Novel Highly Pathogenic Avian Influenza A(H5N1) Clade 2.3.4.4b Virus in Wild Birds, South Korea.

We isolated 5 highly pathogenic avian influenza A(H5N1) clade 2.3.4.4.b viruses from wild waterfowl feces in South Korea during November 2022. Whole-genome sequencing and phylogenetic analysis revealed novel genotypes produced by reassortment with Eurasian low pathogenicity avian influenza viruses. Enhanced surveillance will be required to improve prevention and control strategies.

Effect of headspace gas composition in kimchi packaging on the quality characteristics of kimchi.

This study evaluated the effects of gas composition in kimchi packaging on kimchi quality. Completely sealed packaging without gas inflow/outflow during fermentation (S1), packaging allowing gas outflow (S2), and packaging allowing gas inflow and outflow (S3) were used. Microbial composition analysis, volatile compound content analysis, and sensory evaluation were performed to determine the differences in kimchi quality among samples. Metabolites were examined using principal component analysis. Gas composition analysis showed that the ratio of CO2 increased during the storage period in S1, the ratio of nitrogen and CO2 contents was constant in S2, and the ratio of oxygen was significantly higher in S3. No significant differences in the lactic acid bacteria number were observed. However, coliforms were only detected in S3, and yeast and mold proliferated faster in S3 than in S2 or S1. The main compounds detected in S1 and S2 were alcohols, whereas those in S3 were esters such as ß-phenethyl acetate produced by yeast. Sensory evaluation showed that S3 had the lowest odor, taste, and overall scores, whereas S2 had the highest. In conclusion, the gas composition inside the kimchi package greatly affects the quality of kimchi. Our findings provide important data that can be useful in the manufacture of commercial kimchi. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-023-05795-z.

Effect of the addition of maltodextrin on metabolites and microbial population during kimchi fermentation.

Gelatinized starch sauce, one of the sub-ingredients have been widely used in kimchi for their roles in increasing viscosity of kimchi seasoning, and fermentation. Gelatinized glutinous rice (GGR), which is one of the most used starch sources in kimchi preparation. However, GGR is accelerated to the fermentation process but lead to a reduction in the shelf life of the kimchi. Therefore, in this study, we demonstrate the effectiveness of using maltodextrin (MD) as a novel starch source instead of GGR to slow down the rate of kimchi fermentation. The properties of the kimchi with MD and GGR fermentation (free sugar content, organic acid content, pH, and acidity) as well as their microbial growth rates after 12 days of fermentation were compared. After fermentation of 12 days, the free sugar of GGR-kimchi (GGRK) increased more rapidly than those of MD-kimchi (MDK), while higher sugar alcohol (mannitol) and organic acid contents were observed for GGRK than for MDK. Furthermore, initial aerobic and lactic acid bacteria counts were higher for GGRK than for MDK. These results indicate that fermentation proceeds at a slower rate in MDK than in GGRK, and they will provide a basis for further research into storage of kimchi. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-023-05742-y.

Elevated Expression of Cathepsin K in Periodontal Ligament Fibroblast by Inflammatory Cytokines Accelerates Osteoclastogenesis via Paracrine Mechanism in Periodontal Disease.

Cathepsin K (CTSK) is a cysteine protease that is mainly produced from mature osteoclasts and contributes to the destruction of connective tissues and mineralized matrix as a consequence of periodontal disease (PD). However, few studies have reported its regulatory role in osteoclastogenesis-supporting cells in inflammatory conditions. Here, we investigated the role of CTSK in osteoclastogenesis-supporting cells, focusing on the modulation of paracrine function. Microarray data showed that CTSK was upregulated in PD patients compared with healthy individuals, which was further supported by immunohistochemistry and qPCR analyses performed with human gingival tissues. The expression of CTSK in the osteoclastogenesis-supporting cells, including dental pulp stem cells, gingival fibroblasts, and periodontal ligament fibroblasts (PDLFs) was significantly elevated by treatment with inflammatory cytokines such as TNFα and IL-1ß. Moreover, TNFα stimulation potentiated the PDLF-mediated osteoclastogenesis of bone marrow-derived macrophages. Interestingly, small interfering RNA-mediated silencing of CTSK in PDLF noticeably attenuated the TNFα-triggered upregulation of receptor activator of nuclear factor kappa-B ligand (RANKL), macrophage colony-stimulating factor, and RANKL/osteoprotegerin ratio, thereby abrogating the enhanced osteoclastogenesis-supporting activity of PDLF. Collectively, these results suggest a novel role of CTSK in the paracrine function of osteoclastogenesis-supporting cells in periodontal disease.

Connective tissue growth factor (CTGF) regulates the fusion of osteoclast precursors by inhibiting Bcl6 in periodontitis.

Connective tissue growth factor (CTGF), an extracellular matrix protein with various biological functions, is known to be upregulated in multiple chronic diseases such as liver fibrosis and congestive heart failure, but the mechanism it undertakes to cause alveolar bone loss in periodontitis remains elusive. The present study therefore investigates the pathways involving CTGF in chronic periodontitis. RNA sequencing revealed a notable increase in the expression of CTGF in chronic periodontitis tissues. Also, TRAP staining, TRAP activity and bone resorption assays showed that osteoclast formation and function is significantly facilitated in CTGF-treated bone marrow-derived macrophages (BMMs). Interestingly, western blotting and immunofluorescence staining results displayed that CTGF had little effect on the osteoclastogenic differentiation mediated by the positive regulators of osteoclastogenesis such as nuclear factor of activated T cells 1 (NFATc1). However, following results showed that both the mRNA and protein expressions of B cell lymphoma 6 (Bcl6), a transcriptional repressor of "osteoclastic" genes, were significantly downregulated by CTGF treatment. Moreover, CTGF upregulated the expressions of v-ATPase V0 subunit d2 (ATP6v0d2) and Dendritic cell-specific transmembrane protein (DC-STAMP) which are osteoclastic genes specifically required for osteoclast cell-cell fusion in pre-osteoclasts. Findings from this study suggest that CTGF promotes the fusion of pre-osteoclasts by downregulating Bcl6 and subsequently increasing the expression of DC-STAMP in periodontitis. Understanding this novel mechanism that leads to increased osteoclastogenesis in periodontitis may be employed for the development of new therapeutic targets for preventing periodontitis-associated alveolar bone resorption.

Letrozole Suppresses the Fusion of Osteoclast Precursors through Inhibition of p38-Mediated DC-STAMP Pathway.

Letrozole is a reversible nonsteroidal aromatase inhibitor that is widely used in postmenopausal breast cancer patients. It is well established that letrozole decreases bone density owing to estrogen depletion; however, few studies have reported its direct effect on bone cells in vitro. Therefore, we investigated the effect of letrozole on bone metabolism, focusing on osteoclastogenesis. Letrozole did not affect the viability, proliferation, or migration of bone marrow-derived macrophages (BMMs); however, it reduced the multinucleation of immature osteoclasts and subsequent bone resorption in vitro. Overall, letrozole inhibited the expression of dendritic cell-specific transmembrane protein (DC-STAMP), tartrate-resistant acid phosphatase, calcitonin receptor, and cathepsin K. Among them, the reduced expression of DC-STAMP was the most prominent. However, this downregulation of DC-STAMP expression following letrozole treatment was not related to the inhibition of major osteoclastogenesis pathways, such as the nuclear factor-κB (NF-κB), c-Fos, and nuclear factor of activated T cell c1 (NFATc1) pathways, but was attributed to the inhibition of p38, which is known to reside upstream of DC-STAMP expression. Notably, the anti-osteoclastogenic effect of letrozole was abolished following treatment with the p38 activator anisomycin. Contrary to our expectations, these results strongly suggest a previously unknown anti-osteoclastogenic activity of letrozole, mediated by the downregulation of the p38/DC-STAMP pathway.

Evaluation of onion juices quality following heat-treatment and their application as a sugar substitute in Kimchi.

This study was conducted to evaluate the quality of onion juices that had been heat-treated for different times as well as their use as a table sugar substitute in Kimchi. The onions were steamed at 100 ∘C for 30 min and boiled at 90 ∘C for 30, 60, and 120 min. The highest cycloalliin (0.76 mM), free-sugar (sucrose 1.66 g/L, glucose 8.62 g/L, and fructose 7.64 g/L), and malic acid (0.82 g/L) contents were observed in onion boiled at 90 ∘C for 120 min. The possibility of using heat-treated onion juices as an alternative to table sugar in Kimchi was evaluated by comparing the lactic acid bacteria count, pH, acidity, organic acid, and free-sugar in these juices with those in Kimchi prepared using table sugar (control). The total viable bacteria and lactic acid bacteria showed similar growth patterns as in the control. The average pH reduction and increase in titratable acidity (%) in all treated Kimchi samples during fermentation for 4 weeks were 1.18 ± 0.05 and 0.81 ± 0.06, respectively. Kimchi with onion juice heat-treated for 120 min (K120) had the most similar lactic acid and acetic acid contents to that in the control after fermentation for 4 weeks. The highest mannitol level after fermentation for 4 weeks was detected in K120, which showed better sensory qualities compared to the control.

Zoledronate Enhances Osteocyte-Mediated Osteoclast Differentiation by IL-6/RANKL Axis.

Bisphosphonates are one of the most widely used synthetic pyrophosphate analogues for the treatment of bone resorbing diseases such as osteoporosis, multiple myeloma, and bone metastases. Although the therapeutic usefulness of bisphosphonates mainly depends on their anti-osteoclastogenic effect, a severe side-effect of bisphosphonates called bisphosphonate-related osteonecrosis of the jaw (BRONJ) could not be explained by the anti-osteoclastogenic effect of bisphosphonates. In the present study, we have evaluated the changes in osteoclastogenesis- or osteoblastogenesis-supporting activities of osteocytes induced by bisphosphonates. Zoledronate, a nitrogen-containing bisphosphonate, markedly increased both the receptor activator of nuclear factor kB ligand (RANKL) as well as sclerostin in osteocyte-like MLO-Y4 cells, which were functionally revalidated by osteoclast/osteoblast generating activities of the conditioned medium obtained from zoledronate-treated MLO-Y4 cells. Of note, the zoledronate treatment-induced upregulation of the RANKL expression was mediated by autocrine interleukin-6 (IL-6) and subsequent activation of the signal transducer and activator of transcription 3 (STAT3) pathway. These results were evidenced by the blunted RANKL expression in the presence of a Janus activated kinase (JAK2)/STAT3 inhibitor, AG490. Also, the osteoclastogenesis-supporting activity was significantly decreased in zoledronate-treated MLO-Y4 cells in the presence of IL-6 neutralizing IgG compared to that of the control IgG. Thus, our results show previously unanticipated effects of anti-bone resorptive bisphosphonate and suggest a potential clinical importance of osteocytes in BRONJ development.

Kimchi extracts as inhibitors of colour deterioration and lipid oxidation in raw ground pork meat during refrigerated storage.

BACKGROUND: Kimchi is a Korean, traditional fermented food made from Korean cabbage, radish, fermented jeotgal, ginger, garlic, and red pepper powder. It is a good source of natural antioxidants such as phenolic compounds, flavonoids, vitamins, and carotenoids. In this study, the antioxidant effects of various kimchi extracts on raw ground pork during refrigerated storage were investigated. Raw ground pork samples were treated with ascorbic acid, butylated hydroxyl toluene, baechu kimchi extract (BKE), gat kimchi extract (GKE), puchu kimchi extract (PKE), and white kimchi extract (WKE) and compared with raw ground pork without antioxidant treatment (NC). RESULTS: Increased metmyoglobin (MetMb), thiobarbituric acid reacting substance (TBARS), and total bacterial counts (TBC) were observed in all meat samples after storage, whereas pH, lightness, and redness values tended to decrease with increased storage time. All treated samples had lower TBARS and MetMb values and TBC compared to the control samples. Various kimchi ethanol extracts protected raw ground pork from lipid oxidation. The most potent antioxidant was GKE, whereas WKE was the weakest. CONCLUSIONS: This study suggests that the tested extracts, especially kimchi, have potential as natural preservatives to reduce colour degradation, lipid oxidation, and bacterial count in raw ground pork meat. © 2018 Society of Chemical Industry.

Effects of Dietary Supplementation of Barodon, an Anionic Alkali Mineral Complex, on Growth Performance, Feed Utilization, Innate Immunity, Goblet Cell and Digestibility in Olive Flounder (Paralichthys olivaceus).

A 15-wk feeding trial was conducted to examine the supplemental effects of Barodon on growth performance, gastrointestinal histology, feed digestibility and innate immunity in olive founder. A basal commercial diet was used as a control and two other diets were prepared by spraying 0.1% or 0.2% of Barodon. Triplicate groups of fish (BW, 145 g) were fed one of the test diets to apparent satiation twice daily. At the end of the feeding trial, fish growth performance was not significantly affected by dietary treatments; however, feed utilization was significantly improved (linear and quadratic, p<0.05) by Barodon supplementation. Significantly higher (p<0.05) survival rates were obtained in fish fed Barodon containing diets. Hepatosomatic index increased significantly in Barodon treated groups. Also, the use of Barodon resulted in significant increase (linear and quadratic, p<0.05) of intestine length and number of goblet cells. Significantly higher (Quadratic, p<0.05) apparent digestibility coefficient of DM was obtained by supplementation of Barodon. Lysozyme and myeloperoxidase activities increased quadratically and linearly, respectively, in Barodon treated fish. Also, significantly higher (linear and quadratic, p<0.05) superoxide dismutase activity was found in Barodon fed fish. The findings in this study show that inclusion of Barodon in diets for olive flounder improves feed utilization and digestibility, and positively affects digestive tract histology and innate immunity.

Insight into the performance and microbial community of anaerobic digestion treating cow manure with a novel iron-functionalized activated biochar.

The main objective of this research was to evaluate the impacts of FeCl3-activated biochar (FA-BC) on anaerobic digestion (AD) treating cow manure. The study focused on improving AD performance and understanding microbial community structure with the addition of FA-BC, while comparing FA-BC with other conductive additives, such as pristine biochar (P-BC), NaOH-activated biochar (NA-BC), and magnetite. Key findings indicated that FA- BC significantly enhanced the AD performance, supported by an increase in CH4 yield of 11-16% and a reduction in the lag phase by 51%. The high surface area and electrical conductivity of FA-BC synergistically facilitated direct interspecies electron transfer (DIET), leading to these improvements. On contrast, P-BC and NA-BC were not efficient in enhancing the AD performance due to relatively low electrical conductivity. P-BC also improved the CH4 yield, but less effectively than FA-BC. The effects of NA-BC varied with its dosage, showing inhibition at higher dosages due to excessive surface area. Magnetite, despite its high conductivity, made the limited enhancement in CH4 yield owing to its low surface area. Additionally, the statistical analyses revealed that each additive differently affected specific bacterial and archaeal groups depending on their physical and chemical properties. Thus, these findings suggest that FA-BC would be a highly promising additive for enhan cing AD systems, with potential applications in waste management and renewable energy production.

Sexual Harassment Experience, Coping, and Awareness Among Nurses Working in Small- and Medium-Sized Hospitals in South Korea.

Introduction: Although over 60% of Korean acute care hospitals are small- or medium-sized, their ability to address sexual harassment may differ from larger hospitals due to differences in resources, policies, and organizational culture. Objective: This study aims to identify sexual harassment experience, coping, and awareness among nurses working in small- and medium-sized hospitals. Methods: This is a descriptive cross-sectional study that collected data from 462 nurses working in nine small- and medium-sized acute care hospitals in two cities in Korea. The study utilized self-report questionnaires, including the coping with sexual harassment questionnaire, perception of sexual, and experience of sexual harassment. Data were analyzed using descriptive statistics, t-tests, and one-way analysis of variance. Results: Most nurses receive sexual harassment prevention education in the workplace every year, but only 77% of them are accurately aware of sexual harassment behavior. Among the types of sexual harassment experienced by the participants, verbal sexual harassment was the most common. Only 192 out of 462 nurses responded to the timing of their sexual harassment experience. Of those, more than 50% reported experiencing sexual harassment within the first year of employment and over 80% within 3 years. The most common perpetrators of sexual harassment were patients, followed by doctors. The more times the nurses received sexual harassment prevention education, the better they were at coping with sexual harassment. Conclusion: To prevent sexual harassment in the workplace, training content should be tailored because attitudes and perceptions vary based on the perpetrator's characteristics. This ensures relevance, addresses risks, and clarifies legal responsibilities. To create a healthy and safe working environment for nurses, institutions and managers should implement methods to raise awareness of sexual harassment. This may include providing anonymous hotlines, online reporting systems, regular audits, and establishing anonymous peer counseling platforms.

Comparative study of exoelectrogenic utilization preferences and hydrogen conversion among major fermentation products in microbial electrolysis cells.

This study comparatively investigated the exoelectrogenic utilization and hydrogen conversion of major dark fermentation products (acetate, propionate, butyrate, lactate, and ethanol) from organic wastes in dual-chamber microbial electrolysis cells (MECs) alongside their mixture as a simulated dark fermentation effluent (DFE). Acetate-fed MECs showed the highest hydrogen yield (1,465 mL/g chemical oxygen demand), near the theoretical maximum yield, with the highest coulombic efficiency (105%) and maximum current density (7.9 A/m2), followed by lactate-fed, propionate-fed, butyrate-fed, mixture-fed, and ethanol-fed MECs. Meanwhile, the highest hydrogen production rate (514 mL/L anolyte∙d) was observed in ethanol-fed MECs despite their lower coulombic efficiency. Butyrate was the least favored substrate, followed by propionate, leading to significantly delayed startup and reaction. The active anodic microbial community structure varied considerably among the MECs utilizing different substrates, particularly between Geobacter and Acetobacterium dominance. The results highlight the substantial effect of the DFE composition on its utilization and current-producing bioanode development.

Increased extra-neurite conductivity of brain in patients with Alzheimer's disease: A pilot study.

The objectives of this study were to investigate how the extra-neurite conductivity (EC) and intra-neurite conductivity (IC) were reflected in Alzheimer's disease (AD) patients compared with old cognitively normal (CN) people and patients with amnestic mild cognitive impairment (MCI) and to evaluate the association between those conductivity values and cognitive decline. To do this, high-frequency conductivity (HFC) at the Larmor frequency was obtained using MRI-based electrical property tomography (MREPT) and was decomposed into EC and IC using information of multi-shell multi-gradient direction diffusion tensor images. This prospective single-center study included 20 patients with mild or moderate AD, 25 patients with amnestic MCI, and 21 old CN participants. After decomposing EC and IC from HFC for all participants, we performed voxel-based and regions-of-interest analyses to compare conductivity between the three participant groups and to evaluate the association with either age or the Mini-Mental State Examination (MMSE) scores. We found increased EC in AD compared to CN and MCI. EC was significantly negatively associated with MMSE scores in the insula, and middle temporal gyrus. EC might be used as an imaging biomarker for helping to monitor cognitive function.

Metabolic shift during fermentation in kimchi according to capsaicinoid concentration.

The cultivar of red pepper used in kimchi contributes to spiciness, red color, and fermentation characteristics. Capsaicinoids are the main components of red pepper. Therefore, understanding changes in metabolites during kimchi fermentation according to capsaicinoid concentration is necessary to control the quality of kimchi. The purpose of this study was to investigate the effect of capsaicinoids on metabolites during kimchi fermentation. To profile the effect of capsaicinoid concentrations on kimchi fermentation, five kimchi samples were prepared using different concentrations of capsaicinoids (4, 12, 30.7, 40.9, and 50.3 mg/kg) and stored at 4 °C for 28 days. During kimchi fermentation, pH, titratable acidity, capsaicinoid concentration, total viable and lactic acid bacteria, free sugars, amino acids, and microbial community were evaluated. Each result was statistically analyzed for changes in capsaicin concentration and fermentation time. The capsaicinoid concentration did not change during kimchi fermentation but the growth of lactic acid bacteria changed. According to the growth of lactic acid bacteria, free sugar, amino acids, and microbial community changed with the capsaicinoid concentration. Overall, the results of this study provide preliminary information on the use of red pepper and capsaicinoids in the kimchi industry.

Microbial Dynamics and Metabolite Profiles in Different Types of Salted Seafood (Jeotgal) During Fermentation.

Salted and fermented seafood (jeotgal) is known for its long shelf life and unique flavor. Despite the existence of various types of salted seafood, the factors influencing this quality have yet to be identified. These factors are essential for improving the quality of salted seafood, optimizing the fermentation process, and advancing the industrialization of fermented foods. Therefore, in this study, we explored microbial dynamics and changes in quality characteristics in three salted seafood items - salted anchovies (MJ), salted cutlass offal (GJ), and salted croakers (HJ), over a 24-month fermentation period. Distinct microbial community profiles, dominated by Tetragenococcus halophilus, Halanaerobium fermentans, and Chromohalobacter canadensis in MJ, GJ, and HJ, respectively, affect the metabolic pathways and the corresponding flavor profiles. The pH of all samples ranged from 5.7-6.0. The titratable acidity was highest in MJ at 1.4% and lowest in HJ at approximately 0.7%. Salinity was below 25% in all samples but slightly lower in MJ. Significant differences were observed in the amino acid, nucleotide, and overall metabolite profiles. MJ exhibited the highest amino acid and nitrogen-related factor levels, such as glutamic acid and hypoxanthine, enhancing flavor complexity. Correlation analysis revealed significant associations among the types, metabolites, and microbial communities. Microbial survival mechanisms in high-salt environments result in the production of unique metabolites, including umami and aroma components as well as precursors of biogenic amines, which can affect the overall quality of the final product. These differences were primarily influenced by the fish type rather than the fermentation time. Our findings provide foundational insights for enhancing fermentation strategies, improving product consistency, and advancing the industrial application of microbial management in seafood fermentation. This study not only fills a significant gap in the current understanding of fermented seafood but also outlines practical approaches for industry applications for the optimization of product quality.

Caught Right on the Spot: Isolation and Characterization of Clade 2.3.4.4b H5N8 High Pathogenicity Avian Influenza Virus from a Common Pochard (Aythya ferina) Being Attacked by a Peregrine Falcon (Falco peregrinus).

We isolated a high pathogenicity avian influenza (HPAI) virus from a common pochard (Aythya ferina) that was being attacked by a bird of prey in South Korea in December 2020. Genetic analyses indicated that the isolate was closely related to the clade 2.3.4.4b H5N8 HPAI viruses found in South Korea and Japan during the winter season of 2020-2021. The histopathological examination revealed multifocal necrotizing inflammation in the liver, kidney, and spleen. Viral antigens were detected in the liver, kidney, spleen, trachea, intestine, and pancreas, indicating the HPAI virus caused a systemic infection. The presence of immunoreactivity for the viral antigen was observed in the cells involved in multifocal necrotic inflammation. Notably, epitheliotropic-positive patterns were identified in the epithelial cells of the trachea, mucosal epithelium of the intestine, and ductular epithelium of the pancreas. These findings provide direct evidence supporting the possibility of HPAI transmission from infected waterfowl to predators.

Detectado en el acto: Aislamiento y caracterización de un virus de la influenza aviar de alta patogenicidad del clado 2.3.4.4b H5N8 de un porrón común (Aythya ferina) atacado por un halcón peregrino (Falco peregrinus). Se aisló un virus de la influenza aviar (HPAI) de alta patogenicidad de un porrón común (Aythya ferina) que estaba siendo atacado por un ave rapaz en Corea del Sur en diciembre de 2020. Los análisis genéticos indicaron que el aislado estaba estrechamente relacionado con virus de influenza aviar de alta patogenicidad H5N8, clado 2.3.4.4 b encontrados en Corea del Sur y Japón durante la temporada de invierno de 2020­2021. El examen histopatológico reveló inflamación necrotizante multifocal en hígado, riñón y bazo. Se detectaron antígenos virales en el hígado, el riñón, el bazo, la tráquea, el intestino y el páncreas, lo que indica que este virus de alta patogenicidad causó una infección sistémica. Se observó la presencia de inmunorreactividad para el antígeno viral en las células involucradas en la inflamación necrótica multifocal. En particular, se identificaron patrones epiteliotrópicos positivos en las células epiteliales de la tráquea, el epitelio mucoso del intestino y el epitelio ductular del páncreas. Estos hallazgos proporcionan evidencia directa que respalda la posibilidad de transmisión de HPAI de aves acuáticas infectadas a especies depredadoras.

Effects of seasonal harvest of kimchi cabbage on microbial and metabolic profiles of kimchi.

Kimchi cabbage, the key ingredient in kimchi, is cultivated year-round to meet high production demands. This study aimed to examine the effects of seasonal harvesting (spring, summer, fall, and winter) on the microbial and metabolic profiles of kimchi during 30 days of fermentation. Lactic acid bacteria distribution is notably influenced by seasonal variations, with Latilactobacillus dominant in fall-harvested kimchi group and Weissella prevailing in spring, summer, and winter. The microbial communities of spring and fall group exhibited similar profiles before fermentation, whereas the microbial communities and metabolic profiles of spring and summer group were similar after 30 days of fermentation. Seasonal disparities in metabolite concentrations, including glutamic acid, serine, and cytosine, persist throughout fermentation. This study provides a comprehensive understanding of the substantial impact of seasonal harvesting of kimchi cabbage on the microbial and metabolic characteristics of kimchi, providing valuable insights into producing kimchi with diverse qualities.

Effect of Mollusca shell extracts on inhibition of kimchi over-acidification.

Mollusca species shell such as oyster shell (OS) and snail shell (SS), are discarded after taking the meat, and the discarded shell causes the environmental problems. Therefore, recycling shell waste could potentially eliminate the environmental problems. This study aimed to evaluate the potential of OS and SS as natural calcium resources. The minerals, calcium, magnesium, potassium, phosphorus and sodium were analyzed in OS and SS extracts. Among them, the calcium content was the highest: 36.87 (%) and 33.42 (%) in the OS and SS extracts, respectively. Further, the content of ionized bioavailable form of calcium in OS and SS was higher than that of CaCO3 under simulated gastrointestinal digestion conditions. Additionally, OS and SS were added to kimchi, and their inhibitory effect on kimchi acidification was evaluated by assessing pH, titratable acidity and microbial analysis. As the results indicated that the addition of OS and SS had little effect on inhibiting the growth of lactic acid bacteria. However, it was confirmed that calcium neutralizes the organic acids produced during fermentation. Overall, the results of this study provide preliminary information on the re-use of OS and SS extracts as ionized natural calcium supplements and fermentation retardants.

Changes in bacterial composition and metabolite profiles during kimchi fermentation with different garlic varieties.

Garlic, a key ingredient in kimchi, is an indispensable source of lactic acid bacteria, which are essential for fermentation. This study explored the effects of various garlic varieties on kimchi fermentation, focusing on changes in microbial communities and metabolite profiles. We observed that the type of garlic used did not significantly alter the microbial community. However, the presence of garlic itself made a significant difference. Specifically, kimchi with garlic showed higher abundance of Leuconostoc and Weissella, which are bacteria primarily responsible for kimchi fermentation. Additionally, kimchi containing garlic had increased levels of mannitol and fructose, which significantly influence taste; however, lactic acid and putrescine levels were decreased. Therefore, the addition of garlic directly contributes to the flavor profile of kimchi. Sixty-two metabolites were identified using gas chromatography and mass spectrometry. The variety of garlic added influenced the metabolite profiles of kimchi, particularly in the later stages of fermentation. These profiles were categorized based on the garlic's origin, whether from southern or northern ecotypes (R2X = 0.933, R2Y = 0.986, Q2 = 0.878). These findings confirm that both the presence and the variety of garlic significantly impact the microbial ecology and metabolites during kimchi fermentation, underscoring its essential role in the process.