹⁶⁹Tm, ¹⁸⁵Re, ¹⁷⁵Lu, and ¹¹⁸Sn) with VIP 1 or higher in the OPLS-DA model. In ROC, the selected elements had an accuracy of 100%. The heatmap confirmed the contents of rare earth elements (REEs) in Korean and Chinese Kimchi, the accuracy of distinguishing classification in CDA is 100%. Such results will help to distinguish the origin of agricultural products through inorganic analysis.

A Review on the Role of Lactic Acid Bacteria in the Formation and Reduction of Volatile Nitrosamines in Fermented Sausages

Nitrosamines are N-nitroso compounds with carcinogenic, mutagenic and teratogenic properties. These compounds could be found at certain levels in fermented sausages. Fermented sausages are considered to be a suitable environment for nitrosamine formation due to acid formation and reactions such as proteolysis and lipolysis during ripening. However, lactic acid bacteria (spontaneous or starter culture), which constitute the dominant microbiota, contribute significantly to nitrosamine reduction by reducing the amount of residual nitrite through nitrite degradation, and pH decrease has an important effect on the residual nitrite amount as well. These bacteria also play an indirect role in nitrosamine reduction by suppressing the growth of bacteria that form precursors such as biogenic amines. In recent years, research interest has focused on the degradation or metabolization of nitrosamines by lactic acid bacteria. The mechanism by which these effects are seen has not been fully understood yet. In this study, the roles of lactic acid bacteria on nitrosamine formation and their indirect or direct effects on reduction of volatile nitrosamines are discussed.

Bacterial community diversity and its potential contributions to the flavor components of traditional smoked horsemeat sausage in Xinjiang, China

Smoked horsemeat sausage is a famous fermented traditional food in Xinjiang, China. However, the microbial diversity and its potential contributions to the flavor components of smoked horsemeat sausage are unclear. In this study, the microbial community and flavor components of smoked horsemeat sausage from six regions of Xinjiang were measured by using amplicon sequencing and headspace solid-phase microextraction combined with gas chromatography–mass spectrometry (HS-SPME-GC–MS) technology, respectively. Relations among microbial communities, flavor components and environmental factors were subsequently predicted based on redundancy analysis (RDA) and Monte Carlo permutation tests. Although smoked horsemeat sausage samples from different regions possessed distinct microbial communities, lactic acid bacteria (LAB) were identified as the dominant consortium in smoked horsemeat sausage. Lactobacillus, Vagococcus, Lactococcus, and Carnobacterium were detected at high abundance in different sausages. The moisture content, nitrite content, and pH of the sausage might be important factors influencing the dominant bacterial community, according to the RDA. Among the dominant consortia, the eight core bacterial genera showed considerable correlations with the formation of sixteen volatile compounds in smoked horsemeat sausage based on multivariate statistical analysis. For example, the levels of Leuconostoc and Lactobacillus were positively correlated with those of 1-hexadecanol, hexyl acetate, 2-methyl-phenol, 1-pentanol, d-limonene, and 2-heptanone, and the levels of Leuconostoc, Lactobacillus, and Weissella were negatively correlated with those of 1-octanol, acetic acid, octanal, heptanal, and 1-hexanol. This study will provide a theoretical basis for understanding the microbial metabolic modes of Xinjiang smoked horsemeat sausages.

Bread Sourdough Lactic Acid Bacteria—Technological, Antimicrobial, Toxin-Degrading, Immune System-, and Faecal Microbiota-Modelling Biological Agents for the Preparation of Food, Nutraceuticals and Feed

This review intends to highlight the fact that bread sourdough is a very promising source of technological, antimicrobial, toxin-degrading, immune system-, and faecal microbiota-modelling biological agents for the preparation of food, nutraceuticals, and feed, which has great potential at industrial biotechnology scale. There are many applications of sourdough lactic acid bacteria (LAB), which are the main microorganisms in spontaneous sourdough. In addition to their application as pure technological strains in the food and feed industries, taking into consideration the specific properties of these microorganisms (antimicrobial, antifungal, immuno-, and microbiota-modulating, etc.), they are used as valuable ingredients in higher-value food as well as nutraceutical formulations. Additionally, a very promising application of LAB is their use in combination with plant- and/or animal-based ingredients to increase the functional properties of the whole combination due to different mechanisms of action, as well as desirable symbiotic activity. In addition to traditional foods prepared using sourdough microorganisms (bread, biscuits, meat products, dairy, beverages, etc.), they could find application in the preparation of added-value ingredients for the food, nutraceutical, and feed industries. Finally, this mini-review gives a brief introduction to the possible applications of sourdough LAB in the food, feed, and nutraceutical industries.

Reduction in Biogenic Amine Content in Baechu (Napa Cabbage) Kimchi by Biogenic Amine-Degrading Lactic Acid Bacteria

This study was performed to mine biogenic amine (BA)-degrading lactic acid bacteria (LAB) from kimchi and to investigate the effects of the LAB strains on BA reduction in Baechu kimchi fermentation. Among 1448 LAB strains isolated from various kimchi varieties, five strains capable of considerably degrading histamine and/or tyramine were selected through in vitro tests and identified as Levilactobacillus brevis PK08, Lactiplantibacillus pentosus PK05, Leuconostoc mesenteroides YM20, L. plantarum KD15, and Latilactobacillus sakei YM21. The selected strains were used to ferment five groups of Baechu kimchi, respectively. The LB group inoculated with L. brevis PK08 showed the highest reduction in tyramine content, 66.65% and 81.89%, compared to the control group and the positive control group, respectively. Other BA content was also considerably reduced, by 3.76–89.26% (five BAs) and 7.87–23.27% (four BAs), compared to the two control groups, respectively. The other inoculated groups showed similar or less BA reduction than the LB group. Meanwhile, a multicopper oxidase gene was detected in L. brevis PK08 when pursuing the BA degradation mechanism. Consequently, L. brevis PK08 could be applied to kimchi fermentation as a starter or protective culture to improve the BA-related safety of kimchi where prolific tyramine-producing LAB strains are present.

Evaluation of the Relationship among Biogenic Amines, Nitrite and Microbial Diversity in Fermented Mustard

Biogenic amines (BAs) and nitrites are both considered harmful compounds for customer health, and are closely correlated with the microorganisms in fermented mustard (FM). In this study, BAs and nitrite contents in fifteen FM samples from different brands were analyzed. The concentrations of cadaverine in one sample and of histamine in one sample were above the toxic level. Moreover, five FM samples contained a high level of nitrite, exceeding the maximum residue limit (20 mg/kg) suggested by the National Food Safety Standard. Then, this study investigated bacterial and fungal communities by high-throughput sequencing analysis. Firmicutes and Basidiomycota were identified as the major bacteria and fungi phylum, respectively. The correlations among microorganisms, BAs and nitrite were analyzed. Typtamine showed a positive correlation with Lactobacillus and Pseudomonas. Cadaverine and nitrite is positively correlated with Leuconostoc. Furthermore, thirteen strains were selected from the samples to evaluate the accumulation and degradation properties of their BAs and nitrite. The results indicated that the Lactobacillus isolates, including L. plantarum GZ-2 and L. brevis SC-2, can significantly reduce BAs and nitrite in FM model experiments. This study not only assessed the contents of BAs and nitrite in FM samples, but also provided potential starter cultures for BAs and nitrite control in the FM products industry.

The function and mechanism of lactic acid bacteria in the reduction of toxic substances in food: a review

N-nitrosamines, heterocyclic amines, polycyclic aromatic hydrocarbons, biogenic amines, and acrylamide are widely distributed and some of the most toxic substances detected in foods. Hence, reduction of these substances has attracted worldwide attention. Lactic acid bacteria (LAB) inoculation has been found to be an effective way to reduce these toxic substances. In this paper, the reduction of toxic substances by LAB and its underlying mechanisms have been described through the review of recent studies. LAB aids this reduction via different mechanisms. First, it can directly decrease these harmful substances through adsorption or degradation. Peptidoglycans on the cell wall of LAB can bind to heterocyclic amines, acrylamide, and polycyclic aromatic hydrocarbons. Second, LAB can indirectly decrease the content of toxic substances by reducing their precursors. Third, antioxidant properties of LAB also contribute to the reduction in toxic substances. Finally, LAB can suppress the growth of amino acid decarboxylase-positive bacteria, thus reducing the accumulation of biogenic amines and N-nitrosamines. Therefore, LAB can contribute to the decrease in toxic substances in food and improve food safety. Further research on increasing the reduction efficiency of LAB and deciphering the mechanisms at a molecular level needs to be carried out to obtain the complete picture.

Metagenomic insights into Chinese northeast suancai: Predominance and diversity of genes associated with nitrogen metabolism in traditional household suancai fermentation

Chinese northeast suancai represents a typical and valuable food product that has been handed down by traditional household procedures over centuries. Nitrite is formed and accumulated during the suancai fermentation process and commonly causes food safety problems. The biogeochemical cycle of nitrite may provide a reference and guidance for the enzymatic degradation of nitrite in fermented food. The potential nitrogen metabolic pathways in the microbially driven suancai fermentation were reasonably inferred through monitoring nitrogen conversions and detecting the genes of different functional enzymes. Complex microbial metabolism is responsible for the unique nitrogen conversions during suancai fermentation. The metagenomic results showed that Pseudomonas with nitrate reductase genes (narG, narH, narI) and nitrite reductase genes (nirB, nirD) contributed the most to both nitrite reduction and nitrate reduction. The majority of the sequences of nitrate reductase and nitrite reductase were derived from the families of Pseudomonadaceae, Erwiniaceae and Yersiniaceae. According to the physicochemical analysis, the nitrite concentration of the fermentation broth reached the peak value (0.48 mM) and gradually decreased to the minimum (0.02 mM). The downward trend of the pH and nitrite concentration were closely associated with the nitrite enzymatic degradation period before the acid degradation period. Our results indicated that nitrite removal in suancai fermentation involved the reduction of nitrite to ammonia and denitrification, which were mainly contributed by the reduction of nitrite to ammonia mediated by the nirB/nirD enzyme (Indentified ECs: 1.7.1.15). This research offers new insights into the metagenome-based bioinformatic roles of the previously unstudied microorganisms in spontaneous suancai fermentation for the enzymatic degradation of nitrite. It provides helpful basis for the detection and even elimination of nitrite in suancai and for improving the safety level of suancai.

Occurrence and Reduction of Biogenic Amines in Kimchi and Korean Fermented Seafood Products

Biogenic amines produced during fermentation may be harmful when ingested in high concentrations. As current regulations remain insufficient to ensure the safety of fermented vegetable products, the current study determined the risks associated with the consumption of kimchi by evaluating the biogenic amine concentrations reported by various studies. Upon evaluation, some kimchi products were found to contain histamine and tyramine at potentially hazardous concentrations exceeding the recommended limit of 100 mg/kg for both histamine and tyramine. The biogenic amines may have originated primarily from metabolic activity by microorganisms during fermentation, as well as from Jeotgal (Korean fermented seafood) and Aekjeot (Korean fermented fish sauce) products commonly used as ingredients for kimchi production. Many studies have suggested that Jeotgal and Aekjeot may contribute to the histamine and tyramine content in kimchi. Microorganisms isolated from kimchi and Jeotgal have been reported to produce both histamine and tyramine. Despite the potential toxicological risks, limited research has been conducted on reducing the biogenic amine content of kimchi and Jeotgal products. The regulation and active monitoring of biogenic amine content during kimchi production appear to be necessary to ensure the safety of the fermented vegetable products.

Formation of Biogenic Amines in Pa (Green Onion) Kimchi and Gat (Mustard Leaf) Kimchi

In this study, biogenic amine content in Pa (green onion) kimchi and Gat (mustard leaf) kimchi, Korean specialty kimchi types, was determined by high-performance liquid chromatography (HPLC). Many kimchi samples contained low levels of biogenic amines, but some samples had histamine and tyramine content over the safe levels. Based on the comparative analysis between the ingredient information on food labels and biogenic amine content of kimchi samples, Myeolchi-aekjeot appeared to be an important source of biogenic amines in both kimchi. Besides, through the 16s rRNA sequence analysis, Lactobacillus brevis appeared to be responsible for the formation of biogenic amines (tyramine, β-phenylethylamine, putrescine, and cadaverine) in both kimchi, in a strain-dependent manner. During fermentation, a higher accumulation of tyramine, β-phenylethylamine, and putrescine was observed in both or one (for putrescine) of kimchi types when L. brevis strains served as inocula. The addition of Myeolchi-aekjeot affected the initial concentrations of most biogenic amines (except for spermidine in Gat kimchi) in both kimchi. Therefore, this study suggests that using appropriately salted and fermented seafood products for kimchi preparation and using biogenic amine-negative and/or biogenic amine-degrading starter cultures would be effective in reducing biogenic amine content in Pa kimchi and Gat kimchi.

The Occurrence of Biogenic Amines and Determination of Biogenic Amine-Producing Lactic Acid Bacteria in Kkakdugi and Chonggak Kimchi

In this study, biogenic amine content in two types of fermented radish kimchi (Kkakdugi and Chonggak kimchi) was determined by high performance liquid chromatography (HPLC). While most samples had low levels of biogenic amines, some samples contained histamine content over the toxicity limit. Additionally, significant amounts of total biogenic amines were detected in certain samples due to high levels of putrefactive amines. As one of the significant factors influencing biogenic amine content in both radish kimchi, Myeolchi-aekjoet appeared to be important source of histamine. Besides, tyramine-producing strains of lactic acid bacteria existed in both radish kimchi. Through 16s rRNA sequencing analysis, the dominant species of tyramine-producing strains was identified as Lactobacillus brevis, which suggests that the species is responsible for tyramine formation in both radish kimchi. During fermentation, a higher tyramine accumulation was observed in both radish kimchi when L. brevis strains were used as inocula. The addition of Myeolchi-aekjeot affected the initial concentrations of histamine and cadaverine in both radish kimchi. Therefore, this study suggests that reducing the ratio of Myeolchi-aekjeot to other ingredients (and/or using Myeolchi-aekjeot with low biogenic amine content) and using starter cultures with ability to degrade and/or inability to produce biogenic amines would be effective in reducing biogenic amine content in Kkakdugi and Chonggak kimchi.

Isolation of nitrite-degrading strains from Douchi and their application to degrade high nitrite in Jiangshui

BACKGROUND

Excessive nitrite in food is potentially harmful to human health because of carcinogenic effects caused by its nitroso-derivatives. Douchi, which widely distributed throughout the country, is a traditional solid fermented soybean food with low nitrite content.

RESULTS

In this study, bacteria which can degrade nitrite were isolated from Douchi and identified from their 16S rDNA sequences. Acinetobacter guillouiae, Acinetobacter bereziniae, Bacillus subtilis, Bacillus tequilensis, Bacillus amyloliquefaciens, Bacillus licheniformis, Bacillus aryabhattai and Bacillus methylotrophicus were selected. It was shown that all strains were able to degrade nitrite to some extent, including Bacillus subtilis NDS1, which was able to degrade 99.41% of nitrite. The enzyme activities of these strains were determined at 24 and 48 h and were shown to correspond with their nitrite degradation rates. The strains were used to inoculate Jiangshui, a kind of traditional fermented vegetable from northwest China that often has a high nitrite content. Of the strains tested, Bacillus subtilis NDS1, Bacillus tequilensis NDS3, Acinetobacter bereziniae NDS4, Bacillus subtilis NDS6, and Bacillus subtilis NDS12 were able to degrade nitrite in Jiangshui more rapidly, with Acinetobacter bereziniae NDS4 degrading almost all nitrite in 48 h compared with 180 h of control.

CONCLUSION

These results indicate that the selected strains have potential to be used as nitrite-degrading agents in food. © 2018 Society of Chemical Industry.

Changes in quality properties of kimchi based on the nitrogen content of fermented anchovy sauce, Myeolchi Aekjeot, during fermentation

This study was conducted to examine the effects of the total nitrogen (TN) concentration in anchovy sauce added to kimchi on chemical properties during kimchi fermentation for 56 days. Kimchi was assigned to one of the following five treatments: CTL (No anchovy sauce addition), T-1 (TN 1.16% anchovy sauce), T-2 (TN 1.41% anchovy sauce), T-3 (TN 1.59% anchovy sauce), T-4 (TN 1.79% anchovy sauce). The quality characteristics of kimchi were determined by measuring the pH, acidity, reducing sugar, volatile basic nitrogen (VBN), amino nitrogen (AN), and microbial composition. During fermentation, the acidity of all treatment groups increased, whereas the reducing sugar content decreased gradually during fermentation. There were no significant differences in pH and acidity or reducing sugar content. The VBN and AN contents increased during fermentation from 15.65 to 31.21%. Overall, these results demonstrate that the TN concentration of anchovy mainly affects the VBN and AN levels in kimchi.

Effects of inoculating autochthonous starter cultures on N-nitrosodimethylamine and its precursors formation during fermentation of Chinese traditional fermented fish

This study investigated the effects of Lactobacillus plantarum 120, Saccharomyces cerevisiae 2018 and Staphylococcus xylosus 135 inoculation on N-nitrosodimethylamine (NDMA) and its precursors formation, and on microbiological characteristics of Chinese traditional fermented fish products (CTFPs). The results indicated that three strains could directly degrade NDMA in culture broth, and the highest degradation rate was observed in L. plantarum 120. The lactic acid bacteria counts in samples inoculated with L. plantarum 120 and mixed starter cultures were significantly (P < 0.05) higher than the others during the initial and middle fermentation stages (≤3 weeks). The final contents of total volatile base nitrogen, trimethylamine, dimethylamine, nitrite and NDMA in inoculated samples were significantly (P < 0.05) lower than those in spontaneous fermentation samples. According to these results, the inoculation with autochthonous starter cultures was a promising method to inhibit the NDMA and its precursors accumulation in CTFPs during fermentation process.