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Microbiological properties of Myanmar traditional shrimp sauce, hmyin-ngan-pya-ye
Abstract
The microbiological properties of Myanmar traditional fermented products were characterized using four different brands of bottled shrimp sauce products sold frequently at a large grocery market. Viable cells of these products were detected at various levels (102–105 cfu/ml) using de Man, Rogosa and Sharpe (MRS) agar medium containing 10% NaCl, and all isolates from the product samples were identified as the halophilic lactic acid bacterium Tetragenococcus muriaticus by 16S rRNA gene analysis. On the other hand, culture-independent bacterial analysis using a combination of clone library analysis and terminal restriction fragment length polymorphism (T-RFLP) analysis targeting the 16S rRNA gene demonstrated that these bacterial communities can be classified into three types. In two shrimp sauce products, a strictly anaerobic non-spore-forming halophile belonging to the genus Halanaerobium was detected as the dominant bacterium. In one shrimp sauce product, Tetragenococcus was the dominant genus. However, in the remaining shrimp sauce product, a number of bacterial species typically found in various environments, including the genera Geosporobacter, Sporohalobacter, Lysinibacillus, Soehngenia, and Tepidiphilus, were detected. These findings suggest that typical fermentation bacterial species found in traditional fermented fishery products, such as those belonging to the genera Tetragenococcus and Halanaerobium, are also frequently found in Myanmar shrimp sauce products.
... In Southeast Asian countries, fermented fishery products such as fish and shrimp sauce are popular condiments or seasonings in daily cooking (Kobayashi et al., 2020). Shrimp sauce is one of the products that uses shrimp waste as a main ingredient. ...
... However, according to Kobayashi et al., (2020), the amino acid content of shrimp sauce protein, specifically glutamic acid and alanine, actively contributes to the umami and sweet taste, which is why it is commonly used as a unique ingredient in Myanmar dishes that provide a delightful taste. ...
One of the innovations to increase the economic value of shrimp waste is the implementation of shrimp waste into shrimp sauce and its use in shrimp sauce tilapia dishes. The purpose of this study was to determine the protein and lead (Pb) content of shrimp waste and shrimp sauce, the degree to which shrimp sauce differed in aroma, taste, and color from commercial oyster sauce, and the degree to which panelists preferred shrimp sauce tilapia dishes via organoleptic tests. This was a two-repetition experimental study with a completely randomized design (CRD). The protein content was determined using the Kjeldahl semi-micro method, whereas the lead content was determined using the spectrophotometric method. The Duo-Trio Test was used to determine the difference in organoleptic properties between shrimp sauce and commercial oyster sauce, whereas ANOVA followed by DMRT was used to analyze the hedonic properties of shrimp sauce tilapia dishes. The results of this study indicate that shrimp waste contains 18.281 percent protein and shrimp sauce contains 6.107 percent protein. The content of lead (Pb) in shrimp waste was 0.750 mg/kg, while the content of lead (Pb) in shrimp sauce was 0.052 mg/kg. The organoleptic tests revealed that shrimp sauce had a distinct aroma, taste, and color from commercial oyster sauce, whereas the hedonic tests revealed no difference in the hedonic properties of the three dishes' aromas, but there were differences in the hedonic properties of their taste and properties. The three dishes exhibit hedonic color. Panelists preferred commercial oyster sauce tilapia dishes over shrimp sauce tilapia dishes and commercial oyster sauce mixed tilapia dishes in terms of aroma, taste, and color (1:1). The shrimp sauce formula should be refined further so that it more closely resembles commercial oyster sauce in terms of aroma, flavor, and color.
Mustard green paocai is a salted vegetable product that is fermented with low salt in the initial stage and preserved with high salt in the middle stage. To reveal the key flavor-producing potential of core bacterial and fungal communities during the 365-day fermentation of industrial-scaled paocai. In this study, microbiome and molecular sensory science were used to analyze potential relationships between microbial diversity and key flavor compounds. The results showed that bacteria were more diverse than fungi. High salinity improved the flavor of industrial paocai and simplified the microbial community. A total of 74 bacterial and yeast strains were isolated and identified throughout the fermentation process. Lactiplantibacillus, Halanaerobium, Halomonas, Pseudomonas, and Enterobacteriaceae were the dominant bacterial genera, and Debaryomyces hansenii was the core fungal genera in paocai. 4-Ethylphenol, anethole, butanoic acid, 4-ethylguaiacol, and 3-methyl-1-butanol were identified as key flavor compounds in industrial paocai with odor activity values greater than 1. Spearman correlation analysis indicated that bacteria have a greater impact on the flavor of paocai than fungi. Halanaerobium and Halomonas were correlated with flavor and spoilage in paocai. This study provides guidance for the production of desirable flavors by multi-bacteria synergistic fermentation of industrial paocai.
This data article reports on the chemical properties of commercial fish sauce products associated with the fish sauce taste and flavor. All products were analyzed in triplicate. Dried solid content was analyzed by moisture analyzer. Fish sauce salinity was determined by a salt meter. pH was measured using a pH meter. The acidity was determined using a titration assay. Amino nitrogen and total nitrogen were evaluated using a titration assay and Combustion-type nitrogen analyzer, respectively. The analyzed products originated from Japan, Thailand, Vietnam, China, the Philippines, and Italy. Data on the chemical properties of the products are provided in table format in the current article.
The distribution and characterization of bacteria including lactic acid bacteria (LAB) in the traditional and popular salted fish yegyo ngapi in Myanmar were studied to clarify the contribution of these bacteria to the curing and ripening of this product. Samples of yegyo ngapi purchased from a market in Yangon were used. Most of the isolates obtained using de Man, Rogosa and Sharpe medium containing 10 % NaCl were identified as coccoid LAB on the basis of their basic phenotypic characteristics. From the results of 16S rRNA gene sequencing and PCR-restriction fragment length polymorphism analysis of this gene, most of the isolates were identified as the halophilic LAB Tetragenococcus muriaticus. Analyses of the 16S rRNA gene based on the clone library using DNA extracted from salted fish products were also performed. The results of these molecular-analysis-based techniques showed that spore-forming and non-spore-forming anaerobic bacteria including the genera Clostridium and Halanaerobium in addition to T. muriaticus were also frequently found in bacterial communities. These findings suggest that the anaerobic condition during curing and ripening resulted in bacterial communities composed of strictly anaerobic bacteria and halophilic LAB, and that these bacteria might also contribute to the manufacturing processes of this product. In addition, DNA sequences similar to that of Clostridium botulinum were found in the clone library analysis. Therefore, despite no reports of botulism poisoning from the region where the samples were taken, closer surveillance should be carried out from the viewpoint of food safety.
An antibacterial-substance-producing bacterium, namely, strain F412, was isolated from a traditional Myanmar shrimp product fermented with boiled rice. It was a gram-positive, spore-forming, and rod-shaped bacterium, and identified as Bacillus mojavensis on the basis of the gyrA sequence. The antibacterial substance of this strain was partially purified from a culture supernatant using two steps of column chromatography. This substance was found to be widely effective against gram-positive bacteria, including Listeria monocytogenes. The antibacterial activity of this substance was not susceptible to treatments with several proteolytic enzymes. The antibacterial activity gradually decreased with increasing treatment temperature, but it remained even after heating for 15 min at 121 °C. This antibacterial substance showed different molecular weights, as shown by the results of gel filtration and electrophoresis analyses. Staining results after electrophoresis suggest that the antibacterial substance might be a glycopeptide with an estimated molecular weight between 3.5 and 8.5 kDa. From the decrease in optical density of a culture of the L. monocytogenes treated with this antibacterial substance, it was suggested that this substance might have bacteriolytic activity.
The screening of malachite green (MG)-degrading microorganisms was carried out using various sources, namely, fish farms and a traditional fermented fishery product in Myanmar and Thailand. The enrichment culture method was performed using MG-containing broth media, and colonies that showed the decolorization of MG on plate media were isolated as MG-degrading candidates. From the results of the sequencing of the D1/D2 domain of the 26S rRNA gene, strain M3, a representative strain of MG-degrading candidates was identified as a halotolerant yeast, Debaryomyces
nepalensis. Liquid chromatography-tandem mass spectrometry (LC–MS/MS) analysis indicated that during the incubation of this strain, the MG concentration gradually decreased and eventually reached undetectable levels. Conversely, the concentration of leucomalachite green (LMG) increased, and the final amount of LMG in the broth culture was estimated to be approximately 40 % of the initial MG amount. In addition, results of proton nuclear magnetic resonance spectroscopy (1H-NMR) analysis also showed that MG and the tautomer of MG or other aromatic decomposition products of MG were not detected as a major component at the end of incubation. These results suggest that strain M3 removed MG and changed approximately 40 % to LMG and 60 % to some metabolites other than LMG.
A bacterial community analysis, using a culture-independent method (polymerase chain reaction-denaturing gradient gel electrophoresis), detected 17 species of bacteria including species of the genera Tetragenococcus, Lactobacillus, Pediococcus, Weissella Halanaerobium, Clostridium, and Sphingomonas in a traditional salty-fermented fish paste known as pla-ra or pa-daek in Thailand and Laos, which is used as a storage-stable multi-purpose seasoning. The representative genus of lactic acid bacteria seemed to vary in the 10 products collected from Thailand and Laos. Tetragenococci were common in products from central Thailand and Vientiane in Laos which had salinities of not less than 11% and pH values ranging from 5.6 to 6.1. However, lactobacilli were common in products from northern Thailand which had the lowest salinities (8.3–8.6%) and pH
values (4.5–4.8) of all the samples examined. Two Lactobacillus and one Tetragenococcus species were detected in one product from northeastern Thailand containing 10% salt. These results suggest that salinity in pla-ra/pa-daek is an important determinant of the representative genus of lactic acid bacteria such as, Tetragenococcus or Lactobacillus. Additionally, differences in the acidity between these two groups seemed to be related to the production of d-/l-lactic acid in the lactic acid bacteria in each product. This is the first study to report a correlation between bacterial community structure and taste components in pla-ra/pa-daek products from various regions. This scientific work on a traditional fermented food will be useful in helping local producers meet differing consumer preferences in various regions.
In this study, an alkaliphilic and heterotrophic iron-reducing bacterial strain, IRF9(T), was isolated from an oil-contaminated soil in the Republic of Korea. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain IRF9(T) belongs to the genus Geosporobacter in the family Clostridiaceae and is most closely related to Geosporobacter subterraneus VNs68(T) (96.9 % sequence similarity). Cells of strain IRF9(T) were observed to be straight or curved rod-shaped, motile and Gram-negative. Optimal growth of strain IRF9(T) was observed at pH 9.0-9.5 and 40 °C. The strain was found to grow within pH and temperature ranges of 6.5-10.0 and 25-45 °C, respectively. NaCl was not required for growth. Fe(III), but not sulfate, thiosulfate or elemental sulfur can be used by strain IRF9(T) as an electron acceptor. A limited number of carbohydrates and amino acids, including D-glucose, D-fructose, D-mannitol, D-ribose and L-arginine, support growth of strain IRF9(T). The main fatty acids (>10 %) of strain IRF9(T) were identified as C14:0 (18.4 %), C16:1 cis9 (13.6 %), C16:0 (12.4 %) and C16:0 dimethyl acetal (17.7 %). Major respiratory quinone was identified as menaquinone MK-5 (V-H2). The main polar lipids were found to be phosphatidylethanolamine, diphosphatidylglycerol and phosphatidylglycerol. The DNA G+C content of strain IRF9(T) was determined to be 37.2 mol%, which is lower than that of G. subterraneus VNs68(T) (42.2 mol%). Based on phenotypic, chemotaxonomic, and phylogenetic studies, we conclude that strain IRF9(T) (=JCM 19987(T) = KCTC 15395(T)) represents a new species of the genus Geosporobacter, for which we propose the name Geosporobacter ferrireducens sp. nov.
This study is a detailed description of the microflora of a traditional fishery product in Myanmar which is fermented with boiled rice. We approached this analysis from two viewpoints; namely, the culture-dependent and culture-independent methods.
In Southeast Asia, there are various types of traditional fermented fishery products. In this study, we isolated and characterized lactic acid bacteria (LAB) from small freshwater fish (tinfoil barb) fermented with boiled rice, a typical Myanmar fermented product, to contribute to the understanding of its fermentation process. Eight fermented fishery products were purchased from different markets in Yangon. Forty-three of the 46 isolates were identified as LAB, and they were classified into two groups: 40 homofermentative and three heterofermentative isolates, on the basis of their phenotypic characteristics. From the results of PCR-restriction fragment length polymorphism (RFLP) analysis and 16S rRNA gene sequencing, our isolates were identified as Lactobacillus plantarum-group, Lactobacillus farciminis, Lactobacillus futsaii, Lactobacillus reuteri,
Weissella paramesenteroides, and Pediococcus pentosaceus. In addition, L. plantarum and L. farciminis were identified as γ-aminobutyric acid (GABA)-producing LAB. Terminal restriction fragment length polymorphism (T-RFLP) analysis was also carried out using DNA samples extracted from these fermented products. In comparison with culture-dependent methods, the results of T-RFLP analysis did not seem to have major contradictions.
Halophilic, obligately anaerobic, Gram-negative bacterial strains were isolated from a sediment sample taken under salt crust of El-Jerid hypersaline lake located in southern Tunisia by using tryptone or glucose as substrate. One of them (strain CEJFT1BT) was characterized phenotypically and phylogenetically. Cells were non-motile, non-spore forming, short rods. Strain CEJFT1BT was able to grow in the presence of 5-30 % (w/v) NaCl (optimum 20 %) and at 30-60 °C (optimum 45 °C). It grew at pH 5.5-7.75 and the optimum pH for growth was 6.75. The isolate required yeast extract for growth. Substrates utilized by strain CEJFT1BT included glucose, fructose, sucrose, pyruvate, casaminoacids and starch. Individual amino acid such as glutamate, lysine, methionine, serine, tyrosine and amino acid mixtures by Stickland reaction such as alanine-glycine, valine-proline, leucine-proline, isoleucine-proline were also utilized. Products of glucose fermentation were acetate (major product), butyrate, isobutyrate, H2 and CO2. The DNA G+C content of strain CEJFT1BT was 32.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain CEJFT1BT could be assigned to the genus Sporohalobacter. The sequence similarity between strain CEJFT1BT and Sporohalobacter lortetii was 98.5%, but DNA-DNA hybridization between the two strains revealed relatedness value of 56.4%, indicating that they are not related at the species level. The combination of phylogenetic analysis, DNA-DNA hybridization data, and differences in substrate utilization supported the view that strain CEJFT1BT represents a new species of the genus Sporohalobacter, for which the name Sporohalobacter salinus sp. nov. is proposed. The type strain is strain CEJFT1BT (DSM 26781 = JCM 19279).
Botulinum neurotoxins (BoNTs) are produced by anaerobic bacteria of the genus Clostridium and cause a persistent paralysis of peripheral nerve terminals, which is known as botulism. Neurotoxigenic clostridia belong to six phylogenetically distinct groups and produce more than 40 different BoNT types, which inactivate neurotransmitter release owing to their metalloprotease activity. In this Review, we discuss recent studies that have improved our understanding of the genetics and structure of BoNT complexes. We also describe recent insights into the mechanisms of BoNT entry into the general circulation, neuronal binding, membrane translocation and neuroparalysis.
γ-Aminobutyric acid (GABA)-producing lactic acid bacteria (LAB) were isolated from four types of Myanmar traditional fermented
fishery products with boiled rice. All of them belonged to the genus Lactobacillus, and comparison of the effects of these representatives on GABA accumulation in fermented fishery products with boiled rice
revealed that Lactobacillus farciminis D323 is the most effective strain as a starter culture. These results may contribute to the development of traditional fermented
fishery products with functional properties. In addition, this study is the first to show in detail the distribution of GABA-producing
LAB in Southeast Asian fermented fishery products.
Keywordsγ-Aminobutyric acid–Fermentation–
Lactobacillus
–Fermented fishery products–Myanmar
Comparative analysis of molecular sequence data is essential for reconstructing the evolutionary histories of species and inferring the nature and extent of selective forces shaping the evolution of genes and species. Here, we announce the release of Molecular Evolutionary Genetics Analysis version 5 (MEGA5), which is a user-friendly software for mining online databases, building sequence alignments and phylogenetic trees, and using methods of evolutionary bioinformatics in basic biology, biomedicine, and evolution. The newest addition in MEGA5 is a collection of maximum likelihood (ML) analyses for inferring evolutionary trees, selecting best-fit substitution models (nucleotide or amino acid), inferring ancestral states and sequences (along with probabilities), and estimating evolutionary rates site-by-site. In computer simulation analyses, ML tree inference algorithms in MEGA5 compared favorably with other software packages in terms of computational efficiency and the accuracy of the estimates of phylogenetic trees, substitution parameters, and rate variation among sites. The MEGA user interface has now been enhanced to be activity driven to make it easier for the use of both beginners and experienced scientists. This version of MEGA is intended for the Windows platform, and it has been configured for effective use on Mac OS X and Linux desktops. It is available free of charge from http://www.megasoftware.net.
Two anaerobic, benzaldehyde-converting bacteria were isolated from an anaerobic upflow anaerobic sludge bed (UASB)-reactor treating potato starch waste water. Strain BOR-Y(T) converted benzaldehyde to benzoate and benzylalcohol in approximately equimolar concentrations. Benzaldehyde conversion did not support growth. Strain BOR-Y(T) was Gram-positive and rod-shaped, and its cells were slightly thickened in the middle. The strain was a mesophilic spore-former that grew between 15 and 40 degrees C, with optimum growth at 30-37 degrees C. The optimum pH for growth was pH 7.0. Strain BOR-Y(T) grew on a wide range of carbohydrates and some other carbon sources including yeast extract, cysteine and serine. The G+C content of its DNA was 42 mol%. According to physiological characteristics and 16S rRNA gene sequence analysis, confirmed by DNA-DNA hybridization with its phylogenetic neighbours, strain BOR-Y(T) belongs to a novel genus of cluster XII of the clostridia, namely Soehngenia; the name Soehngenia saccharolytica is proposed for the type species (type strain BOR-Y(T)=DSM 12858(T)=ATCC BAA-502(T)). Strain BR-10(T) reduced benzaldehyde to benzylalcohol. This conversion was coupled to growth. In a medium containing yeast extract, the presence of benzaldehyde resulted in the accumulation of more than twofold more cells. Strain BR-10(T) was a Gram-positive organism that was characterized by oval- or rod-shaped cells with oval ends, which occurred singly, in pairs or sometimes in chains. The strain was moderately thermophilic and grew between 20 and 60 degrees C, with optimum growth at 45 degrees C. The optimum pH for growth was between pH 7.0 and 7.5. Strain BR-10(T) grew on a wide range of carbon sources including carbohydrates, yeast extract, casein and some amino acids. The G+C content of its DNA was 32 mol%. As determined by 16S rRNA gene sequence analysis, strain BR-10(T) represents a novel species of cluster XIVa of the clostridia; the name Clostridium amygdalinum is proposed for this novel species (type strain BR-10(T)=DSM 12857(T)=ATCC BAA-501(T)).
Lactic acid bacteria from "terasi" shrimp paste, a highly popular fermented seafood in Indonesia were isolated and characterized. Viable cell counts were 10(4) to 10(6) cfu/g on MRS medium. All the isolates were catalase-negative, gram-positive cocci and were able to grow at 15% NaCl. Numerical phenotypic analysis showed that the isolates clustered into one group. However, they could be classified into two types: the Tetragenococcus halophilus group and the T. muriaticus group as revealed by a restriction fragment length polymorphism (RFLP) analysis and sequencing of the 16S rRNA gene. This study is the first to show that both species of Tetragenococcus are distributed in Indonesian fermented foods.
Three strains of a spore-forming, Gram-positive, motile, rod-shaped and boron-tolerant bacterium were isolated from soil. The strains, designated 10a(T), 11c and 12B, can tolerate 5 % (w/v) NaCl and up to 150 mM boron, but optimal growth was observed without addition of boron or NaCl in Luria-Bertani agar medium. The optimum temperature for growth was 37 degrees C (range 16-45 degrees C) and the optimum pH was 7.0-8.0 (range pH 5.5-9.5). A comparative analysis of the 16S rRNA gene sequence demonstrated that the isolated strains were closely related to Bacillus fusiformis DSM 2898(T) (97.2 % similarity) and Bacillus sphaericus DSM 28(T) (96.9 %). DNA-DNA relatedness was greater than 97 % among the isolated strains and 61.1 % with B. fusiformis DSM 2898(T) and 43.2 % with B. sphaericus IAM 13420(T). The phylogenetic and phenotypic analyses and DNA-DNA relatedness indicated that the three strains belong to the same species, that was characterized by a DNA G+C content of 36.5-37.9 mol%, MK-7 as the predominant menaquinone system and iso-C(15 : 0) (32 % of the total) as a major cellular fatty acid. In contrast to the type species of the genus Bacillus, the strains contained peptidoglycan with lysine, aspartic acid, alanine and glutamic acid. Based on the distinctive peptidoglycan composition, phylogenetic analyses and physiology, the strains are assigned to a novel species within a new genus, for which the name Lysinibacillus boronitolerans gen. nov., sp. nov. is proposed. The type strain of Lysinibacillus boronitolerans is strain 10a(T) (=DSM 17140(T)=IAM 15262(T)=ATCC BAA-1146(T)). It is also proposed that Bacillus fusiformis and Bacillus sphaericus be transferred to this genus as Lysinibacillus fusiformis comb. nov. and Lysinibacillus sphaericus comb. nov., respectively.
Four coagulase-negative, novobiocin-resistant cocci, designated CW1(T), PM34, MM3 and RW78, were isolated from the respiratory tract of goats kept in the Himalayan region. The four isolates were assigned to a single species on the basis of almost identical biochemical and physiological traits, protein profiles obtained after SDS-PAGE and identical genomic fingerprints generated after enterobacterial repetitive intergenic consensus (ERIC)-PCR. Strain CW1(T) showed highest 16S rDNA sequence similarities to Staphylococcus cohnii subsp. urealyticus ATCC 49330(T), Staphylococcus saprophyticus subsp. saprophyticus ATCC 15305(T), S. cohnii subsp. cohnii ATCC 29974(T), Staphylococcus arlettae ATCC 43957(T), Staphylococcus gallinarum ATCC 35539(T), Staphylococcus succinus ATCC 700337(T) and Staphylococcus xylosus ATCC 29971(T) (99.0, 98.8, 98.8, 98.4, 98.2, 98.1 and 98.1 %, respectively), indicating its classification within the genus Staphylococcus. The polar lipid composition, fatty acid profiles, quinone systems and diagnostic cell-wall diamino acid were in agreement with the characteristics of the genus Staphylococcus. DNA-DNA hybridization with closely related Staphylococcus species suggested that strain CW1(T) represents an as-yet unrecognized species. Based on these results, a novel species of the genus Staphylococcus is described, Staphylococcus nepalensis sp. nov. The type strain is CW1(T) (=DSM 15150(T)=CCM 7045(T)) and the most dissimilar strain is PM34 (=DSM 15151=CCM 7046).
Food fermentation technologies have developed through years of experience rather than scientific findings. Therefore, many small-scale manufacturers are unwilling to accept changes and to modify fermentation processes. Still, traditional fermented foods have had an essential role in human nutrition for thousands of years. A wide range of diverse cereals, legumes, vegetables, fruits, fish, seafood, and meat are used as raw materials for the production of these fermented foods by back-slopping (a process where material from a previous successful batch is added to facilitate the initiation of a new batch) or naturally occurring microorganisms. Various microorganisms that influence the quality, safety, sensory properties, acceptability, and consistency of these products are present. Lactic acid bacteria with their beneficial characteristics are generally a significant contributor. Identification and profiling of microorganisms in fermented foods are of particular interest. But so far such information has not been explored in detail for some fermented products from the lower Mekong subregion. Improving the safety, quality, and acceptability of fermented foods, while reducing their production costs and maintaining their authenticity and uniqueness, is important. This can be achieved through starter culture application and greater attention to food safety, such as HACCP approaches. Recent scientific advances have led to the development of defined microbial starters, leading to the transfer of artisanal food production to more controlled and industrialized fermentation. The aim of this review is to determine the gaps in the knowledge of traditional fermented foods of the lower Mekong subregion and to present current information on the diversity of involved microorganisms. These data will be helpful for defining future strategies toward the sustainable production of safe fermented foods particularly those from southeast Asia.
The main objective of this work was to investigate the effects of bacterial community and free amino acids on the content of biogenic amines in Yu-lu during fermentation. Four major biogenic amines (histamine, tyramine, cadaverine, and putrescine) were identified, and the content of tyramine was positively correlated with histamine (R value = 0.9113). Aspartic acid, glutamic acid, histidine, leucine, and lysine were the dominant free amino acids. 16S rRNA sequencing showed that the composition of the bacterial community changed significantly during fermentation of Yu-lu. Principal component analysis revealed the crucial links between microbial community and biogenic amines. For example, Halanaerobium was probably associated with the formation of putrescine, while Halomonas might be associated with the degradation of biogenic amines at the end of fermentation of Yu-lu. This study provided a detailed evaluation of the Yu-lu fermentation process, enabling development of better strategies for biogenic amine control in fish sauce.
Microbial flora of an indigenous food to Japan, fermented puffer fish ovaries, “fugunoko nukazuke”, were examined. Samples used for the examinations were salted ovaries of puffer fish Fugu stictonotum for 2 months and 1 year, exudate from ovaries after 2 months' and 1 year's salting, ovaries fermented in rice-bran for 4 months and 2 years, and rice-bran fermented for 4 months and 2 years.
The viable bacterial counts obtained from these samples were different dependingon the culture conditions and manufacturing process. However, high counts of 10⁷ cfu/g and 10⁷ cfu/ml were obtained in some samples of fermented rice-bran and exudate.
Most isolates which were tolerant to high levels of salt concentration can be tentativelydivided into four groups: lactic acid cocci, halophilic anaerobes, Pseudomonas-like halophiles, and halophilic archaea. These four groups of bacteria were found insalted ovaries and exudate, while in the samples fermented with rice-bran the dominant microflora were lactic acid cocci. Bacillus, Corynebacterium, and Staphylococcus were also isolated, but the counts of these were much lower.
Fermentation is one of the oldest and most widely used food preservation methods in households and small-scale food industries as well as in large enterprises. Most fermented foods including the major products that are common in the western world, as well as many of those from other sources that are less well characterized, are dependent on lactic acid bacteria (LAB) to mediate the fermentation process. Lactic acid fermentation is widely used in tropical countries as a low-cost method of enhancing food quality, safety and shelf life. Salt has been used for centuries to increase the shelf life of foodstuffs and remains a frequently used component to create an unfavourable environment for food spoilage microorganisms and pathogens. The need for quality improvement and process innovation in the area of fish fermentation have been widely recognized in recent years.
Eighty strains of homofermentative tetrad-forming lactic acid bacteria were isolated from fish sauce fermentation in Thailand. These bacteria were divided into three groups based on the phenotypic and chemotaxonomic characteristics including DNA relatedness. Forty strains (Group I)showed high degrees (70.0% to 109.1%) DNA-DNA homology with Tetragenococcus halophilus ATCC 33315. They were identified as T. halophilus. Thirty-eight strains (Group II) showed high degrees (70.9% to 105.6%) of DNA-DNA homology with Tetragenococcus muriaticus JCM 10006. They were identified as T. muriaticus. Two strains (Group III) showed low degrees (3.7% to 16.3%)of DNA-DNA homology with T. halophilus ATCC 33315, T. muriaticus JCM 10006, and Aerococcus uiridans TISTR 393. Then they were left unidentified. Group I and Group II strains are halophilic which grew in 25% NaCl. All the strains tested produced L-lactic acid and contained cellular fatty acids with C18: 1 as the major component. Some of the selected strains produced histamine ranging from 0.04 to 52.29mg/100 ml. The differentiation of Tetragenococcus strains is discussed.
Myeolchi-aekjeot (MA) is a Korean traditional fish sauce, made by fermenting salted [approximately 25% (w/v)] anchovies. Three sets of MA samples, S-MA, M-MA, and L-MA, were prepared using small (5-8cm), medium (8-10cm), and large (10-13cm) anchovies, respectively, and their bacterial communities and metabolites were investigated for 280days. Bacterial community analysis using pyrosequencing revealed that, in S-MA, the initially dominant genera, including Phychrobacter, Photobacterium, and Vibrio, disappeared rapidly and Salinivibrio, Staphylococcus, and Tetragenococcus/Halanaerobium appeared sequentially as the major populations. In contrast, in M-MA and L-MA, the initially dominant genera were maintained relatively well during the early fermentation period, but eventually Tetragenococcus became predominant without the growth of Halanaerobium. The changes in the bacterial community occurred more quickly in MA prepared with smaller anchovies than in those prepared with larger anchovies. Metabolite analysis using (1)H NMR showed that amino acids, glycerol, acetate, and lactate rapidly increased in all MA samples during the early fermentation period. Amino acids increased more quickly and then decreased after reaching their maximum level in S-MA, while they increased continually until the end of fermentation in L-MA. This suggests that the complete fermentation of L-MA may require more time than that for S-MA. A correlative analysis between bacterial communities and metabolites revealed that the increase in acetate, butyrate, and putrescine in S-MA was associated with the growth of Halanaerobium, which may be a useful indicator of anchovy sauce quality.
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A total of 33 bacterial strains from ngapi, a Burmese salted and fermented shrimp paste, were screened for antioxidant and antibacterial activities. Two strains, NP1-1 and NP3-2, which showed high free radical scavenging and antibacterial activities, were selected. Radical scavenging activities of the ethyl acetate extracts were compared with those of BHA using DPPH. The antioxidant activity of extracts was determined according to the thiocyanate method. Moreover, the filtrate extracts from the two strains were found to have broad inhibitory activity against target bacteria. NP1-1 and NP3-2 strains were respectively identified as Bacillus subtilis and Bacillus sp. based on the 16S rDNA sequences.
Abstract On April 17, 2012, two adult females presented to the hospital with symptoms of botulism. Patient A displayed shortness of breath, increasing lethargy, ptosis, and fixed and dilated pupils, and was intubated after admission. Patient B presented with shortness of breath, vomiting, and stridor. Both patients consumed a meal consisting of a traditionally prepared salted fish, fesikh, on the evening of April 16 during a gathering to celebrate Sham el-Nessim, an Egyptian holiday marking the beginning of spring. Foodborne botulism was suspected based on symptoms and consumption of potentially hazardous food. Antitoxin was administered to both patients on April 18. Another attendee of the Sham el-Nessim gathering (patient C), who also consumed the implicated food, developed symptoms consistent with botulism on April 18. Clinical specimens from all three symptomatic attendees tested positive for either Clostridium botulinum or type E botulinum neurotoxin. Fesikh remaining from the shared meal contained both type E botulinum neurotoxin and C. botulinum type E organisms. Unsold fesikh shad and fesikh sardines tested positive for C. botulinum type E, while unsold fesikh mullet pieces in oil tested positive for both C. botulinum type E and type E botulinum neurotoxin. After consultation with public health investigators, all fesikh products were voluntarily withheld from sale by the manufacturer prior to laboratory confirmation of contamination. Additional illnesses were likely prevented by these precautionary holds, which underscores the importance of timely public health action based on epidemiological evidence available in advance of laboratory results. This is the first documented outbreak of foodborne botulism associated with fesikh to occur in Canada.
Jeotgal, which is widely consumed as a nutritional supplement in Korea, is traditional type of preserved seafood that is prepared by salting and fermenting. Here, we report on the bacterial community structure and diversity of jeotgal obtained from the Korean island of Jeju, which has a subtropical climate. Two samples of Jeotgal were collected from Jeju, made from either damselfish (Chromis notata; jari-dom-jeot, J1 and J2) or silver-stripe round herring (Spratelloides gracilis; ggot-myulchi-jeot, K1 and K2). The physical characteristics (pH and salinity) were assessed and the bacterial communities characterized using 16S rRNA gene-clone library analysis and cultural isolation. No difference was found in the community composition between the J and K fermented seafoods. Both fermented seafoods had relatively high salinity (26% to 33%) and high pH values (pH 6.08 to 6.72). Based on the 16S rRNA gene sequences, the halophilic lactic-acid bacteria Tetragenococcus halophilus and T. muriaticus were observed to be dominant in the J and K fermented seafoods, accompanied by halophilic bacteria including Halanaerobium spp., Halomonas spp., and Chromohalobacter spp. When compared with 7 other types of fermented seafood from a previous study, the communities of the J and K fermented seafoods were separated by the most influential group, the genus Tetragenococcus. The results suggest that these 2 types of traditional salted fermented seafood from Jeju have distinct communities dominated by Tetragenococcus spp., which are derived from the raw ingredients and are dependent on the physical conditions. This may explain how the seafoods that are made in Jeju may differ from other jeotgals.
Forty-one tetrad-forming halophilic lactic acid bacteria were isolated from 7 kinds of fermented foods in Thailand. All the isolates were identified as the genus Tetragenococcus by their phenotypic characteristics. On the basis of 16S rRNA gene restriction analysis using MboI and AluI and 16S rRNA gene sequence analyses, 41 isolates could be divided into two groups (groups A and B). All 22 isolates in Group A were identified as T. halophilus. 16S rRNA gene sequences of the representative isolates, SP37-2 and KS87-1 exhibited 99.4–99.5 % similarity to that of T. halophilus ATCC 33315T. Nineteen isolates in Group B were identified as T. muriaticus. 16S rRNA gene sequences of the representative isolates, KM1-5 and KS87-14, showed 99.0–99.6 % similarity to that of T. muriaticus JCM 10006T. Histamine formation was determined by using HPLC and the histidine decarboxylase (hdc) gene of the newly isolated histamine-producing strain was partially sequenced. The strain KS87-14 prolifically formed histamine 10 times higher than the reported T. muriaticus JCM 10006T. The positive detection of KS87-14 was achieved by using hdcA gene-specific primers JV16HC and JV17HC.
Liquid fish sauces (n=61) collected from seven Southeast and East Asian countries were analyzed for free amino acids, organic acids, nucleosides and nucleic acid bases as well as creatine, creatinine, pH, salt content, moisture, and total nitrogen. The fish sauces were only made from fish species such as anchovy and sardine. A high nitrogen recovery of 97.9% was obtained for all nitrogen-containing compounds in a Vietnamese fish sauce. The fish sauces of Vietnam, Japan, and Thailand showed high concentrations of these compounds except for organic acids and a very close amino acid pattern whereas those of Myanmar and Laos exhibited the lowest contents and a different amino acid pattern from those of the above three countries. Korean and Chinese fish sauces showed intermediate contents and the same amino acid pattern. Of all organic acids determined, acetate dominated in Myanmar and Chinese fish sauces, suggesting that acetic acid fermentation is predominant. In the fish sauces from other countries, pyroglutamate and lactate were high. These data will give a standard for the chemical composition of fish sauces from various Southeast and East Asian countries and during the production of fish sauce. These results also indicate that creatinine which originates from creatine during fish sauce fermentation and receives only small bacterial decomposition is a possible marker for the quality control in fish sauce factories, because its determination is much easier and time saving than for the other compounds.
Saeu-jeot is made by the fermentation of highly salted [approximately 25% (w/v)] shrimp in Korea. Saeu-jeot samples were prepared in triplicate and their cell number, bacterial community, and metabolites were monitored periodically for 183 days. Quantitative PCR showed that bacterial populations were much more abundant than archaeal populations during the entire saeu-jeot fermentation period, which suggested that bacterial populations, not archaeal populations, might be primarily responsible for saeu-jeot fermentation. Pyrosequencing analysis revealed that Proteobacteria were dramatically replaced with halophilic Firmicutes as the fermentation progressed and members of Pseudoalteromonas, Staphylococcus, Salimicrobium, and Alkalibacillus were sequentially dominant and, eventually, Halanaerobium predominated after 66 days of fermentation. Halophilic archaeal genera, Halorubrum, Halolamina, Halobacterium, Haloarcula, and Haloplanus belonging to Euryarchaeota, were dominant, but their communities were relatively constant over the entire fermentation period. Metabolite analysis using a (1)H NMR spectroscopy showed that the amount of metabolites including amino acids, glycerol, and nitrogen compounds rapidly increased during the early fermentation stage, but their levels were relatively constant or they decreased after approximately 49 days of fermentation. A statistical analysis based on bacterial communities and metabolites demonstrated that members of Halanaerobium might be responsible for the production of acetate, butyrate, and methylamines after 66 days of fermentation, which could be considered as a potential indicator to decide the appropriate seafood fermentation time. This study will provide insights into the microbial succession and metabolites of fermented seafood and allow for a greater understanding of the relationships between the microbial community and metabolites in seafood fermentation.
The two Staphylococcus strains that had been isolated from fish sauce mush (moromi) made from frigate mackerel in Japan and proved to improve fish sauce odor, were examined for their taxonomic positions. The sequence analysis based on 16S rRNA and rpoB showed that the two strains, R4Nu and R5G, had an identical sequence with sequence identities of 99.5% and 99.0% to the above two genes from the closest species of S. nepalensis, respectively. A DNA hybridization test of the two strains showed more than 80% DNA similarity with S. nepalensis, thus confirming the above-mentioned species identification. Polymerase chain reaction primers specific to the strain isolated from fish sauce mush were designed from rpoB and examined for the distribution of this species to various fish sauces made in Asian countries as well as to fish sauce starter (malt) made from soy beans and barley in Toyama Prefecture, Japan. The amplified DNA fragment bearing the S. nepalensis gene was detected in the enriched culture of the malt, although no positive reaction was shown with fish sauce samples. These results suggest that S. nepalensis indebted to improve fish sauce odor was originated from the fish sauce starter malt.
The distribution of Clostridium botulinum in sediments and fish from coastal and inland areas of India was investigated. Seventy-one samples of sediments from brackish water/freshwater farms on the west coast and from the seashores of both west and east coasts were analysed. The overall prevalence of C. botulinum in sediments was 21% and the predominant types were types C and D (18%) followed by type A (3%). Sixty-eight samples of wild and farmed shellfish samples from the west coast were examined. Fifteen samples (22%) harboured C. botulinum and the identified C. botulinum types included type C (9%), type D (9%) and type A (4%). Sixty-one samples representing cultivable fish from the west coast and east coast (20), trash fish from the west coast (30) and farmed fish from the west coast (11) were screened and C. botulinum was detected in four (20%), eight (27%) and two (18%) samples, respectively. An overall prevalence of 22% was found in fish. The identified C. botulinum types on the surfaces of wild fish included type D (8%), type C (6%), type A (6%) and type B (2%), whereas the intestine samples harboured types A (4%) and C (2%). In farmed fish, C. botulinum type C was detected in the intestine sample. The present study revealed that C. botulinum types C and D are the predominant types seen in fish and aquatic environments of the tropical Indian subcontinent.
Halophilic lactic acid bacteria were isolated from fish sauce mashes fermented at 1 to 12 months. Seven out of sixty-four isolates were selected according to their proteolytic activity and growth at 25% NaCl for characterization and investigation of volatile compound production. All selected isolates were Gram-positive cocci with pairs/tetrads and grew at 0-25% NaCl, pH 4.5-9.0. Results of 16S rRNA gene sequence analysis showed 99% homology to Tetragenococcus halophilus ATCC 33315. The restriction fragment length polymorphism (RFLP) patterns of all isolates were also similar to those of T. halophilus ATCC 33315. These isolates were, thus, identified as T. halophilus. All isolates hydrolyzed fish protein in the medium containing 25% NaCl. Intracellular aminopeptidase of 7 isolates exhibited the highest activity of 2.85-3.67 U/ml toward Ala-p-nitroanilide (Ala-pNA). T.halophilus strains MS33 and M11 showed the highest alanyl aminopeptidase activity (P<0.05), and produced histamine in mGYP broth containing 5 and 25% NaCl in the level of 6.62-22.55 and 13.14-20.39 mg/100ml, respectively. Predominant volatile compounds of fish broth containing 25% NaCl inoculated with T. halophilus MS33 and MRC5-5-2 were 1-propanol, 2-methylpropanal, and benzaldehyde, corresponding to major volatile compounds in fish sauce. T.halophilus appeared to play an important role in volatile compound formation during fish sauce fermentation.
The sensitivity of the commonly used progressive multiple sequence alignment method has been greatly improved for the alignment
of divergent protein sequences. Firstly, individual weights are assigned to each sequence in a partial alignment in order
to downweight near-duplicate sequences and up-weight the most divergent ones. Secondly, amino acid substitution matrices are
varied at different alignment stages according to the divergence of the sequences to be aligned. Thirdly, residue-specific
gap penalties and locally reduced gap penalties in hydrophilic regions encourage new gaps in potential loop regions rather
than regular secondary structure. Fourthly, positions in early alignments where gaps have been opened receive locally reduced
gap penalties to encourage the opening up of new gaps at these positions. These modifications are incorporated into a new
program, CLUSTAL W which is freely available.
In April 1991, 91 hospitalized patients in Cairo were reported to the Egyptian Ministry of Health with botulism intoxication.
To define the spectrum of illness and identify a food vehicle, 45 patients were interviewed and a case-control investigation
was conducted among families of 5 hospitalized patients. Clinical specimens and specimens of implicated food were tested for
toxin and cultured for Clostridium botulinum. Hospitalized patients had symptoms consistent with botulism; 18 (20%) of91 reported patients died. Illness was associated
with eating faseikh (uneviscerated, salted mullet fish; lower 95% confidence limit of odds ratio = 6.6, P < .001). All 5 case-families purchased faseikh from one shop. Very high levels of type E botulinal toxin were detected in faseikh reported to be purchased from the implicated shop; C. botulinum type E was isolated from cultures of clinical specimens and from the faseikh. This is the first documented outbreak of botulism in Egypt and the largest type E outbreak ever reported.
A total of 11 strains of moderately halophilic histamine-producing bacteria isolated from fermented squid liver sauce were studied phenotypically, genotypically, and phylogenetically. These strains are considered members of the genus Tetragenococcus based on their physiological, morphological, and chemotaxonomic characteristics. A 16S rRNA gene sequence analysis showed that these strains clustered with, but were separate from, Tetragenococcus halophilus. The results of DNA-DNA hybridization experiments indicated that the new isolates represent a new Tetragenococcus species, for which we propose the name Tetragenococcus muriaticus; strain X-1 (= JCM 10006) is the type strain of this species.
Strictly anaerobic halophiles were isolated from canned Swedish fermented herrings (Surströmming). All isolates were phenotypically uniform with some exceptions and were identified as the genus Haloanaerobium and assigned to either Haloanaerobium praevalens or Haloanaerobiuim alcaliphilum. A comparative analysis of 16S rDNA sequences revealed that the representative strain S-8 of the isolates was identical to that of Haloanaerobium praevalens DSM 2228T. Furthermore, this strain exhibited high levels (> 80%) of DNA-DNA homology with Haloanaerobium praevalens DSM 2228T. This is a novel report of halophilic anaerobes isolated from a food product. Such anaerobes may contribute to the intense flavor and the swollen can characteristics of Swedish fermented herring.
Tetragenococcus strains isolated from the manufacturing process of Japanese puffer fish ovaries fermented with rice-bran were characterized and differentiated phenotypically and genotypically. A total of 413 Tetragenococcus isolates were evaluated. On the basis of five representative substrates, the isolates were grouped into seven groups. An RFLP (restriction fragment length polymorphisms) analysis of the 16S rRNA gene of representative strains of major groups revealed that they could be grouped into two groups: one was identified as the most prominent halophilic lactic acid coccus, Tetragenococcus halophilus, and the other as T. muriaticus, which has recently been added to the genus Tetragenococcus as a new species. Physiologically, the major differences between the two groups were found in the ability to grow in medium not supplemented with NaCl and the fermentation of L-arabinose, sucrose and D-mannitol, and several other carbohydrates.
Histamine (or scombroid) fish poisoning (HFP) is reviewed in a risk-assessment framework in an attempt to arrive at an informed characterisation of risk. Histamine is the main toxin involved in HFP, but the disease is not uncomplicated histamine poisoning. Although it is generally associated with high levels of histamine (> or =50 mg/100 g) in bacterially contaminated fish of particular species, the pathogenesis of HFP has not been clearly elucidated. Various hypotheses have been put forward to explain why histamine consumed in spoiled fish is more toxic than pure histamine taken orally, but none has proved totally satisfactory. Urocanic acid, like histamine, an imidazole compound derived from histidine in spoiling fish, may be the "missing factor" in HFP. cis-Urocanic acid has recently been recognised as a mast cell degranulator, and endogenous histamine from mast cell degranulation may augment the exogenous histamine consumed in spoiled fish. HFP is a mild disease, but is important in relation to food safety and international trade. Consumers are becoming more demanding, and litigation following food poisoning incidents is becoming more common. Producers, distributors and restaurants are increasingly held liable for the quality of the products they handle and sell. Many countries have set guidelines for maximum permitted levels of histamine in fish. However, histamine concentrations within a spoiled fish are extremely variable, as is the threshold toxic dose. Until the identity, levels and potency of possible potentiators and/or mast-cell-degranulating factors are elucidated, it is difficult to establish regulatory limits for histamine in foods on the basis of potential health hazard. Histidine decarboxylating bacteria produce histamine from free histidine in spoiling fish. Although some are present in the normal microbial flora of live fish, most seem to be derived from post-catching contamination on board fishing vessels, at the processing plant or in the distribution system, or in restaurants or homes. The key to keeping bacterial numbers and histamine levels low is the rapid cooling of fish after catching and the maintenance of adequate refrigeration during handling and storage. Despite the huge expansion in trade in recent years, great progress has been made in ensuring the quality and safety of fish products. This is largely the result of the introduction of international standards of food hygiene and the application of risk analysis and hazard analysis and critical control point (HACCP) principles.
A strain of strictly anaerobic and moderately halophilic bacteria isolated from salted puffer fish ovaries was studied phenotypically, genotypically and phylogenetically. On the basis of its physiological and morphological characteristics, the new isolate is considered to be a member of the genus Haloanaerobium. It is a motile, rod-shaped, non-spore-forming, gram-negative, obligate anaerobe that grows in the presence of 25% (w/v) NaCl. The optimum salt concentration for growth is 10% (w/v). It grows well at 15 and 45 degrees C, but not at 10 or 50 degrees C. The optimum temperature for growth is 35 degrees C. It grows at pH 6.0-9.0 and the optimum pH for growth is 7.5. It ferments N-acetylglucosamine, cellobiose, fructose, galactose, D-glucose, lactose, maltose, D-mannose, raffinose, D-ribose, sucrose and D-xylose. It ferments D-glucose with the production of hydrogen, carbon dioxide, ethanol and organic acids such as acetate, formate and lactate. 16S rRNA gene sequence information confirmed the phylogenetic position of the new isolate, strain R-9T, as a member of the genus Haloanaerobium. DNA-DNA hybridization data revealed that isolate R-9T exhibited low levels of reassociation (less than 30%) with previously described Haloanaerobium species. Based on these results, the new isolate appears to represent a new Haloanaerobium species, for which the name Haloanaerobium fermentans sp. nov. is proposed. The type strain is R-9T (= JCM 10494T).
We examined histamine formation in cultures of Tetragenococcus muriaticus, a halophilic lactic acid bacterium isolated from fish sauce. T. muriaticus formed histamine in low acidity (pH 5.8), O2 limiting conditions with optimal NaCl and glucose concentrations of 5-7% (w/v) and above 1%, respectively. Histamine formation could not be prevented even at 20% (w/v) NaCl, indicating that NaCl could not prevent histamine formation by this bacterium. A conspicuous amount of histamine accumulated only during the late stationary phase regardless of the growth conditions. Studies of cell suspension experiments confirmed the results obtained from cultured cells.
A histidine decarboxylase from Tetragenococcus muriaticus, a halophilic histamine-producing bacterium isolated from Japanese fermented squid liver sauce, was purified to homogeneity, for the first time.
The enzyme was purified 16-fold from cell-free extract by ammonium sulphate precipitation, anion exchange chromatography and hydroxyapatite chromatography. The pure enzyme consisted of two polypeptide chains with molecular mass of 28.8 and 13.4 kDa. The N-terminal amino acid sequences of these polypeptides highly correlated with those of the alpha- and beta-chains of other Gram-positive bacterial histidine decarboxylases. The optimum and stable pH for the enzyme was 4.5-7.0 and 4.0-7.0, respectively. This enzyme did not decarboxylate lysine, arginine, tyrosine, tryptophan and ornithine. The enzyme activity decreased with the addition of NaCl. At pH 4.8, the Vmax and Km values were 16.8 micromol histamine min-1 mg-1 and 0.74 mmol l-1, respectively.
The very similar physiological properties of this enzyme and almost identical N-terminal amino acid sequences to those from other Gram-positive bacteria indicated that this enzyme may be evolutionally highly conserved among Gram-positive bacteria.
Information on this enzyme could be useful for studying the mechanism of histamine accumulation in salted foods. In addition, the N-terminal amino acid sequence can be utilized to design oligonucleotide probes, which may prove valuable in the rapid monitoring of halophilic histamine producers in salted products.
A moderately thermophilic bacterium is described, strain N2-214(T), that was isolated from an enrichment culture, growing on caprolactone, obtained from a sample from a water-treatment sludge aerobic digester operating at temperatures around 60 degrees C. The organism was aerobic, Gram-negative, oxidase- and catalase-positive, with a polar flagellum, and capable of growth at temperatures as high as 61 degrees C. The major fatty acids of strain N2-214(T) were C(16 : 0), C(18 : 1) and cyclo-C(19 : 0). The phylogenetic relationships of the strain, derived from 16S rRNA gene sequence comparisons, demonstrated it to be a member of the beta-subclass of the PROTEOBACTERIA: The highest 16S rDNA sequence similarity of isolate N2-214(T) was to Azoarcus buckelii (91.9 %), Thauera aromatica (92 %) and Hydrogenophilus thermoluteolus (92.7 %). On the basis of phylogenetic analyses and physiological and chemotaxonomic characteristics, it is proposed that isolate N2-214(T) (=DSM 15129(T)=LMG 21637(T)) represents a new genus and species, Tepidiphilus margaritifer gen. nov., sp. nov.
To investigate the effects of the salt concentration, incubation temperature and initial pH of the medium on the fermentative ability of the halophilic lactic acid bacteria, Tetragenococcus muriaticus and T. halophilus.
The growth, lactic acid production and pH reduction ability of five strains of T. muriaticus and T. halophilus in MRS broth medium under various culture conditions such as salt concentration (3, 7, 15 and 23% NaCl), temperature (20, 30 and 40 degrees C), and initial medium pH (5.8, 6.5 and 7.5) were investigated. Those of T. halophilus were seriously affected by a high salinity (23% NaCl); in contrast, those of T. muriaticus were affected by a low initial pH (5.8).
The results indicate that high saline concentrations and low pH values have significant impact on the growth, lactic acid production and pH reduction ability of T. halophilus and T. muriaticus, respectively.
This study appears to be important in biopreservation during the manufacture of fermented food products. Both T. muriaticus and T. halophilus may support each other in reducing pH in hypersaline or low pH environment. To our knowledge, this is the first report on the fermentation ability of T. muriaticus.
A colorimetric enzyme assay for the quantitative analysis of histamine in food has been developed using a new histamine dehydrogenase (HDH) from Rhizobium sp. The HDH specifically catalyzes the oxidation of histamine but not other biogenic amines such as putrescine and cadaverine. The principle of our photometric assay is as follows. The HDH catalyzes the oxidative deamination of histamine in the presence of 1-methoxy PMS (electron carrier), which converts WST-8 (tetrazolium salt) to a formazan. This product is measured in the visible range at 460 nm. The correlation between the histamine level and absorbance was acceptable, ranging from 0 to 96 microM with histamine standard solutions, corresponding to 0 to 30 microM of the reaction solution (r = 1.000, CV = 1.0% or less). Assays of canned tuna (in oil and soup) and raw tuna with 45-675 micromol/kg histamine added showed good recoveries of 96-113, 98-108, and 100-106%. The histamine contents of a commercial canned tuna and fish meal containing histamine at high concentrations were determined using the new method and other reference methods (HPLC method, Association of Official Analytical Chemists official method, and two commercial enzyme immunoassay test kits). This simple and rapid enzymatic method is as reliable as the conventional methods.
Understanding dynamic processes and diversity in microbial communities is of key importance for combating pathogens and for stimulating beneficial bacteria. We have addressed these challenges utilising multivariate statistics for analyses of microbial community structures. We based our microbial community analyses on 16S rRNA gene data. This gene is by far the most widely applied genetic marker for phylogenetic and microbial community studies. Both probe and clone library data were analysed. We analysed the clone library data using a newly developed coordinate-based phylogenetic approach. By using coordinates, we avoid both DNA sequence alignments and the need for definition of operational taxonomic units (OTUs). The basic principle is to transform the sequence data to frequencies of multimers (short sequences of n=2 to 6), and then to use principal component analyses (PCA) for data compression into an orthogonal coordinate space. We used our coordinate method for global 16S rRNA gene analyses of prokaryotes. When comparing microbial communities, it is often important to determine the relationship between the microflora and knowledge about the samples analysed. We used partial least square regression (PLSR) to relate physical/chemical properties to microbial community composition. This was done by analysing both probe and clone library data using the effect of modified atmosphere packaging (MAP) on fish microflora as an example. We are currently investigating approaches to describe dynamic microbial community interactions. Our ultimate goal is to understand and model the main dynamic interactions in complete microbial communities.
In the last two decades major changes have occurred in how microbial ecologists study microbial communities. Limitations associated with traditional culture-based methods have pushed for the development of culture-independent techniques, which are primarily based on the analysis of nucleic acids. These methods are now increasingly applied in food microbiology as well. This review presents an overview of current community profiling techniques with their (potential) applications in food and food-related ecosystems. We critically assessed both the power and limitations of these techniques and present recent advances in the field of food microbiology attained by their application. It is unlikely that a single approach will be universally applicable for analyzing microbial communities in unknown matrices. However, when screening samples for well-defined species or functions, techniques such as DNA arrays and real-time PCR have the potential to overtake current culture-based methods. Most importantly, molecular methods will allow us to surpass our current culturing limitations, thus revealing the extent and importance of the 'non-culturable' microbial flora that occurs in food matrices and production.
In: Steinkraus KH (ed) Industrialization of indigenous fermented foods, 2nd edn, revised and expanded
- M T Tyn
- MT Tyn
Tyn MT (2004) Industrialization of Myanmar fish paste and sauce
fermentation. In: Steinkraus KH (ed) Industrialization of
indigenous fermented foods, 2nd edn, revised and expanded.
Marcel Dekker, New York, pp 737-762