Histidine Decarboxylase Activity Research Articles

Elucidating the potential of chlorogenic acid for controlling Morganella psychrotolerans growth and histamine formation.

To investigate the inhibitory impact of chlorogenic acid (CGA) on the growth of Morganella psychrotolerans and its ability to form histamine. The antimicrobial effect of CGA on M. psychrotolerans was evaluated using the minimum inhibitory concentration (MIC) method, revealing an MIC value of 10mg ml-1. The alkaline phosphatase (AKP) activity, cell membrane potential, and scanning electron microscopy images revealed that CGA treatment disrupted cell structure and cell membrane. Moreover, CGA treatment led to a dose-dependent decrease in crude histidine decarboxylase (HDC) activity and gene expression of histidine decarboxylase (hdc). Molecular docking analysis demonstrated that CGA interacted with HDC through hydrogen bonds. Furthermore, in situ investigation confirmed the efficacy of CGA in controlling the growth of M. psychrotolerans and significantly reducing histamine formation in raw tuna. CGA had good activity in controlling the growth of M. psychrotolerans and histamine formation.

Insight into a natural novel histidine decarboxylase gene deletion in Enterobacter hormaechei RH3 from traditional Sichuan-style sausage.

Histamine (HIS) is primarily formed from decarboxylated histidine by certain bacteria with histidine decarboxylase (hdc) activity and is the most toxic biogenic amine. Hdc, which is encoded by the hdc gene, serves as a key enzyme that controls HIS production in bacteria. In this paper, we characterized the changes in microbial and biogenic amines content of traditional Sichuan-style sausage before and after storage and demonstrated that Enterobacteriaceae play an important role in the formation of HIS. To screen for Enterobacteriaceae with high levels of HIS production, we isolated strain RH3 which has a HIS production of 2.27mg/mL from sausages stored at 37°C for 180 days, using selective media and high-performance liquid chromatography. The strain RH3 can produce a high level of HIS after 28h of fermentation with a significant hysteresis. Analysis of the physicochemical factors revealed that RH3 still retained its ability to partially produce HIS in extreme environments with pH 3.5 and 10.0. In addition, RH3 exhibited excellent salt tolerance (6.0% NaCl and 1.0% NaNO2 ). Subsequently, RH3 was confirmed as Enterobacter hormaechei with hdc gene deletion by PCR, western blot, and whole-genome sequencing analysis. Furthermore, RH3 exhibited pathogenicity rate of 75.60% toward the organism, indicating that it was not a food-grade safe strain, and demonstrated a high level of conservation in intraspecific evolution. The results of this experiment provide a new reference for studying the mechanism of HIS formation in microorganisms. PRACTICAL APPLICATION: This study provides a new direction for investigating the mechanism of histamine (HIS) formation by microorganisms and provides new insights for further controlling HIS levels in meat products. Further research can control the key enzymes that form HIS to control HIS levels in food.

IRF3 Activation in Mast Cells Promotes FcεRI-Mediated Allergic Inflammation.

(1) Background: This study aims to elucidate a novel non-transcriptional action of IRF3 in addition to its role as a transcription factor in mast cell activation and associated allergic inflammation; (2) Methods: For in vitro experiments, mouse bone-marrow-derived mast cells (mBMMCs) and a rat basophilic leukemia cell line (RBL-2H3) were used for investigating the underlying mechanism of IRF3 in mast-cell-mediated allergic inflammation. For in vivo experiments, wild-type and Irf3 knockout mice were used for evaluating IgE-mediated local and systemic anaphylaxis; (3) Results: Passive cutaneous anaphylaxis (PCA)-induced tissues showed highly increased IRF3 activity. In addition, the activation of IRF3 was observed in DNP-HSA-treated mast cells. Phosphorylated IRF3 by DNP-HSA was spatially co-localized with tryptase according to the mast cell activation process, and FcεRI-mediated signaling pathways directly regulated that activity. The alteration of IRF3 affected the production of granule contents in the mast cells and the anaphylaxis responses, including PCA- and ovalbumin-induced active systemic anaphylaxis. Furthermore, IRF3 influenced the post-translational processing of histidine decarboxylase (HDC), which is required for granule maturation; and (4) Conclusion: Through this study, we demonstrated the novel function of IRF3 as an important factor inducing mast cell activation and as an upstream molecule for HDC activity.

Characterization of Histamine-Producing Bacteria Isolated During Processing of Indonesian Salted-Boiled Longtail (Thunnus sp.) and Eastern Little Tuna (Euthynnus sp.)

ABSTRACT Histamine-producing bacteria (HPB) were isolated from Longtail and Eastern Little tuna harvested from Indonesian waters and processed as salted-boiled fish (SBF). Mesophilic and psychrophilic bacteria were isolated on Niven’s agar, screened for histidine decarboxylase activity and the presence of the hdc gene, and then histamine production was quantified. Six genera of HPB were identified: Enterobacter, Erwinia, Hafnia, Klebsiella, Serratia and Shigella. At stationary growth phase , mesophilic isolates produced approximately 400 times more histamine than psychrotrophic isolates. The proportion of hdc-positive isolates increased with SBF processing steps, indicating the importance of food safety measuresto minimize HPB growth and histamine production.

Rapidly and accurately screening histidine decarboxylase inhibitors from Radix Paeoniae alba using ultrafiltration–high performance liquid chromatography/mass spectrometry combined with enzyme channel blocking and directional enrichment technique

Histidine Decarboxylase (HDC), an unique enzyme responsible for the synthesis of histamine, which is an important mediator in allergy. Inhibition of HDC activity to decrease histamine production is one way to alleviate allergic symptoms. Traditional Chinese medicines (TCMs) with reported anti-allergy effect is one of important source to search for natural HDC inhibitor. Ultrafiltration combined with high–performance liquid chromatography/mass spectrometry (UF–HPLC/MS) is an effective method for screening HDC inhibitor from TCMs. Nevertheless, false-positive and false-negative results caused by the non-specific binding and the neglection of the trace active compounds are major problems in this method. In this study, an integrated strategy that combined UF–HPLC/MS with enzyme channel blocking (ECB) technique and directional enrichment (DE) technique was developed to seek natural HDC inhibitors from Radix Paeoniae alba (RPA), and at the same time, to reduce false-positive and false-negative results. HDC activity was detected to determine the validity of the screened compounds by RP–HPLC–FD in vitro. Molecular docking was applied to assay the binding affinity and binding sites. As a result, three compounds were screened from low content components of RPA after the DE. Among them, two non-specific compounds were eliminated by ECB, and the specific compound was identified as catechin, which has obvious HDC inhibition activity with IC50 0.52 mM. Furthermore, gallic acid (IC50 1.8 mM) and paeoniflorin (IC50>2 mM) from high content components of RPA were determined having HDC inhibitory activity. In conclusion, the integrated strategy of UF–HPLC/MS combined with ECB and DE technique is an effective mode for rapid and accurate screening and identification of natural HDC inhibitors from TCMs.

Ameliorative Effect of a Neoteric Regimen of Catechin plus Cetirizine on Ovalbumin-Induced Allergic Rhinitis in Rats.

Allergic rhinitis (AR) affects 20–50% of the global population. Available treatments are limited by their adverse effects. We investigated the anti-allergic effects of catechin alone and combined with cetirizine against ovalbumin-induced AR. Rats were sensitized with ovalbumin and received catechin (14 days) and then challenged with aerosolized ovalbumin (1%) to determine AR clinical scores. Histamine, histamine release, and histidine decarboxylase (HDC) activity were determined in blood, peritoneal mast cells, and stomachs, respectively. Vascular permeability and safety were assessed using Evans blue leakage and barbiturate-induced sleeping-time assays, respectively. Catechin and cetirizine binding with HDC was investigated by docking and binding energy analyses. The clinical scores of the combination regimen were superior to either drug alone. All treatments reduced vascular leakage, with no effect on barbiturate-induced sleeping time. Only the catechin-treated rats showed reduced histamine levels and HDC activity. Docking studies revealed that catechin has a 1.34-fold higher extra-precision docking score than L-histidine. The binding energy scores for catechin-HDC, L-histidine-HDC, and histamine-HDC were −50.86, −37.64, and −32.27 kcal/mol, respectively. The binding pattern of catechin was comparable to the standard HDC inhibitor, histidine methyl ester, but with higher binding free energy. Catechin binds the catalytic residue S354, unlike cetirizine. The anti-allergic effects of catechin can be explained by HDC inhibition and possible antihistaminic activity.

Histamine avoidance through three gustatory receptors in Drosophila melanogaster

Histamine is a fermented food product that exerts adverse health effects on animals when consumed in high amounts. This biogenic amine is fermented by microorganisms from histidine through the activity of histidine decarboxylase. Drosophila melanogaster can discriminate histidine and histamine using GR22e and IR76b in bitter-sensing gustatory receptor neurons (GRNs). In this study, RNA interference screens were conducted to examine 28 uncharacterized gustatory receptor genes using electrophysiology and behavioral experiments, including the binary food choice and proboscis extension response assays. GR9a and GR98a were first identified as specific histamine receptors by evaluating newly generated null mutants and recovery experiments by expressing their wild-type cDNA in the bitter-sensing GRNs. We further determined that histamine sensation was mainly mediated by the labellum but not by the legs, as demonstrated by the proboscis extension response assay. Our findings indicated that toxic histamine directly activates bitter-sensing GRNs in S-type sensilla, and this response is mediated by the GR9a, GR22e, and GR98a gustatory receptors.

Effect of Non-thermal Atmospheric Plasma on Viability and Histamine-Producing Activity of Psychotrophic Bacteria in Mackerel Fillets.

Non-thermal atmospheric plasma (NTAP) has gained attention as a decontamination and shelf-life extension technology. In this study its effect on psychrotrophic histamine-producing bacteria (HPB) and histamine formation in fish stored at 0–5°C was evaluated. Mackerel filets were artificially inoculated with Morganella psychrotolerans and Photobacterium phosphoreum and exposed to NTAP to evaluate its effect on their viability and the histidine decarboxylase (HDC) activity in broth cultures and the accumulation of histamine in fish samples, stored on melting ice or at fridge temperature (5°C). NTAP treatment was made under wet conditions for 30 min, using a dielectric barrier discharge (DBD) reactor. The voltage output was characterized by a peak-to-peak value of 13.8 kV (fundamental frequency around 12.7 KHz). This treatment resulted in a significant reduction of the number of M. psychrotolerans and P. phosphoreum (≈3 log cfu/cm2) on skin samples that have been prewashed with surfactant (SDS) or SDS and lactic acid. A marked reduction of their histamine-producing potential was also observed in HDC broth incubated at either 20 or 5°C. Lower accumulation of histamine was observed in NTAP-treated mackerel filets that have been inoculated with M. psychrotolerans or P. phosphoreum and pre-washed with either normal saline or SDS solution (0.05% w/v) and stored at 5°C for 10 days. Mean histamine level in treated and control groups for the samples inoculated with either M. psychrotolerans or P. phosphoreum (≈5 log cfu/g) varied from 7 to 32 and from 49 to 66 μg/g, respectively. No synergistic effect of SDS was observed in the challenge test on meat samples. Any detectable amount of histamine was produced in the meat samples held at melting ice temperature (0–2°C) for 7 days. The effects of NTAP on the quality properties of mackerel’s filets were negligible, whereas its effect on the psychrotrophic HPB might be useful when time and environmental conditions are challenging for the cool-keeping capacity throughout the transport/storage period.

Relationship between Salinity and Histamine Accumulation in Padaek, a Salt-Fermented Freshwater Fish Paste from Laos

Padaek is a salt-fermented freshwater fish product popularly used in Laos as a shelf-stable all-purpose seasoning. For padaek production, the fish is fermented with salt and rice bran at ambient temperature. Although it is considered edible after 2 to 3 months of fermentation, 6 to 12 months is required to enhance its palatability. Its long shelf life and abundance of free amino acids, such as glutamate and lysine, are distinctive features of the product. Although commercial products are currently available, the tradition of making and consuming padaek at home continues, particularly in rural areas, to make use of indigenous freshwater fish, which provides a continuous supply of food and nutrition. Histamine can cause foodborne intoxication. Occasionally, its excessive accumulation occurs in amino acid-containing food, such as fermented fish products, because of the growth of microorganisms with histidine decarboxylase activity. We found a negative correlation between salinity and histamine content in homemade padaek products collected from rural households. Experimental padaek fermentation with initial salinity conditions of 10 and 6.5% exhibited significant histamine accumulation after 2 weeks of incubation at 30°C and exceeded 1,000 ppm within 6 months, but no histamine was detected in fermentation with an initial salinity of 18% over the same period. This indicated that salinity was a critical factor for controlling the risk of histamine accumulation during padaek fermentation. We, therefore, created and used a simplified calculation chart to help local households adjust the initial salinity to a sufficient level to reduce histamine accumulation during padaek fermentation. This producer-friendly approach for reducing the risk of histamine accumulation in this popular fermented food in Laos should be widely implemented to enhance food safety management in the country.

Expression of histidine decarboxylase in melanocytes of the human skin

Histamine-producing cells include storage-type cells (e.g., mast cells and basophils), which store histamine intracellularly, and inducible-type cells (e.g., keratinocytes and macrophages), which induce histidine decarboxylase (HDC, a key enzyme for histamine biosynthesis) activity but do not have a storage pool of histamine. Most of the studies focused on identifying HDC-expressing cells by using cultured cells, and few on investigating the localization of HDC by using skin tissues. Hence, this study conducted immunohistochemical studies using human healthy skin samples. HDC-positive and cytokeratin 14 (a marker of basal keratinocytes)-negative cells were present around the basal layer of the epidermis. These cells did not immunohistochemically react with mast cell tryptase but expressed tyrosinase (a key enzyme for melanin biosynthesis) and microphthalmia-associated transcription factor (MITF, a transcription factor controlling the expression of tyrosinase genes). Melanin granules were clearly observed around HDC-positive and MITF-positive cells. Moreover, HDC mRNA and protein were both detected in cultured normal human epidermal melanocytes. In conclusion, HDC-positive and cytokeratin 14-negative cells around the basal layer of the epidermis are melanocytes.

Anti-Allergic Potential of Cinnamaldehyde via the Inhibitory Effect of Histidine Decarboxylase (HDC) Producing Klebsiella pneumonia.

Allergy is an immunological disorder that develops in response to exposure to an allergen, and histamines mediate these effects via histidine decarboxylase (HDC) activity at the intracellular level. In the present study, we developed a 3D model of Klebsiella pneumoniae histidine decarboxylase (HDC) and analyzed the HDC inhibitory potential of cinnamaldehyde (CA) and subsequent anti-allergic potential using a bacterial and mammalian mast cell model. A computational and in vitro study using K. pneumonia revealed that CA binds to HDC nearby the pyridoxal-5′-phosphate (PLP) binding site and inhibited histamine synthesis in a bacterial model. Further study using a mammalian mast cell model also showed that CA decreased the levels of histamine in the stimulated RBL-2H3 cell line and attenuated the release of β-hexoseaminidase and cell degranulation. In addition, CA treatment also significantly suppressed the levels of pro-inflammatory cytokines TNF-α and IL-6 and the nitric oxide (NO) level in the stimulated mast cells. A gene expression and Western blotting study revealed that CA significantly downregulated the expressions of MAPKp38/ERK and its downstream pro-allergic mediators that are involved in the signaling pathway in mast cell cytokine synthesis. This study further confirms that CA has the potential to attenuate mast cell activation by inhibiting HDC and modifying the process of allergic disorders.

Histidine and tyrosine decarboxylase activities of lactic acid bacteria in sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax)

Biogenic amines (BAs) are formed by decarboxylation of amino acids, amination and transamination of aldehyde and ketone groups. The excess of BAs is harmful to human health. BAs play a significant role in determining the shelf life and quality of foods. Released type and amount of BAs depend on factors such as the quality of the raw material, the diversity of natural microbiota, processing and storage conditions. In fish, the release of BAs is affected primarily from microbial growth as well as other reasons and may cause poisoning. It was aimed to determine the possibility of histidine decarboxylase activity gene (hdc) and tyrosine decarbocylase activity gene (tyrdc) in lactic acid bacteria (LAB) which were isolated from sea bream and sea bass. A total of 18 Gram positive-catalase negative LAB was isolated from 84 fish samples from 14 different fish markets. It was found that 12 out of 18 LAB (67%) isolates showed negative histidine and tyrosine decarboxylase activities. While 2 out of 6 (11%) LAB isolates were determined positive only tyrosine decarboxylase and 4 of them (22%) were positive for histidine and tyrosine decarboxylase. As a result of the Polymerase Chain Reaction (PCR), 9 out of 12 LAB isolates (75%) were found to have histidine decarboxylase activity gene. As a result, the prevalence of histidine decarboxylase activity gene in the LAB has detected more extensive than tyrosine decarboxylase activity gene. Increasing the studies examining the presence of aminobiogenic microorganisms in fish is important for the protection of public health.

Characterization of a novel enzyme from Photobacterium phosphoreum with histidine decarboxylase activity

Histamine or scombrotoxin fish poisoning is caused by ingestion of bacterially produced histamine in fish. Histamine-producing bacteria generally contain the histidine decarboxylase gene (hdc). However, some strains of Photobacterium phosphoreum are known to produce significant levels of histamine, although the hdc gene in these strains has not been recognized. The objective of this study was to investigate a previously unidentified mechanism of histamine production by P. phosphoreum. We identified a protein with histidine decarboxylase (HDC) activity comparable to activity of the pyridoxal-5-phosphate (PLP) dependent HDC from P. kishitanii and M. morganii. The newly identified protein (HDC2) in P. phosphoreum and P. kishitanii strains, was approximately 2× longer than the HDC protein from other Gram-negative bacteria and had 12% similarity to previously identified HDCs. In addition, the hdc2 gene cluster in P. phosphoreum was identical to the hdc gene cluster in P. kishitanii. HDC2 had optimal activity at 20–35 °C, at pH 4, and was not affected by 0–8% NaCl concentrations. Compared to the hdc gene from P. kishitanii, expression of the hdc2 gene was constitutive and not affected by pH or excess histidine. This newly identified protein explains possible mechanisms of histamine production in P. phosphoreum. Characterization of this protein will help in designing control measures to prevent or reduce histamine production in fish.

Growth Rate and Histamine Production of Klebsiella sp. CK02 Isolated from Skipjack Tuna Compared with Morganella morganii ATCC 25830 at Various Incubation Temperatures

One of an important quality parameter in tuna is the level of histamine content. The contamination of histamine in tuna is mainly due to the activity of histidine decarboxylase produced by the bacteria. A rapid growth of histamine producing bacteria is correlated with the practice of temperature abuse during handling. This study aimed to develop predictive growth modeling of two histamine-producing bacteria in the function of temperature. The growth and histamine production of Klebsiella sp. CK02 and Morganella morganii ATCC 25830 at various temperatures were measured in tryptic soy broth histidine (TSBH) and tuna fish infusion broth (TFIB) growth media. Broths were incubated at 4°C and 15°C for 7 days, and at 30°C and 40°C for 24 hours. The Baranyi and Roberts model was used with DMFit to determine primary growth kinectics, and the Ratkowsky square root model to describe bacterial growth rate as a function of temperature. Histamine production was enumerated by the apparent yield factor (pYhis/CFU) value. Growth rate increased with temperature, with a maximum rate at 40°C for Klebsiella sp. CK02 (0.740 log CFU/h) and M. morganii (0.578 log CFU/h). The Tmin for Klebsiella sp. CK02 in TFIB was -8.9°C, indicating better survival in low storage temperature, compare to M. morganii ATCC 25830. In addition, Klebsiella sp. CK02 produced a lower pYhis/CFU at 15 and 30°C compared to M. morganii ATCC 25830.

Histamine and histidine decarboxylase: Immunomodulatory functions and regulatory mechanisms

Histamine is a bioactive monoamine that is synthesized by the enzymatic activity of histidine decarboxylase (HDC) in basophils, mast cells, gastric enterochromaffin‐like (ECL) cells and histaminergic neuronal cells. Upon a series of cellular stimuli, these cells release stored histamine, which elicits allergies, inflammation, and gastric acid secretion and regulates neuronal activity. Recent studies have shown that certain other types of myeloid lineage cells also produce histamine with HDC induction under various pathogenic stimuli. Histamine has been shown to play a series of pathophysiological roles by modulating immune and inflammatory responses in a number of disease conditions, whereas the mechanistic aspects underlying induced HDC expression remain elusive. In the present review, we summarize the current understanding of the regulatory mechanism of Hdc gene expression and the roles played by histamine in physiological contexts as well as pathogenic processes. We also introduce a newly developed histaminergic cell‐monitoring transgenic mouse line (Hdc‐BAC‐GFP) that serves as a valuable experimental tool to identify the source of histamine and dissect upstream regulatory signals.

Development of the Genus and Species Determination Method for Histamine Producing Bacteria Isolated from Fishery Product with High-Resolution Melting Analysis

Histamine in foods with a high histidine content may be produced by bacteria with histidine decarboxylase activity. Consumption of food enriched in histamine can produce symptoms of histamine poisoning that include flushing, headache, and urticaria. The number of histamine poisoning cases in Japan has decreased with developments in food hygiene management technology. However, approximately 10 cases are still reported each year. In addition, there have been cases where histamine was detected in the end products, prompting large product recalls. To prevent and identify causes of histamine toxicity, manufacturers must identify the bacteria causing the illness. A simple method of identification is needed, since sequence-based identification is complicated to perform and the analysis takes a long time. High-Resolution Melting Analysis (HRMA) is a method that detects differences in the base sequences of PCR products manifested as varied melting temperatures of double-stranded DNA. The present study was intended to develop a rapid identification method for major histamine-producing bacteria using HRMA. Species-specific HRMA primers were designed that specifically targeted the hdcA gene of 20 Gram-negative histamine-producing bacterial strains. The designed primers were used for HRM analysis of the 20 histamine-producing bacterial strains. The strains were divided into three groups (A, B, and C) based on differences in melting temperature values obtained by Tm Calling analysis program. Group A comprised terrestrial bacteria, such as Morganella, Enterobacter, and Raoultella, while Groups B and C comprised marine bacteria, such as those belonging to the genera Vibrio and Photobacterium. The melting profiles obtained in Group A by HRMA were used to identify the aforementioned terrestrial bacteria. The findings indicated that HRMA can easily identify the major gram-negative histamine-producing bacteria. A flow chart was created to identify histamine-producing bacterial species. This method enables the identification of histamine-producing bacterial species more quickly and easily than conventional sequence-based methods. Therefore, the method could be valuable for food companies to screen raw materials and products and track the source of contamination, which will in turn contribute to the prevention of histamine-food poisoning and investigation of its causes.

Transcriptome profiling reveals the response process of tomato carrying Cf-19 and Cladosporium fulvum interaction

BackgroundDuring tomato cultivation, tomato leaf mould is a common disease caused by Cladosporium fulvum (C. fulvum). By encoding Cf proteins, which can recognize corresponding AVR proteins produced by C. fulvum, Cf genes provide resistance to C. fulvum, and the resistance response patterns mediated by different Cf genes are not identical. Plants carrying the Cf-19 gene show effective resistance to C. fulvum in the field and can be used as new resistant materials in breeding. In this study, to identify key regulatory genes related to resistance and to understand the resistance response process in tomato plants carrying Cf-19, RNA sequencing (RNA-seq) was used to analyse the differences between the response of resistant plants (CGN18423, carrying the Cf-19 gene) and susceptible plants (Moneymaker (MM), carrying the Cf-0 gene) at 0, 7 and 20 days after inoculation (dai).ResultsA total of 418 differentially expressed genes (DEGs) were identified specifically in the CGN18423 response process. Gene Ontology (GO) analysis revealed that GO terms including “plasma membrane (GO_Component)”, “histidine decarboxylase activity (GO_Function)”, and “carboxylic acid metabolic process (GO_Process)”, as well as other 10 GO terms, were significantly enriched. The “plant hormone signal transduction” pathway, which was unique to CGN18423 in the 0–7 dai comparison, was identified. Moreover, ten key regulatory points were screened from the “plant hormone signal transduction” pathway and the “plant pathogen interaction” pathway. Hormone content measurements revealed that the salicylic acid (SA) contents increased and peaked at 7 dai, after which the contents deceased and reached minimum values in both CGN18423 and MM plants at 20 dai. The jasmonic acid (JA) content increased to a very high level at 7 dai but then decreased to nearly the initial level at 20 dai in CGN18423, while it continued to increase slightly during the whole process from 0 to 20 dai in MM.ConclusionsThe initial responses are very different between the resistant and susceptible plants. The “plant hormone signal transduction” pathway is important for the formation of Cf-19-mediated immunity. In addition, both JA and SA play roles in regulating the Cf-19-dependent resistance response.

Safety and Stability Assessment of Potential Probiotic Strains from Fermented Mango Brine Pickle.

Fermented foods are known to be rich source of valuable nutrients and probiotics. Previously, our study reported the isolation and characterization of eight potential probiotic strains from traditional mango brine pickle, which has been conventionally consumed for ages in raw form in Southern India. The present study reports on the safety assessment of these strains for the selection of prospective probiotic candidates. Hydrogen peroxide production, histidine decarboxylase activity (production of histamine), DNase activity, and presence of the virulence factor genes (assessed by PCR) were carried out to evaluate its safety. Bacillus licheniformis KT921419 and B. methylotrophicus KT921422 was found to show no adverse safety characteristics. These two strains were further assessed for their ability to survive in the native substrate (mango brine pickle) as single and mixed inoculums. Above strains maintained significant viability in mango brine pickle for a period of 6 months during storage at the room temperature. Results clearly proved the safety and stability of two of the potential probiotic strains, which can be further utilized in food applications under harsh conditions of high salt, low pH, and room temperature making these strains unique.

바이오제닉 아민 생성 및 분해균의 혼합 배양으로 제조한 청국장의 품질 특성

The objective of this study was to evaluate biogenic amine (BA) formation and degradation abilities of Bacillus strain and lactic acid bacteria (LAB) isolated from meju and doenjang and to determine the microbiological and physicochemical qualities of Cheonggukjang prepared by mixed culture of these strains. Accumulation of cadaverine (421.7 ± 11.0 mg/L) and histamine (628.7 ± 24.1 mg/L) was assessed in the culture media of Bacillus subtilis MJ226 that displayed lysine and histidine decarboxylase activities. No ability to form cadaverine, histamine, putrescine, tryptamine, and tyramine by Lactobacillus acidophilus D11, L. acidophilus D38, Lactobacillus sakei D44, Lactobacillus plantarum D70, which exhibited high BA degradation ability. The amino nitrogen and free amino acid contents were significantly (p<0.05) increased in Cheonggukjang prepared by the mixed culture of LAB (L. sakei D44, L. plantarum D70, or L. pentosus D74) and B. subtilis MJ226, whereas the ammonia nitrogen and BA (cadaverine and histamine) contents were significantly (p<0.05) decreased. Consequently, it was confirmed that BA formation in Cheonggukjang prepared by starter culture of B. subtilis was effectively inhibited by the certain strains of LAB having BA-degrading ability.

Novel and Rapid Methods for Histamine Quantification in Wine and Culture Medium

Fermented beverages are frequently contaminated with histamine produced by lactic acid bacteria exhibiting histidine decarboxylase activity. In wine, the presence of histamine is associated with a lack of hygiene during the winemaking process. Determination of histamine is important because it can be toxic to humans. Therefore, we developed two rapid, inexpensive, and simple methods—a colorimetric technique and a thin-layer chromatography technique—to determine histamine concentration in wine and culture medium without the need for complicated extraction procedures. The new colorimetric method showed a good correlation between absorbance and histamine concentration in the range of 1.0 to 100 mg/L of histamine in wine and Moeller culture broth samples (r2 = 0.9981 and 0.9941, respectively). Thin-layer chromatography with a new visualization reagent also demonstrated a good correlation between histamine concentrations of 5.0 to 100 mg/L and absorbance (r2 = 0.9882 and 0.9839 for wine and Moeller culture broth samples, respectively). Both methods showed a high correlation with ELISA (colorimetric method: r2 = 0.9972; thin-layer chromatography: 0.9968) and exhibited good histamine recovery (higher than 87%). The detection limits of the new methods were comparable to those of existing analytical methods. Both methods seem suitable for routine analysis to monitor histamine in any research or quality-control laboratory.