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Mixed thermophilic and mesophilic commercial starter cultures (CSCs), particularly those including Streptococcus thermophilus as a primary milk acidifier, have been found to reduce growth and counteract in situ nisin A (NisA+) antilisterial effects by the novel, indigenous Lactococcus lactis subsp. cremoris M78 costarter in traditional Graviera thermized milk cheese curds. Therefore, this model challenge study evaluated growth and in situ NisA+ activity of strain M78 in coculture with S. thermophilus ST1 singly in sterilized raw milk (SRM). Strain ST1, derived from a CSC for cheese, was challenged at two inoculation levels (5 and 7 log CFU/mL) in SRM against 6 and 3 log CFU/mL of strain M78 and Listeria monocytogenes, respectively. Pure cultures of each strain and cocultures of strain ST1 with the CSC L. lactis LL2, in replacement of strain M78, served as controls. At the high (7-log) inoculation level, the rapid, competitive growth (>9.3 log CFU/mL) of S. thermophilus ST1 reduced growth of both L. lactis by at least 10-fold; the industrial strain LL2 retained slightly higher relative population densities (7.4 to 9.1%) than the wild NisA+ strain M78 (3.8 to 5.6%) after 6 h at 37°C, followed by an additional 66 h of incubation at 22°C. In full contrast, at the low (5-log) inoculation level, S. thermophilus ST1 failed to predominate in SRM at 6 h; thus, the starter lactic acid bacteria populations were reversed in favor of L. lactis. Notably, strain M78 retained higher relative population densities (83.0 to 90.1%) than the CSC strain LL2 (80.3 to 85.2%) at 22°C. Moreover, at the 5-log ST1 level, the direct and deferred in situ NisA+ activities of strain M78 were at similar levels with its pure culture with L. monocytogenes in SRM, whereas at the 7-log ST1 level, the respective NisA+ effects were counteracted. Hence, 10- to 100-fold lowered inoculation levels of CSC S. thermophilus are required to enhance the performance of the M78 costarter in traditional Greek cheese technologies.

Accumulating evidence suggests that Lactococcus lactis subsp. cremoris YRC3780 isolated from kefir has the potential to alleviate allergic responses. Herein, we investigated the effect of YRC3780 on a murine model of Japanese cedar pollinosis (JCP). BALB/c mice immunized with cedar pollen extract (CPE) exhibited an increase in serum immunoglobulin E and developed nasal inflammatory responses including sneezing, nasal hyperresponsiveness, and nasal eosinophil accumulation upon intranasal allergen challenge. These responses were suppressed by the oral administration of YRC3780, although the effects on CPE-induced sneezing response and eosinophil infiltration were not statistically significant. Total fecal microbiota diversity was not affected by allergen immunization and challenge or by YRC3780 administration. However, the abundances of Bifidobacteriales, Veillonellaceae, Lactococcus, and Lactococcus lactis were larger and that of Bacteroides was smaller in YRC3780-treated mice compared with those in CPE-challenged and YRC3780-untreated mice. Our findings suggest the usefulness of YRC3780 for alleviating JCP.

Gas chromatography mass spectrometry (GC-MS) and headspace gas chromatography mass spectrometry (HS/GC-MS) were used to study metabolites produced by Lactococcus lactis subsp. cremoris MG1363 grown at a temperature of 30 °C with and without agitation at 150 rpm, and at 37 °C without agitation. It was observed that L. lactis produced more organic acids under agitation. Primary alcohols, aldehydes, ketones and polyols were identified as the corresponding trimethylsilyl (TMS) derivatives, whereas amino acids and organic acids, including fatty acids, were detected through methyl chloroformate derivatization. HS analysis indicated that branched-chain methyl aldehydes, including 2-methylbutanal, 3-methylbutanal, and 2-methylpropanal are degdradation products of isoleucine, leucine or valine. Multivariate analysis (MVA) using partial least squares discriminant analysis (PLS-DA) revealed the major differences between treatments were due to changes of amino acids and fermentation products.

The complex microbiota of cheese starters plays a key role in determining the structure and flavour of the final product, primarily through their acid-forming capacity, protease activity, and exopolysaccharide synthesis. However, the specific microbial communities underlying the unique qualities of artisanal cheeses remain poorly understood. This study presents the microbiological and molecular genetic characterisation of the microbiome isolated from an artisanal cheese starter in Kosh-Agach, Altai, Russia. Metagenomic analysis of this starter revealed the presence of three bacterial genomes corresponding to those of Lactococcus lactis. Pure cultures from this starter were obtained by sequential subculture, and seventeen colonies displaying distinct characteristics on differential media were selected. Genome sequencing was performed for each colony. Bioinformatic analysis based on the rpoB gene grouped the isolates into three clusters, each corresponding to a distinct strain of Lactococcus lactis subsp. diacetilactis. This classification was further confirmed by microbiological and microscopic analyses. A notable finding was that none of the strains produced the characteristic aroma compounds of L. l. subsp. diacetilactis, namely, diacetyl and CO2. The functional properties and metabolic characteristics of this starter consortium are discussed.

Lactococcus lactis subsp. cremoris MG1363 is a paradigm strain for lactococci used in industrial dairy fermentations. However, despite of its importance for process development, no genome-scale metabolic model has been reported thus far. Moreover, current models for other lactococci only focus on growth and sugar degradation. A metabolic model that includes nitrogen metabolism and flavor-forming pathways is instrumental for the understanding and designing new industrial applications of these lactic acid bacteria. A genome-scale, constraint-based model of the metabolism and transport in L . lactis MG1363, accounting for 518 genes, 754 reactions, and 650 metabolites, was developed and experimentally validated. Fifty-nine reactions are directly or indirectly involved in flavor formation. Flux Balance Analysis and Flux Variability Analysis were used to investigate flux distributions within the whole metabolic network. Anaerobic carbon-limited continuous cultures were used for estimating the energetic parameters. A thorough model-driven analysis showing a highly flexible nitrogen metabolism, e.g., branched-chain amino acid catabolism which coupled with the redox balance, is pivotal for the prediction of the formation of different flavor compounds. Furthermore, the model predicted the formation of volatile sulfur compounds as a result of the fermentation. These products were subsequently identified in the experimental fermentations carried out. Thus, the genome-scale metabolic model couples the carbon and nitrogen metabolism in L . lactis MG1363 with complete known catabolic pathways leading to flavor formation. The model provided valuable insights into the metabolic networks underlying flavor formation and has the potential to contribute to new developments in dairy industries and cheese-flavor research.

The composition of intestinal microbiota is widely believed to not only affect gut health but also influence behaviour. This study aimed to evaluate the probiotic characteristics, antioxidant activity, and antidepressant- and anxiolytic-like activities of Lactococcus lactis subsp. cremoris LL95. This strain showed probiotic properties such as resistance in a simulated gastric tract model and survival at different concentrations of NaCl and bile salts. Moreover, antioxidant activity of LL95 was demonstrated through DPPH radical scavenging activity, scavenging of ABTS•+ radical and ferric ion reducing antioxidant power (FRAP) assays. Female C57BL/6 mice received LL95 orally at a dose of 109 UFC/day for 28 days. LL95 improved depressive- and anxiety-like behaviour, demonstrated by decreased immobility time in the tail suspension test and forced swim test and increased per cent of time spent in the open arms on the elevated plus maze. These findings indicate the potential antioxidant activity of LL95 and its role in behaviour, suggesting that probiotic may have therapeutic applications.

Lactococcus lactis and Lactococcus cremoris are broadly utilized as starter cultures for fermented dairy products and are inherently impacted by bacteriophage (phage) attacks in the industrial environment. Consequently, the generation of bacteriophage-insensitive mutants (BIMs) is a standard approach for addressing phage susceptibility in dairy starter strains. In this study, we characterized spontaneous BIMs of L. lactis DGCC12699 that gained resistance against homologous P335-like phages. Phage resistance was found to result from mutations in the YjdB domain of yccB, a putative autolysin gene. We further observed that alteration of a fused tail-associated lysin-receptor binding protein (Tal-RBP) in the phage restored infectivity on the yccB BIMs. Additional investigation found yccB homologs to be widespread in L. lactis and L. cremoris and that different yccB homologs are highly correlated with cell wall polysaccharide (CWPS) type/subtype. CWPS are known lactococcal phage receptors, and we found that truncation of a glycosyltransferase in the cwps operon also resulted in resistance to these P335-like phages. However, characterization of the CWPS mutant identified notable differences from the yccB mutants, suggesting the two resistance mechanisms are distinct. As phage resistance correlated with yccB mutation has not been previously described in L. lactis, this study offers insight into a novel gene involved in lactococcal phage sensitivity.

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.

Background A previous study showed that prebiotics and synbiotics administered in ovo into the egg air cell on the 12th day of incubation enhance the growth and development of chickens. However, the influence of this procedure on the development and efficiency of the innate immune system of broiler chickens is unclear. Therefore, the aim of this study was to evaluate whether the early (on the 12th day of embryo development) in ovo administration of selected prebiotics (inulin − Pre1 and Bi 2 tos − Pre2) and synbiotics (inulin + Lactococcus lactis subsp. lactis IBB SL1 − Syn1 and Bi 2 tos +  L. lactis subsp. cremoris IBB SC1 − Syn2) influences the innate immune system. Results Chickens (broiler, Ross 308) that were treated with Pre1 exhibited a decreased H/L ratio on D7, but an increased H/L ratio was observed on D21 and D35. In the remaining experimental groups, an increase in the H/L ratio was observed on D21 and D35. The oxidative potential of leukocytes measured using the NBT test increased on D21 in Pre2 and Syn1 groups. The rate of the phagocytic ability of leukocytes increased in Pre1 and Syn1 groups on D21. The phagocytic index decreased in Pre1 and Syn2 groups on D21 and D35. Concurrently, the count of WBC in circulating blood decreased on D21 in Pre1, Pre2, and Syn1 groups. The hematocrit value was increased in Syn1 chickens on D21, in Pre1 chickens on D35, and in Syn2 chickens on both time points. Conclusions Early in ovo treatment of chicken embryos with prebiotics and synbiotics may temporarily modulate not only the production/maturation of leukocytes but also their reactivity.

Background Bovine mastitis is a major challenge in dairy farms. Since the agents commonly used for pre- and post-dipping can affect the udder health by modifying milk microbiota, alternative products are needed. This study aimed to evaluate the effect of the use of pre- and post-dipping formulations containing the fermented broth of Nisin A-producing Lactococcus cremoris FT27 strain (treated group, TR) on the abundance and biodiversity of milk microbiota as compared to iodine-based commercial disinfectants (control group, CTR) during a three-month trial. The experiment was conducted on 20 dairy cows, divided into two groups (CTR and TR) of 10 lactating cows each. Milk samples were collected from two selected healthy quarters of each cow at 3 time-points. Microbial communities were investigated by cultural and sequence-based methods, and analyzed through bioinformatic and statistical approaches. Results Clear differences in bacterial community composition were observed among groups, with higher species richness in TR, especially of Staphylococcus , Enterococcus , Lactococcus , and Streptococcus genera. The microbiota was dominated by Firmicutes , followed by Actinobacteriota , Proteobacteria , and Bacteroidota . Staphylococcaceae family was significantly higher in TR ( p  < 0.009), whereas Carnobacteriaceae , Mycobacteriaceae , and Pseudomonadaceae were significantly lower ( p  = 0.005, p  = 0.001, and p  = 0.040, respectively). CTR had considerably higher abundances of the genera Alkalibacterium ( p  = 0.011), Pseudomonas_E ( p  = 0.045), Corynebacterium ( p  = 0.004), and Alloiococcus ( p  = 0.004), and lower abundances of Staphylococcus ( p  < 0.009). Milk microbiota changed noticeably during the experimental period, regardless of treatment. A significant decrease was observed in both groups for Firmicutes_A phylum, with an increment in Actinobacteriota phylum, Propionibacteriaceae family, and Cutibacterium genus. Streptococcaceae significantly decreased in CTR ( p  = 0.013) and rose in TR ( p  = 0.001). Several differences were observed between the two groups during the experimental period. Streptococcus genus almost disappeared in CTR ( p  = 0.013), whereas it significantly increased in TR ( p  = 0.001). Three and twelve enriched groups were significantly identified respectively in CTR and TR using LEfSe. Conclusions The use of Nisin A-based teat dip formulations could be linked to greater microbial diversity compared to commercial products. Despite the influence of seasonality, the experimental formulations maintained higher milk biodiversity, suggesting that lactic acid bacteria metabolites prevent alterations in the milk microbiota.