Isolation and characterization of lactic acid bacteria from suan-tsai (fermented mustard), a traditional fermented food in Taiwan

Identification of Capsular Polysaccharide Synthesis Loci Determining Bacteriophage Susceptibility in Tetragenococcus halophilus

Bacteriophages infecting Tetragenococcus halophilus, a halophilic lactic acid bacterium, have been a major industrial concern due to their detrimental effects on the quality of food products. Previously characterized tetragenococcal phages displayed narrow host ranges, but there is little information on these mechanisms. Here, we revealed the host's determinant factors for phage susceptibility using two virulent phages, phiYA5_2 and phiYG2_4, that infect T. halophilus YA5 and YG2, respectively. Phage-resistant derivatives were obtained from these host strains, and mutations were found at the capsular polysaccharide (CPS) synthesis (cps) loci. Quantification analysis verified that capsular polysaccharide production by the cps derivatives from YG2 was impaired. Transmission electron microscopy observation confirmed the presence of filamentous structures outside the cell walls of YG2 and their absence in the cps derivatives of YG2. Phage adsorption assays revealed that phiYG2_4 adsorbed to YG2 but not its cps derivatives, which suggests that the capsular polysaccharide of YG2 is the specific receptor for phiYG2_4. Interestingly, phiYA5_2 adsorbed and infected cps derivatives of YG2, although neither adsorption to nor infection of the parental strain YG2 by phiYA5_2 was observed. The plaque-surrounding halos formed by phiYA5_2 implied the presence of the virion-associated depolymerase that degrades the capsular polysaccharide of YA5. These results indicated that the capsular polysaccharide is a physical barrier rather than a binding receptor for phiYA5_2 and that phiYA5_2 specifically overcomes the capsular polysaccharide of YA5. Thus, it is suggested that tetragenococcal phages utilize CPSs as binding receptors and/or degrade CPSs to approach host cells. IMPORTANCE T. halophilus is a halophilic lactic acid bacterium that contributes to the fermentation processes for various salted foods. Bacteriophage infections of T. halophilus have been a major industrial problem causing fermentation failures. Here, we identified the cps loci in T. halophilus as genetic determinants of phage susceptibility. The structural diversity of the capsular polysaccharide is responsible for the narrow host ranges of tetragenococcal phages. The information provided here could facilitate future studies on tetragenococcal phages and the development of efficient methods to prevent bacteriophage infections.

Soybean fermentation: Microbial ecology and starter culture technology

Fermented soybean products, including Soya sauce, Tempeh, Miso, and Natto have been consumed for decades, mainly in Asian countries. Beans are processed using either solid-state fermentation, submerged fermentation, or a sequential of both methods. Traditional ways are still used to conduct the fermentation processes, which, depending on the fermented products, might take a few days or even years to complete. Diverse microorganisms were detected during fermentation in various processes with Bacillus species or filamentous fungi being the two main dominant functional groups. Microbial activities were essential to increase the bean's digestibility, nutritional value, and sensory quality, as well as lower its antinutritive factors. The scientific understanding of fermentation microbial communities, their enzymes, and their metabolic activities, however, still requires further development. The use of a starter culture is crucial, to control the fermentation process and ensure product consistency. A broad understanding of the spontaneous fermentation ecology, biochemistry, and the current starter culture technology is essential to facilitate further improvement and meet the needs of the current extending and sustainable economy. This review covers what is currently known about these aspects and reveals the limited available information, along with the possible directions for future starter culture design in soybean fermentation.

Determination of the Bacterial Community of Mustard Pickle Products and Their Microbial and Chemical Qualities

We assessed the microbial and chemical qualities and microbiomes of 14 mustard pickle products coded sequentially from A to N and sold in traditional Taiwanese markets. The results showed that the aerobic plate count and lactic acid bacteria count of commercially available mustard pickle products were 2.18-4.01 and <1.0-3.77 log CFU/g, respectively. Moreover, no coliform bacteria, Escherichia coli, Staphylococcus aureus, Salmonella spp., or Listeria monocytogenes were detected in any of the samples. Analysis of the chemical quality showed that the sulfite content of all samples exceeded 30 ppm, which is the food additive limit in Taiwan. Furthermore, the mean contents of eight biogenic amines in the mustard pickle product samples were below 48.0 mg/kg. The results of high-throughput sequencing showed that the dominant bacterial genera in sample A were Proteus spp. (25%), Vibrio (25%), and Psychrobacter (10%), in sample C they were Weissella (62%) and Lactobacillus (15%), in sample E it was Lactobacillus (97%), and in sample J it was Companilactobacillus (57%). Mustard pickle product samples from different sources contained different microbiomes. The dominant bacterial family was Lactobacillaceae in all samples except for sample A. In contrast, the microbiome of sample A mainly consisted of Morganellaceae and Vibrionaceae, which may have resulted from environmental contamination during storage and sales. The result of this work suggests it may be necessary to monitor sulfite levels and potential sources of bacterial contamination in mustard pickle products, and to take appropriate measures to rule out any public health risks.

Comparative Genomics of Closely Related Tetragenococcus halophilus Strains Elucidate the Diversity and Microevolution of CRISPR Elements

Tetragenococcus halophilus – a halophilic lactic acid bacterium – is frequently used as a starter culture for manufacturing fermented foods. Tetragenococcus is sometimes infected with bacteriophages during fermentation for soy sauce production; however, bacteriophage infection in starter bacteria is one of the major causes of fermentation failure. Here, we obtained whole-genome sequences of the four T. halophilus strains YA5, YA163, YG2, and WJ7 and compared them with 18 previously reported genomes. We elucidated five types of clustered regularly interspaced short palindromic repeat (CRISPR) loci in seven genomes using comparative genomics with a particular focus on CRISPR elements. CRISPR1 was conserved in the four closely related strains 11, YA5, YA163, and YG2, and the spacer sequences were partially retained in each strain, suggesting that partial deletions and accumulation of spacer sequences had occurred independently after divergence of each strain. The host range for typical bacteriophages is narrow and strain-specific thus these accumulation/deletion events may be responsible for differences in resistance to bacteriophages between bacterial strains. Three CRISPR elements, CRISPR1 in strains 11, YA5, YA163, and YG2, CRISPR2 in strain WJ7, and CRISPR2 in strain MJ4, were inserted in almost the same genomic regions, indicating that several independent insertions had occurred in this region. As these elements belong to class 1 type I-C CRISPR group, the results suggested that this site is a hotspot for class 1, type I-C CRISPR loci insertion. Thus, T. halophilus genomes may have acquired strain-specific bacteriophage-resistance through repeated insertion of CRISPR loci and accumulation/deletion events of their spacer sequences.

The relationships between microbiota and the amino acids and organic acids in commercial vegetable pickle fermented in rice-bran beds

The microbial community during fermented vegetable production has a large impact on the quality of the final products. Lactic acid bacteria have been well-studied in such processes, but knowledge about the roles of non-lactic acid bacteria is limited. This study aimed to provide useful knowledge about the relationships between the microbiota, including non-lactic acid bacteria, and metabolites in commercial pickle production by investigating Japanese pickles fermented in rice-bran. The samples were provided by six manufacturers, divided into two groups depending on the production conditions. The microbiological content of these samples was investigated by high-throughput sequencing, and metabolites were assessed by liquid chromatography-mass spectrometry and enzymatic assay. The data suggest that Halomonas, halophilic Gram-negative bacteria, can increase glutamic acid content during the pickling process under selective conditions for bacterial growth. In contrast, in less selective conditions, the microbiota consumed glutamic acid. Our results indicate that the glutamic acid content in fermented pickle is influenced by the microbiota, rather than by externally added glutamic acid. Our data suggest that both lactic acid bacteria and non-lactic acid bacteria are positive key factors in the mechanism of commercial vegetable fermentation and affect the quality of pickles.

A Holistic Review on Euro-Asian Lactic Acid Bacteria Fermented Cereals and Vegetables

Lactic acid fermentation is one of the oldest methods used worldwide to preserve cereals and vegetables. Europe and Asia have long and huge traditions in the manufacturing of lactic acid bacteria (LAB)-fermented foods. They have different cultures, religions and ethnicities with the available resources that strongly influence their food habits. Many differences and similarities exist with respect to raw substrates, products and microbes involved in the manufacture of fermented products. Many of them are produced on industrial scale with starter cultures, while others rely on spontaneous fermentation, produced homemade or in traditional events. In Europe, common LAB-fermented products made from cereals include traditional breads, leavened sweet doughs, and low and non-alcoholic cereal-based beverages, whereas among vegetable ones prevail sauerkraut, cucumber pickles and olives. In Asia, the prevailing LAB-fermented cereals include acid-leavened steamed breads or pancakes from rice and wheat, whereas LAB-fermented vegetables are more multifarious, such as kimchi, sinki, khalpi, dakguadong, jiang-gua, soidon and sauerkraut. Here, an overview of the main Euro-Asiatic LAB-fermented cereals and vegetables was proposed, underlining the relevance of fermentation as a tool for improving cereals and vegetables, and highlighting some differences and similarities among the Euro-Asiatic products. The study culminated in "omics"-based and future-oriented studies of the fermented products.

Lactobacillus suantsaicola sp. nov. and Lactobacillus suantsaiihabitans sp. nov., isolated from suan-tsai, a traditional fermented mustard green product of Taiwan

Four Gram-stain-positive strains, R7T, R11, R19T and R27, were isolated from suan-tsai, a traditional fermented mustard green product of Taiwan. Cells were rod-shaped, non-motile, non-haemolytic, asporogenous, facultatively anaerobic, heterofermentative, and did not exhibit catalase and oxidase activities. Comparative analyses of 16S rRNA, pheS and rpoA gene sequences demonstrated that these novel strains were members of the genus Lactobacillus . 16S rRNA and the concatenated pheS and rpoA gene sequence similarities between strains R7T and R11, and strains R19T and R27 were very high (>99.8 % similarity), respectively. On the basis of 16S rRNA gene sequence similarities, the type strains of Lactobacillus paralimentarius (98.5 %), Lactobacillus kimchii (98.5 %), Lactobacillus alimentarius (98.1 %) and Lactobacillus bobalius (98.1 %) were the closest neighbours to strains R7T and R11, and the type strains of Lactobacillus brevis (98.9 %), Lactobacillus cerevisiae (98.4 %), Lactobacillus hammesii (98.4 %), Lactobacillus koreensis (98.4 %) and Lactobacillus yonginensis (98.0 %) were the closest neighbours to strains R19T and R27, respectively. The average nucleotide identity values of R7T and R19T with the closely related type strains were 78.9–80.1% and 75.7–80.5 %, respectively. The digital DNA–DNA hybridization values were 22.8–23.6% and 21.0–23.1 %, respectively. Phenotypic and genotypic test results demonstrated that these strains represent two novel species of the genus Lactobacillus , for which the name Lactobacillus suantsaicola sp. nov. (R7T=BCRC 81127T=NBRC 113530T) and Lactobacillus suantsaiihabitans sp. nov. (R19T=BCRC 81129T=NBRC 113532T) are proposed.

Genomic insights into the non-histamine production and proteolytic and lipolytic activities of Tetragenococcus halophilus KUD23

Tetragenococcus halophilus KUD23, a non-histamine producer, was isolated from a traditional Korean high-salt fermented soybean paste, doenjang. The strain was safe in terms of antibiotic susceptibility, hemolytic activity and biofilm formation. It could grow on De Man-Rogosa-Sharpe agar containing 21% (w/v) NaCl, exhibited acid production at 15% NaCl, and had strain-specific proteolytic and lipolytic activities under salt stress. Complete genome analysis of T. halophilus KUD23 and comparative genomic analysis shed light on the genetic background behind these phenotypic characteristics, including non-production of histamine and proteolytic and lipolytic activities.

Thai Fermented Foods as a Versatile Source of Bioactive Microorganisms—A Comprehensive Review

Fermented foods are known for several health benefits, and they are generally used among the Asian people. Microorganisms involved in the fermentation process are most responsible for the final quality of the food. Traditional fermented (spontaneous fermentation) foods are a versatile source of bioactive molecules and bioactive microbes. Several reports are available regarding the isolation and characterization of potent strains from traditional fermented foods. A collection of information for easy literature analysis of bioactive microbes derived from Thai fermented food is not yet available. The current manuscript compiled information on bioactive (antimicrobial- and enzyme-producing probiotic) microbes isolated from naturally fermented Thai foods.

Impact of Fermented Foods on Human Cognitive Function-A Review of Outcome of Clinical Trials

Food is an essential need for all living creatures which provides the energy to maintain life and grow further. Fermentation is a process used to preserve and advance the quality of foods, and those foods are known as fermented foods. Some foods offer health benefits to consumers apart from nutrition, and such foods are called as functional foods. Most functional foods are fermented foods, and the fermenting microorganism plays a precious role in the functional property of the food. Cognitive decline is closely associated with the productivity of an individual and the society. Even though cognitive decline is connected to aging, dietary pattern influences memory, anxiety and other social behaviors. Many scientific studies have explained the link between food habits and cognitive functions by in vitro and in vivo models. The present review compiled the clinical data on the impact of fermented foods on human cognitive function.

Use of Lactobacillus plantarum as Starter Culture and Its Influence on Physicochemical, Microbiological, and Sensory Characteristics of Kunnu-Aya Produced from Sorghum and Tigernut

Kunun-aya is a traditional nonalcoholic beverage in the northern part of Nigeria, normally prepared from cereals. In this investigation Lactobacillus plantarum, isolated from fermenting kunun, was applied as starter culture during production of kunun-aya from varying combinations of sorghum and tigernut. The quality attributes of the product indicated increase in ash and protein contents of product inoculated with starter culture (PISC) over the uninoculated control sample (UCS). The highest values of 4.43% and 6.95% were recorded for ash and protein, respectively, in the product from fifty percent each of sorghum and tigernut (50SOR/50TIG). Titratable acidity was higher in PISC compared to UCS; the 50SOR/50TIG sample had the highest value of 0.92. The PISC recorded reduced counts of Salmonella, coliforms, and Staphylococci. The SCIS were preferred by panellists in the sensory attributes of appearance, aroma, taste, mouthfeel, and general acceptability. It was concluded that the use of L. plantarum as starter culture in the production of kunun-aya was advantageous as a result of enhanced nutritional, sensory, and microbial qualities recorded compared to UCS. Reduction in Salmonella, coliforms, and Staphylococci in PISC may be of public health significance. This on quality improvement of the traditional beverage has not been previously reported.

Composition and Metabolic Activities of the Bacterial Community in Shrimp Sauce at the Flavor-Forming Stage of Fermentation As Revealed by Metatranscriptome and 16S rRNA Gene Sequencings

The bacterial community and the metabolic activities involved at the flavor-forming stage during the fermentation of shrimp sauce were investigated using metatranscriptome and 16S rRNA gene sequencings. Results showed that the abundance of Tetragenococcus was 95.1%. Tetragenococcus halophilus was identified in 520 of 588 transcripts annotated in the Nr database. Activation of the citrate cycle and oxidative phosphorylation, along with the absence of lactate dehydrogenase gene expression, in T. halophilus suggests that T. halophilus probably underwent aerobic metabolism during shrimp sauce fermentation. The metabolism of amino acids, production of peptidase, and degradation of limonene and pinene were very active in T. halophilus. Carnobacterium, Pseudomonas, Escherichia, Staphylococcus, Bacillus, and Clostridium were also metabolically active, although present in very small populations. Enterococcus, Abiotrophia, Streptococcus, and Lactobacillus were detected in metatranscriptome sequencing, but not in 16S rRNA gene sequencing. Many minor taxa showed no gene expression, suggesting that they were in dormant status.

Review: Diversity of Microorganisms in Global Fermented Foods and Beverages

Culturalable and non-culturable microorganisms naturally ferment majority of global fermented foods and beverages. Traditional food fermentation represents an extremely valuable cultural heritage in most regions, and harbors a huge genetic potential of valuable but hitherto undiscovered strains. Holistic approaches for identification and complete profiling of both culturalable and non-culturable microorganisms in global fermented foods are of interest to food microbiologists. The application of culture-independent technique has thrown new light on the diversity of a number of hitherto unknown and non-cultural microorganisms in naturally fermented foods. Functional bacterial groups ("phylotypes") may be reflected by their mRNA expression in a particular substrate and not by mere DNA-level detection. An attempt has been made to review the microbiology of some fermented foods and alcoholic beverages of the world.

Lactobacillus formosensis sp. nov., a lactic acid bacterium isolated from fermented soybean meal

A Gram-reaction-positive, catalase-negative, facultatively anaerobic, rod-shaped lactic acid bacterium, designated strain S215(T), was isolated from fermented soybean meal. The organism produced d-lactic acid from glucose without gas formation. 16S rRNA gene sequencing results showed that strain S215(T) had 98.74-99.60 % sequence similarity to the type strains of three species of the genus Lactobacillus (Lactobacillus farciminis BCRC 14043(T), Lactobacillus futsaii BCRC 80278(T) and Lactobacillus crustorum JCM 15951(T)). A comparison of two housekeeping genes, rpoA and pheS, revealed that strain S215(T) was well separated from the reference strains of species of the genus Lactobacillus. DNA-DNA hybridization results indicated that strain S215(T) had DNA related to the three type strains of species of the genus Lactobacillus (33-66 % relatedness). The DNA G+C content of strain S215(T) was 36.2 mol%. The cell walls contained peptidoglycan of the d-meso-diaminopimelic acid type and the major fatty acids were C18 : 1ω9c, C16 : 0 and C19 : 0 cyclo ω10c/C19 : 1ω6c. Phenotypic and genotypic features demonstrated that the isolate represents a novel species of the genus Lactobacillus, for which the name Lactobacillus formosensis sp. nov. is proposed. The type strain is S215(T) ( = NBRC 109509(T) = BCRC 80582(T)).

Fermented fruits and vegetables of Asia: a potential source of probiotics

As world population increases, lactic acid fermentation is expected to become an important role in preserving fresh vegetables, fruits, and other food items for feeding humanity in developing countries. However, several fermented fruits and vegetables products (Sauerkraut, Kimchi, Gundruk, Khalpi, Sinki, etc.) have a long history in human nutrition from ancient ages and are associated with the several social aspects of different communities. Among the food items, fruits and vegetables are easily perishable commodities due to their high water activity and nutritive values. These conditions are more critical in tropical and subtropical countries which favour the growth of spoilage causing microorganisms. Lactic acid fermentation increases shelf life of fruits and vegetables and also enhances several beneficial properties, including nutritive value and flavours, and reduces toxicity. Fermented fruits and vegetables can be used as a potential source of probiotics as they harbour several lactic acid bacteria such as Lactobacillus plantarum, L. pentosus, L. brevis, L. acidophilus, L. fermentum, Leuconostoc fallax, and L. mesenteroides. As a whole, the traditionally fermented fruits and vegetables not only serve as food supplements but also attribute towards health benefits. This review aims to describe some important Asian fermented fruits and vegetables and their significance as a potential source of probiotics.

Lactococcus formosensis sp. nov., a lactic acid bacterium isolated from yan-tsai-shin (fermented broccoli stems)

A coccal-shaped organism, designated 516T, was isolated from yan-tsai-shin (fermented broccoli stems), a traditional fermented food in Taiwan. 16S rRNA gene sequencing results showed that strain 516T had 98.9 % sequence similarity to that of the type strain Lactococcus garvieae NBRC 100934T. Comparison of three housekeeping genes, rpoA, rpoB and pheS, revealed that strain 516T was well separated from Lactococcus garvieae NBRC 100934T. DNA–DNA hybridization studies indicated that strain 516T had low DNA relatedness with Lactococcus garvieae NBRC 100934T (46.1 %). The DNA G+C content of strain 516T was 38.1 mol% and the major fatty acids were C16 : 0 (22.7 %), C19 : 0 cyclo ω8c (17.9 %) and summed feature 7 (29.0 %). Based on the evidence, strain 516T represents a novel species of the genus Lactococcus , for which the name Lactococcus formosensis sp. nov. is proposed. The type strain is 516T ( = NBRC 109475T = BCRC 80576T).

Enterococcus saccharolyticus subsp. taiwanensis subsp. nov., isolated from broccoli

A coccal strain isolated from fresh broccoli was initially identified as Enterococcus saccharolyticus ; however, molecular identification and phenotypic traits did not support this identification. DNA–DNA hybridization with the type strain of E. saccharolyticus (76.4 % relatedness), DNA G+C content (35.7 mol%), phylogenetic analysis based on 16S rRNA, pheS and rpoA gene sequences, rep-PCR fingerprinting and profiles of cellular fatty acids, whole-cell proteins and enzyme activities, together with carbohydrate metabolism characteristics, indicated that this strain is distinct and represents a novel subspecies, for which the name Enterococcus saccharolyticus subsp. taiwanensis subsp. nov. is proposed. The type strain is 812T ( = NBRC 109476T = BCRC 80575T). Furthermore, we present an emended description of Enterococcus saccharolyticus and proposal of Enterococcus saccharolyticus subsp. saccharolyticus subsp. nov. (type strain ATCC 43076T = CCUG 27643T = CCUG 33311T = CIP 103246T = DSM 20726T = JCM 8734T = LMG 11427T = NBRC 100493T = NCIMB 702594T).

Lactococcus taiwanensis sp. nov., a lactic acid bacterium isolated from fresh cummingcordia

One coccal strain, designated 0905C15T, was isolated from fresh cummingcordia, which is the main ingredient of pobuzihi (fermented cummingcordia), a traditional fermented food in Taiwan. 16S rRNA gene sequencing results showed that strain 0905C15T had 98.22–98.82 % sequence similarity to that of the type strains of four Lactococcus lactis subspecies ( L. lactis subsp. lactis BCRC 12312T, L. lactis subsp. cremoris BCRC 12586T, L. lactis subsp. hordniae BCRC 80474T and L. lactis subsp. tructae BCRC 80475T). Comparison of two housekeeping genes, recA and rpoB, revealed that strain 0905C15T was well separated from the reference strains of the genus Lactococcus . DNA–DNA hybridization studies indicated that strain 0905C15T had low DNA relatedness to the four Lactococcus lactis subspecies (9.7–15.24 %). The DNA G+C content of strain 0905C15T was 39.6 mol %. Based on the evidence, strain 0905C15T represents a novel species of the genus Lactococcus , for which the name Lactococcus taiwanensis sp. nov. is proposed. The type strain is 0905C15T ( = NBRC 109049T = BCRC 80460T).

Isolation and characterisation of lactic acid bacteria from jiang-gua (fermented cucumbers), a traditional fermented food in Taiwan

BACKGROUND

Jiang-gua (fermented cucumbers) is a popular traditional fermented food in Taiwan. The microflora of lactic acid bacteria (LAB) in jiang-gua have not been investigated in detail. In this study, LAB from jiang-gua were isolated, characterised and identified.

RESULTS

A total of 103 LAB were isolated; 70 cultures were isolated from jiang-gua samples and 33 cultures were isolated from its raw substrate, cucumber. These isolates were mainly characterised phenotypically and then divided into seven groups (A-G) by restriction fragment length polymorphism analysis and sequencing of 16S ribosomal DNA. The isolates were identified as Enterococcus casseliflavus, Leuconostoc lactis, Leuconostoc mesenteroides, Lactobacillus pentosus, Lactobacillus plantarum, Lactobacillus paraplantarum, Lactococcus lactis subsp. lactis, Weissella cibaria and Weissella hellenica. The antibacterial activities of the isolates were determined and 11 Lc. lactis subsp. lactis strains showed inhibitory activity against the indicator strain Lactobacillus sakei JCM 1157(T) .

CONCLUSION

Heterofermentative W. cibaria and Leu. lactis were the major LAB found in jiang-gua samples without soy sauce. In soy sauce-added samples, homofermentative L. pentosus and L. plantarum were the most abundant LAB. In addition, the results also suggested that HhaI and RsaI restriction enzymes could be applied to distinguish W. hellenica and Weissella paramesenteroides.

Diversity of lactic acid bacteria in sian-sianzih (fermented clams), a traditional fermented food in Taiwan

BACKGROUND

Sian-sianzih (fermented clams) is a popular traditional fermented food in Taiwan. The lactic acid bacteria (LAB) microflora in sian-sianzih have not been studied in detail. In this study, LAB from sian-sianzih were isolated, characterized and identified.

RESULTS

A total of 186 cultures of LAB were isolated from seven sian-sianzih samples and 29 cultures were isolated from its main raw substrate: clams. The identification results revealed up to 11 distinct bacterial species belonging to five genera in sian-sianzih, and three species belonging to two genera in clams. The most common bacterial genera in sian-sianzih were Lactobacillus and Weissella, followed by Leuconostoc, Pediococcus and Lactococcus. A regional similarity in LAB, with differences in diversity, was observed in the current study. On the other hand, Lactococcus lactis subsp. lactis was the most common species found in raw clam samples. The results also suggested that greater LAB diversity could be observed in wild clams than in cultured ones. Furthermore, antibacterial activities of the isolates were determined, and one Weisella hellenica strain showed inhibitory activity against the indicator strain Lactobacilluas sakei JCM 1157(T) . A sensory assessment of seven sian-sianzih samples was also performed and the results indicated that diversity of LAB has a great effect on its aroma and taste formation.

CONCLUSION

The results demonstrate that various LAB species are distributed in sian-sianzih and have a great effect on the flavor of sian-sianzih.

Isolation and characterisation of lactic acid bacteria from yan-jiang (fermented ginger), a traditional fermented food in Taiwan

BACKGROUND

Yan-jiang (fermented ginger) is a popular traditional fermented food in Taiwan. The lactic acid bacteria (LAB) microflora in yan-jiang has not been studied in detail. In this study, LAB from yan-jiang were isolated, characterised and identified.

RESULTS

A total of 176 LAB were isolated; 160 cultures were isolated from yan-jiang samples and 16 cultures were isolated from raw ginger. These isolates were characterised phenotypically and then divided into nine groups (A to I) by restriction fragment length polymorphism analysis and sequencing of 16S ribosomal DNA. Lactobacillus sakei and Lactococcus lactis subsp. lactis were the major LAB found in the initial 2 days of fermentation without pickled plums; these species were mostly replaced by Weissella cibaria and L. plantarum after 3 days of fermentation. In the fermentation bucket with added pickled plums, W. cibaria was the most abundant LAB found during fermentation. The antibacterial activities of the isolates were determined. Twenty-four Lc. lactis subsp. lactis and 19 W. cibaria strains showed inhibitory activity against the indicator strain L. sakei JCM 1157(T) .

CONCLUSION

Results demonstrate that various LAB species were more numerous when fermentation was carried out without pickled plums. LAB also had effects on the aroma and flavour of yan-jiang.

Characterization of Tetragenococcus strains from sugar thick juice reveals a novel species, Tetragenococcus osmophilus sp. nov., and divides Tetragenococcus halophilus into two subspecies, T. halophilus subsp. halophilus subsp. nov. and T. halophilus subsp. flandriensis subsp. nov

Most bacteria recovered so far from sugar thick juice during storage represent strains of the species Tetragenococcus halophilus. Recently, several Gram-positive, non-motile, non-spore-forming cocci with other physiological and genetic traits were isolated from sugar thick juice samples from different origins. In this study, representative isolates were investigated using a polyphasic taxonomic approach. The 16S rRNA gene sequence similarity between these isolates and their closest relative, Tetragenococcus muriaticus, was 97.4%. The level of DNA-DNA relatedness between isolate T1(T), representing the newly found Tetragenococcus isolates, and T. muriaticus was 57%. Isolate T1(T) had a DNA G+C content of 36.7 mol%. Phylogenetic data and genomic and phenotypic features demonstrated that the isolates represent a novel species, for which the name Tetragenococcus osmophilus sp. nov. is proposed with T1(T) as the type strain (=LMG 26041(T) =DSM 23765(T)). Additionally, T. halophilus isolates from high-salt and high-sugar environments showed clear differences in several physiological and genetic characteristics like RAPD fingerprints and 16S rRNA gene sequences. DNA-DNA hybridizations, however, showed 79 to 80% relatedness between osmophilic and halophilic T. halophilus isolates, demonstrating that the different strains belong to the same species. Based on the phenotypic and genotypic differences observed, as well as the different origins of the strains and the industrial relevance of thick juice degradation, two subspecies of T. halophilus are described in this manuscript: T. halophilus subsp. halophilus subsp. nov. for the strains isolated from salt media and T. halophilus subsp. flandriensis subsp. nov. for the strains isolated from sugar-rich environments, which were first isolated in Flanders, Belgium. The type strains for the subspecies are IAM 1676(T) (=LMG 11490(T) =DSM 20339(T)) and T5(T) (=LMG 26042(T) =DSM 23766(T)), respectively.

Isolation and characterization of lactic acid bacteria from jiang-sun (fermented bamboo shoots), a traditional fermented food in Taiwan

BACKGROUND

In this study, lactic acid bacteria (LAB) were isolated, characterized and identified from jiang-sun (fermented bamboo shoots; a traditional fermented food in Taiwan). Samples were collected at seven time intervals from a fixed fermenting bucket during the fermentation process of jiang-sun and its initial ingredients, dochi (fermented soybeans) and bamboo shoots.

RESULTS

A total of 57 LAB cultures were isolated; 42 cultures were isolated from jiang-sun samples and 15 cultures were isolated from dochi and bamboo shoots. These isolates were characterized phenotypically and then divided into three groups (A-C) by restriction fragment length polymorphism analysis and sequencing of 16S ribosomal DNA. Alteration of microbial populations during the fermentation process was observed. While various LAB were found in the dochi and bamboo shoots, it was mostly replaced by Lactobacillus plantarum after 1 day of fermentation. Furthermore, the antibacterial activities of the isolates were determined, and one Enterococcus faecium strain showed inhibitory activity against all the indicator strains.

CONCLUSION

Results suggest that L. plantarum is the main LAB present during the fermentation of jiang-sun. To our knowledge, this is the first report describing the distribution and varieties of LAB that exist in the jiang-sun fermentation process.

Lactobacillus pobuzihii sp. nov., isolated from pobuzihi (fermented cummingcordia)

Twenty-one homofermentative lactic acid bacteria were isolated from fermented cummingcordia (pobuzihi), a traditional food in Taiwan. The isolates had identical 16S rRNA gene sequences that were distinct from those of other lactobacilli, and their closest neighbours in the 16S rRNA gene sequence phylogenetic tree were strains of Lactobacillus acidipiscis. Levels of DNA–DNA relatedness between representative pobuzihi isolates and strains of L. acidipiscis were 17 % and below. Furthermore, the new isolates could be differentiated clearly from L. acidipiscis NBRC 102163T and NBRC 102164 in terms of acid production from l-arabinose, rhamnose, mannitol, lactose and 5-ketogluconate. It was concluded that the new isolates represent a single novel species of the genus Lactobacillus, for which the name Lactobacillus pobuzihii sp. nov. is proposed. The type strain is E100301T (=RIFY 6501T =NBRC 103219T =KCTC 13174T).

Identification of lactic acid bacteria associated with the production of plaa-som, a traditional fermented fish product of Thailand

Plaa-som is a Thai fermented fish product for which whole fish or fish fillets are fermented with either cooked rice or steamed sticky rice, salt, and garlic. A total of 762 lactic acid bacteria (LAB) were isolated during plaa-som fermentation by culture on CaCO(3)-MRS agar plates. They were screened and grouped by amplified ribosomal DNA restriction analysis (ARDRA), giving six groups that were identified by ribosomal DNA sequencing as Lactococcus garvieae, Streptococcus bovis, Weissella cibaria, Pediococcus pentosaceus, Lactobacillus plantarum, and Lactobacillus fermentum. Freshly mixed ingredients contained low populations of LAB (less than 10 CFU/g) that subsequently grew during fermentation to final populations of approximately 10(7)CFU/g. Early stages of the process were dominated by the presence of Lc. garvieae, S. bovis, and W. cibaria. At 48 h into fermentation, W. cibaria, P. pentosaceus, and Lb. plantarum were prevalent, and gave way to a dominance of Lb. plantarum that completed the fermentation. A mixture of these LAB species could be considered as species for development of a starter culture for plaa-som fermentation.

Protective effect of hop ?-acids on microbial degradation of thick juice during storage

AIMS

This study assessed the value of a commercial alkaline solution of hop beta-acids (HBA) for prevention of microbial degradation of thick juice, a concentrated intermediate product in the production of beet sugar.

METHODS AND RESULTS

The antimicrobial effect of different concentrations of HBA against microbial degradation of thick juice was tested in a pilot-scale storage experiment. Chemical, biochemical and microbial parameters were monitored during thick juice storage. Thick juice degradation, indicated as a decrease in pH, was generally accompanied by an increase in the count of fastidious bacteria (FB) on Columbia Agar with Sheep Blood (CAwSB), which were mainly identified as Tetragenococcus halophilus. Addition of HBA delayed juice acidification and the development of FB in a concentration-dependent manner. The susceptibility of FB to HBA was determined by plating degraded thick juice (FB > 10(5) CFU ml(-1) on CAwSB plates with different concentrations of HBA (0-160 ppm). None of the HBA concentrations tested reduced the number of FB colonies formed, but increasing HBA concentrations extended the lag time of colony formation.

CONCLUSIONS

HBA produce no measurable bactericidal effect, but retard the development of FB in thick juice. Moreover, HBA do not prevent the thick juice from deteriorating, but significantly delay its degradation.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results indicate that adding a commercially available HBA formulation can prolong the storage life of thick juice in the sugar industry, although degradation cannot be eliminated. Future research will focus on the detailed characterization of FB consistently isolated from degraded thick juice and on determining their role in thick juice degradation.