Novel Leuconostoc citreum starter culture system for the fermentation of kimchi, a fermented cabbage product

Leuconostoc citreum: A Promising Sourdough Fermenting Starter for Low-Sugar-Content Baked Goods

This review highlights Leuconostoc citreum's promising possibilities as a proficient mannitol producer and its potential implications for sugar reduction, with a focus on its use in sourdough-based baked good products. Mannitol, a naturally occurring sugar alcohol, has gained popularity in food items due to its low calorie content and unique beneficial qualities. This study summarizes recent research findings and investigates the metabolic pathways and culture conditions that favor increased mannitol production by Leuconostoc citreum. Furthermore, it investigates the several applications of mannitol in baked goods, such as its function in increasing texture, flavor and shelf life while lowering the sugar content. Sourdough-based products provide an attractive niche for mannitol integration, as customer demand for healthier and reduced-sugar options increases.

Isolation and Identification of Lactic Acid Bacteria and Their Effects on the Off-odor of Burdocks

Burdocks have diverse nutritional and pharmacological functions, but their unique odor is unwelcome. Here, the effect and mechanism of lactic acid bacteria fermentation on the off-odor of burdocks were investigated. The sensory evaluation showed that burdocks had earthy, musty, grassy, and pepper odors. 2-Isobutyl-3-methoxypyrazine (IBMP) and 2-secbutyl-3-methoxypyrazine (IPMP) mainly contributed to burdock's unique off-odor and were identified by gas chromatography-mass spectrometry combined with headspace-solid phase microextraction (HS-SPME-GC-MS) and relative odor activity value (ROAV) analysis. Weissella cibaria ZJ-5 from screened strains performed with the strongest ability to remove the off-odor and generate a fragrant odor, as determined by sensory evaluation. When incubated aerobically together with IBMP during fermentation, ZJ-5 degraded IBMP directly from 149.56 ± 0.72 to 71.55 ± 1.81 ng/mL. Additionally, linoleic acid content in fermented burdocks was significantly decreased compared with unfermented burdocks. (E,Z)-2,6-Nonadienal, which mainly contributed to fermented burdock's odor, may have been generated from linoleic acid during ZJ-5 fermentation, through the acid catalysis pathway. It indicated that LAB fermentation could improve burdock odor by degrading off-odor compounds and precursors and by generating new aldehydes.

Lactic Acid Bacteria-Fermentable Cereal- and Pseudocereal-Based Beverages

Plant beverages are becoming more popular, and fermented cereal- or pseudocereal-based beverages are increasingly used as alternatives for fermented products made from cow milk. This review aimed to describe the basic components of cereal- or pseudocereal-based beverages and determine the feasibility of fermenting them with lactic acid bacteria (LAB) to obtain products with live and active LAB cells and increased dietary value. The technology used for obtaining cereal- or pseudocereal-based milk substitutes primarily involves the extraction of selected plant material, and the obtained beverages differ in their chemical composition and nutritional value (content of proteins, lipids, and carbohydrates, glycemic index, etc.) due to the chemical diversity of the cereal and pseudocereal raw materials and the operations used for their production. Beverages made from cereals or pseudocereals are an excellent matrix for the growth of LAB, and the lactic acid fermentation not only produces desirable changes in the flavor of fermented beverages and the biological availability of nutrients but also contributes to the formation of functional compounds (e.g., B vitamins).

Impact of Blanching, Freezing, and Fermentation on Physicochemical, Microbial, and Sensory Quality of Sugar Kelp (Saccharina latissima)

Low seaweed consumption in the West is due to lack of availability and consumer familiarity. In this study, the effects of preservation processes on quality aspects of Saccharina latissima products were assessed. First, a blanching (100 °C for 1 or 3 min) treatment was used to produce seaweed salad. In a second study, effects of blanching, freezing, and fermentation on kelp quality were assessed and processed kelp was used to produce sauerkraut. Blanching significantly decreased (p ≤ 0.05) the instrumental kelp a* value and firmness. The a* value negatively correlated with overall liking of salads. To prepare sauerkraut, raw, raw/frozen (-20 °C), blanched (100 °C, 1 min), or blanched/frozen kelp were mixed with cabbage, salted, inoculated with starter cultures and fermented. Inconsistent trends in L* values, firmness, and fungi enumeration were observed after fermentation. Consumers evaluated kelp salad (n = 100) and sauerkraut (n = 80) for acceptability. Blanched kelp salad had higher hedonic scores than raw kelp salad. A 100% cabbage sauerkraut control and blanched kelp/cabbage blends were compared; kelp blends were similar to control for appearance, color, and texture but were lower for overall acceptability. Results suggest improved quality and enhanced consumer acceptability of seaweed products with use of minimal processing.

Characterization of the Psychrotrophic Lactic Acid Bacterium Leuconostoc gelidum subsp. aenigmaticum LS4 Isolated from Kimchi Based on Comparative Analyses of Its Genomic and Phenotypic Properties

With the aim of developing a new food starter culture, twenty-three psychrotrophic lactic acid bacteria (LAB) were isolated from 16 kimchi samples. One strain, Leuconostoc gelidum subsp. aenigmaticum LS4, which had typical psychrotrophic characteristics, was selected, and its phenotypic and genomic properties as a starter culture were investigated. The complete genome of L. aenigmaticum LS4 consisted of one circular chromosome (1,988,425 bp) and two plasmids (19,308 bp and 11,283 bp), with a guanine–cytosine content of 36.8%. L. aenigmaticum LS4 could grow at 5 °C but not at 37 °C, and maximum cell growth was obtained at 15~25 °C. L. aenigmaticum LS4 did not show any harmful characteristics such as hemolysis, undesirable enzyme activities, biogenic amine production, or antibiotic resistance. L. aenigmaticum LS4 was investigated for its suitability for technological processes (pH, temperature and NaCl treatment). L. aenigmaticum LS4 exhibited strong antimicrobial activity caused by the production of organic acids and bacteriocin, and it produced an exopolysaccharide composed of glucose with a molecular weight of 3.7 × 10⁶ Da. Furthermore, L. aenigmaticum LS4 improved the organoleptic qualities of kimchi juice. Our results indicate that L. aenigmaticum LS4 could be used as a functional starter culture for food (vegetable or fruit) fermentation at low temperatures.

Microbial characterization of the Japanese traditional pickle senmaizuke produced by two different manufacturing processes

Senmaizuke, a traditional turnip pickle, prepared in Kyoto, Japan, is produced via two types of manufacturing processes: with and without vinegar for fermentation. The aim of this study was to reveal the microbial community and growth behavior in the products and manufacturing processes of two types of senmaizuke. Microbial growth analysis of commercial senmaizuke products showed that both types harbored 102-108 colony forming units (CFU)/g of lactic acid bacteria (LAB) and 102-104 of yeast. The fermented-type products showed successive growth of LAB during the pickling and ripening processes, whereas LAB in vinegar-type products showed growth only at the preliminary pickling step before vinegar addition; however, the bacteria were viable at the ripening step. LAB in the vinegar-type products showed growth when the pH of the pickle was neutralized, indicating that acidification via vinegar retards LAB growth. Metagenomic sequencing showed that the fermented-type products harbored Lactobacillus, Leuconostoc, and other halophilic and psychrophilic bacteria, with a higher bacterial diversity than in the vinegar-type products. In the vinegar-type products, Lactobacillus, Leuconostoc, or both were predominant. Culture tests using LAB isolates and turnip medium suggested that a change in the dominance of Leuconostoc to Lactobacillus members observed in the fermented-type products during pickling and ripening processes was attributed to the low pH sensitivity of Leuconostoc as well as a relatively long lag phase of growth for adapting to the pickling environment. The findings of this study will be useful for the appropriate quality control and assurance procedure of senmaizuke.

Selenium bio-enrichment of Mediterranean fruit juices through lactic acid fermentation

This work was carried out to elaborate selenium (Se) bio-enriched fermented Mediterranean fruit juices. To this purpose, pomegranate and table red grape juices were added with sodium selenite (Na₂SeO₃) and fermented by Levilactobacillus brevis CRL 2051 and Fructobacillus tropaeoli CRL 2034 individually or combined. To better evaluate the effect of selenite addition and starter strain inoculums on the total bacterial community of the fruit juices, fermentation trials were performed with raw and pasteurized fruit juices. No statistical significant differences were observed for total mesophilic microorganisms (TMM) and rod-shaped lactic acid bacteria (LAB) levels among raw and pasteurized juices inoculated with the starter strains, while significant differences between those juices with and without selenite were registered. LAB cocci, Pseudomonadaceae and yeasts were detected only for the raw juice preparations. The dominance of L. brevis CRL 2051 and F. tropaeoli CRL 2034 was confirmed by randomly amplified polymorphic DNA (RAPD)-PCR analysis. After fermentation, pH dropped for all inoculated trials and control raw juices. The soluble solid content (SSC) levels of the raw juices were higher than the corresponding pasteurized trials. The thermal treatment affected consistently yellowness of grape juice trials and redness of pomegranate juices. No microbial Se accumulation was registered for pomegranate juices, while F. tropaeoli CRL 2034 accumulated the highest amount of Se (65.5 μg/L) in the grape juice. For this reason, only trials carried out with raw grape juices were investigated by metagenomics analysis by Illumina MiSeq technology. Non-inoculated grape juices were massively fermented by acetic acid bacteria while Fructobacillus and Lactobacillus (previous genus name of Levilactobacillus) represented the highest operational taxonomy units (OTUs) relative abundance % of the trials inoculated with the starter strains as confirmed by this technique.

Fermentation as a tool for increasing food security and nutritional quality of indigenous African leafy vegetables: the case of Cucurbita sp

Sub-Saharan region is often characterized by food and nutrition insecurity especially "hidden hunger" which results from inadequate micronutrients in diets. African indigenous leafy vegetables (AILVs) can represent a valid food source of micronutrients, but they often go to waste resulting in post-harvest losses. In an attempt to prolong AILVs shelf-life while enhancing their nutritional quality, fermentation was studied from a microbiological and nutritional point of view. Pumpkin leaves (Cucurbita sp.) were spontaneously fermented using the submerged method with 3% NaCl and 3% sucrose. Controls were set up, consisting of leaves with no additions. During fermentation, samples of both treatments were taken at 0, 24, 48, 72 and 168 h to monitor pH and characterize the microbial population through culture-based and molecular-based analyses. Variations between fresh and treated leaves in B-group vitamins, carotenoids, polyphenols, and phytic acid were evaluated. Data revealed that the treatment with addition of NaCl and sucrose hindered the growth of undesired microorganisms; in controls, unwanted microorganisms dominated the bacterial community until 168 h, while in treated samples Lactobacillaceae predominated. Furthermore, the content in folate, β-carotene and lutein increased in treated leaves compared to the fresh ones, while phytic acid diminished indicating an amelioration in the nutritional value of the final product. Thus, fermentation could help in preserving Cucurbita sp. leaves, avoiding contamination of spoilage microorganisms and enhancing the nutritional values.

A new Leuconostoc citreum strain discovered in the traditional sweet potato sour liquid fermentation as a novel bioflocculant for highly efficient starch production

Sour liquid fermentation is commonly used in the sedimentation process of traditional starch production, where bacteria play a critical role in starch flocculation. In this study, the dynamic changes of bacterial compositions during sweet potato sour liquid (SPSL) fermentation were profiled using the single-molecule real-time (SMRT) sequencing, unveiling that Leuconostoc citreum, Leuconostoc pseudomesenteroides, Lactococcus lactis, and Lactobacillus plantarum were the dominant microorganisms in the process, and Leuconostoc citreum exhibited a strong positive correlation with starch flocculation rate (FR). In total, 75 lactic acid bacterial (LAB) strains were isolated from the SPSL, but only 7 of them caused starch flocculation. For the first time, Leuconostoc citreum strains were reported with excellent starch-flocculating abilities (up to 55.56% FR in 20 min), which might be attributed to their ability to connect starch granules through the cell surface to form large aggregation. This study provides a comprehensive understanding of the bacterial dynamics in SPSL fermentation at the species level. A starch flocculation yield of 93.63% was achieved within 1 h by using the newly discovered Leuconostoc citreum SJ-57. The time required for total starch sedimentation was reduced from 10 h to 4 h, compared with the traditional process. These results suggest that this novel bioflocculant is more suitable for modernizing the traditional SPSL fermentation process and achieving rapid and highly efficient starch sedimentation.

Levan from Leuconostoc citreum BD1707: production optimization and changes in molecular weight distribution during cultivation

Background

Levan is a well-known homopolymer of fructose composed predominantly of β-(2, 6) fructofuranosyl linkages in the backbone with occasional β-(2, 1) linkages in the branch chains with varied applications. However, high production cost due to low yield of microbial levan has become a bottleneck for its practical applications. Furthermore, factors affecting the molecular mass of the synthesized levan by Leuconostoc spp. during prolonged cultivation is not fully elucidated.

Methods

The cultivation condition for Leuconostoc citreum BD1707 to synthesize levan was optimized by single-factor experiments and subsequently with response surface methodology (RSM). The average molecular weight (Mw) of levan synthesized by the strain L.citreum BD1707 under the optimized cultivation conditions was monitored by high-performance size exclusion chromatography (HPSEC). Finally, the enzyme with levan-degrading activity was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).

Results

The levan yield of BD1707 reached 34.86 g/L with a corresponding productivity of 7.47 g/L/d under the optimal cultivation conditions deduced by RSM, i.e., cultivation at 26 °C and 200 rpm for 112 h in tomato juice supplemented with 172 g/L sucrose with an initial pH value of 6.12. The Mw of levan reached a peak value of 2.320 × 10⁷ Da at 6 h of cultivation under the optimized cultivation conditions and then gradually decreased to 8.809 × 10⁶ Da after 120 h of cultivation.

Conclusion

The levan yield of the strain L.citreum BD1707 could be sufficiently enhanced via cultivation condition optimization. The decrease in molecular mass of the synthesized levan was attributed predominantly to the hydrolytic activity of levansucrase secreted by L.citreum BD1707 during cultivation, with an estimated Mw of 130 KD by SDS-PAGE, while the effect of acid hydrolysis could be nearly neglected.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12896-021-00673-y.

Sichuan paocai fermented by mixed-starter culture of lactic acid bacteria

To satisfy the demand of industrial production, selecting strains suitable for fermentation initiation is necessary. In this study, the effects of mixed-starter culture including Leuconostoc, Lactobacillus, and Weissella on the quality of Sichuan pickle were discussed. Results showed that mixed-starter culture can accelerate fermentation and had the highest efficiency for nitrite degradation, that is, the maximum nitrite concentration was 8.97 g/kg on day 1 and decreased to 1.88 mg/kg after 3 days. The mixed-starter culture improved the sensory properties of pickles, which easily produced acids but had reduced amounts of total acids. The pickle products fermented by the mixed-starter culture contained increased lactic acid (17.52 g/kg), mannitol (0.62%), umami (35.85), and sweet (11.36) amino acids on day 4. The strains Weissella paramesenteroides C2-2 and Lactobacillus brevis ZP11-2 grew well in the mixed-starter culture fermentation.

Enzymatic Process Yielding a Diversity of Inulin-Type Microbial Fructooligosaccharides

The specificity of fructooligosaccharides as prebiotics depends on their size and structure, which in turn depend on their origin or the synthesis procedure. In this work we describe the application of an inulosucrase (IslA) from Leuconostoc citreum CW28 to produce high molecular weight inulin from sucrose alongside a commercial endoinulinase (Novozym 960) produced by Aspergillus niger for a simultaneous or sequential reaction to synthesize fructooligosaccharides (FOS). The simultaneous reaction resulted in a higher substrate conversion and a wide diversity of FOS when compared to the sequential reaction. A shotgun MS analysis of the commercial endoinulinase preparation surprisingly revealed an additional enzymatic activity: a fructosyltransferase, responsible for the synthesis of FOS from sucrose. Consequentially, the range of FOS obtained in reactions combining inulosucrase from Ln. citreum with the fructosyltransferase and endoinulinase from A. niger with sucrose as substrate may be extended and regulated.

Expanded cardboard waste sorting and occupational exposure to microbial species

Member states of the European Union have to maximize recycling. The current, Danish cardboard recycling system can be improved by increasing the kinds of cardboard products that can be recycled to include e.g. used beverage cartons and pizza boxes (i.e. an expanded cardboard fraction (ECF)). This study aims to obtain knowledge about exposure to airborne endotoxin and microorganisms at species level at different collection frequencies of ECF, and whether an increase in waste sorted fractions means that each waste fraction is collected less frequently. Bacterial and endotoxin concentrations were associated significantly with temperature inside the waste containers and endotoxin and fungal exposures with collection frequency. The concentration of fungi was highest at the truck back and for reduced collection frequencies. The geometric mean diameters of particles with bacteria were between 3.0 and 5.2 μm and with fungi between 3.8 μm and 6.0 μm. In total, 81 and 25 different bacterial and fungal species were found at the waste receiving plant, respectively. Work with ECF caused exposures to food-related microorganisms (e.g. Arthrobacter arilaitensis and Penicillium camemberti), potential pathogens (e.g. Bacillus cereus, Salmonella sp. and P. expansum), and commensal bacteria. Bacillus cereus and Salmonella were found in the particle size fraction often being swallowed. Workers collecting EFC will be at risk of being exposed to microbial species that normally are related to residual waste. It seems to be advisable with an EFC collection frequency shorter than eight weeks. However, introduction of new waste fractions has generally been associated with reduced collection frequencies.

Characterization of Diversity and Probiotic Efficiency of the Autochthonous Lactic Acid Bacteria in the Fermentation of Selected Raw Fruit and Vegetable Juices

The diversity of indigenous lactic acid bacteria (LAB) in fermented broccoli, cherry, ginger, white radish, and white-fleshed pitaya juices was analyzed using culture-independent and -dependent approaches. The major properties of selected probiotic strains, including dynamic variations in pH, viable cell counts, antibiotic resistance, bacterial adhesion to hydrophobic compounds, and survivability during simulated gastrointestinal transit, were investigated using broccoli as the fermentation substrate. In broccoli and ginger juices, the genus Lactobacillus occupied the dominant position (abundances of 79.0 and 30.3%, respectively); in cherry and radish juices, Weissella occupied the dominant position (abundances of 78.3 and 83.2%, respectively); and in pitaya juice, Streptococcus and Lactococcus occupied the dominant positions (52.2 and 37.0%, respectively). Leuconostoc mesenteroides, Weissella cibaria/soli/confusa, Enterococcus gallinarum/durans/hirae, Pediococcus pentosaceus, Bacillus coagulans, and Lactococcus garvieae/lactis subspecies were identified by partial 16S rRNA gene sequencing. In general, the selected autochthonous LAB isolates displayed no significant differences in comparison with commercial strains with regard to growth rates or acidification in fermented broccoli juice. Among all the isolates, L. mesenteroides B4-25 exhibited the highest antibiotic resistance profile (equal to that of L. plantarum CICC20265), and suitable adhesion properties (adhesion of 13.4 ± 5.2% ∼ 36.4 ± 3.2% and 21.6 ± 1.4% ∼ 69.6 ± 2.3% to ethyl acetate and xylene, respectively). Furthermore, P. pentosaceus Ca-4 and L. mesenteroides B-25 featured the highest survival rates (22.4 ± 2.6 and 21.2 ± 1.4%, respectively), after simulated gastrointestinal transit. These results indicated a high level of diversity among the autochthonous bacterial community in fermented fruit and vegetable juices, and demonstrated the potential of these candidate probiotics for applications in fermentation.

Quality characteristics of sauerkraut fermented by using a Lactobacillus paracasei starter culture grown in tofu whey

The quality parameters of sauerkraut fermented using Lactobacillus paracasei in terms of its lactic acid bacteria count, texture, colour and biochemical properties were studied. As a starter culture L. paracasei grown in tofu whey was used for sauerkraut fermentation. The experiments were planned using central composite rotatable design of response surface methodology for input variables – culture volume (ml), fermentation time (days) and salt concentration (g/100 g). The linear and interactive effect of variables on responses was understood by statistically significant (p < 0.01) second-order models. Amongst all the input variables culture volume was found to have an overwhelming effect over all the responses. There was a significant (p < 0.01) increase in the lactic acid bacteria count of finished product; it was less hard but there was a departure in colour from the traditional product. The optimized condition for sauerkraut fermentation in terms of culture volume (ml), fermentation time (day) and salt concentration (g/100 g) was 30 ml, 28 days and 1 g/100 g, respectively. It was also observed that phenolics content was better in starter culture sauerkraut over the one traditionally prepared.

Genome Sequence of Leuconostoc citreum DmW_111, Isolated from Wild Drosophila

Isolates of the lactic acid bacterium Leuconostoc citreum are a major part of fermentation processes, especially in Korean kimchi. Here, we present the genome of L. citreum DmW_111, isolated from wild Drosophila melanogaster; analysis of this genome will expand the diversity of genome sequences for non-Lactobacillus spp. isolated from D. melanogaster.

Health benefits of kimchi (Korean fermented vegetables) as a probiotic food

Kimchi is a traditional Korean food manufactured by fermenting vegetables with probiotic lactic acid bacteria (LAB). Many bacteria are involved in the fermentation of kimchi, but LAB become dominant while the putrefactive bacteria are suppressed during salting of baechu cabbage and the fermentation. The addition of other subingredients and formation of fermentation byproducts of LAB promote the fermentation process of LAB to eventually lead to eradication of putrefactive- and pathogenic bacteria, and also increase the functionalities of kimchi. Accordingly, kimchi can be considered a vegetable probiotic food that contributes health benefits in a similar manner as yogurt as a dairy probiotic food. Further, the major ingredients of kimchi are cruciferous vegetables; and other healthy functional foods such as garlic, ginger, red pepper powder, and so on are added to kimchi as subingredients. As all of these ingredients undergo fermentation by LAB, kimchi is regarded as a source of LAB; and the fermentative byproducts from the functional ingredients significantly boost its functionality. Because kimchi is both tasty and highly functional, it is typically served with steamed rice at every Korean meal. Health functionality of kimchi, based upon our research and that of other, includes anticancer, antiobesity, anticonstipation, colorectal health promotion, probiotic properties, cholesterol reduction, fibrolytic effect, antioxidative and antiaging properties, brain health promotion, immune promotion, and skin health promotion. In this review we describe the method of kimchi manufacture, fermentation, health functionalities of kimchi and the probiotic properties of its LAB.

Characterization of Lactic Acid Bacteria Isolated from Sauce-type Kimchi

This study was carried out to investigate the isolation and characterization of lactic acid bacteria (LAB) from naturally fermented sauce-type kimchi. Sauce-type kimchi was prepared with fresh, chopped ingredients (Korean cabbage, radish, garlic, ginger, green onion, and red pepper). The two isolated bacteria from sauce-type kimchi were identified as Pediococcus pentosaceus and Lactobacillus brevis by 16S rDNA sequencing and tentatively named Pediococcus sp. IJ-K1 and Lactobacillus sp. IJ-K2, respectively. Pediococcus sp. IJ-K1 was isolated from the early and middle fermentation stages of sauce-type kimchi whereas Lactobacillus sp. IJ-K2 was isolated from the late fermentation stage. The resistance of Pediococcus sp. IJ-K1 and Lactobacillus sp. IJ-K2 to artificial gastric and bile acids led to bacterial survival rates that were 100% and 84.21%, respectively.

Microbial succession and metabolite changes during fermentation of dongchimi, traditional Korean watery kimchi

Dongchimi, one of the most common types of watery kimchi in Korea, was prepared using radish and its pH values, microbial cell numbers, bacterial communities, and metabolites were monitored periodically to investigate the fermentation process of watery kimchi. The bacterial abundance increased quickly during the early fermentation period and the pH values concurrently decreased rapidly without any initial pH increase. After 15 days of fermentation, the bacterial abundance decreased rapidly with the increase of Saccharomyces abundance and then increased again with a decrease of Saccharomyces abundance after 40 days of fermentation, suggesting that bacteria and Saccharomyces have a direct antagonistic relationship. Finally, after 60 days of fermentation, a decrease in bacterial abundance and the growth of Candida were concurrently observed. Community analysis using pyrosequencing revealed that diverse genera such as Leuconostoc, Lactobacillus, Pseudomonas, Pantoea, and Weissella were present at initial fermentation (day 0), but Leuconostoc became predominant within only three days of fermentation and remained predominant until the end of fermentation (day 100). Metabolite analysis using (1)H NMR showed that the concentrations of free sugars (fructose and glucose) were very low during the early fermentation period, but their concentrations increased rapidly although lactate, mannitol, and acetate were produced. After 30 days of fermentation, quick consumption of free sugars and production of glycerol and ethanol were observed concurrently with the growth of Saccharomyces, levels of which might be considered for use as a potential indicator of dongchimi quality and fermentation time.

Bacterial community dynamics, lactic acid bacteria species diversity and metabolite kinetics of traditional Romanian vegetable fermentations

BACKGROUND

Artisanal vegetable fermentations are very popular in Eastern European countries. Fresh vegetables undergo a spontaneous fermentation in the presence of salt, which is mainly carried out by lactic acid bacteria (LAB).

RESULTS

Culture-dependent and culture-independent analyses of end-samples of various spontaneous vegetable fermentations carried out in houses of the Chiodju region (central Romania) revealed Lactobacillus plantarum and Lactobacillus brevis as the most frequently isolated LAB species. Leuconostoc mesenteroides and Leuconostoc citreum were also found. Furthermore, the community dynamics of spontaneous cauliflower and mixed-vegetable (green tomatoes, carrots and cauliflower) fermentations revealed three steps: an initial phase characterised by the presence of Enterobacteriaceae and a wide LAB species diversity, encompassing Weissella species; a second phase from day 3 onwards wherein L. citreum and Lb. brevis occurred; and a final phase characterised by the prevalence of Lb. brevis and Lb. plantarum. Metabolite target analysis revealed that glucose and fructose were mostly depleted at the end of fermentation. The main products of carbohydrate metabolism were lactic acid, acetic acid, ethanol and small amounts of mannitol, indicating heterolactate fermentation.

CONCLUSION

Given their prevalence at the end of vegetable fermentations, Lb. brevis and Lb. plantarum appear to be good candidate starter cultures for controlled vegetable fermentation processes.

Novel Podoviridae family bacteriophage infecting Weissella cibaria isolated from Kimchi

The first complete genome sequence of a phage infecting Weissella cibaria (Weissella kimchii) is presented. The bacteriophage YS61 was isolated from kimchi, a Korean fermented vegetable dish. Bacteriophages are recognized as a serious problem in industrial fermentations; however, YS61 differed from many virulent phages associated with food fermentations since it was difficult to propagate and was very susceptible to resistance development. Sequence analysis revealed that YS61 resembles Podoviridae of the subfamily Picovirinae. Within the subfamily Picovirinae, the 29-like phages have been extensively studied, and their terminal protein-primed DNA replication is well characterized. Our data strongly suggest that YS61 also replicates by a protein-primed mechanism. Weissella phage YS61 is, however, markedly different from members of the Picovirinae with respect to genome size and morphology. Picovirinae are characterized by small (approximately 20-kb) genomes which contrasts with the 33,594-bp genome of YS61. Based on electron microscopy analysis, YS61 was classified as a member of the Podoviridae of morphotype C2, similar to the 29-like phages, but its capsid dimensions are significantly larger than those reported for these phages. The novelty of YS61 was also emphasized by the low number of open reading frames (ORFs) showing significant similarity to database sequences. We propose that the bacteriophage YS61 should represent a new subfamily within the family Podoviridae.

Genome sequences of three Leuconostoc citreum strains, LBAE C10, LBAE C11, and LBAE E16, isolated from wheat sourdoughs

Leuconostoc citreum is a key microorganism in fermented foods of plant origin. Here we report the draft genome sequence for three strains of Leuconostoc citreum, LBAE C10, LBAE C11, and LBAE E16, which have been isolated from traditional French wheat sourdoughs.

Effects of Leuconostoc mesenteroides starter cultures on microbial communities and metabolites during kimchi fermentation

Kimchi fermentation usually relies upon the growth of naturally-occurring various heterofermentative lactic acid bacteria (LAB). This sometimes makes it difficult to produce kimchi with uniform quality. The use of Leuconostoc mesenteroides as a starter has been considered to produce commercial fermented kimchi with uniform and good quality in Korea. In this study, a combination of a barcoded pyrosequencing strategy and a (1)H NMR technique was used to investigate the effects of Leu. mesenteroides strain B1 as a starter culture for kimchi fermentation. Baechu (Chinese cabbage) and Chonggak (radish) kimchi with and without Leu. mesenteroides inoculation were prepared, respectively and their characteristics that included pH, cell number, bacterial community, and metabolites were monitored periodically for 40 days. Barcoded pyrosequencing analysis showed that the numbers of bacterial operational taxonomic units (OTU) in starter kimchi decreased more quickly than that in non-starter kimchi. Members of the genera Leuconostoc, Lactobacillus, and Weissella were dominant LAB regardless of the kimchi type or starter inoculation. Among the three genera, Leuconostoc was the most abundant, followed by Lactobacillus and Weissella. The use of Leu. mesenteroides as a starter increased the Leuconostoc proportions and decreased the Lactobacillus proportions in both type of kimchi during kimchi fermentation. However, interestingly, the use of the kimchi starter more highly maintained the Weissella proportions of starter kimchi compared to that in the non-starter kimchi until fermentation was complete. Metabolite analysis using the (1)H NMR technique showed that both Baechu and Chonggak kimchi with the starter culture began to consume free sugars earlier and produced a little greater amounts of lactic and acetic acids and mannitol. Metabolite analysis demonstrated that kimchi fermentation using Leu. mesenteroides as a starter was completed earlier with more production of kimchi metabolites compared to that not using a starter, which coincided with the decreases in pH and the increases in bacterial cell number. The PCA strategy using all kimchi components including carbohydrates, amino acids, organic acids, and others also showed that starter kimchi fermented faster with more organic acid and mannitol production. In conclusion, the combination of the barcoded pyrosequencing strategy and the (1)H NMR technique was used to effectively monitor microbial succession and metabolite production and allowed for a greater understanding of the relationships between the microbial community and metabolite production in kimchi fermentation.

Genome analysis of food grade lactic Acid-producing bacteria: from basics to applications

Whole-genome sequencing has revolutionized and accelerated scientific research that aims to study the genetics, biochemistry and molecular biology of bacteria. Lactic acid-producing bacteria, which include lactic acid bacteria (LAB) and bifidobacteria, are typically Gram-positive, catalase-negative organisms, which occupy a wide range of natural plant- and animal-associated environments. LAB species are frequently involved in the transformation of perishable raw materials into more stable, pleasant, palatable and safe fermented food products. LAB and bifidobacteria are also found among the resident microbiota of the gastrointestinal and/or genitourinary tracts of vertebrates, where they are believed to exert health-promoting effects. At present, the genomes of more than 20 LAB and bifidobacterial species have been completely sequenced. Their genome content reflects its specific metabolism, physiology, biosynthetic capabilities, and adaptability to varying conditions and environments. The typical LAB/bifidobacterial genome is relatively small (from 1.7 to 3.3 Mb) and thus harbors a limited assortment of genes (from around 1,600 to over 3,000). These small genomes code for a broad array of transporters for efficient carbon and nitrogen assimilation from the nutritionally-rich niches they usually inhabit, and specify a rather limited range of biosynthetic and degrading capabilities. The variation in the number of genes suggests that the genome evolution of each of these bacterial groups involved the processes of extensive gene loss from their particular ancestor, diversification of certain common biological activities through gene duplication, and acquisition of key functions via horizontal gene transfer. The availability of genome sequences is expected to revolutionize the exploitation of the metabolic potential of LAB and bifidobacteria, improving their use in bioprocessing and their utilization in biotechnological and health-related applications.

Improvements in the quality and shelf life of kimchi by fermentation with the induced bacteriocin-producing strain, Leuconostoc citreum GJ7 as a starter

To improve the quality and self-life of kimchi, the induced bacteriocin-producing lactic acid bacteria (LAB), Leuconostoc citreum GJ7, was introduced into kimchi fermentation as a starter. The kimchi preparations were incubated at 7 degrees C for 12 to 15 d, and then stored at -1 degrees C. Thereafter, changes in their characteristics were monitored for 125 d. When a kimchi starter was introduced into a nonsterile and open kimchi fermentation system, over-ripening of kimchi was prevented during 125 d of storage. In the starter kimchi, Leuc. citreum GJ7 was the dominant organism, comprising 70% to 90% of the total flora, and no yeasts were detected during the entire storage period. However, in the nonstarter kimchi, the predominant LAB could not be determined and yeasts were detected after 50 d of storage. The viable cell number of the starter kimchi was 2 log CFU/mL higher than in the nonstarter kimchi at 125 d of storage. The texture (firmness) of the starter kimchi at 95 to 125 d of storage was similar to that of the nonstarter kimchi at 20 d of storage. Sensory evaluations of texture, off-flavor, and carbonated mouthfeel were significantly improved by the starter-fermentation. The results indicate that the application of the bacteriocin-enhanced Leuc. citreum GJ7 as a starter culture exerts microbial control, prevents over-ripening, and extends the shelf life of kimchi.

PRACTICAL APPLICATION

Presently, we have shown that under the optimum fermentation condition the induced bacteriocin-producing LAB, Leuc. citreum GJ7, can regulate natural kimchi fermentation and has extended dominance within the microbial ecology of kimchi. The result is improved quality and shelf life of kimchi. Moreover, to control the growth of other microorganisms in open-fermentation and nonsterile conditions, this system may be usefully adapted for other food or environmental control systems.

New functional probiotic Lactobacillus sakei probio 65 alleviates atopic symptoms in the mouse

The purpose of this study was to investigate the improvement of allergic dermatitis in chemical allergen-induced mice by Lactobacillus sakei probio 65. L. sakei probio-65 was isolated from kimchi, a traditional Korean fermented food. This strain was resistant to gastric acidity, bile, and several antibiotics and possessed antimicrobial activity against several pathogenic microorganisms. To investigate whether the probiotic activity of L. sakei probio 65 was effective for treating allergic dermatitis, the organism was supplied to mice triggered by allergen (1-chloro-2,4-dinitrobenzene). Mice that received L. sakei probio 65 showed a more rapid recovery compared to control mice, as assessed by visual evaluation of the severity of allergic dermatitis and levels of immunoglobulin (Ig) E and interleukin (IL)-4. L. sakei probio 65 exhibited good probiotic properties in vitro and in mice and was effective in reducing allergen-induced skin inflammation through the regulation of both elevated IgE and IL-4 in sensitized mice.

Microbial population dynamics and temperature changes during fermentation of kimjang kimchi

A distinct subset of lactic acid bacteria that are greatly influenced by temperature play an important role during kimchi fermentation. However, microbial population dynamics and temperature control during kimjang kimchi fermentation, which is traditionally fermented underground, are not known. Here we show that Lactobacillus sakei predominates in kimjang kimchi, perhaps due to suitable fermentation (5 approximately 9 degrees C) and storage (-2 degrees C) temperatures. The temperature of this kimchi gradually decreased to 3.2 degrees C during the first 20 days of fermentation (-0.3 degrees C/day) and then was stably maintained around 1.6 degrees C, indicating that this simple approach is very efficient both for fermentation and storage. These findings provide important information towards the development of temperature controlling systems for kimchi fermentation.