scholarly journals Functional strain redundancy and persistent phage infection in Swiss hard cheese starter cultures

2021 ◽  
Author(s):  
Vincent Somerville ◽  
Hélène Berthoud ◽  
Remo S. Schmidt ◽  
Hans- Peter Bachmann ◽  
Yi Hélène Meng ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Evolutionary Dynamics ◽  
Temporal Dynamics ◽  
Negative Impact ◽  
Bacterial Species ◽  
Starter Culture ◽  
Streptococcus Thermophilus ◽  
Starter Cultures ◽  
Lactobacillus Delbrueckii ◽  
Shotgun Metagenomics

AbstractUndefined starter cultures are poorly characterized bacterial communities from environmental origin used in cheese making. They are phenotypically stable and have evolved through domestication by repeated propagation in closed and highly controlled environments over centuries. This makes them interesting for understanding eco-evolutionary dynamics governing microbial communities. While cheese starter cultures are known to be dominated by a few bacterial species, little is known about the composition, functional relevance, and temporal dynamics of strain-level diversity. Here, we applied shotgun metagenomics to an important Swiss cheese starter culture and analyzed historical and experimental samples reflecting 82 years of starter culture propagation. We found that the bacterial community is highly stable and dominated by only a few coexisting strains of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. lactis. Genome sequencing, metabolomics analysis, and co-culturing experiments of 43 isolates show that these strains are functionally redundant, but differ tremendously in their phage resistance potential. Moreover, we identified two highly abundant Streptococcus phages that seem to stably coexist in the community without any negative impact on bacterial growth or strain persistence, and despite the presence of a large and diverse repertoire of matching CRISPR spacers. Our findings show that functionally equivalent strains can coexist in domesticated microbial communities and highlight an important role of bacteria-phage interactions that are different from kill-the-winner dynamics.

scholarly journals Functional strain redundancy and persistent phage infection in Swiss hard cheese starter cultures

2021 ◽  
Author(s):  
Vincent Somerville ◽  
Hélène Berthoud ◽  
Remo S. Schmidt ◽  
Hans-Peter Bachmann ◽  
Yi Hélène Meng ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Evolutionary Dynamics ◽  
Temporal Dynamics ◽  
Negative Impact ◽  
Bacterial Species ◽  
Starter Culture ◽  
Streptococcus Thermophilus ◽  
Starter Cultures ◽  
Lactobacillus Delbrueckii ◽  
Shotgun Metagenomics

AbstractUndefined starter cultures are poorly characterized bacterial communities from environmental origin used in cheese making. They are phenotypically stable and have evolved through domestication by repeated propagation in closed and highly controlled environments over centuries. This makes them interesting for understanding eco-evolutionary dynamics governing microbial communities. While cheese starter cultures are known to be dominated by a few bacterial species, little is known about the composition, functional relevance, and temporal dynamics of strain-level diversity. Here, we applied shotgun metagenomics to an important Swiss cheese starter culture and analyzed historical and experimental samples reflecting 82 years of starter culture propagation. We found that the bacterial community is highly stable and dominated by only a few coexisting strains of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. lactis. Genome sequencing, metabolomics analysis, and co-culturing experiments of 43 isolates show that these strains are functionally redundant, but differ tremendously in their phage resistance potential. Moreover, we identified two highly abundant Streptococcus phages that seem to stably coexist in the community without any negative impact on bacterial growth or strain persistence, and despite the presence of a large and diverse repertoire of matching CRISPR spacers. Our findings show that functionally equivalent strains can coexist in domesticated microbial communities and highlight an important role of bacteria-phage interactions that are different from kill-the-winner dynamics.

scholarly journals Improvement of the Texture of Yogurt by Use of Exopolysaccharide Producing Lactic Acid Bacteria

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Xue Han ◽  
Zhe Yang ◽  
Xueping Jing ◽  
Peng Yu ◽  
Yingchun Zhang ◽  
...  
Keyword(s):  
Dairy Products ◽  
Starter Culture ◽  
Streptococcus Thermophilus ◽  
Fermented Milk ◽  
Starter Cultures ◽  
Lactobacillus Delbrueckii ◽  
Exopolysaccharide Production ◽  
Fermented Dairy Products ◽  
Fermented Dairy

19Streptococcus thermophiluswith high exopolysaccharide production were isolated from traditional Chinese fermented dairy products. The exopolysaccharide and viscosity of milk fermented by these 19 isolates were assayed. The strains ofStreptococcus thermophiluszlw TM11 were selected because its fermented milk had the highest exopolysaccharide content (380 mg/L) and viscosity (7716 mpa/s). ThenStreptococcus thermophiluszlw TM11 was combined withLactobacillus delbrueckiisubsp.bulgaricus3 4.5 and the combination was named SH-1. The quality of the yogurt fermented by SH-1 and two commercial starter cultures (YO-MIX 465, YF-L711) were compared. It was shown that the exopolysaccharide content of yogurt fermented by SH-1 was similar to that of yogurt fermented by YF-L711 and significantly higher than YO-MIX 465 (p<0.05). In addition, the yogurt fermented by SH-1 had the lowest syneresis (8.5%) and better texture and sensory than the samples fermented by YO-MIX 465 and YF-L711. It manifested that the selected higher exopolysaccharide production starter SH-1 could be used as yogurt starter and reduce the amount of adding stabilizer, which can compare with the imported commercial starter culture.

scholarly journals Research of rheological properties of fermented milk ice cream with high content of exopolysaccharides

2021 ◽  
Vol 30 ◽  
pp. 01015
Author(s):  
Ekaterina Pozhidaeva ◽  
Lyubov Golubeva ◽  
Anton Sadchenko ◽  
Yana Dymovskih
Keyword(s):  
Starter Culture ◽  
Control Sample ◽  
Ice Cream ◽  
Streptococcus Thermophilus ◽  
Fermented Milk ◽  
Starter Cultures ◽  
Lactobacillus Delbrueckii ◽  
Lactobacillus Bulgaricus ◽  
Thawing Rate ◽  
Milk Mixture

As a result of scientific and technological research, the ingredient composition and the feasibility of using complex bacterial starter cultures as part of fermented milk ice cream have been substantiated. The objects of the study were samples of mixtures for the production of fermented milk ice cream were considered, which included dairy and non-dairy components, including complex bacterial starter cultures: YF-L812 (Streptococcus thermophilus, Lactobacillus bulgaricus) - control sample and YO-PROX 777 (Streptococcus thermophilus, Lactobacillus delbrueckii ssp.bulgaricus), as well as pectin stabilizers “Grindsted Pektin LC 710” and “Cremodan SE 334” with a concentration of 0.1-0.7%. It was found that a prototype sample with starter culture YO-PROX 777 has increased values of dynamic viscosity compared with the control sample with similar stabilizers and their identical concentrations, which is evidence of the accumulation of exopolysaccharides in the fermented fermented milk mixture. A prototype of fermented milk ice cream has better shape stability during temperature control, the thawing rate is reduced by 1.6 times compared to the control. The degree of overrun of the prototype fermented milk ice cream is 37.6%, which is 1.2 times higher compared to the control.

Effect of Carbon Dioxide under High Pressure on the Survival of Cheese Starter Cultures

2000 ◽  
Vol 63 (6) ◽  
pp. 758-762 ◽  
Author(s):  
DIANE L. VAN HEKKEN ◽  
KATHLEEN T. RAJKOWSKI ◽  
PEGGY M. TOMASULA ◽  
MICHAEL H. TUNICK ◽  
VIRGINIA H. HOLSINGER
Keyword(s):  
High Pressure ◽  
Starter Culture ◽  
Streptococcus Thermophilus ◽  
Processing Method ◽  
Starter Cultures ◽  
Lactobacillus Delbrueckii ◽  
Processing Conditions ◽  
New Process ◽  
New Processing ◽  
Mrs Broth

A new processing method that rapidly forms curds and whey from milk has the potential to improve cheesemaking procedures if cheese starter cultures can tolerate the processing conditions. The survival of Lactobacillus delbrueckii ssp. bulgaricus, Lactococcus lactis ssp. lactis, or Streptococcus thermophilus through this new process was evaluated. Inoculated milk containing 0, 1, or 3.25% fat or Lactobacillus MRS broth or tryptone yeast lactose broth (depending on microorganism used) was sparged with CO2 to a pressure of 5.52 MPa and held for 5 min at 38°C. Broth contained 7.93 to 8.78 log CFU/ml before processing and 7.84 to 8.66 log CFU/ml afterward. Before processing, milk inoculated with L. bulgaricus, L. lactis, or S. thermophilus contained 6.81, 7.35, or 6.75 log CFU/ml, respectively. After processing, the curds contained 5.68, 7.32, or 6.50 log CFU/g, and the whey had 5.05, 6.43, or 6.14 log CFU/ml, respectively. After processing, the pHs of control samples were lower by 0.41 units in broth, 0.53 units in whey, and 0.89 units in curd. The pH of the processed inoculated samples decreased by 0.3 to 0.53 units in broth, 0.32 to 0.37 units in whey, and 0.93 to 0.98 units in the curd. Storing curds containing L. lactis at 30°C or control curds and curds with L. bulgaricus or S. thermophilus at 37°C for an additional 48 h resulted in pHs of 5.22, 5.41, 4.53, or 4.99, respectively. This study showed that milk inoculated with cheese starter cultures and treated with CO2 under high pressure to precipitate casein-produced curds that contained sufficient numbers of viable starter culture to produce lactic acid, thereby decreasing the pH.

scholarly journals A Cryptic Non-Inducible Prophage Confers Phage-Immunity on the Streptococcus thermophilus M17PTZA496

Viruses ◽  
2018 ◽  
Vol 11 (1) ◽  
pp. 7 ◽  
Author(s):  
Vinícius da Silva Duarte ◽  
Sabrina Giaretta ◽  
Stefano Campanaro ◽  
Laura Treu ◽  
Andrea Armani ◽  
...  
Keyword(s):  
Mitomycin C ◽  
Defense Mechanisms ◽  
Large Subunit ◽  
Bacterial Species ◽  
Dairy Industry ◽  
Model Organism ◽  
Streptococcus Thermophilus ◽  
Starter Cultures ◽  
Economic Losses ◽  
Important Species

Streptococcus thermophilus is considered one of the most important species for the dairy industry. Due to their diffusion in dairy environments, bacteriophages can represent a threat to this widely used bacterial species. Despite the presence of a CRISPR-Cas system in the S. thermophilus genome, some lysogenic strains harbor cryptic prophages that can increase the phage-host resistance defense. This characteristic was identified in the dairy strain S. thermophilus M17PTZA496, which contains two integrated prophages 51.8 and 28.3 Kb long, respectively. In the present study, defense mechanisms, such as a lipoprotein-encoding gene and Siphovirus Gp157, the last associated to the presence of a noncoding viral DNA element, were identified in the prophage M17PTZA496 genome. The ability to overexpress genes involved in these defense mechanisms under specific stressful conditions, such as phage attack, has been demonstrated. Despite the addition of increasing amounts of Mitomycin C, M17PTZA496 was found to be non-inducible. However, the transcriptional activity of the phage terminase large subunit was detected in the presence of the antagonist phage vB_SthS-VA460 and of Mitomycin C. The discovery of an additional immune mechanism, associated with bacteriophage-insensitive strains, is of utmost importance, for technological applications and industrial processes. To our knowledge, this is the first study reporting the capability of a prophage integrated into the S. thermophilus genome expressing different phage defense mechanisms. Bacteriophages are widespread entities that constantly threaten starter cultures in the dairy industry. In cheese and yogurt manufacturing, the lysis of Streptococcus thermophilus cultures by viral attacks can lead to huge economic losses. Nowadays S. thermophilus is considered a well-stablished model organism for the study of natural adaptive immunity (CRISPR-Cas) against phage and plasmids, however, the identification of novel bacteriophage-resistance mechanisms, in this species, is strongly desirable. Here, we demonstrated that the presence of a non-inducible prophage confers phage-immunity to an S. thermophilus strain, by the presence of ltp and a viral noncoding region. S. thermophilus M17PTZA496 arises as an unconventional model to study phage resistance and potentially represents an alternative starter strain for dairy productions.

Enumeration of starter cultures in fermented milks

1996 ◽  
Vol 63 (1) ◽  
pp. 151-158 ◽  
Author(s):  
Hamid B. Ghoddusi ◽  
Richard K. Robinson
Keyword(s):  
Quality Control ◽  
Prussian Blue ◽  
Yeast Extract ◽  
Streptococcus Thermophilus ◽  
Starter Cultures ◽  
Lactobacillus Delbrueckii ◽  
Proteose Peptone ◽  
Different Strains ◽  
Differential Counts

SummarySome media available for the isolation and enumeration of starter cultures employed for the manufacture of cheese, yogurt and bio-yogurt were examined. Reddy's medium or a modification of Elliker's medium was found to be most satisfactory forLactococcusspp., while trypticase phytone yeast (TPY) agar with a mixture of antibiotics proved suitable for the discrete enumeration ofBifidobacteriumspp. The inclusion of Prussian blue (PB) in reinforced clostridial medium or tryptone proteose peptone yeast extract (TPPY) agar gave excellent differential counts for the starter bacteria in yogurt even when the culture was imbalanced, while TPPY (PB) agar allowed the visible separation of all four of the organisms that might be found in a typical bio-yogurt, namelyLactobacillus delbrueckiisubsp.bulgaricus, Streptococcus thermophilus, a,Bifidobacteriumsp. andLb. acidophilus. It was noted that variation among different strains of any given species could change the expected reactions, so for quality control purposes the suggested media may need to be modified to cope with the specific cultures in use.

scholarly journals Unleashing Natural Competence in Lactococcus lactis by Induction of the Competence Regulator ComX

2017 ◽  
Vol 83 (20) ◽  
Author(s):  
Joyce Mulder ◽  
Michiel Wels ◽  
Oscar P. Kuipers ◽  
Michiel Kleerebezem ◽  
Peter A. Bron
Keyword(s):  
Lactococcus Lactis ◽  
Genetic Manipulation ◽  
Bacterial Species ◽  
Streptococcus Thermophilus ◽  
Starter Cultures ◽  
Natural Competence ◽  
Content Type ◽  
Competence Gene ◽  
Gene Sets ◽  
Novel Traits

ABSTRACT In biotechnological workhorses like Streptococcus thermophilus and Bacillus subtilis, natural competence can be induced, which facilitates genetic manipulation of these microbes. However, in strains of the important dairy starter Lactococcus lactis, natural competence has not been established to date. However, in silico analysis of the complete genome sequences of 43 L. lactis strains revealed complete late competence gene sets in 2 L. lactis subsp. cremoris strains (KW2 and KW10) and at least 10 L. lactis subsp. lactis strains, including the model strain IL1403 and the plant-derived strain KF147. The remainder of the strains, including all dairy isolates, displayed genomic decay in one or more of the late competence genes. Nisin-controlled expression of the competence regulator comX in L. lactis subsp. lactis KF147 resulted in the induction of expression of the canonical competence regulon and elicited a state of natural competence in this strain. In contrast, comX expression in L. lactis NZ9000, which was predicted to encode an incomplete competence gene set, failed to induce natural competence. Moreover, mutagenesis of the comEA-EC operon in strain KF147 abolished the comX-driven natural competence, underlining the involvement of the competence machinery. Finally, introduction of nisin-inducible comX expression into nisRK-harboring derivatives of strains IL1403 and KW2 allowed the induction of natural competence in these strains also, expanding this phenotype to other L. lactis strains of both subspecies. IMPORTANCE Specific bacterial species are able to enter a state of natural competence in which DNA is taken up from the environment, allowing the introduction of novel traits. Strains of the species Lactococcus lactis are very important starter cultures for the fermentation of milk in the cheese production process, where these bacteria contribute to the flavor and texture of the end product. The activation of natural competence in this industrially relevant organism can accelerate research aiming to understand industrially relevant traits of these bacteria and can facilitate engineering strategies to harness the natural biodiversity of the species in optimized starter strains.

scholarly journals Yogurt Produced by Novel Natural Starter Cultures Improves Gut Epithelial Barrier In Vitro

2020 ◽  
Vol 8 (10) ◽  
pp. 1586 ◽  
Author(s):  
Nikola Popović ◽  
Emilija Brdarić ◽  
Jelena Đokić ◽  
Miroslav Dinić ◽  
Katarina Veljović ◽  
...  
Keyword(s):  
Dairy Product ◽  
Starter Culture ◽  
Streptococcus Thermophilus ◽  
Starter Cultures ◽  
Added Value ◽  
Lactobacillus Bulgaricus ◽  
Intestinal Epithelial ◽  
Beneficial Effects ◽  
Health Promoting

Yogurt is a traditional fermented dairy product, prepared with starter cultures containing Streptococcus thermophilus and Lactobacillus bulgaricus that has gained widespread consumer acceptance as a healthy food. It is widely accepted that yogurt cultures have been recognized as probiotics, due to their beneficial effects on human health. In this study, we have characterized technological and health-promoting properties of autochthonous strains S. thermophilus BGKMJ1-36 and L. bulgaricus BGVLJ1-21 isolated from artisanal sour milk and yogurt, respectively, in order to be used as functional yogurt starter cultures. Both BGKMJ1-36 and BGVLJ1-21 strains have the ability to form curd after five hours at 42 °C, hydrolyze αs1-, β-, and κ- casein, and to show antimicrobial activity toward Listeria monocytogenes. The strain BGKMJ1-36 produces exopolysaccharides important for rheological properties of the yogurt. The colonies of BGKMJ1-36 and BGVLJ1-21 strains that successfully survived transit of the yogurt through simulated gastrointestinal tract conditions have been tested for adhesion to intestinal epithelial Caco-2 cells. The results reveal that both strains adhere to Caco-2 cells and significantly upregulate the expression of autophagy-, tight junction proteins-, and anti-microbial peptides-related genes. Hence, both strains may be interesting for use as a novel functional starter culture for production of added-value yogurt with health-promoting properties.

scholarly journals Effects of Germination and Fermentation on the Functionality of Whole Soy Flour

2016 ◽  
Vol 73 (2) ◽  
pp. 126 ◽  
Author(s):  
Livia Patrascu ◽  
Iuliana Banu ◽  
Ina Vasilean ◽  
Iuliana Aprodu
Keyword(s):  
Wheat Flour ◽  
Starter Culture ◽  
Rheological Behaviour ◽  
Streptococcus Thermophilus ◽  
Starter Cultures ◽  
Soy Flour ◽  
Bread Making ◽  
White Wheat ◽  
Germination Process ◽  
Starch Gel

Nutritional quality and technological performances of grains can be modulated through germination and controlled fermentation. The aim of the work was to estimate the effect of germination (72 h at 23oC) and fermentation on the fundamental rheological properties of the soy flour based suspensions and sourdoughs, and to assess the bread making potential of the whole soy flours by considering the thermo-mechanical functionality of soy in admixture with white wheat flour. Soy flour based sourdough were prepared using three different starter cultures, consisting of mixtures of lactic acid bacteria like Lactobacillus plantarum, Lb. brevis, Lb. rhamnosus, Lb. casei, Lb. acidophilus, Bifidobacterium BB12®, and Streptococcus thermophilus and/or yeast Kluyveromyces marxianus subsp. Marxianus. The rheological behaviour of the suspensions and sourdoughs was influenced by the soy germination and fermentation processes. The stress sweep tests indicated significant narrowing of the linear viscoelastic regions, as well as the decrease of the stress values required for the beginning of flow. The temperature ramp test showed more intense swelling in case of the germinated and fermented samples. Both native and germinated soy flours were used to replace 15% of the wheat flour, and the Mixolab test indicated that the germination process caused the decrease of protein weakening and dough stability. The sourdoughs addition to the wheat flour resulted in significant changes of the thermo-mechanical properties of the dough. Properties related to stability of starch gel during heating, starch gelatinization and retrogradation depended on the type of starter culture used for fermentation.

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