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The main objective of this study is to isolate and identify lactic acid bacteria (LAB) from various Egyptian dairy products, examine their antibacterial and hemolysis potential, and ensure their safety when used as starter cultures in different dairy industries. Egyptian dairy products are often made without the use of commercial starter cultures, using raw milk and artisanal methods. The most popular traditional dairy products are Laban Rayeb and Zabady, as well as the cheese varieties of Ras, Domiati, and Karish. The microbial communities used for fermentation and the diversity of lactic acid bacteria are the most important factors that can affect the quality of these products. In order to investigate the diversity of cocci lactic acid bacteria in Egyptian dairy products, 70 samples of raw or fermented milk and cheeses were collected from traditional cheese-making factories, local markets, and farmhouses located in the Delta area of Egypt. Following this, the LAB were isolated from the samples. One hundred fifty-seven isolates of Gram-positive, catalase-negative, and cocci bacterial species were identified via rep-PCR, and some isolates were confirmed using pheS and 16S rRNA gene sequencing, as follows: Streptococcus infantarius subsp. infantarius (three isolates), Enterococcus hirae (three isolates), Enterococcus faecium (ninety-six isolates), Enterococcus faecalis (forty isolates), Enterococcus durans (six isolates), Lactococcus garvieae (one isolate), Pediococcus acidilactici (seven isolates), and Lactococcus lactis subsp. Lactis (one isolate). These findings validate that five strains have strong antibacterial activity against Escherichia coli, Salmonella typhimurium, and Listeria monocytogenes, and one hundred thirty-four strains were safe for hemolysis. The five strains were selected as protective cultures, including Pediococcus acidilactici, Lactococcus lactis subsp. lactis, E. faecalis, and E. faecium. [ABSTRACT FROM AUTHOR]

Summary: This study investigated the inhibition of Clostridium species, isolated from cheeses with late‐blowing defects, by lactic acid bacteria (LAB). Four batches of Turkish white cheeses were produced; control cheese, cheese sample containing Lactococcus lactis subsp. lactis (PY91K) and Lactiplantibacillus plantarum (Y48) as protective cultures (LAB), a cheese sample containing the protective culture and inoculated with Clostridium sporogenes spores (CL‐LAB) and finally a cheese sample containing only Cl. sporogenes spores (CL). White cheese's microbiological and physicochemical properties were also determined throughout the 90‐day storage period at 4 °C. Approximately 1 log reduction in Cl. sporogenes (ZMP‐1‐4) spores was observed in the LAB co‐inoculated Turkish white cheese samples. [ABSTRACT FROM AUTHOR]

Introduction: This study aimed to explore the anti-oxidative and antiinflammatory properties of Lactococcus lactis subsp. lactis HFY14 (LLSLHFY14) and investigate its effects on the intestinal barrier, cranial nerve, and motor function in mice treated with antibiotics. Methods: Mice were administered an antibiotic mixture (neomycin 5 mg/mL, vancomycin 25 mg/mL, amphotericin B 0.1 mg/mL, ampicillin 10 mg/mL, metronidazole file 5 mg/mL, and lipopolysaccharide 1.5 mg/mL) intraperitoneally, and oxidative stress and inflammatory markers in the serum and brain tissues, and liver index were measured. H&E staining was performed to detect pathological alterations in brain tissues. The expression of intestinalbarrier- related genes and that of genes involved in inflammatory pathways in the brain were detected using polymerase chain reaction (PCR). Results: LLSLHFY14 administration extended the weight-loaded swimming and running times of mice and decreased the liver index. Moreover, the levels of malondialdehyde (MDA), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-a) in the serum and brain tissue were reduced, whereas those of superoxide dismutase (SOD), glutathione (GSH), and interleukin-10 (IL-10) were elevated. Elevated brain expression of the protein kinase B (AKT)/cAMPresponse element binding protein (CREB)/brain-derived neurotrophic factor (BDNF)/extracellular signal-regulated kinase 1 (ERK1) pathway, decreased brain expression of the IL-6 gene, and elevated cecum expression of zonula occludens-1 (ZO-1), occludin-1, and claudin-1 genes were noted. LLSLHFY14 supplementation significantly increased Bacteroidetes expression but decreased Firmicutes expression, thus increasing the Bacteroidetes/Firmicutes ratio. Discussion: Overall, LLSLHFY14 supplementation ameliorated antibioticinduced oxidative stress and inflammation in the mouse central nervous system, intestinal barrier dysfunction, and increased motor function, thus confirming its potential application as probiotics. [ABSTRACT FROM AUTHOR]

The main objective of this study is to isolate and identify lactic acid bacteria (LAB) from various Egyptian dairy products, examine their antibacterial and hemolysis potential, and ensure their safety when used as starter cultures in different dairy industries. Egyptian dairy products are often made without the use of commercial starter cultures, using raw milk and artisanal methods. The most popular traditional dairy products are Laban Rayeb and Zabady, as well as the cheese varieties of Ras, Domiati, and Karish. The microbial communities used for fermentation and the diversity of lactic acid bacteria are the most important factors that can affect the quality of these products. In order to investigate the diversity of cocci lactic acid bacteria in Egyptian dairy products, 70 samples of raw or fermented milk and cheeses were collected from traditional cheese-making factories, local markets, and farmhouses located in the Delta area of Egypt. Following this, the LAB were isolated from the samples. One hundred fifty-seven isolates of Gram-positive, catalase-negative, and cocci bacterial species were identified via rep-PCR, and some isolates were confirmed using pheS and 16S rRNA gene sequencing, as follows: Streptococcus infantarius subsp. infantarius (three isolates), Enterococcus hirae (three isolates), Enterococcus faecium (ninety-six isolates), Enterococcus faecalis (forty isolates), Enterococcus durans (six isolates), Lactococcus garvieae (one isolate), Pediococcus acidilactici (seven isolates), and Lactococcus lactis subsp. Lactis (one isolate). These findings validate that five strains have strong antibacterial activity against Escherichia coli, Salmonella typhimurium, and Listeria monocytogenes, and one hundred thirty-four strains were safe for hemolysis. The five strains were selected as protective cultures, including Pediococcus acidilactici, Lactococcus lactis subsp. lactis, E. faecalis, and E. faecium.

Lactococcus lactis subsp. lactis (L. lactis subsp. lactis) is a commonly used starter cultures in fermented dairy products, contributing distinct flavor and texture characteristics with high application value. However, the strains from different isolates have different contributions to milk fermentation. Therefore, this study aimed to investigate the influence of L. lactis subsp. lactis isolated from various sources on the volatile metabolites present in fermented milk. In this study, L. lactis subsp. lactis from different isolation sources (yogurt, koumiss and goat yogurt) was utilized as a starter culture for fermentation. The volatile metabolites of fermented milk were subsequently analyzed by headspace solid phase microextraction gas chromatography-mass spectrography (HS-SPME-GC-MS). The results indicated significant differences in the structure and abundance of volatile metabolites in fermented milk produced with different isolates (R2Y = 0.96, Q2 = 0.88). Notably, the strains isolated from goat yogurt appeared to enhance the accumulation of ketones (goat yogurt vs yogurt milk: 50 %; goat yogur vs koumiss: 27.3 %)and aldehydes (goat yogurt vs yogurt milk: 21.4 %; goat yogurt vs koumiss: 54.5 %) in fermented milk than strains isolated from koumiss and yogurt milk. It significantly promoted the production of 8 flavor substances (1 substance with OAV ≥ 1 and 6 substances with OAV > 0.1) and enhanced the biosynthesis of valine, leucine, and isoleucine. This study provides valuable insights for the application of Lactococcus lactis subsp. lactis isolated from different sources in fermented dairy production and screening of potential starter cultures.

To ensure the safety of dairy products, a comparison was made between coastal‐derived Lactococcus lactis strains and the type strain regarding antimicrobial resistance (AMR) and their genes. The test discs revealed that the AMR of 31 strains against streptomycin, gentamicin and kanamycin was higher than that of the type strain. The clear zone ratio of the type strain to that of Himuka‐SU2 was 3.0–3.5. However, both strains exhibited identical AMR genes. Pre‐incubation in broth containing 3.4% (w/v) NaCl increased the AMR of the type strain compared to the Himuka‐SU2 strain. These results are significant for the development of starters for fermented milk. [ABSTRACT FROM AUTHOR]

[Display omitted] Traditional fermented milks are produced by inoculating technique, which selects well-adapted microorganisms that have been passed on through generations. Few reports have used naturally fermented milks as model ecosystems to investigate the mechanism of formation of intra-species microbial diversity. Here, we isolated and whole-genome-sequenced a total of 717 lactic acid bacterial isolates obtained from 12 independent naturally fermented milks collect from 12 regions across five countries. We further analyzed the within-sample intra-species phylogenies of 214 Lactobacillus helveticus isolates, 97 Lactococcus lactis subsp. lactis isolates, and 325 Lactobacillus delbrueckii subsp. bulgaricus isolates. We observed a high degree of intra-species genomic and functional gene diversity within-/between-sample(s). Single nucleotide polymorphism-based phylogenetic reconstruction revealed great within-sample intra-species heterogeneity, evolving from multiple lineages. Further phylogenetic reconstruction (presence-absence gene profile) revealed within-sample inter-clade functional diversity (based on carbohydrate-active enzyme- and peptidase-encoding genes) in all three investigated species/subspecies. By identifying and mapping clade-specific genes of intra-sample clades of the three species/subspecies to the respective fermented milk metagenome, we found extensive potential inter-/intra-species horizontal gene transfer events. Finally, the microbial composition of the samples is closely linked to the nucleotide diversity of the respective species/subspecies. Overall, our results contribute to the conservation of lactic acid bacteria resources, providing ecological insights into the microbial ecosystem of naturally fermented dairy products. [ABSTRACT FROM AUTHOR]

Nisin is a naturally occurring bioactive small peptide produced by Lactococcus lactis subsp. lactis and belongs to the Type A (I) lantibiotics. Due to its potent antimicrobial activity, it has been broadly employed to preserve various food materials as well as to combat a variety of microbial pathogens. The present review discusses the antimicrobial properties of nisin and different types of their derivatives employed to treat microbial pathogens with a detailed underlying mechanism of action. Several alternative strategies such as combination, conjugation, and nanoformulations have been discussed in order to address several issues such as rapid degradation, instability, and reduced activity due to the various environmental factors that arise in the applications of nisin. Furthermore, the evolutionary relationship of many nisin genes from different nisin-producing bacterial species has been investigated. A detailed description of the natural and bioengineered nisin variants, as well as the underlying action mechanisms, has also been provided. The chemistry used to apply nisin in conjugation with natural or synthetic compounds as a synergetic mode of antimicrobial action has also been thoroughly discussed. The current review will be useful in learning about recent and past research that has been performed on nisin and its derivatives as antimicrobial agents. [ABSTRACT FROM AUTHOR]

In this study, climbing perch larvae were administrated with different diet treatments: Artemia nauplii enriched with 108 CFU mL−1L. lactis (LA); nauplii enriched with 0.5 g L−1 sodium alginate (SA); nauplii enriched with 0.5 g L−1 sodium alginate containing 108 CFU mL−1L. lactis (LSA); and non-enriched nauplii as the control (A). Throughout the 14-day observation period, fish larvae survival rate significantly increased to 50% (P <.05) in the group fed with LSA, followed by LA (41.7%) and SA (31.7%) while only 20% survival rate was observed in the control. The highest lysozyme activity was recorded in LSA (13.89 units mg−1 protein), followed by LA, SA, and A. Fish larvae treated with LA also showed a significant increase in lipase (P =.024) and amylase activities (P=.003) compared to those treated with LSA and SA. Our study indicated that L. lactis and alginate or the combination of both treatments (LSA) could improve the survival rate by upregulating their innate immune response. [ABSTRACT FROM AUTHOR]

An in silico study that featured the effect of starter cultures on the bioactivity and other health benefits of peptides in semi-hard cheese is presented in this contribution. Model Caciotta-type cheese samples were obtained in laboratory conditions in two variations. Sample A included starter cultures of Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris. Sample B included starter cultures of Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris, and a culture of lactobacilli Lacticaseibacillus casei. The in silico method showed that the peptides inhibited angiotensin-converting enzymes (ACE) and ipeptidyl peptidase IV (DPP-4), as well as possessed antioxidant properties. Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris had a greater effect on the formation of bioactive peptides. [ABSTRACT FROM AUTHOR]

There are numerous factors restricting wide application of lactic acid bacteria (LAB) in dairy industry, causing urgent demands for novel bioprotectants. Protective effects and metabolites of Lactococcus lactis subsp. lactis (L. lactis) from ultraviolet (UV)-induced supernatant were investigated and the protective mechanism was explored. The strain viability of the group treated with the supernatant of continuous UV irradiation (V1) and the group with intermittent UV irradiation (V2) was 8.45 and 14.13 times of the control group, respectively. Further exploration on the protective of L. lactis supernatant, under different dose of UV treatment, showed it was dose-dependent. The condition for the supernatant with best protective effect was vertical distance 50.00 cm, horizontal distance 25.00 cm, intermittent UV irradiation (30 s interval 30 s) for 4.5 min (V2), which was chose for untargeted metabolite analysis. And that in V1 was for comparative study. There were 181 up-regulated metabolites in V1 and 161 up-regulated metabolites in V2, respectively. Most of the up-regulated metabolites were related to secondary metabolite synthesis, environmental microbial metabolism, antibiotic synthesis and amino acid biosynthesis. Notably, production of dithiothreitol (DTT) in V2 was 65.2-fold higher than that in the control group. Trehalose in ABC transporter pathway was also up-regulated in the metabolites induced by UV. Results indicated that L. lactis could adapt to the UV stress by adjusting metabolic pathways and producing special metabolites to protect itself. This research offers the basis for robust strain development and contributes to initial study on potential bioprotectant. [ABSTRACT FROM AUTHOR]

An in silico study that featured the effect of starter cultures on the bioactivity and other health benefits of peptides in semi-hard cheese is presented in this contribution. Model Caciotta-type cheese samples were obtained in laboratory conditions in two variations. Sample A included starter cultures of Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris. Sample B included starter cultures of Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris, and a culture of lactobacilli Lacticaseibacillus casei. The in silico method showed that the peptides inhibited angiotensin-converting enzymes (ACE) and ipeptidyl peptidase IV (DPP-4), as well as possessed antioxidant properties. Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris had a greater effect on the formation of bioactive peptides.

Probiotic and prebiotic have many advantages and are employed as a method for aquaculture yield improvement. The main goal of the current study is to evaluate the effect of dietary Lactococcus lactis subsp. lactis as well as chitin on growth performance, carcass composition and feed digestibility in common carp, Cyprinus carpio. So that, 360 juvenile carps with mean initial weight of 12 ± 1.5 g were randomly distributed in 6 treatments based on adding different chitin levels including 0, 1, and 2% and probiotic including 0 and 2% (1×107 CFU/g) to a basal diet and cultured for 8 weeks. At the end of the experiment, growth indices, survival rate, carcass composition and nutrient digestibility were measured. Maximum final weight, weight gain, feed conversion ratio, daily growth rate, feed efficiency and condition factor as well as the lowest FCR were observed in treatments fed with probiotic 2%, chitin 1% and probiotic 2% + chitin 1% (P0.05). The experimental treatments did not influence the carcass composition and nutrient digestibility. In conclusion, it seems that adding 2% probiotic and 1% chitin can improve some growth indices in common carp, but can not affect carcass composition and nutrient digestibilty.

Abstract Background Cholesterol removal by isolated Lactococcus lactis subsp. lactis was investigated in vitro. The studied mechanisms were (1) assimilation of cholesterol by growing bacterial cells, (2) deconjugation of bile salts by bile salt hydrolase, (3) precipitation of cholesterol with deconjugated bile, (4) binding of cholesterol to the cell membrane, and (5) incorporation of cholesterol into the cell membrane. Result Levels of cholesterol assimilated by growing cells (43.70%) were significantly higher than those assimilated by resting cells (12.93%) or counterpart dead cells (6.35%). Scanning electron micrographs indicated that cholesterol adsorbed to the bacterial cell wall. A comparison of IR spectra of Lactococcus lactis subsp. lactis grown with and without cholesterol using an FTIR spectroscopy database revealed intensity changes associated with sulfamide bonds, P–H stretching and the C≡C bonds. Precipitation of cholesterol upon deconjugation of glycocholate was higher (5.53 μg/ml) than that observed upon taurocholate (3.7 μg/ml). Conclusions The present study suggested the ability of probiotic Lactococcus lactis subsp. lactis to reduce its cholesterol level through several different mechanisms. Consequently, this probiotic bacterium showed an interested potential of application in cholesterol reduction to be a novel and save prospect in resolving hypocholesteremia and related diseases.

Nisin is a green, safe and natural food preservative. With the expansion of nisin application, the demand for nisin has gradually increased, which equates to increased requirements for nisin production. In this study, Lactococcus lactis subsp. lactis lxl was used as the original strain, and the compound mutation method was applied to induce mutations. A high-yielding and genetically stable strain (Lactobacillus lactis A32) was identified, with the nisin titre raised by 332.2% up to 5089.29 IU/mL. Genome and transcriptome sequencing was used to analyse A32 and compare it with the original lxl strain. The comparative genomics results show that 107 genes in the A32 genome had mutations and most base mutations were not located in the four well-researched nisin-related operons, nisABTCIPRK, nisI, nisRK and nisFEG: 39 single-nucleotide polymorphisms (SNPs), 34 insertion mutations and 34 deletion mutations. The transcription results show that the expression of 92 genes changed significantly, with 27 of these differentially expressed genes upregulated, while 65 were downregulated. Our findings suggest that the output of nisin increased in L. lactis strain A32, which was accompanied by changes in the DNA replication-related gene dnaG, the ABC-ATPase transport-related genes patM and tcyC, the cysteine thiometabolism-related gene cysS, and the purine metabolism-related gene purL. Our study provides new insights into the traditional genetic mechanisms involved nisin production in L. lactis, which could provide clues for a more efficient metabolic engineering process.

Aphanizomenon flos-aquae, a freshwater cyanobacterium harvested from Upper Klamath Lake, Oregon, USA, is employed as a functional food material. Aphanizomenon flos-aquae can be fermented with Lactobacillus plantarum and Lactococcus lactis subsp. lactis. Here, to determine the dietary effects of A. flos-aquae (AFA) and fermented A. flos-aquae (F-AFA) on the mouse gut microbiome, high-sucrose diet containing no dietary fibre (NF), 5% AFA or 5% F-AFA was administered to ICR mice for 14 days. Compared with those in mice fed the NF, lower body weight gains and epididymal fat pad tissue weights were observed in mice fed the diet containing F-AFA. After feeding, the caecal microbiome was analysed by 16S rRNA (V4) gene amplicon sequencing using the Illumina MiSeq system. Sequences were clustered into operational taxonomic units, with a 97% identity cutoff, using the QIIME2 workflow script and SILVA database. The caecal microbiome alpha diversity was high in mice fed the F-AFA diet. The abundances of Muribaculum- and Alistipes inops-like bacteria belonging to the phylum Bacteroidetes and Ruminococcaceae UCG-014-like bacteria belonging to phylum Firmicutes were higher in the F-AFA group than in the AFA group. Isolation of typical F-AFA-susceptible gut indigenous bacteria and functional studies of the isolates in the presence of F-AFA are warranted to validate the current findings. [ABSTRACT FROM AUTHOR]

It is well known that consumers are keen to try fermented milk products with different flavors and starter cultures are important in determining the resulting fermented dairy products. Here, we present the phenome of 227 Lactococcus lactis subsp. lactis isolates from traditionally fermented dairy products and the selection of potential starter strains. Large-scale phenotyping revealed significant technological diversity in fermentation characteristics amongst the isolates including variation in fermentation time, viscosity, water holding capacity (WHC) and free amino nitrogen (FAN) production. The 16 isolates with the best fermentation characteristics were compared, in a sensory evaluation, with the commercial starter Chr. Hansen R-704 as excellent fermentation characteristics to identify potential starter isolates and find the isolate which can product good flavors. From these, and from solid phase micro extraction (SPME) – gas chromatography (GC)-mass spectrometry (MS) analysis, we identified IMAU11823 and IMAU11919 as producing 3-methyl butanal and 3-methyl-2-butanone which contribute to the malt aroma. This study expands the characterization of L. lactis subsp. lactis phenotypic dataset and technological diversity and identified isolates with potential culture starter in the fermentation industry.

The aim of this work was to demonstrate the feasibility of nisin and lactic acid production from corn stover through simultaneous saccharification and fermentation using Lactococcus lactis subsp. lactis ATCC 11454. The optimum conditions for nisin and lactic acid production were cellulose concentration of 30 g/L, a cellulase loading of 25 FPU/g cellulose and an initial pH of 6.0 in a 10 g/L yeast extract and 10 g/L peptone broth. The optimized bioprocess achieved nisin titer of 1635 IU/mL and lactic acid concentration of 15.2 g/L. The results indicated that simultaneous saccharification and fermentation with corn stover is a promising bioprocess for the economic production of nisin and lactic acid simultaneously.

L. lactis is known as industrial starter in the fermentation of dairy and meat products, and it plays an important role in human health as an edible probiotic. During industrial production, L. lactis often experiences different stresses that delay the growth and decrease the survival in some serious conditions. In this study, the protective effects of hydroxypropyl β‐cyclodextrin (HP β‐CD) on L. lactis under multiple stresses were investigated. The microbial cells were treated with different stresses including heat, NaCl, cold, and H2O2 stresses, and the results were showed by measuring the OD600 or spot plating method. The growth and tolerance were improved when HP β‐CD was added during different stress conditions, better than that of trehalose. Besides, the scanning electron microscopic and fluorescence spectrum studies showed that HP β‐CD could combine with L. lactis to protect the cell structure, suggesting that HP β‐CD may act as a protective agent of L. lactis. Therefore, HP β‐CD could be considered as a potential protective agent to be applied in food industry, and its protective mechanism on L. lactis still needs further investigation. [ABSTRACT FROM AUTHOR]

The combination of cost-effective synthesis of l-lanthionine in conjunction with a fermentation process could be considered as an original approach. Innovative biosynthesis of nisin is easy to scale-up. After the selective organic synthesis of the thioether building block, cultivation medium M17 broth with glucose (0.5% w/w) was supplemented with l-lanthionine (0.78, 3.91 and 7.82 mg ml−1) to stimulate nisin biosynthesis by lactococci. The viability of nisin-producing Lactococcus lactis subsp. lactis strains (CCDM 731, NIZO R5, LTM 32, CCDM 416) and nisin production were evaluated. Nisin synthesis was significantly influenced by l-lanthionine supplementation and it increased for all the strains tested in comparison with a control. The most significant increase in nisin concentration was observed for strains CCDM 731 and LTM 32, where up to 88.6% and 90.0%, respectively, were achieved. The influence of l-lanthionine concentration was shown to be strain specific. [ABSTRACT FROM AUTHOR]

• Ultrasound increased viable cell count and specific growth rate of L. lactis subsp. Lactis. • Membrane permeability increased by 3.0–22.8% after ultrasound treatment. • In general, ultrasound improved the fermentative activities of L. lactis subsp. Lactis. • Ultrasound effects were depending on ultrasound amplitudes and irradiation time. The present study was carried out to investigate the effects of low intensity ultrasound (20% and 30% amplitudes for 3 min and 5 min) on the growth kinetics and metabolic activity of Lactococcus lactis subsp. Lactis. The results revealed that the viable cell counts increased by 6.21–21.82% under ultrasound treatment. Confocal scanning laser microscopy showed 3.03–22.88% reduction in the percentage of intact cells after ultra-sonication. The specific growth rate of ultrasonicated L. lactis subsp. Lactis also increased by 7.09–23.22%. The pH values and titratable acidity were lower and higher, respectively, for most treatments. The treatments increased β-galactosidase activity. This was accompanied with a faster rate in lactic acid yield. The protein concentrations significantly decreased with increasing ultrasound amplitude and duration of irradiation, whilst at the same conditions the degree of protein hydrolysis was higher. Results suggest that ultrasound can stimulate the growth of L. lactis subsp. Lactis and its metabolic activity. Therefore, ultrasound can potentially play a significant role in stimulating fermentative activities of starter cultures and may successfully be employed in fermentation industries. [ABSTRACT FROM AUTHOR]

By employing co-cultivation technique on Komagataeibacter xylinum and Lactococcus lactis subsp. lactis , bacterial cellulose (BC)/nisin films with improved antibacterial activity and mechanical properties were successfully produced. The findings demonstrated that increased nisin production is associated with an upregulation of gene expression. Furthermore, results from Scanning electronic microscopy (SEM), Fourier transform infrared (FTIR), X-ray diffraction (XRD), and Thermogravimetric analysis (TG) confirmed the integration of nisin within BC. While being biocompatible with human cells, the BC/nisin composites exhibited antimicrobial activity. Moreover, mechanical property analyses showed a noticeable improvement in Young's modulus, tensile strength, and elongation at break by 161, 271, and 195 %, respectively. Additionally, the nisin content in fermentation broth was improved by 170 % after co-culture, accompanied by an 8 % increase in pH as well as 10 % decrease in lactate concentration. Real-time reverse transcription PCR analysis revealed an upregulation of 11 nisin-related genes after co-cultivation, with the highest increase in nisA (5.76-fold). To our knowledge, this is the first study which demonstrates that an increase in secondary metabolites after co-culturing is modulated by gene expression. This research offers a cost-effective approach for BC composite production and presents a technique to enhance metabolite concentration through the regulation of relevant genes. [Display omitted] • Bacterial cellulose (BC)/nisin film from co-cultivation has antibacterial property. • Results from SEM, FTIR, XRD and TG confirmed the integration of nisin in into BC. • Co-culture enhances Young's modulus, tensile strength, and elongation at break by 161, 271, and 195 % in BC/nisin. • Co-culture leads to >170 % increase in nisin production. • Increased nisin production is associated with the upregulation of gene expression. [ABSTRACT FROM AUTHOR]

Lactococcus lactis subsp. lactis is a common starter culture in the dairy industry. In this study, the key pathway of five strains of Lactococcus lactis subsp. Lactis regarding their fermentation characteristics in milk systems were studied by metabolomic approach, fermentation characterization and sensory evaluation. Strains DSCAB11M15 and DYNDL21-2, which express the cell wall proteinase PrtM/P, exhibited rapid proliferation and acidification, with significant differences in volatile and non-volatile metabolites including upregulation of flavor compounds such as ethyl butyrate and 2,3-butanedione. Additionally, DYNDL21-2, which carries the α-ketoacid decarboxylase gene, significantly increased the content of 3-methyl-butyric aldehyde, a compound that imparts a caramel-like flavor, in fermented milk. This study offers guidance for the comprehensive investigation of starter cultures with multiple approaches. [Display omitted] • The differential metabolites in fermented milk were related to pyruvate metabolism pathway, etc. • Lactococcus lactis strains containing prtP/M had better fermentation characteristics. • The α-ketoacid decarboxylase gene is closely related to caramel flavor metabolites. [ABSTRACT FROM AUTHOR]

Lactococcus lactis subsp. lactis ( L. lactis subsp. lactis ) is a commonly used starter cultures in fermented dairy products, contributing distinct flavor and texture characteristics with high application value. However, the strains from different isolates have different contributions to milk fermentation. Therefore, this study aimed to investigate the influence of L. lactis subsp. lactis isolated from various sources on the volatile metabolites present in fermented milk. In this study, L. lactis subsp. lactis from different isolation sources (yogurt, koumiss and goat yogurt) was utilized as a starter culture for fermentation. The volatile metabolites of fermented milk were subsequently analyzed by headspace solid phase microextraction gas chromatography-mass spectrography (HS-SPME-GC-MS). The results indicated significant differences in the structure and abundance of volatile metabolites in fermented milk produced with different isolates (R 2 Y = 0.96, Q 2  = 0.88). Notably, the strains isolated from goat yogurt appeared to enhance the accumulation of ketones (goat yogurt vs yogurt milk: 50 %; goat yogur vs koumiss: 27.3 %)and aldehydes (goat yogurt vs yogurt milk: 21.4 %; goat yogurt vs koumiss: 54.5 %) in fermented milk than strains isolated from koumiss and yogurt milk. It significantly promoted the production of 8 flavor substances (1 substance with OAV ≥ 1 and 6 substances with OAV > 0.1) and enhanced the biosynthesis of valine, leucine, and isoleucine. This study provides valuable insights for the application of Lactococcus lactis subsp. lactis isolated from different sources in fermented dairy production and screening of potential starter cultures., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author(s).)

This work was aimed to screen bacteriocin-producing LAB from freshwater fish, select a prominent strain and evaluate its safety, characterise the bacteriocin produced, and evaluate its potential to be used as biopreservatives. Isolate 3MT showed the ability to produce bacteriocin-like substances and was identified as Lactococcus lactis subsp. lactis. This strain proved to be free from virulence factors as well as biogenic amine production and antibiotic resistance patterns. The bacteriocin produced displayed high resistance to heat, pH, detergents, and its partial purification led to a 4.35-fold increase in specific activity. Moreover, this bacteriocin showed the ability to inhibit the growth of Vibrio sp. 1T1 in fish pâté stored at 10 °C for 20 days, without altering its sensory properties. The bacteriocin can be used successfully as a preservative to improve the hygienic quality and enhance the shelf life of fish paté in particular and food products in general. Lactococcus lactis subsp. lactis strain 3MT can also be safely used as a protective culture. [ABSTRACT FROM AUTHOR]

Abstract This work was aimed to isolate bacteriocin-producing lactic acid bacteria (LAB) from freshwater fish in Cameroon, characterize the bacteriocin and investigate its production as well as growth optimization in low-cost media. From the 144 isolates obtained, two showed the ability to produce bacteriocin-like inhibitory substances. Isolate 2 MT, selected for its high bacteriocin production capacity was identified as Lactococcus lactis subsp. lactis using 16S rDNA sequencing. The bacteriocin expressed high stability to heat, pH and chemical agents. Lactococcus lactis subsp. lactis 2 MT harbored the gene for the production of nisin Z, and the bacteriocin molecular mass was estimated at 4.10 kDa. This bacteriocin also exhibited a wide range of antimicrobial activity against spoilage and pathogenic Gram-positive and Gram-negative bacteria. The fish processing byproducts-based formulated medium SP 1 M showed the significantly highest bacteriocin production capacity. Using Doehlert design, a sugar cane molasses concentration of 42.72 g/l, a temperature of 28.40 °C, and an incubation time of 17.05 h were recorded as the optimum conditions for bacteriocin production. The optimization led to a 4.5-fold increase in nisin, compared with the non-optimized conditions, and a 9-fold increase when compared with non-optimized MRS broth. Highlights • Nisin Z-producing Lactococcus lactis subsp. lactis isolated from Nile tilapia. • Bacteriocin showed resistance to heat, pH, detergents and NaCl. • Bacteriocin activity against Gram-positive and Gram-negative bacteria. • Development of a low-cost medium from industrial byproducts for nisin production. • Optimization led to a 9-fold increase when compared with non-optimized MRS broth. [ABSTRACT FROM AUTHOR]

In this study, the effect of sourdough fermented with nisin producer Lactococcus lactis subsp. lactis CGMCC1.2030 on the shelf life and quality characteristics of fresh noodles fortified with it was investigated. The shelf life of fresh noodles with sourdough increased from 12 days to 22 days compare to the blank control during storage at 4 °C. Slight antimould activity was observed in sourdough fortified fresh noodles, and the brightened color of these noodles improved their appearance, which related to a decrease in the b* value of the noodle sheet from 12.35 to 8.47 over the storage period. Furthermore, the hardness and chewiness of sourdough-fortified fresh noodles decreased by 25.96% and 18.57%, respectively, which was lower than the 35.59% and 36.50% reduction observed in the blank control after the whole storage period. Confocal laser scanning microscopy (CLSM) analysis revealed less aggregated and more continuous gluten networks, which in combination with mitigated water migration might result in the delayed deterioration of texture quality of sourdough-fortified fresh noodles. • Lactococcus lactis fermented sourdough extended the shelf life of fresh noodles • A synergetic effect of sourdough inhibited the growth of bacteria and fungi • Water distribution and gluten network greatly impact the qualities of fresh noodles • Sourdough fortified fresh noodles retard qualities deterioration during storage [ABSTRACT FROM AUTHOR]

This research investigated the technological and safety effects of the nisin Z producer Lactococcus lactis subsp. lactis CBM 21, tested as an adjunct culture for the making of Squacquerone cheese in a pilot-scale plant. The biocontrol agent remained at a high level throughout the cheese refrigerated storage, without having a negative influence on the viability of the conventional Streptococcus thermophilus starter. The inclusion of CBM 21 in Squacquerone cheesemaking proved to be more effective compared to the traditional one, to reduce total coliforms and Pseudomonas spp. Moreover, the novel/innovative adjunct culture tested did not negatively modify the proteolytic patterns of Squacquerone cheese, but it gave rise to products with specific volatile and texture profiles. The cheese produced with CBM 21 was more appreciated by the panelists with respect to the traditional one.

Abstract: This work demonstrates that Lactococcus lactis subsp. lactis strains that display antimicrobial activity with respect to test cultures (potential pathogens) synthesize biogenic amines. Strains K-205 and F-116 produce submicromolar amounts of dopamine and its 2,3-dihydroxyphenylalanine precursor (DOPA) in a medium that is devoid of dopamine and DOPA. It was also revealed that exogenous neuromediators such as adrenaline (epinephrine), dopamine, and serotonin stimulated the growth and antimicrobial activity of some strains at micromolar concentrations. The growth of L. lactis subsp. lactis strain 194 was threefold accelerated by all the neurotransmitters. The stimulatory effect was observed after 6 and 12 h of cultivation. Epinephrine and serotonin failed to produce a statistically significant effect on the growth of the other tested strains (K-205, 729, and F-116). Among the neurochemicals under study, dopamine exerted the maximum (40%) stimulatory effect on the antimicrobial activity of the tested strains with both gram-positive and negative bacteria. However, these strains only insignificantly influenced the growth of fungi, presumably because this process was activated by the neurochemicals. [ABSTRACT FROM AUTHOR]

Predominance of beneficial bacteria helps to establish a healthy microbiota in fish gastrointestinal system and thus to reduce emerging pathogen. In this study, the colonization efficacy of Lactococcus lactis subsp. lactis CF4MRS in Artemia franciscana and its potential as a probiotic in suppressing Edwardsiella sp. infection were investigated in vivo. The colonization extent of the bioencapsulated L. lactis was established through visualization of gfp gene-transformed L. lactis in A. franciscana. Here, we demonstrate that when A. franciscana is administrated with L. lactis at 108 CFU mL−1 for 8 h, the highest relative percentage of survival (RPS = 50.0) is observed after inoculation with Edwardsiella sp. The total counts of L. lactis entrapped in Artemia were the highest (ranged from 3.2 to 5.1 × 108 CFU mL−1), when 108-109 CFU mL−1 of L. lactis was used as starting inoculum, with the bioencapsulation performed within 8-24 h. Fluorescent microscopy showed gfp-transformed L. lactis colonized the external trunk surfaces, mid-gut and locomotion antennules of the A. franciscana nauplii. These illustrations elucidate the efficiency of colonization of L. lactis in the gastrointestinal tract and on the body surfaces of Artemia. In conclusion, L. lactis subsp. lactis CF4MRS shows a good efficacy of colonization in Artemia and has the potential for biocontrol/probiotic activity against Edwardsiella sp. infection. [ABSTRACT FROM AUTHOR]

Lactic Acid Bacteria (LAB) have a great potential as bio-preservatives. The live cells and supernatant Lactococcus lactis subsp. lactis induced bacteriological changes in Onchorhynchus mykiss fillet by spray and immersion methods was studied during vacuumpackaged storage at 4 ° C for 15 days. 40 kg of O. mykiss were prepared from a culture farm in Oshnavieh (Northwest Iran) and 112 fillet samples (100g) were prepared by aseptic method. L. lactis subsp. lactis (PTCC1336) bacteria was cultured in MRS culture medium. Its supernatant (2%, 4%) was extracted and 106 CFUml-1 dilutions of LAB were prepared and tested on the fillets to enhance their shelf life. All samples were evaluated regarding to growth of psychrotrophic, psychrophilic, mesophilic bacteria, molds and yeasts. Four characteristics including of odor, flavor, texture and color of fillets after and before cooking were evaluated for sensory analysis on days 1, 5, 10 and 15 and compared with control samples. The 4% supernatant and live bacteria were more effective than that of 2% and control (p<0.05). The amounts of corrosive bacteria in 4% and live cells in storage time were less than human consumption limits (7log CFUg-1), whereas in control and 2% supernatant treatments were more than that limits. The results showed that increasing the percentage of supernatant was more effective on bacteriologic factors and enhanced sensory characteristics of rainbow trout fillets (p<0.05). [ABSTRACT FROM AUTHOR]

Nisin is a safe, approved and commercial bacteriocin that is produced by Lactococcus lactis subsp. lactis. Since lactate accumulation in fermentation medium reduces L. lactis growth and nisin production, Yarrowia lipolytica , a lactate consuming yeast and L. lactis subsp. lactis , were simultaneously cultured in a molasses based medium. Y. lipolytica is not able to consume sucrose as carbon source, but rather consumes lactate and hence decrease lactic acid titer by 10% in the medium. Lactic acid consumption, 15% increased pH value and stimulated L. lactis growth. In the mixed culture, nisin production and L. lactis growth were 50% and 49% higher than that of pure culture, respectively. Also the results showed that specific growth rate of L. lactis increased 4 times more than that of the pure culture. [ABSTRACT FROM AUTHOR]

In the present study, evaluation of antimicrobial activities of Lactococcus lactis subsp. lactis CF4MRS bacteriocin-like substances (BLIS) against various fish pathogens was performed using an agar well diffusion assay. The cell-free supernatant (CFS) was first pre-treated using four different bioassays. In the first treatment T1, CFS was treated with catalase, and the pH was adjusted to 6.5 with NaOH to eliminate the inhibitory effect of H2O2 and/or lactic acid. In T2, CFS was treated with only 1 mg/mL catalase. In T3, only the pH was modified and adjusted (6.5). For T4, no pretreatment was done on the CFS. Our results showed all tested pathogens: Pseudomonas fluorescens ATCC 13525, P. aeruginosa ATCC 10145, Klebsiella pneumonia ATCC 10031, Escherichia coli ATCC 25922, Aeromonas hydrophila ATCC 49140, Edwardsiella tarda BCRC 16703 and Serratia marcescens (Monash culture collection), were susceptible to L. lactis CFS (T4). This bacterial inhibition activity was presumably due to BLIS present in CFS. However, the CFS lost its antimicrobial activity when pH was adjusted and treated with enzyme catalase (T1 and T3). This inhibitory effect would be attributed to either organic acid or H2O2 produced by the bacterium. On the other hand, CFS treated with only catalase (T2) exerted similar inhibitory effect against the pathogens as showed by the untreated CFS (T4). BLIS in CFS were subsequently determined using HPLC method. Our results revealed that lactic acid in BLIS indeed plays the important role in bacterial inhibition, suggesting the bacteria could be potentially used in managing and controlling fish diseases. [ABSTRACT FROM AUTHOR]

Information on the ecology of the "phage-bacterial host" system is given. The interaction of cultures of lactococci from the collection of the Siberian Research Institute of Cheese with associations of phages was investigated. Infection of sensitive cells with bacteriophage led to cell lysis, which was manifested by negative colonies on the lawn of a lactococcal culture. Characteristics of the biological properties of bacteriophages in the composition of phage associations are given (lytic activity, spectrum of lytic activity, specificity of action). Differentiation of species lysotypes of bacteriophages of mesophilic lactococci, selected at a single cheese enterprise in the Altai Territory was noted. The index of the lytic activity of the investigated phage associations ranged from 0.19 (sample of Lactococcus lactis subsp. Lactis biovar diacetylactis) to 0.24 (sample of Lactococcus lactis subsp. Lactis) from studied strains. The value of the lyotype updated coefficient for the entire array of data varied from 0.25 to 1.00. It is concluded that the specificity of cheese biotechnology together with the evolutionary and genetic determinants of the microworld predetermine a constant high risk of cell phagolysis of starter cultures. Experimental studies confirmed the need to consider the phagocyte of lactic acid bacteria in biotechnology. [ABSTRACT FROM AUTHOR]

Environmental contamination caused by heavy metals poses a major threat to the wildlife and human health for their toxicity and intrinsically persistent nature. Some specific food grade bacteria have properties that enable them to eliminate heavy metals from food and water. Lactococcus lactis subsp. lactis , newly isolated from pickles, is a cadmium (Cd) tolerant bacteria. Cd resistant properties of the lactis was evaluated under different Cd stresses. Cd accumulation in different cellular parts was determined by ICP-MS and cell morphology changes were measured by SEM-EDS and TEM-EDS. In addition, functional groups associated with Cd resistance were detected by infrared spectroscopic analysis. The results indicated that Cd mainly accumulated in the cell surface structures including cytoderm and cytomembrane. Functional groups such as OH and NH 2 in the cell surface played essential roles in Cd biosorption. The elements of O, P, S, and N of polysaccharide, membrane protein and phosphatidate in the cell surface structures might be responsible for Cd biosorption for their strong electronegativity. This study indicated that ultrastructural analysis can be a supplemental method to study heavy metal resistance mechanism of microorganism and the newly isolated lactococcus lactis subsp. lactis has great potential to be applied to decontamination of heavy metals. [ABSTRACT FROM AUTHOR]

The presented study aimed to verify the effect of different pH values, enzyme solutions and heat treatments on the antimicrobial activity of the bacteriocinogenic strain Lactococcus lactis subsp. lactis Lc08 and to test their antimicrobial activity against Listeria monocytogenes in reconstituted skim milk at refrigeration temperatures. This strain was previously described as a nisin Z producer and capable of inhibiting L. monocytogenes growth in in vitro tests. The antimicrobial activity of the bacteriocin cell-free supernatant of Lc08 was sensitive to enzyme treatments (except papain). The pH values and heating (65ºC for 30min, 75ºC for 15s) had no apparent effect on the antimicrobial activity of the bacteriocin produced by Lc08. Only treatment at autoclave conditions result in loss of their antimicrobial activity. Lc08 presented antimicrobial activity against L. monocytogenes in the milk system after 12h at 25ºC. No effect was found at 7ºC. The results show the application viability of the Lc08 in food systems as a biopreservative against L. monocytogenes.

Eight isolates of Lactococcus lactis subsp. lactis were isolated and identified by phenotypic and molecular characterisation out of 23 isolates of lactic acid bacteria (LAB) from different dairy and non-dairy sources. Out of eight strains, four were obtained from dairy and four from non-dairy sources. All eight strains of L. lactis subsp. lactis were able to produce zones of inhibition against the Lactobacillus acidophilus NCDC 015. The antimicrobial agent produced by the isolates inhibited the growth of a range of related lactic acid bacteria and certain Gram positive food-borne microorganisms. The antimicrobial agent, i.e. nisin, produced by the strains was confirmed by PCR amplification of nisin gene sequences of 174 bp size. Antibiotic susceptibility test to 21 different types of antibiotics was evaluated. All the isolates were resistant to fosfomycin, cefepime, amikacin, kanamycin, neomycin, nalidixic acid, pipemidic acid, norfloxacin, sulphadiazine, colistin, polymixin, teicoplanin, nystatin, and amphotericin B but susceptible to ampicillin, erythromycin, spiramycin, spectinomycin, ciprofloxacin, rifampicin, and trimethoprim.

[Display omitted] • Metabolic characteristics of Lactococcus lactis strains are described. • Fermentation profile correlates with metabolic profile. • Peptides, esters and tributyrin may affect the growth of Lactococcus lactis strains. • Peptides, esters and tributyrin can be used as markers for fast acid-producing strains. The bacterial starter has a crucial role in fermentation of dairy products; however, knowledge about metabolic differences in Lactococcus (L.) lactis subsp. lactis strains with different fermentation rates is limited. We analyzed the fermentation capacity and metabolic profiles of 17 L. lactis subsp. lactis strains through ultra-performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry Elevated Energy. Metabolomics results revealed significant differences in metabolites between the fast group (fermentation time < 16 h) and slow group (fermentation time ≥ 16 h). In the fast group, 98 and 55 metabolites were increased and decreased, respectively. The fast group was enriched with peptides and lipids, and we found that peptides, esters, and tributyrin can be used as biomarkers to distinguish between groups. Our results implicated that tributyrin plays a role in regulating strain growth. This study provides a novel insight into the metabolic cause of different acid production rates between individuals L. lactis subsp. lactis strains. [ABSTRACT FROM AUTHOR]

Resumen Objetivo: Aislar, purificar y conservar cepas de Streptococcus spp. y Lactobacillus spp. de la cavidad bucal, y enfrentarlas “in vitro” a bacterias lácticas. Materiales y métodos: Se seleccionaron individuos con caries activas y se recolectaron muestras de saliva. Para recuperar Streptococcus spp., se empleó medio Mitis Salivarius (Difco,™ Detroit, MI, Estados Unidos) y para Lactobacillus spp. se usó Rogosa (Biokar Diagnostics, Beauvais, Francia). Como cepas productoras de bacteriocinas, se utilizaron 7 cepas de Lactococcus lactis subsp. lactis, 2 de Leuconostoc mesenteroides y 1 de Lactococcus lactis subsp. diacetylactis. La actividad antagónica de las bacterias lácticas al crecimiento “in vitro” de bacterias cariogénicas se determinó con el método de difusión en agar. Resultado: El desarrollo y la multiplicación de las cepas de Streptococcus spp. de origen bucal ensayadas se vieron afectados por la presencia de metabolitos generados por las cepas de Lactococcus lactis subsp. lactis. Conclusión: El crecimiento de las cepas de Streptococcus spp. fue inhibido por efecto de L. lactis subsp. lactis. Palabras clave: Lactococcus lactis subsp. lactis, microorganismos cariogénicos, metabolitos antagónicos, bacterias lácticas. Resumen Objetivo: Aislar, purificar y conservar cepas de Streptococcus spp. y Lactobacillus spp. de la cavidad bucal, y enfrentarlas “in vitro” a bacterias lácticas. Materiales y métodos: Se seleccionaron individuos con caries activas y se recolectaron muestras de saliva. Para recuperar Streptococcus spp., se empleó medio Mitis Salivarius (Difco,™ Detroit, MI, Estados Unidos) y para Lactobacillus spp. se usó Rogosa (Biokar Diagnostics, Beauvais, Francia). Como cepas productoras de bacteriocinas, se utilizaron 7 cepas de Lactococcus lactis subsp. lactis, 2 de Leuconostoc mesenteroides y 1 de Lactococcus lactis subsp. diacetylactis. La actividad antagónica de las bacterias lácticas al crecimiento “in vitro” de bacterias cariogénicas se determinó con el método de difusión en agar. Resultado: El desarrollo y la multiplicación de las cepas de Streptococcus spp. de origen bucal ensayadas se vieron afectados por la presencia de metabolitos generados por las cepas de Lactococcus lactis subsp. lactis. Conclusión: El crecimiento de las cepas de Streptococcus spp. fue inhibido por efecto de L. lactis subsp. lactis. Palabras clave: Lactococcus lactis subsp. lactis, microorganismos cariogénicos, metabolitos antagónicos, bacterias lácticas.

Heavy metal contamination poses a major threat to the environment and human health for their potential toxicity and non-biodegradable properties. At present, some probiotics bacteria are reported to have great potential to eliminate heavy metals from food and water. In this study, resistance properties of a newly isolated Lactococcus lactis subsp. lactis for cadmium were studied by antioxidant assays and proteomics analysis. Antioxidant capacity of this strain was significantly activated under cadmium stress indicated by Fenton reaction, DPPH assay, SOD assay and GSH assay. Intracellular antioxidant enzyme systems, such as superoxide dismutase, glutathione reductase and catalase were suggested to play vital roles in the activated antioxidant capacity. The up-regulated cad A was associated with the activated P-type ATPases that plays an important role in cadmium resistance. Proteomics analysis identified 12 over-expressed proteins under 50 mg/L cadmium stress and these proteins are abundant in oxidative stress response and energy metabolism regulation, which were considered as consequences as cadmium resistance of the strain. Thus, the probiotics Lactococcus lactis subsp. lactis may resist cadmium stress through antioxidant approach and enhanced energy metabolism. The food grade lactis strain may be applied in metal decontamination in environment and food/feed. [ABSTRACT FROM AUTHOR]

Six lactic acid bacteria strains (four Lactobacillus plantarum strains and one each of Lactococcus lactis subsp. lactis and Pediococcus pentosaceus ) have been isolated and shown to possess anti-oxidant activity. In this study, we determined their acid, bile, salt resistance, and adhesion activity on human enterocyte-like HT-29-Luc and Caco-2 cells. An isolate Lc. lactis S-SU2 showed highest bile resistance and adhesion activity compared to type strains. S-SU2 could ferment both 10% skimmed milk and soy milk while the type strain could not ferment soy milk. Soy milk fermented with S-SU2 showed an increased nitric oxide (NO) secretion in the mouse macrophage RAW264.7 cells without bacterial lipopolysaccharide (LPS). Furthermore, the inhibitory effects of the fermented soy milk on Escherichia coli O111 LPS-induced NO secretion were higher than those of fresh soy milk. Inflammatory bowel disease (IBD) was induced in mice fed either 5% (w/v) dextran sodium sulfate (DSS) in drinking water or 50% soy milk in drinking water. Shortening of colon length, breaking of epithelial cells, lowering liver and thymus weights, and enlargement of spleen are some of the characteristics observed in the IBD, which were prevented by the use of soy milk fermented with Lc. lactis S-SU2. [ABSTRACT FROM AUTHOR]

Data on the dependence of growth characteristics of Lactococcus lactis subsp. lactis 729 and TB2 extracted from milk and homemade curd on the content of casein peptone (CP) as the main source of nitrogen in the agar medium is presented. The number of colony-forming units (CFUs), cell division rate (CDR), and mean hourly doubling time (HDT) were compared between two time segments of cultivation: from 1 to 2.5 h, and from 2.5 to 3.5 h. In liquid media, logarithmic growth was observed for the 729 strain in all groups for 3.5 h at minimal pH of 6.5. The maximum biomass production rate (2.5 × 10 cells/mL) was observed in the media containing the meat extract; the minimal HDT was in the biomass transferred from the minimal MA4 medium to the enriched M7 medium. In contrast with the TB2 strain, the 729 strain does not form colonies on agar media at CP concentrations below 0.4%. The colonies of the TB2 strain increase in size from 2.85 mm to 5 mm when decreasing CP concentration from 1 to 0.4%. The yeast extract has a stimulating effect in liquid media at said concentration ratios, leading to an increase in the efficiency of cell division at lower rates of lactic acid production, to pH of 5.5 when oligopeptide transport is blocked. The meat extract provides adaptation of bacteria to the conditions of excessive acidity and has positive effect on cell division in the 729 strain at later stages of bacterial colony development. The smaller size of colonies of the strain might be evidence of active acid formation. [ABSTRACT FROM AUTHOR]