Bacteria Streptococcus Thermophilus Research Articles

Lactic Acid Bacteria (Lactobacillus bulgaricus and Streptococcus thermophillus) in Yogurt Inhibit the Growth of Escherichia coli, Salmonella typhimurium, and Shigella sp. In Vitro

Diarrhea is defecation with a frequency more often than usual (three times or more) a day (10 mL/kg/day) with a soft or liquid consistency, even in the form of water alone. Pathogenic bacteria, such as Escherichia coli, Salmonella typhimurium, and Shigella sp., play a role in many cases, to which antibiotics are prescribed as the first-line therapy. However, since antibiotic resistance cases are often found, preventive therapies are needed, such as consuming yogurt, which is produced through a fermentation process by lactic acid bacteria (LAB). This research aimed to determine the activity of lactic acid bacteria (Liactobacillus bulgaricus and Streptococcus thermophilus) in yogurt in inhibiting the growth of the pathogenic bacteria E. coli, S. typhimurium, and Shigella sp. The research applied in vitro with the liquid dilution test method and the true experimental design research method with post-test-only and control group design. The design was used to see the inhibitory effect of yogurt LAB on the growth of E. coli, S. typhimurium, and Shigell sp. to compare the effect of several different yogurt concentrations, namely 20%, 40%, 60%, and 80%. The results of the Least Significance Different analysis showed that there was a significant difference between yogurt with a concentration of 0% and that with various concentrations in inhibiting the growth of E. coli, S. typhimurium, and Shigella sp. with a p-value of <0.05. Whereas, there was no significant difference in the various concentrations of yogurt in inhibiting the growth of the three kinds of bacteria with a p-value of > 0.05.Â

STUDY OF PROPERTIES OF YOGHURTS MADE USING VIVO STARTER CULTURES

The article presents the results of experimental studies of qualitative indicators of milk and fermented milk products (yoghurts) made using VIVO starter cultures. VIVO starter cultures contain thermophilic lactic acid bacteria Streptococcus thermophilus, Lactobacillus delbrueckii ssp., Lactobacillus acidophilus and others.
 The determination of organoleptic and physico-chemical parameters of cow's milk and dairy products based on it was carried out according to generally accepted methods. During the organoleptic evaluation of milk and lactic acid products, the appearance and texture, smell, taste and color of milk were examined. Determination of active acidity was carried out in accordance with GOST 26781. Titratable acidity in degrees Turner was determined according to GOST 3624. The content of fat, protein, dry matter was determined according to GOST 2661: 2010.
 A study was made of the organoleptic characteristics of yogurts obtained by fermentation by using of VIVO starter cultures. The high activity of VIVO starter cultures was established, the products on the basis of which have a pleasant taste characteristic of these products.
 The results of physico-chemical analysis of yogurt samples obtained by using of VIVO starter cultures confirmed their compliance with DSTU 4343: 2004.
 Lactic acid products made with VIVO sourdough are functional products. It is recommended to use yogurts based on VIVO starter cultures to restore intestinal microflora, normalize digestion, strengthen immunity, and reduce the risk of colds and SARS.

Starter bacteria as producers of CLA in ripened cheese.

The profile of polyunsaturated fatty acids in cheeses obtained through fermentation by lactic acid bacteria Lactobacillus helveticus and Streptococcus thermophilus were evaluated. The milk used to make the cheeses came from cows fed with flaxseed oil and annato. The cheeses presented microbiological and physic-chemical quality with in the standards established by the legislation for Staphylococci and Listeria. With maturation, there was a reduction in the coliform values ​​for both treatments. Regarding the counts of lactic acid bacteria, these remained viable until the 30th day of maturation and the proteolytic bacteria decreased. For antioxidant capacity, the treatment containing the combination of the strains obtained high ABTS values. There was no significant difference between the treatments with respect to the color of the samples. For texture, there was a significant difference for the parameters cohesion and elasticity. No increase in CLA content was observed in the form of its two main isomers, however, the levels of polyunsaturated fatty acids were increased.

Effect of a probiotic on blood pressure in grade 1 hypertension (HYPRO): protocol of a randomized controlled study

BackgroundArterial hypertension is a major risk factor for cardiovascular disease and leads to target organ damage including stroke, heart failure, and kidney disease. About 1.5 billion people worldwide have hypertension, and it is estimated that it causes about 8 million deaths each year. Although there are several drugs available to lower blood pressure (BP), a great proportion of treated patients does not reach recommended treatment targets. Typical antihypertensive drugs target the vessels, the kidneys, and the heart. However, our gut microbiota also influences cardiovascular health, and gut dysbiosis is associated with hypertension. In this study protocol, we investigate the potential BP-lowering effect of a probiotic in patients with grade 1 hypertension.MethodsThis study is an exploratory, randomized, double-blind, placebo-controlled, parallel-group study. One hundred ten patients with grade 1 hypertension (treated or untreated) will be randomized to either the probiotic Vivomixx® or placebo. The primary endpoint is the nocturnal systolic BP measured by ambulatory blood pressure monitoring after 8 weeks adjusted for the baseline value. The secondary endpoints are changes from baseline in nocturnal diastolic BP, antihypertensive medication, fecal microbiome composition, fecal and serum metabolome, immune cell phenotypes, glucose variability after three standardized breakfasts, and health-related quality of life (PROMIS-29). We also assess the safety profile of the intervention.DiscussionWe postulate that various administrated bacteria (Lactobacilli, Bifidobacteria, and Streptococcus thermophilus) convert dietary components into active metabolites that positively affect immune cell function. A reduction of pro-inflammatory immune cell function could promote a BP-lowering effect.Trial registrationClinicalTrials.gov NCT03906578. Registered on 08 April 2019

Peynir Altı Suyu Proteini Hidrolizatının Ayranda Yoğurt Starter Kültürleri ve Probiyotik Bakteriler Üzerine Etkilerinin İncelenmesi

This study aims to monitor the effect of whey protein hydrolysate (WPH) on the growth and activity of probiotic bacteria (Streptococcus thermophilus, Lactobacillus delbrueckii spp. bulgaricus, Lactobacillus acidophilus, and Bifidobacterium lactis) in ayran, and also to enhance the functionality of ayran by addition of the probiotics. Effects of WPH and probiotics addition as 0%, 0.25%, 0.5% and 1% on the growth of probiotic bacteria were studied before and after the fermentation and 7th, 14th, and 21st days of the storage. WPH and probiotics had a significant effect (p<0.05) on the growth of target microorganisms and the biochemical variables. The addition of WPH and probiotics significantly (p<0.05) increased the growth of probiotics compared to the control after the fermentation up to the 21st day of storage. The samples containing different WPH levels had lower (p<0.05) pH levels compared to the control during the study time. The mixing of WPH at 1% had the highest total solids and protein content compared to the control samples. The WPH decreased (p<0.05) the viscosity and Hunter color parameters in added the samples. Results indicated that WPH had great potential for enhancing the growth of probiotic bacteria and the nutritional of ayran.

Technology of functional dairy products

Milk and dairy products are main constituents of daily diet due to its nutritive characteristics and health benefits. Milk, known as a good source of proteins, fats, and major minerals, is considered as a nearly complete food with significant amount of biologically active components. Thus, all the mentioned benefits about milk labeled milk and dairy products as a functional food. Milk is a complex mixture of a broad variety of bioactive substances such as essential amino acids, fatty acids, carbohydrates, minerals, vitamins, enzymes and etc. Consumer’s interest about balanced nutrition and personal health are reasons of increased consumption of functional dairy products, targeted for special consumer groups (age and health condition). Progressive scientific research and creation of new functional ingredients followed by application of new technologies, open various opportunities for production and market of functional dairy products. Nowadays, the high demand for products with lower content of fat and higher content of easy to digest proteins, tailor variety of new diary low fat products, enriched with minerals and vitamins, hydrolyzed lactose or proteins for specific consumer groups. Besides of that, it has been noticed an increasing trend in consumption of different types of fermented dairy products, characterized by optimized texture and flavor and addition of various components such as probiotics and prebiotics, whey proteins in form of isolates or concentrates, and other different components (powder milk, skimmed powder milk, whey powder, skimmed whey powder, natural sugar etc.). Different fermented dairy products can be produced according to the chosen strain used during fermentation. In production of plain traditional yoghurt traditional thermophilic bacteria Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus were used. Introduction of new species of probiotic bacteria originated from Lactobacillus and Bifidobacterium led to significant progress in modern technology of fermented dairy products. The probiotic species from Lactobacillus and Bifidobacterium possess beneficial effect on human health and they were known as a part of human intestines microbiome. However, the most often used as a starter culture in modern production of fermented dairy products are lactic acid bacteria (LAB). In yoghurt production, besides the traditional and probiotic cultures, other starter culture can be used such as bacteria Lactobacillus lactis, Lactococcus lactis, Leuconostoc spp., or different yeast species, individually or in a chosen combinations. Despite the fact that fermented goat beverages were not sufficiently researched, production of these beverages has been getting more attention due to therapeutic characteristics of goat milk. Additionally, when fermented goat milk is enriched with probiotic bacteria and prebiotic supplements such as inulin, it meets the level of functional food standards. Beany taste of soya milk, as a main disadvantage of soy products, can be masked during the fermentation followed by reduced level of oligosaccharides, raphinosis and stachyoses. Due to this, fermented soy products are in consumer’s demand and are getting more attention. Soya milk is usually fermented with lactic acid bacteria (LAB), specific mold species or probiotic bacteria. Considering the well-known role and health benefits of dairy products that are constantly developing into new and improved generation of products with advanced functional properties and high nutritional value, it is understandable that dairy products are progressively gaining established scientific credibility.

Use of Yogurt Prepared with the Probiotic Streptococcus Salivarius BIO5 Strain in the Control of Bacterial Tonsillitis in Children

This double-blinded study aims to verify whether the yogurt prepared with a Streptococcus salivarius BIO5 probiotic strain can control recurrent tonsillitis in children. To this end, children with recurrent Streptococcus pyogenes tonsillitis consumed one of the two yogurt preparations daily for one year. The placebo group received the yogurt prepared with normal yogurt bacteria (Streptococcus thermophilus and Lactobacillus bulgaricus) whereas the treatment group received the yogurt prepared with the S. salivarius subsp. salivarius BIO5 strain. In the children completing the study, the recurrence of tonsillitis was about 89% in the placebo vs. about 12% in the treatment group. Furthermore, the children who dropped out from the treatment group showed about 3 times higher rate of infection. These data support the prevention of bacterial tonsillitis in children by daily consumption of the yogurt prepared with the BIO5 Streptococcus salivarius probiotic.

A short overview of the CRISPR-Cas adaptation stage.

CRISPR research began over 30 years ago with the incidental discovery of an unusual nucleotide arrangement in the Escherichia coli genome. It took 20 years to find the main function of CRISPR-Cas systems as an adaptive defence mechanism against invading nucleic acids, and our knowledge of their biology has steadily increased ever since. In parallel, the number of applications derived from CRISPR-Cas systems has risen spectacularly. The CRISPR-based genome editing tool is arguably the most exciting application in both basic and applied research. Lately, CRISPR-Cas research has partially shifted to the least understood aspect of its biology: the ability of CRISPR-Cas systems to acquire new immunities during the so-called adaptation step. To date, the most efficient natural system to readily acquire new spacers is the type II-A system of the gram-positive dairy bacterium Streptococcus thermophilus. The discovery of additional systems able to acquire new spacers will hopefully draw more attention to this step of CRISPR-Cas biology. This review focuses on the breakthroughs that have helped to unravel the adaptation phase and on questions that remain to be answered.

A modified reinforced clostridial medium for the isolation and enumeration of Lactobacillus delbrueckii ssp. bulgaricus in a mixed culture

In this study, we modified reinforced clostridial medium (RCM) to selectively enumerate and isolate Lactobacillus delbrueckii ssp. bulgaricus, a probiotic and important starter culture in the dairy industry. The disparity in the reported carbohydrate fermentation pattern of L. delbrueckii ssp. bulgaricus was used to develop a growth medium not only selective for L. delbrueckii ssp. bulgaricus but significantly inhibitory to the growth of other lactic acid bacteria. A recently modified RCM (mRCM) was optimized for this study by the addition of 0.5% fructose, 0.5% dextrose, 1% maltose, and 0.25% sodium pyruvate while replacing lactose as a carbohydrate source. The cell recovery and bacterial counts of L. delbrueckii ssp. bulgaricus in tested products (pure L. delbrueckii ssp. bulgaricus strains, starter culture, probiotic supplements, and yogurt) using our mRCM with sodium pyruvate (mRCM-PYR) were significantly higher than in the recently modified RCM and the common de Man, Rogosa, and Sharpe (MRS) culture medium. The growth of other lactic acid bacteria (Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus rhamnosus, and Lactobacillus reuteri) and Bifidobacteria was retarded in this modified medium compared with their growth in MRS and mRCM. This result is a significant improvement in the enumeration and differentiation of L. delbrueckii ssp. bulgaricus in mRCM-PYR compared with the results in MRS and mRCM where the high background growth of similar species interferes with the accuracy of bacterial population counts. Our results thus suggest that mRCM-PYR could be recommended as a reliable alternative growth medium for the selective enumeration and isolation of L. delbrueckii ssp. bulgaricus in a mixed culture.

Utilization of Lesser Yam (Dioscorea esculenta L.) Flour as Prebiotic in Yogurt to Total Lactic Acid Bacteria (LAB), Sugar Reduction, and Organoleptic Properties

This study aims to determine the effect of the concentration the addition of lesser yam as prebiotic to total Lactic Acid Bacteria (LAB), reducing sugar content, crude fiber, viscosity, and organoleptic properties of yogurt with a combination of three bacteria (Streptococcus thermophilus, Lactobacillus bulgaricus, and Lactobacillus acidophilus). The design of this study used a completely randomized design (CRD) with 4 treatments and 5 replications with variations in the addition of lesser yam tuber, namely T1 with a concentration of 0%, T2 with a concentration of 2%, T3 with a concentration of 4% and T4 with a concentration of 6%. The raw materials used are pasteurized fresh cow's milk, lesser yam tuber flour, and yogurt starter. The results showed that the addition of different lesser yam tuber flour had a significant effect (P <0.05) on total LAB, sugar reduction, crude fiber, viscosity, and organoleptic properties of yogurt. The ideal treatment for the addition of lesser yam tuber flour is the concentration of 2% lesser yam tuber, which produces a total LAB is 9.2 x 109, a sugar reduction is 0.653 mg/mL, crude fiber is 1.3%, 82.25 cPs, and organoleptic properties had sour taste and viscosity is rather thick which the most preferred.<br>

Influence of incorporated Spirulina platensis on the growth of microflora and physicochemical properties of ayran as a functional food

The aim of this study was to enhance the growth and activity of probiotic bacteria (Streptococcus thermophilus, Lactobacillus delbrueckii spp. bulgaricus, Lactobacillus acidophilus, and Bifidobacterium lactis) by the addition of Spirulina platensis into ayran. The effects of S. platensis at 0 %, 0.25 %, 0.5 %, and 1 % concentrations on the growth of probiotic bacteria were studied before and after fermentation and on the 7th, 14th, and 21st days of storage. The S. platensis had a significant effect on the growth of S. thermophilus, L. delbrueckii spp. bulgaricus, L. acidophilus and B. lactis and the biochemical variables. The addition of S. platensis, significantly increased the growth of probiotics compared to the control after fermentation and within storage. Samples containing S. platensis had significantly higher titratable acidity levels compared to the control during the study period. The mixing of S. platensis at 1 % gave the highest total solid and protein content compared to the control samples. Viscosity values of samples having S. platensis decreased during storage time. The addition of algal biomass at 0.25 %, 0.5 %, and 1 % significantly decreased Hunter color parameters; L* and b* values compared to the control. Spirulina platensis has great potential for enhancing the growth of probiotic bacteria and the nutritional content of ayran.

Microbial and enzymatic hydrolysis of dromedary whey proteins and caseins: techno-functional, radical scavenging, antimicrobial properties and incorporation in beverage formulation

Comparative study of functional properties, radical scavenging and antimicrobial activities of dromedary whey protein and casein hydrolysates was investigated. Dromedary protein hydrolysates were prepared by treatment with digestive proteases (pepsin and pancreatin) and by the proteolytic system of two lactic acid bacteria (Streptococcus thermophilus and Lactobacillus bulgaricus). Solubility and interfacial properties like emulsifying capacity are improved after enzymatic hydrolysis of both whey protein and casein. Whereas, foam capacity and stability are more important in whey protein hydrolysates than casein hydrolysates and are widely influenced by the method of hydrolysis. All hydrolysates showed radical scavenging activities. The highest antioxidant activity is exhibited by WPHE (whey protein hydrolysated by gastro-intestinal enzymes “pepsin and pancreatin”) for DPPH (2,2-diphenyl-1-picrylhydrazyl) test and CNHE (casein hydrolysated by pepsin and pancreatin) for ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) assay. Further, whey protein hydrolysates displayed antibacterial activity and WPHE was the most effective, particularly against Escherichia coli and Staphylococcus epidermidis. Based on the results, we conclude that WPHE has great technological applicability in food ingredients, as a promising source of functional hydrolysate with antioxidant and antimicrobial activities. For this reason, WPHE was added to the dromedary milk based beverage and chemical, microbiological and sensory properties of the resulting product were investigated. Formulated beverage flavored with strawberry or banana possessed a good microbiological quality. The sensory analysis demonstrated a good acceptance mainly in taste and consistency of the beverage samples. There is only significant difference in the color of the different formulated beverages.

Variability in the durability of CRISPR-Cas immunity.

The durability of host resistance is challenged by the ability of pathogens to escape the defence of their hosts. Understanding the variability in the durability of host resistance is of paramount importance for designing more effective control strategies against infectious diseases. Here, we study the durability of various clustered regularly interspaced short palindromic repeats-Cas (CRISPR-Cas) alleles of the bacteria Streptococcus thermophilus against lytic phages. We found substantial variability in durability among different resistant bacteria. Since the escape of the phage is driven by a mutation in the phage sequence targeted by CRISPR-Cas, we explored the fitness costs associated with these escape mutations. We found that, on average, escape mutations decrease the fitness of the phage. Yet, the magnitude of this fitness cost does not predict the durability of CRISPR-Cas immunity. We contend that this variability in the durability of resistance may be because of variations in phage mutation rate or in the proportion of lethal mutations across the phage genome. These results have important implications on the coevolutionary dynamics between bacteria and phages and for the optimal deployment of resistance strategies against pathogens and pests. Understanding the durability of CRISPR-Cas immunity may also help develop more effective gene-drive strategies based on CRISPR-Cas9 technology. This article is part of a discussion meeting issue 'The ecology and evolution of prokaryotic CRISPR-Cas adaptive immune systems'.

Evaluation of Physicochemical, Nutritional and Sensory Properties of the Wet Tarhana

The wet tarhana is a fermented product that prepared with wheat flour, yogurt, tarhana herb ( Echiophora sibthorpiana ) and some chopped vegetables and spices. The basic difference of wet tarhana from other tarhana types is that it is prepared without a drying step. During its spontaneous fermentation process about 10 days, yogurt bacteria ( Streptococcus thermophilus and Lactobacillus bulgaricus ) produce several organic acids such as lactic acid and some other organic compounds. The ingredients and long fermentation process gain characteristic flavor and unique taste to the tarhana. Tarhana is similar to sourdough due to its' long spontaneous fermentation time. The aim of the study was to investigate physicochemical, nutritional and microbiological properties of wet tarhana, and to evaluate the relationships between them. For this purpose, wet tarhana samples were collected from different districts, and some physicochemical properties (pH, total acidity, dry matter, fat, and soluble ash content), antioxidant activity, phytic acid content, bioavailability, viscosity and counts of microbiota were performed. The results showed that the level of mineral digestibility was ranged from 67.22% to 88.88%, and a negative correlation was determined between mineral bioavailability and phytic acid content. The vitality of the microbiota especially lactic acid bacteria maintained during the storage period. Moreover, tarhana soups were prepared with the samples and their viscosity and sensory assessment were performed. Although the wet tarhana and soup samples had different viscosities initially, all the samples indicated pseudoplastic flow behavior. Furthermore, it was determined that the physicochemical properties of the samples affected the preference of the panelists in terms of sensorial assessment. Keywords: tarhana, fermented products, bioavailability, viscosity DOI : 10.7176/FSQM/83-08

Karakter Rasa dan pH Yoghurt Susu Kambing pd lama dan Jenis Starter yang Berbeda

Goat milk is one of the commodities of farming products that is highly nutritious and useful for health. However, goat milk has not been currently preferable due to its smell characteristic. One of the ways in order to make goat milk be able to gain consumers’ interests is by turning it into processed product, such as yoghurt. Yoghurt is a drinking product made as the result of milk fermentation yielded from controlled LAB bacteria. This study is the result of organoleptic assessment, in the form of pH and the flavor of one of PUPPIK skim dedicated products. The flavor organoleptic observation with students as the panelists was using de Garmo analytical hedonic test in order to find the most appropriate treatment and the most favorite flavor based on the consumers’ interests. The pH data and data analysis used ANOVA test. The design of this research was RALF (Rancangan Acak Lengkap pola Faktorial/ Factorial Pattern Completely Randomized Design), which consists of 2 factors: fermentation duration (6, 12, 18, and 24 hours) with the temperature of 37OC and the types of starter bacteria (Streptococcus thermophilus, Lactobacillus bulgaricus and combination). Therefore, there were 12 treatments which were repeated 3 times.The result of de Garmo test observation is that the fermentation duration interaction and types of starter bacteria which is mostly preferred by the panelists is the one which is in 24-hour duration of fermentation using Lactobacillus bulgaricus bacteria, with the highest flavor product score of 1,89 (little sour, not bitter), while in term of pH, there is no difference.

Improving the Health of Teeth in Cats and Dogs with Live Probiotic Bacteria

Background: Periodontal infections are the most common disease of cats and dogs. About 70% - 80% of them suffer from these infections during their lifetime. These infections occur in two forms, gingivitis and periodontitis. Gingivitis is a reversible inflammation of the gingiva which can be cured. As with humans, the harmful bacteria can cause infections also in organs such as the heart, liver and kidneys. Besides veterinary treatment, also the owner’s everyday care is essential. Objective: The aim of the study was to develop and clinically test easy home care probiotic product for cats’ and dogs’ oral health. Methods: Nine cats and thirteen dogs were given a combination of selected bacteria Streptococcus thermophilus SP4, Lactobacillus plantarum 14D and Lactobacillus rhamnosus SP1 (Petguide powder) in powder form daily for four weeks on top of the dry feed. Microbiological samples were taken before and after the intervention from each dog and cat. The samples were analyzed with flow cytometric analysis using Porphyromonas gingivalis and Fusobacterium sp. as indicators for oral health. Results: The home care treatment with these specific, live probiotic bacteria was shown to prevent the growth of infectious bacteria within four weeks. Petguide probiotic powder reduced the relative abundance of infectious microbes significantly (p = 0.005) in cats and dogs. Conclusion: The results suggest that the probiotic product with three live strains of probiotic bacteria prevents the growth of infectious bacterial species that are known to cause infections in pets’ mouths. Therefore, this probiotic combination could be used to improve the oral health of pets and increase their quality of life.

Cell Wall Glycans Mediate Recognition of the Dairy Bacterium Streptococcus thermophilus by Bacteriophages.

Receptors on the cell surfaces of bacterial hosts are essential during the infection cycle of bacteriophages. To date, the phage receptors of the industrial relevant dairy starter bacterium Streptococcus thermophilus remain elusive. Thus, we set out to identify cell surface structures that are involved in host recognition by dairy streptococcal phages. Five industrial S. thermophilus strains sensitive to different phages (pac type, cos type, and the new type 987), were selected to generate spontaneous bacteriophage-insensitive mutants (BIMs). Of these, approximately 50% were deselected as clustered regularly interspaced short palindromic repeat (CRISPR) mutants, while the other pool was further characterized to identify receptor mutants. On the basis of genome sequencing data, phage resistance in putative receptor mutants was attributed to nucleotide changes in genes encoding glycan biosynthetic pathways. Superresolution structured illumination microscopy was used to visualize the interactions between S. thermophilus and its phages. The phages were either regularly distributed along the cells or located at division sites of the cells. The cell wall structures mediating the latter type of phage adherence were further analyzed via phenotypic and biochemical assays. Altogether, our data suggested that phage adsorption to S. thermophilus is mediated by glycans associated with the bacterial cell surface. Specifically, the pac-type phage CHPC951 adsorbed to polysaccharides anchored to peptidoglycan, while the 987-type phage CHPC926 recognized exocellular polysaccharides associated with the cell surface.IMPORTANCEStreptococcus thermophilus is widely used in starter cultures for cheese and yoghurt production. During dairy fermentations, infections of bacteria with bacteriophages result in acidification failures and a lower quality of the final products. An understanding of the molecular factors involved in phage-host interactions, in particular, the phage receptors in dairy bacteria, is a crucial step for developing better strategies to prevent phage infections in dairy plants.

Characteristics of Milk Fermented by Streptococcus thermophilus MGA45-4 and the Profiles of Associated Volatile Compounds during Fermentation and Storage.

The lactic acid bacterium Streptococcus thermophilus is a major starter culture for the production of dairy products. In this study, the physiochemical characteristics of milk fermented by the MGA45-4 isolate of S. thermophilus were analyzed. Our data indicate that milk fermented using S. thermophilus MGA45-4 maintained a high viable cell count (8.86 log10 colony-forming units/mL), and a relatively high pH (4.4), viscosity (834.33 mPa·s), and water holding capacity (40.85%) during 14 days of storage. By analyzing the volatile compound profile using solid-phase microextraction and gas chromatography/mass spectrometry, we identified 73 volatile compounds in the fermented milk product, including five carboxylic acids, 21 aldehydes, 13 ketones, 16 alcohols, five esters, and 13 aromatic carbohydrates. According to the odor activity values, 11 of these volatile compounds were found to play a key role in producing the characteristic flavor of fermented milk, particularly octanal, nonanal, hexanal, 2,3-butanedione, and 1-octen-3-ol, which had the highest odor activity values among all compounds analyzed. These findings thus provide more insights in the chemical/molecular characteristics of milk fermented using S. thermophilus, which may provide a basis for improving dairy product flavor/odor during the process of fermentation and storage.

Effect of High-Pressure Processing on Quality and Microbiological Properties of a Fermented Beverage Manufactured from Sweet Whey Throughout Refrigerated Storage

The production of fermented beverages is a promising way to valorize by-products of dairy manufacturing. However, the shelf-life of these products is often limited by the post-acidification process that occurs during storage. In this work, we manufactured a fermented beverage from sweet whey by using the starter lactic acid bacteria (SLAB) Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus. High-pressure processing (HPP) at 200 MPa for 10 min or 400 MPa for 1 min were applied after manufacturing. The aim of this study was to evaluate the effect of HPP on the quality of the beverage and on the behavior of the SLAB. Both high hydrostatic pressure treatments preserved flavor and texture attributes until 45 days post-HPP, without affecting chromatic parameters. Plate counts for both species were lower in HPP-treated beverages (HB) than in control beverages (CB), although treatment at 200 MPa maintained optimal amounts of total SLAB (6.6–7.9 log CFU/mL). Conversely, quantitative PCR (qPCR) and reverse transcription-qPCR (RT-qPCR) revealed that bacterial DNA or mRNA levels persisted after HPP (> 1.4 × 105 genome or cDNA copies/mL), even upon 400-MPa treatments. As a whole, this study indicated that HPP preserved the quality of the beverage until 45 days post-HPP, which is longer than the shelf-life of conventional fermented beverages obtained from milk. Moreover, our results obtained with these SLAB in a fermented dairy beverage upon HPP extend previous findings regarding the limitations of culture-dependent methods to assess microbial viability.

Preparation of Probiotic Apple Juice by Lactic Acid Fermentation

Fermentation of apple juice was done for 72 hrs by lactic acid bacteria (Lactobacillus plantarum and Streptococcus thermophilus)and physico-chemical characteristics of fermented apple juices were recorded at 0. 24, 48 and 72 hrs intervals. On the basis of highest lactic acid bacterial counts, rate of fermentation (°B/24hr), acidity, sugar utilization percentage, retention of ascorbic acid and total phenols, antioxidant activity and antimicrobial activity against pathogenic bacteria such as E. coli and S. aureus, while lowest pH, coliform, yeast and mold counts, the best treatments L. plantarum 107cfu/ml for apple fermented apple juice was selected for storage study viz. During fermentation both vitamin C and total phenols declined, while, the antioxidant activity, antimicrobial activity, viable cell counts and lactic acid bacteria counts were increased. As the antimicrobial activity increased, the counts of coliform, yeast and mold declined. During storage of selected treatment of fermented apple juice for four weeks at 4°C retained physico-chemical parameters above the value of significance. Lactic acid bacteria remained viable in prescribed number (4.76–6.00 × 106 cfu/ml), acid and bile resistance, imparted antimicrobial activity and antioxidant activity to the apple juices during storage and thus, could be called as probiotics juices. Based on the sensory evaluation (visual colour and flavours) of fermented apple juice, it was concluded that lactic acid fermentation did not influence the desirable characteristics of apple juices. So the probiotic juices were acceptable. Identification of lactic acid bacteria by biochemical test concluded that the bacteria were L. plantarum in apple juices which were inoculated in juices for fermentation, after storage apple juice were suitable for lactic acid fermentation to produce a probiotic beverage. So, this juice can serve as healthy beverage for vegetarians and lactose allergic consumers.