Leuconostoc Strains Research Articles

Influence of Culture Media Formulated with Agroindustrial Wastes on the Antimicrobial Activity of Lactic Acid Bacteria.

The discarding of wastes into the environment is a significant problem for many communities. Still, food waste can be used for lactic acid bacteria (LAB) growth. Here, we evaluated three growth media equivalent to de Mann Rogosa Sharpe (MRS), using apple bagasse, yeast waste, fish flour, forage oats, and cheese whey. Cell-free supernatants of eight LAB strains were tested for antimicrobial activity against nine indicator microorganisms. The supernatants were also evaluated for protein content, reducing sugars, pH, and lactic acid concentration. Cell-free supernatants from fish flour broth (FFB) LAB growth were the most effective. The strain Leuconostoc mesenteroides PIM5 presented the best activity in all media. L. mesenteroides CAL14 completely inhibited L. monocytogenes and strongly inhibited Bacillus cereus (91.1%). The strain L. mesenteroides PIM5 consumed more proteins (77.42%) and reducing sugars (56.08%) in FFB than in MRS broth (51.78% and 30.58%, respectively). Culture media formulated with agroindustrial wastes positively improved the antimicrobial activity of selected LAB, probably due to the production of antimicrobial peptides or bacteriocins.

Potential of a Techno-Functional Sourdough and Its Application in Sugar-Reduced Soft Buns

Functional lactic acid bacteria (LAB) as starter cultures used in sourdough fermentation have been researched for years. This study evaluated the LAB strains Leuconostoc citreum DCM65 (mannitol, exopolysaccharide producing, antifungal activity) and Lactiplantibacillus plantarum subsp. plantarum MA418 (amylolytic activity) and their potential as single or co-culture starters in sourdough fermented buns containing different levels of sugar (control 9% and reduced 0, 3, 6%). Cell counts, pH development, and organic acids were determined before and after sourdough fermentation (30 °C, 24 h) and physical properties (color, volume, pore structure, and texture) of buns produced thereof were determined after baking. Sourdoughs started with DCM65 and/or MA418 developed up to log 9.2 CFU/g presumptive LAB after 24 h, assertiveness of the added starter cultures species was confirmed by MALDI-TOF MS. Acetic acid and mannitol were only detected in sourdough fermented with DCM65 (single or co-culture) up to 2.5 mg/g and 9.8 mg/g, respectively. The starter cultures applied influenced physical properties of buns. Sourdough buns started with MA418 had higher volume and slice area, and softer crumb; in contrast, buns fermented with DCM65 had a finer pore structure. In summary, both starter cultures showed high potential in sourdough buns with reduced sugar content.

Optimization of dextran production from Leuconostoc strains isolated from different dairy products from Ouargla region Algeria

Leuconostoc (Ln) sp. belongs to a group of lactic acid bacteria, which has the capacity to produce dextran (an exopolysaccharides) in the presence of su-crose. dextran is industrially important, it was the first microbial exopolysac-charide affirmed for commercial use. This study aimed to optimize the pro-duction of the synthesized dextran by Ln strains species isolated from differ-ent dairy products. Morphological, cultural, physiological and biochemical characteristics were employed to identify 23 isolated strains. We have identi-fied the species: Ln. gelidum, Ln. carnosum, Ln. citreum, Ln. fallax, Ln. mesen-teroides subsp mesenteroides, Ln. mesenteroides subsp dextranicum, Ln. mesenteroides subsp cremoris. 20 strains had the capacity to produce dex-tran from sucrose. The precipitation and quantification of EPS on MRSs (Mark rogosa et sharpe sucrose) medium revealed a difference between the strains, by the total sugars assay method, the amount of EPS varied between 0.63 ± 0.19 and 2.41 ± 0.17 g / L of strains LnF70 and LnC1 (isolated from goat's milk), respectively. The dextran production from MRSs medium was better than from liquid MSE. The optimization of production on MRSs medi-um with different concentration of glucose, yeast extract and sucrose showed that the strains had good production with a concentration of 2% glucose, 0.3% yeast extract and 10% sucrose.

Comparative genome analysis of four Leuconostoc strains with a focus on carbohydrate-active enzymes and oligosaccharide utilization pathways

Leuconostoc is mostly found in food, plants, and dairy products. Due to their innate genomic features, such as the presence of carbohydrate-active enzymes, bacteriocins, and plasmids, Leuconostoc spp. have great biotechnological potential. In this study, four strains were isolated and identified as Leuconostoc mesenteroides SG315 (LA), L. citreum SG255 (LB), L. lactis CCK940 (LC), and L. lactis SBC001 (LD). Comparative analysis was performed using their draft genome sequences. Differences among the four strains were analyzed using the average nucleotide identity, dot plot, and multiple alignments of conserved genomic sequences. Functional profiling revealed 2134, 1917, 1751, and 1816 open reading frames; 2023, 1823, 1655, and 1699 protein-coding genes; 60, 57, 83, and 82 RNA-coding genes; and GC content of 37.5 %, 38.8 %, 43.3 %, and 43.2 %, in LA, LB, LC, and LD, respectively. The total number of genes encoding carbohydrate-active enzymes was 76 (LA), 73 (LB), 57 (LC), and 67 (LD). These results indicate that the four strains shared a large number of genes, but their gene content is different. Furthermore, most genes with unknown functions were observed in the prophage regions of the genome. This study also elucidated the oligosaccharide utilization and folate biosynthesis pathways in Leuconostoc spp. Taken together, our findings provide useful information on the genomic diversity of CAZymes in the four Leuconostoc strains and suggest that these species could be used for potent exploitation.

Hsp60 gene as a reliable target for taxonomical identification and discrimination of Leuconostoc species of dairy origin

The taxonomic characterisation of Leuconostoc species is still controversial and the methods applied including cultivation, phenotypic/biochemical and non–specific molecular methods (RAPD, PFGE, RFLP, MALDI–TOF MS and sequencing of the gene coding for 16S rRNA), could lead to misidentifications. Sequencing of 16S rRNA gene is still the most applied, although several closely–related species are not always properly differentiated. In this work, a phylogenetic tree constructed by the alignment of a fragment from hsp60 gene of 71 Leuconostoc strains of dairy origin (Ln. mesenteroides, Ln. pseudomesenteroides, Ln. lactis and Ln. citreum) was analysed and compared with that obtained with 16S rRNA sequences. The phylogenetic tree resulted from hsp60 sequences showed greater discrimination, even at the intra–species level, compared with that obtained with 16S rRNA fragments. These results demonstrated that this target sequence could be considered an excellent molecular tool for the identification of Leuconostoc species of dairy importance.

Multiple Techno-Functional Characteristics of Leuconostoc and Their Potential in Sourdough Fermentations.

In this study, the potential of Leuconostoc as non-conventional sourdough starter cultures was investigated. A screening for antifungal activities of 99 lactic acid bacteria (LAB) strains revealed high suppression of bakery-relevant moulds in nine strains of Leuconostoc with activities against Penicillium sp., Aspergillus sp., and Cladosporium sp. Mannitol production was determined in 49 Leuconostoc strains with >30 g/L mannitol in fructose (50 g/L)-enriched MRS. Further, exopolysaccharides (EPS) production was qualitatively determined on sucrose (40 g/L)-enriched MRS agar and revealed 59 EPS positive Leuconostoc strains that harboured dextransucrase genes, as confirmed by PCR. Four multifunctional Lc. citreum strains (DCM49, DCM65, MA079, and MA113) were finally applied in lab-scale sourdough fermentations (30 °C, 24 h). Lc. citreum was confirmed by MALDI-TOF MS up to 9 log CFU/g and pH dropped to 4.0 and TTA increased to 12.4. Antifungal compounds such as acetic acid, phenyllactic and hydroxyphenyllactic acids were determined up to 1.7 mg/g, 2.1 µg/g, and 1.3 µg/g, respectively, mannitol up to 8.6 mg/g, and EPS up to 0.62 g/100 g. Due to the observed multifunctionalities and the competitiveness in the natural flour microbiota present in sourdoughs, non-conventional LAB genera such as Leuconostoc seem promising for application in sourdough-based bakery products.

Functionalisation of wheat and oat bran using single-strain fermentation and its impact on techno-functional and nutritional properties of biscuits

The adequate intake of dietary fibre is linked to several health benefits, for example, reducing the risk of non-communicable diseases, such as cardiovascular disease and diabetes. However, the population’s intake of dietary fibre is below the dosage recommended by the World Health Organisation. The incorporation of fibre ingredients, such as bran, in cereal based products affects the techno-functional and sensory properties, resulting in inferior product quality. To compensate quality loss, wheat bran (WB) and oat bran (OB) were fermented using the lactic acid bacterium strain Leuconostoc citreum TR116 prior to the application in a biscuit system. Two types of fermentation, one without any addition of sugars (FB) and one with the supplementation of 5% fructose and 5% sucrose to trigger the production of mannitol (FB +), were conducted and sugar and acid profiles as well as pH and total titratable acids (TTA) were evaluated. Fermented WB showed a higher TTA (+ 58%) compared to fermented OB. Furthermore, FOB + resulted in higher microbial cell count and higher residual sugars after 48 h of fermentation. The application of fermented brans in a biscuit system showed a decrease in dough stickiness (− 41.7%) and an increase in dough hardness (+ 32%). The type of bran (WB and OB) as well as the type of fermentation (FB or FB +) influenced the results of biscuit dough and biscuit quality (p < 0.005). Fermentation increased biscuit spreading, influenced biscuit snap force, enhanced crunchiness and colour formation, and lowered the predicted glycaemic index. Fermented OB (FOB +) resulted in a sensory profile comparable to the control.

Potential antimicrobial and antiadhesive activity of crude bio-surfactants produced by Leuconostoc sp strains coated on rubber-silicone tubes

The present study focused on screening of biosurfactants produced by Leu-conostoc strains isolated from dromedary milk with antimicrobial and antiad-hesive properties against various pathogenic microorganisms and its poten-tial application in medical fields as an antibiofilm agent. After identification of the selected strains by mass spectrometry, screening methods for biosur-factants production were used, including drop collapse, oil displacement, surface tension and emulsification index. Antiadhesive assays were carried out against six pathogenic microorganisms in polystyrene surface, and ap-plied on rubber silicone tubes. Four lactic acid bacteria were isolated and identified as Leuconostoc sp according to MALDITOF MS spectrometry. Bio-surfactants isolated from Leuconostoc strains reduced tension surface from 72.0 to 45.7 by strain BY14, with an emulsification efficiency (E24) after 24h of 63%. The crude biosurfactants were effective against most pathogenic microorganisms with inhibition percentage from 92.3% to 44.3% after adhe-sion to polystyrene. Otherwise, the antiadhesive activity displayed values from 75.67% to 13.2%. The result of application test demonstrated that the selected crude biosurfactants reduced significantly all the deposited microbi-al biofilm from rubber silicone tubes. This study suggest that biosurfactants could have a promising role as an effective antibiofilm to prevent microbial colonization on medical devices.

Reducing FODMAPs and improving bread quality using type II sourdough with selected starter cultures

This study focussed on lactic acid bacteria (LAB) screening for sourdough type II elaboration and evaluating the effects of sourdough fermentation in bread making, focussing mainly on reducing FODMAPs. After a technological performance screening, six strains (Levilactobacillus brevis, Weissella minor, Lactiplantibacillus plantarum, Leuconostoc citreum, Limosilactobacillus fermentum, and Companilactobacillus farciminis) were selected for sourdough preparation. Total titratable acidity, pH, specific volume, and enumeration of microorganisms were carried out on sourdoughs, doughs, and breads. Breads were subjected to texture profile and colour analysis, moulds and yeast enumeration, and total fructans (main group of FODMAPs) quantification. Breads produced with sourdough showed a significant reduction of fructans, greater acidity, volume, and better performance during storage when compared to fermentation using only baker’s yeast. Including specific cultures as starters in sourdough reduced fructans content by >92%, thereby producing a low FODMAP bread suitable for Irritable Bowel Syndrome patients with improved nutritional and technological properties.

Enzymatically synthesized exopolysaccharide of a probiotic strain Leuconostoc mesenteroides NTM048 shows adjuvant activity to promote IgA antibody responses

ABSTRACT Leuconostoc mesenteroides strain NTM048 produces an exopolysaccharide (EPS; glucose polymers 94% and fructose polymers 6%) with adjuvanticity for mucosal vaccination. Strain NTM048 includes three putative EPS-synthesizing genes, gtf1 and gtf2 for synthesizing glucose polymers, and lvnS for synthesizing fructose polymer. To elucidate the key polymer structure for adjuvanticity, two genes, gtf1 and gtf2, which were annotated as glycoside hydrolase family 70 enzyme genes, were expressed in Escherichia coli. Glycosyl-linkage composition analysis and NMR analysis showed that the recombinant enzyme Gtf1 produced a soluble form of α-1,6-glucan, whereas the recombinant enzyme Gtf2 produced glucans with approximately equal percentages of α-1,6- and α-1,3-glucose residues both in the supernatant (S-glucan) and as a precipitate (P-glucan). Comparison of polysaccharides synthesized by Gtf1, Gtf2, and LvnS revealed that Gtf2-S-glucan, which was produced in the supernatant by Gtf2 and formed particles of 7.8 µm, possessed 1.8-fold higher ability to stimulate IgA production from murine Peyer’s patch cells than native NTM048 EPS. Evaluation of adjuvanticity by intranasal administration of mice with an antigen (ovalbumin) and Gtf2-S-glucan or NTM048 EPS showed that Gtf2-S-glucan induced the production of higher antigen-specific antibodies in the airway mucosa and plasma, suggesting a pivotal role of Gtf2-S-glucan in the adjuvanticity of NTM048 EPS.

Leuconostoc falkenbergense sp. nov., isolated from a lactic culture, fermentating string beans and traditional yogurt.

In the present study, the taxonomic positions of five strains (C, 17-2, LMG 10779T, LMG 18969 and LMG 11483) of Leuconostoc pseudomesenteroides were re-evaluated by a polyphasic approach, including the analyses of 16S rRNA, pheS and rpoA gene sequences, cellular fatty acids, average nucleotide and amino acid identities (ANI and AAI), digital DNA-DNA hybridization (dDDH), and phenotypic features. Based on rpoA sequence analysis, the five strains and L. pseudomesenteroides LMG 11482T were divided into two groups: strains C, LMG 10779T and LMG 18969; strains 17-2, LMG 11483 and LMG 11482T. Each of the two groups had almost identical rpoA sequences. The rpoA sequence similarity between strain LMG 10779T and L. pseudomesenteroides LMG 11482T was 95.6 %. Strains LMG 11483 and 17-2 had 98.1 and 97.2 % ANI values, 83.5 and 73.2 % dDDH values, and a 97.0 % AAI value with L. pseudomesenteroides LMG 11482T, greater than the threshold for species demarcation, indicating that strains LMG 11483 and 17-2 belong to L. pseudomesenteroides. Strains LMG 18969 and C shared 97.1 and 98.2 % ANI values, 73.4 and 83.2 % dDDH values, and 96.9 and 96.6 % AAI values with strain LMG 10779T, greater than the threshold for species demarcation, indicating that strains LMG 10779T, LMG 18969 and C represent the same species. The ANI, dDDH and AAI values between strain LMG 10779T and the type strains of phylogenetically related species were 75.2-92.5, 20.0-48.2 and 75.3-93.9 %, respectively, below the thresholds for species demarcation, indicating that strain LMG 10779T represents a novel species within the genus Leuconostoc. On the basis of the results presented here, (i) strains 17-2 and LMG 11483 belong to L. pseudomesenteroides, and (ii) strains LMG 10779T, LMG 18969 and C are considered to represent a novel species within the genus Leuconostoc, for which the name Leuconostoc falkenbergense sp. nov. is proposed with the type strain LMG 10779T (=CCUG 27119T).

Leuconostoc citreum TR116 as a Microbial Cell Factory to Functionalise High-Protein Faba Bean Ingredients for Bakery Applications.

Grain legumes, such as faba beans, have been investigated as promising ingredients to enhance the nutritional value of wheat bread. However, a detrimental effect on technological bread quality was often reported. Furthermore, considerable amounts of antinutritional compounds present in faba beans are a subject of concern. Sourdough-like fermentation can positively affect baking performance and nutritional attributes of faba bean flours. The multifunctional lactic acid bacteria strain Leuconostoc citreum TR116 was employed to ferment two faba bean flours with different protein contents (dehulled flour (DF); high-protein flour (PR)). The strain’s fermentation profile (growth, acidification, carbohydrate metabolism and antifungal phenolic acids) was monitored in both substrates. The fermentates were applied in regular wheat bread by replacing 15% of wheat flour. Water absorption, gluten aggregation behaviour, bread quality characteristics and in vitro starch digestibility were compared to formulations containing unfermented DF and PR and to a control wheat bread. Similar microbial growth, carbohydrate consumption as well as production of lactic and acetic acid were observed in both faba bean ingredients. A less pronounced pH drop as well as a slightly higher amount of antifungal phenolic acids were measured in the PR fermentate. Fermentation caused a striking improvement of the ingredients’ baking performance. GlutoPeak measurements allowed for an association of this observation with an improved gluten aggregation. Given its higher potential to improve protein quality in cereal products, the PR fermentate seemed generally more promising as functional ingredient due to its positive impact on bread quality and only moderately increased starch digestibility in bread.

Identification of Clinically Relevant Streptococcus and Enterococcus Species Based on Biochemical Methods and 16S rRNA, sodA, tuf, rpoB, and recA Gene Sequencing.

Streptococci and enterococci are significant opportunistic pathogens in epidemiology and infectious medicine. High genetic and taxonomic similarities and several reclassifications within genera are the most challenging in species identification. The aim of this study was to identify Streptococcus and Enterococcus species using genetic and phenotypic methods and to determine the most discriminatory identification method. Thirty strains recovered from clinical samples representing 15 streptococcal species, five enterococcal species, and four nonstreptococcal species were subjected to bacterial identification by the Vitek® 2 system and Sanger-based sequencing methods targeting the 16S rRNA, sodA, tuf, rpoB, and recA genes. Phenotypic methods allowed the identification of 10 streptococcal strains, five enterococcal strains, and four nonstreptococcal strains (Leuconostoc, Granulicatella, and Globicatella genera). The combination of sequencing methods allowed the identification of 21 streptococcal strains, five enterococcal strains, and four nonstreptococcal strains. The 16S rRNA and rpoB genes had the highest identification potential. Only a combination of several molecular methods was sufficient for unambiguous confirmation of species identity. This study will be useful for comparison of several identification methods, both those used as a first choice in routine microbiology and those used for final confirmation.

Effect of pH on the growth of three lactic acid bacteria strains isolated from sour cream

Lactic acid bacteria (LAB) have an important role in the food industry because they are used in the production of fermented fo ds. To use these microorganisms in the food industry, it is necessary to obtain a high amount of biomass. One of the most important environmental factors in the growth of LAB is pH. Most of LAB species can tolerate a pH below 5.0, however, a suboptimal pH is expected to limit LAB growth. For this reason, the LAB strains Leuconostoc mesenteroides 67-1, Lactobacillus plantarum 60-1, and Streptococcus infantarius 46-3, isolated from sour cream, were grown in culture media under four different intial pH values to determine their optimal growth pH. Growth was assesed via colony-forming unit (CFU/ml) determination. We found that the growth of each LAB was affected by culture medium pH. We determined that the setpoints of pH for Leuconostoc mesenteroides 67-1, Streptococcus infantarius 46-3, and Lactobacillus plantarum 60-1 were of 4.5 (± 0.5), 5.5 (± 0.5), and 6.0 (± 0.5), respectively. We thus conclude that the growth of these LAB strains is pH-dependent (p &lt; 0.05).

Screening for texturing Leuconostoc and genomics behind polysaccharide production.

ABSTRACTSynthesis of polysaccharides by Leuconostoc can result in improved texture of fermented products. A total of 249 Leuconostoc strains were screened for homo-polysaccharide production and for texturing capabilities in milk. A total of six Ln. mesenteroides strains with superior texturing properties had the genetic blueprint for both homo- (HoPS) and hetero-polysaccharide (HePS) synthesis. Only one strain produced texture in milk without added sucrose, suggesting HePS synthesis via the Wzy dependent pathway. In milk acidification experiments with added sucrose, all six strains depleted the sucrose and released fructose. Thus, they can be used for both texture and possibly also for sweetness enhancement.

The role of dextran production in the metabolic context of Leuconostoc and Weissella Tunisian strains

High molecular weight dextrans improve the rheological properties of fermented products and have immunomodulatory and antiviral activity. We report on 5.84 × 107–2.61 × 108 Da dextrans produced by Leuconostoc lactis AV1n, Weissella cibaria AV2ou and Weissella confusa V30 and FS54 strains. Dextransucrases catalyze dextran synthesis by sucrose hydrolysis concomitant with fructose generation. The four bacteria have dextransucrases with molecular weight of about 160 kDa detected by zymograms. Each bacterium showed different interplay of dextran production and metabolic fluxes. All bacteria produced lactate, and AV2ou apart, synthesized mannitol from fructose. FS54 hydrolyzed dextran blue and the concentration of dextran produced by this bacterium decreased during the stationary phase. The AV1n binding to Caco-2 cells and polystyrene plates was higher under conditions for dextran synthesis. Thus, this is the first instance of a Weissella dextranase, associated with a dextransucrase ability, and of a positive influence of dextran on adhesion and aggregation properties of a bacterium.

Antimicrobial Activity of Microorganisms Isolated from Ant Nests of Lasius niger.

In this study, the microbial communities of two nests of black garden ants (Lasius niger) in the hollows of stem branches of old apple trees were found to have similar species compositions: each community contained representatives of three species from the Bacillaceae family and one species of actinomycetes from the genus Streptomyces. In total, four types of bacilli and two actinomycetes were isolated. Actinomycetes were identified as Streptomyces antibioticus-like and Streptomyces sp. None of the bacilli had antibiotic activity, whereas both streptomycetes produced antibiotics that inhibited the growth of Gram-positive bacteria in vitro, including isolates from their community. Antibiotic compounds of S. antibioticus-like strain INA 01148 (Institute of New Antibiotics) were identified as actinomycin D and its closest homologue, actinomycin A. Actinomycins presumably change the microbial community of the ant nest substrate as they act against Gram-positive bacteria and against fungi and Gram-negative bacteria. The antibiotic activity of the isolated Streptomyces sp. INA 01156 is of interest, since the substances produced by this strain inhibit the growth of drug-resistant bacteria, including methicillin-resistant Staphylococcus aureus INA 00761 (MRSA) and vancomycin-resistant strain Leuconostoc mesenteroides VKPM B-4177 (VR) (VKPM–National Collection of Industrial Microorganisms (Russian acronym)).

Dynamics of interaction of lactic acid microorganisms in paired consortia aiming at fermentation of vegetable raw materials

Relevance. Cabbage is one of the most popular products, which is mainly fermented with the addition of various vegetables. When fermentation is not only the original nutrients such as vitamin C, amino acids, dietary fibers, etc., but also develop functional microorganisms such as lactic acid bacteria. Fermentation has an important effect on the quality and taste of cabbage, so it is important to study the fermentation process, microbial diversity and changes in nutrients and chemical elements in the fermentation process. L. mesenteroides is considered to be the dominant species on heterofermentative early stages of fermentation. However, there is little information on the diversity of species and strains of Leuconostoc involved in fermentation of sauerkraut. Studies that used traditional biochemical methods to study fermentation of sauerkraut showed that four main types of lactic acid bacteria were involved in the fermentation process: Leuconostoc mesenteroides, Lactobacillus plantarum, Pediococcus pentosaceus and Lactobacillus brevis. Taking into account the importance of two-stage fermentation of vegetable raw materials in order to create optimal conditions for the development of the "main" pool of lactic acid microorganisms at the first stage, it becomes urgent to conduct a complex of studies aimed at reproducing the "natural" process in which the main role is played by bacteria of the genus Leuconostoc mesenteroides at the second stage – monocultures of lactic acid microorganisms and their consortia.Methods. The paper studies the dynamics of the type of interaction of lactic acid microorganisms in paired consortiums on model media pretreated by the culture of the species Leuconostoc mesenteroides, at the main stage of step fermentation of white cabbage of the "Parus" variety.Results. It is established that the sum of the criteria, the consortium "L. mesenteroides \ L. casei + L. plantarum" demonstrates the most pronounced advantage compared with monoculture cultivation of appropriate format of pseudotensorial; despite the pronounced synergy in the cultivation of the consortium "L. mesenteroides \ L. brevis + L. plantarum", the dynamics of the comparison index on the rate of increase in the concentration of microorganisms indicates the need for additional research.

The probiotic, Leuconostoc mesenteroides, inhibits Listeria monocytogenes biofilm formation

AbstractListeria monocytogenes biofilm formation renders these cells highly resistant to current sanitation methods, and probiotics may be a promising approach to the efficient inhibition of Listeria biofilms. In the present study, three Leuconostoc mesenteroides strains of lactic acid bacteria isolated from kimchi were shown to be effective probiotics for inhibiting Listeria biofilm formation. Biofilms of two L. monocytogenes serotypes, 1/2a (ATCC15313) and 4b (ATCC19115), in dual‐species culture with each probiotic strain were decreased by more than 40‐fold as compared with single‐species Listeria biofilms; for instance, a reduction from 5.4 × 106 colony forming units (CFU)/cm2 L. monocytogenes ATCC19115 in single‐species biofilms to 1.1 × 105 CFU/cm2 in dual‐species biofilms. Most likely, one of the Leuconostoc strains, L. mesenteroides W51, led to the highest Listeria biofilm inhibition without affecting the growth of L. monocytogenes. The cell‐free supernatant from the L. mesenteroides W51 culture containing large protein molecules (&gt;30 kDa) also inhibited Listeria biofilms. These data indicate that Leuconostoc probiotics can be used to repress L. monocytogenes biofilm contamination on surfaces at food processing facilities.

Interaction of Rhizoctonia solani and Leuconostoc spp. causing sugar beet root rot and tissue pH changes in Idaho

Late season Rhizoctonia root rot in sugar beet is a serious yield limiting disease problem caused by an interaction between Rhizoctonia solani and Leuconostoc spp. in Idaho. To better understand this interaction, the two most common Leuconostoc haplotypes were co-inoculated with 17 R. solani strains representing the range of genetic diversity established previously. The study was conducted twice by inoculating sugar beet roots in the field using a plug assay and measuring root rot and tissue pH. L. mesenteroides strain L12311 (17 mm of rot) had significantly (P < 0.0001) more rot than L. pseudomesenteroides strain L12487 (13 mm) when combined with the fungal strains. The R. solani anastomosis group (AG) 2–2 IIIB strains (16 mm of rot) led to significantly (P < 0.0001–0.0073) more rot than strains associated with other AGs: 2–2 IV (11 mm), 4 HG-I (5 mm) and 4 HG-II (3 mm). When R. solani AG-2-2 IIIB strains from three phylogenetic groups were compared, rot ranged from 15 to 17 mm and did not differ (P = 0.1275–0.5565). The pH for root tissue with at least 30 mm of rot was lower (4.0–4.2 ± 0.2–0.4) than tissue with < 2 mm of rot and water checks (6.2–6.4 ± 0.1–0.2). Both isolations and tissue pH suggest late season sugar beet root rot is primarily associated with Leuconostoc and secondary organisms. However, damage was minor without both R. solani AG-2-2 and Leuconostoc strains present when internal rot initiates.