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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]

Background: Silage emits climate- and environment-relevant gases during fermentation and feed-out periods. This trial aimed to determine the unknown carbon dioxide (CO2), methane, nitrous oxide, ethanol, and ethyl acetate emissions of constant maize silage material over both periods. The results will be published in two consecutive articles (Part A: anaerobic fermentation period, Part B: aerobic storage period). Methods: The untreated control (CON) was compared with the chemical additive treatment (CHE; 0.5 g sodium benzoate and 0.3 g potassium sorbate per kg fresh matter) and the biological additive treatment (BIO; 108 colony-forming units (CFU) Lentilactobacillus buchneri and 107 CFU Lactiplantibacillus plantarum per kg fresh matter). Barrel silos (n = 4) were connected to gas bags to quantify gas formation during anaerobic fermentation (30 or 135 ensiling days). Glass jar silos (n = 12) were used for laboratory silage analysis. Results: CHE produced significantly (p < 0.05) less gas (6.7 ± 0.3 L per kg dry matter ensiled material (kgDM) until ensiling day 14.0 ± 0.0) and ethanol (8.6 ± 1.5 mg kgDM–1) than CON did (8.5 ± 0.2 L kgDM–1 until ensiling day 19.5 ± 6.4; 12.2 ± 1.5 (mg ethanol) kgDM–1). BIO indicates prolonged gas formation (9.1 ± 0.9 L kgDM–1 until ensiling day 61.3 ± 51.9; 12.0 ± 2.1 mg kgDM–1). CO2 is the main component of the gas formed. All treatments formed methane and nitrous oxide in small quantities. CON emitted significantly more CO2eq emissions than BIO and less than CHE (p < 0.05). Additives had no effect on ethyl acetate gas emissions. For BIO, ethanol concentrations in the material (rS = 0.609, p < 0.05) and gas quantities (rS = 0.691, p < 0.05) correlate with ethyl acetate gas quantities. All the treatments exhibited decreasing gas and CO2 quantities, and the dry matter mass increased between ensiling days 14 and 30 (− 0.810 ≤ rS ≤ 0.442; p < 0.05 to p = 0.20). Conclusion: Silage generates climate- and environmental-relevant gases during fermentation and silage additives affect this pattern. Gas formation exceeds the fixation potential, and the carbon footprint of silage fermentation is negative. [ABSTRACT FROM AUTHOR]

Natural whey cultures (NWC) are undefined multiple-strain bacterial starter communities that can be affected by even small changes along the entire dairy chain. We applied a multidisciplinary approach to investigate how the addition of 2 mycotoxin-detoxifying agents [sodium smectite and lignocellulose-based material (B1); leonardite and betaine (B2)] to cow diets modified the microbiota of the NWC in manufacture of a Grana-like cheese. Microbiological and flow cytometry analyses showed that the content and viability of lactic acid bacteria (LAB) and the total whey microbiota were not affected by the detoxifying agents, and Streptococcus thermophilus , Lactobacillus helveticus , and Limosilactobacillus fermentum were the dominant taxa. Random amplified polymorphic DNA-PCR fingerprinting and metagenomic analysis highlighted differences in the bacterial community of the NWC and in the relative abundance of Bacteroidetes that increased when B1 and B2 were included in the diet. Two of 6 St. thermophilus biotypes were detected only in control samples; conversely, none of the Lb. helveticus biotypes found in control samples were isolated from B1 and B2. In vitro tests showed that the 2 binders did not significantly affect the development of St. thermophilus , but they stimulated the growth of Lb. helveticus strains recovered only from B1 and B2 NWC. The addition of binders in cow feed can affect the LAB biotypes present in NWC. [ABSTRACT FROM AUTHOR]

Introduction: Constructed wetlands (CWs) are nature-based solutions for wastewater treatment where the root system microbiome plays a key role in terms of nutrient and pollutant removal. Nonetheless, little is known on plant-microbe interactions and bacterial population selection in CWs, which are mostly characterized in terms of engineering aspects. Methods: Here, cultivation-independent and cultivation-based analyses were applied to study the bacterial communities associated to the root systems of Phragmites australis and Typha domingensis co-occurring in the same cell of a CW receiving primary treated wastewaters. Results and discussion: Two endophytic bacteria collections (n = 156) were established aiming to find novel strains for microbial-assisted phytodepuration, however basing on their taxonomy the possible use of these strains was limited by their low degrading potential and/or for risks related to the One-Health concept. A sharp differentiation arose between the P. australis and T. domingensis collections, mainly represented by lactic acid bacteria (98%) and Enterobacteriaceae (69%), respectively. Hence, 16S rRNA amplicon sequencing was used to disentangle the microbiome composition in the root system fractions collected at increasing distance from the root surface. Both the fraction type and the plant species were recognized as drivers of the bacterial community structure. Moreover, differential abundance analysis revealed that, in all fractions, several bacteria families were significantly and differentially enriched in P. australis or in T. domingensis. CWs have been also reported as interesting options for the removal of emerging contaminants (e.g, antibiotic resistance genes, ARGs). In this study, ARGs were mostly present in the rhizosphere of both plant species, compared to the other analyzed fractions. Notably, qPCR data showed that ARGs (i.e., ermB, blaTEM, tetA) and intl1 gene (integrase gene of the class 1 integrons) were significantly higher in Phragmites than Typha rhizospheres, suggesting that macrophyte species growing in CWs can display a different ability to remove ARGs from wastewater. Overall, the results suggest the importance to consider the plant-microbiome interactions, besides engineering aspects, to select the most suitable species when designing phytodepuration systems. [ABSTRACT FROM AUTHOR]

Pulse proteins are playing significant roles in the alternative protein space due to the demand for foods produced in an environmentally sustainable manner and, most importantly, due to the demand for foods of nutritious value. There has been extensive research to mimic animal-derived meat texture, flavour, mouthfeel, etc. However, there is still the perception that many of the plant-based proteins that have been texturized to mimic meat are still highly processed and contain chemicals or preservatives, reducing their appeal as being healthy and precluding any sustainable benefits. To counter this notion, the biotransformation of pulse proteins using enzymes or fermentation offers unique opportunities. Thus, this review will address the significance of pulse proteins in the alternative protein space and some of the processing aids leading to the isolation and modification of such protein concentrates in a sustainable manner. Fermentation-based valorization of pulse proteins will also be discussed as a "clean label" strategy (further adding to sustainable nutritious plant protein production), although some of the processes like the extensive use of water in submerged fermentation need to be addressed. [ABSTRACT FROM AUTHOR]

Introduction: Lactic acid bacteria (LAB) communities shape the sensorial and functional properties of artisanal hard-cooked and long-ripened cheeses made with raw bovine milk like Parmigiano Reggiano (PR) cheese. While patterns of microbial evolution have been well studied in PR cheese, there is a lack of information about how this microbial diversity affects the metabolic and functional properties of PR cheese. Methods: To fill this information gap, we characterized the cultivable fraction of natural whey starter (NWS) and PR cheeses at different ripening times, both at the species and strain level, and investigated the possible correlation between microbial composition and the evolution of peptide profiles over cheese ripening. Results and discussion: The results showed that NWS was a complex community of several biotypes belonging to a few species, namely, Streptococcus thermophilus, Lactobacillus helveticus, and Lactobacillus delbrueckii subsp. lactis. A new species-specific PCR assay was successful in discriminating the cheese-associated species Lacticaseibacillus casei, Lacticaseibacillus paracasei, Lacticaseibacillus rhamnosus, and Lacticaseibacillus zeae. Based on the resolved patterns of species and biotype distribution, Lcb. paracasei and Lcb. zeae were most frequently isolated after 24 and 30 months of ripening, while the number of biotypes was inversely related to the ripening time. Peptidomics analysis revealed more than 520 peptides in cheese samples. To the best of our knowledge, this is the most comprehensive survey of peptides in PR cheese. Most of them were from β-caseins, which represent the best substrate for LAB cell-envelope proteases. The abundance of peptides from β-casein 38-88 region continuously increased during ripening. Remarkably, this region contains precursors for the anti-hypertensive lactotripeptides VPP and IPP, as well as for β-casomorphins. We found that the ripening time strongly affects bioactive peptide profiles and that the occurrence of Lcb. zeae species is positively linked to the incidence of eight anti-hypertensive peptides. This result highlighted how the presence of specific LAB species is likely a pivotal factor in determining PR functional properties. [ABSTRACT FROM AUTHOR]

Purpose: Gamma-aminobutyric acid (GABA) is a four-carbon and nonprotein amino acid, made by various microorganisms, especially lactic acid bacteria (LAB) and probiotics. GABA has various physiological roles, for instance, insomnia, depression, hypotensive activity as well as diuretic effects. The production of GABA-based foods is a favorable result from GABA's biological and functional properties. The purpose of this study is to investigate different methods of improving GABA production in probiotics and LAB to select the superlative method and bacterial strain. Design/methodology/approach: In this review paper, all articles from five electronic databases containing Google Scholar, Web of Science, PubMed, Scopus and Science Direct were considered from 2000 to January 11, 2023, with keywords "Optimization" OR "Enhance" OR "Increase" AND "Gamma-aminobutyric acid" OR "GABA" AND "Probiotics" OR "Lactic acid bacteria" and selected according to the purpose of the study. Findings: It seems that among all the investigated methods, an effective fermentation procedure with optimal conditions including fermentation medium, 5 L; glutamic acid, 295 g/L; incubation temperature, 32°C; inoculum, 10% (v/v); and agitation, 100 rpm, after 48 h of fermentation led to producing 205,800 mg/L of GABA from the effective bacterial strain Lactobacillus brevis NCL912. Originality/value: With a simple but optimized fermentation, L. brevis NCL912 can be used for the efficient GABA production in the pharmacy and food factories. [ABSTRACT FROM AUTHOR]

Swiss-type artisanal cheese is highly appreciated sensorially, its flavor is often associated with the lactic acid bacteria involved in its production, which in many cases are indigenous. Three artisanal Swiss-type cheeses of greatest preference in the market of Huaraz (Ancash) were selected. The main LAB were isolated and identified and their safety properties and technological potential for their application in new cheeses were verified in vitro and evaluated by consumers. Eleven strains were confirmed as LAB by Gram-positive and catalase- negative biochemical tests; according to 16S rDNA, seven strains belonged to Lacticaseibacillus paracasei (KQ3, EQ1, CQ1, YQ1, LQ2, GQ2 and TQ1), three strains to Lentilactobacillus parabuchneri (BQ2, OQ2 and RQ3), and one to Lactiplantibacillus sp. (QQ3). In safety assays, LAB did not exhibit gelatinase or hemolytic activities. In addition, L. paracasei KQ3, GQ2 and L. parabuchneri BQ2 effectively inhibited pathogens such as S. aureus, E. coli and L. monocytogenes. Antibiotic susceptibility was variable among strains. L. paracasei CQ1, EQ1, KQ3, TQ1 and Lactiplantibacillus sp. QQ3 showed high milk acidification capacity (0.16-1.44%) and reduced pH from 6.6 to 3.5 after 72 h of incubation. L. paracasei CQ1, Lactiplantibacillus sp. QQ3 and L. paracasei KQ3 showed the highest casein degradation zones (20.8-11.5 mm). All strains showed lipolytic activity, with Lactiplantibacillus sp. QQ3, L. paracasei CQ1 and L. parabuchneri BQ2 standing out with halos of 30.8-36.3 mm. Lactiplantibacillus sp. QQ3 and L. paracasei TQ1 showed ability to produce diacetyl. The best strains were tested in cheese production where L. paracasei CQ1 showed the best sensory qualities. Finally, the native BAL strains showed a high potential for the production of natural, safe and sensorially acceptable dairy products. [ABSTRACT FROM AUTHOR]

Plant-based desserts are becoming increasingly popular with and appreciated by consumers. However, they are limited by the choice of ingredients, which are often expensive and unstable with a random texture. Therefore, the aim of the research is to propose a new product that offers an advantageous texture and flavour in a fermented dessert based on a flour mix supplemented with an enzymatic hydrolysate. This study involved the development of two processes: (i) an enzymatic hydrolysis of oat flour and (ii) a fermentation of a flour mixture (oat, chickpea, and coconut) by lactic acid bacteria (Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus). The result of the oat flour hydrolysate shows a significant decrease in starch after 60 min of reaction, followed by an increase in sugar content. During 23 days of storage at 4 °C, the formulations used showed post-acidification, water retention capacity decrease, and hardness increase related to the hydrolysate rate (p < 0.05). All formulations allowed the viability of lactic bacteria (over 5 log10 CFU/mL) and verified their ability to produce exopolysaccharides (0.23–0.73 g/100 g). The prototyping of such a product represents a key step in meeting the growing demand for plant-based alternatives, with qualitative sensory characteristics without additives. [ABSTRACT FROM AUTHOR]

Butyric acid (C4) and pyroglutamic acid (pGlu) exert significant beneficial effects on human health. In this study, the influence of probiotics (Lactobacillus acidophilus and Bifidobacteria) and/or prebiotics (1 and 3% inulin and fructo-oligosaccharides) on the content of C4 and pGlu in yoghurt during the shelf-life period was evaluated. The contents of C4 and pGlu were determined in probiotic, prebiotic and synbiotic yoghurts during 30 days of storage at 4 °C by solid-phase microextraction coupled with gas chromatography/mass spectrometry and HPLC analysis. Traditional yoghurt and uninoculated milk were used as control. Prebiotic yoghurt contained more C4 (2.2–2.4 mg/kg) than the uninoculated milk, and no increase was detected with respect to traditional yoghurt. However, probiotic yoghurt showed 10% more C4 than traditional yoghurt. Adding fibre to probiotics (synbiotic yoghurt) the C4 content increased by 30%. Regarding pGlu, probiotic yoghurt presented the highest content of approximately 130 mg/100 g. Fibre did not affect pGlu content. Finally, C4 and pGlu contents generally increased up to 20 days of storage and then decreased up to 30 days of storage. The results might be useful for the preparation of other functional foods rich in C4 and pGlu using lactic acid bacteria. [ABSTRACT FROM AUTHOR]

Recently, probiotics are increasingly being used for human health. So far, only lactic acid bacteria isolated from the human gastrointestinal tract were recommended for human use as probiotics. However, more authors suggest that probiotics can be also isolated from unconventional sources, such as fermented food products of animal and plant origin. Traditional fermented products are a rich source of microorganisms, some of which may have probiotic properties. A novel category of recently isolated microorganisms with great potential of health benefits are next-generation probiotics (NGPs). In this review, general information of some "beneficial microbes", including NGPs and acetic acid bacteria, were presented as well as essential mechanisms and microbe host interactions. Many reports showed that NGP selected strains and probiotics from unconventional sources exhibit positive properties when it comes to human health (i.e., they have a positive effect on metabolic, human gastrointestinal, neurological, cardiovascular, and immune system diseases). Here we also briefly present the current regulatory framework and requirements that should be followed to introduce new microorganisms for human use. The term "probiotic" as used herein is not limited to conventional probiotics. Innovation will undoubtedly result in the isolation of potential probiotics from new sources with fascinating new health advantages and hitherto unforeseen functionalities. [ABSTRACT FROM AUTHOR]

Antimicrobial resistance (AMR) is a global and increasing threat to human health. Several genetic determinants of AMR are found in environmental reservoirs, including bacteria naturally associated with widely consumed fermented foods. Through the food chain, these bacteria can reach the gut, where horizontal gene transfer (HGT) can occur within the complex and populated microbial environment. Numerous studies on this topic have been published over the past decades, but a conclusive picture of the potential impact of the non-pathogenic foodborne microbial reservoir on the spread of AMR to human pathogens has not yet emerged. This review critically evaluates a comprehensive list of recent experimental studies reporting the isolation of AMR bacteria associated with fermented foods, focusing on those reporting HGT events, which represent the main driver of AMR spread within and between different bacterial communities. Overall, our analysis points to the methodological heterogeneity as a major weakness impairing determination or a causal relation between the presence of AMR determinants within the foodborne microbial reservoir and their transmission to human pathogens. The aim is therefore to highlight the main gaps and needs to better standardize future studies addressing the potential role of non-pathogenic bacteria in the spread of AMR. [ABSTRACT FROM AUTHOR]

Using culture enrichment methods, 100 strains of bacilli of lactic acid bacteria (LAB) were isolated from honeybee Apis mellifera intermissa and fresh honey, collected from apiaries located in the north-east of Algeria. Amongst all of the isolated LAB, 19 selected strains were closely affiliated to four species—Fructobacillus fructosus (10), Apilactobacillus kunkeei (5), Lactobacillus kimbladii and/or Lactobacillus kullabergensis (4)—using phylogenetic and phenotypic approaches. The in vitro probiotic characteristics (simulated gastrointestinal fluids tolerance, autoaggregation and hydrophobicity abilities, antimicrobial activity and cholesterol reduction) and safety properties (hemolytic activity, antibiotic resistance and absence of biogenic amines) were evaluated. The results indicated that some strains showed promising potential probiotic properties. In addition, neither hemolytic activity nor biogenic amines were produced. The carbohydrate fermentation test (API 50 CHL) revealed that the strains could efficiently use a broad range of carbohydrates; additionally, four strains belonging to Apilactobacillus kunkeei and Fructobacillus fructosus were found to be exopolysaccharides (EPS) producers. This study demonstrates the honeybee Apis mellifera intermissa and one of her products as a reservoir for novel LAB with potential probiotic features, suggesting suitability for promoting host health. [ABSTRACT FROM AUTHOR]

The S‐layer or surface layer protein (SLP) is the most ancient biological envelope, highly conserved in several Bacteria and Archaea. In lactic acid bacteria (LAB), SLP is only found in species belonging to the Lactobacillaceae family, many of them considered probiotic microorganisms. New reclassification of members within the Lactobacillaceae family (International Journal of Systematic and Evolutionary Microbiology, 2020, 70, 2782) and newly sequenced genomes demands an updated revision on SLP genes and domain organization. There is growing information concerning SLP occurrence, molecular biology, biophysical properties, and applications. Here, we focus on the prediction of slp genes within the Lactobacillaceae family, and specifically, on the neat interconnection between the two different modular SLP domain organizations and the new reclassified genera. We summarize the results in a concise tabulated manner to review the present knowledge on SLPs and discuss the most relevant and updated concepts regarding SLP sequence clustering. Our assessment is based on sequence alignments considering the new genera classification and protein domain definition with post‐translational modifications. We analyse the difficulties encountered to resolve the SLPs 3D structure, describing the need for structure prediction approaches and the relation between protein structure and its anchorage mechanism to the cell wall. Finally, we enumerate new SLP applications regarding heterologous display, pathogen exclusion, immunostimulation, and metal binding. [ABSTRACT FROM AUTHOR]

The human oral cavity contains a diversity of microbial habitats that have been adopted and adapted to as homeland by an amazingly heterogeneous population of microorganisms collectively referred to as the oral microbiota. These microbes generally co-habit in harmonious homeostasis. However, under conditions of imposed stress, as with changes to the host's physiology or nutritional status, or as a response to foreign microbial or antimicrobial incursions, some components of the oral "microbiome" (viz. the in situ microbiota) may enter a dysbiotic state. This microbiome dysbiosis can manifest in a variety of guises including streptococcal sore throats, dental caries, oral thrush, halitosis and periodontal disease. Most of the strategies currently available for the management or treatment of microbial diseases of the oral cavity focus on the repetitive "broad sweep" and short-term culling of oral microbe populations, hopefully including the perceived principal pathogens. Both physical and chemical techniques are used. However, the application of more focused approaches to the harnessing or elimination of key oral cavity pathogens is now feasible through the use of probiotic strains that are naturally adapted for oral cavity colonization and also are equipped to produce anti-competitor molecules such as the bacteriocins and bacteriocin-like inhibitory substances (viz BLIS). Some of these probiotics are capable of suppressing the proliferation of a variety of recognized microbial pathogens of the human mouth, thereby assisting with the restoration of oral microbiome homeostasis. BLIS K12 and BLIS M18, the progenitors of the BLISproducing oral probiotics, are members of the human oral cavity commensal species Streptococcus salivarius. More recently however, a number of other streptococcal and some non-streptococcal candidate oral probiotics have also been promoted. What is becoming increasingly apparent is that the future for oral probiotic applications will probably extend well beyond the attempted limitation of the direct pathological consequences of oral microbiome dysbiosis to also encompass a plethora of systemic diseases and disorders of the human host. The background to and the evolving prospects for the beneficial modulation of the oral microbiome via the application of BLIS-producing S. salivarius probiotics comprises the principal focus of the present review. [ABSTRACT FROM AUTHOR]

Isoflavones are phenolic compounds (considered as phytoestrogens) with estrogenic and antioxidant function, which are highly beneficial for human health, especially in the aged population. However, isoflavones in foods are not bioavailable and, therefore, have low biological activity. Additionally, their transformation into bioactive compounds by microorganisms is necessary to obtain bioavailable isoflavones with beneficial effects on human health. Many lactic acid bacteria (LAB) can transform the methylated and glycosylated forms of isoflavones naturally present in foods into more bioavailable aglycones, such as daidzein, genistein and glycitein. In addition, certain LAB strains are capable of transforming isoflavone aglycones into compounds with a greater biological activity, such as dihydrodaidzein (DHD), O-desmethylangolensin (O-DMA), dihydrogenistein (DHG) and 6-hydroxy-O-desmethylangolensin (6-OH-O-DMA). Moreover, Lactococcus garviae 20-92 is able to produce equol. Another strategy in the bioconversion of isoflavones is the heterologous expression of genes from Slackia isoflavoniconvertens DSM22006, which have allowed the production of DHD, DHG, equol and 5-hydroxy-equol in high concentrations by engineered LAB strains. Accordingly, the consequences of isoflavone metabolism by LAB and its application in the development of foods enriched in bioactive isoflavones, as well as health benefits attributed to their consumption, will be addressed in this work. [ABSTRACT FROM AUTHOR]

A total of 26 lactic acid bacteria isolates from both Italian and Brazilian cheeses were tested for their use in cheesemaking. Isolates were screened for salt tolerance, exopolysaccharide and diacetyl production, lipolytic, acidifying, and proteolytic activities. In addition, the aminopeptidase (Pep N and Pep X) activities, were evaluated. Most of the strains demonstrated salt tolerance to 6% of NaCl, while only two L. delbruekii (P14, P38), one L. rhamnosus (P50) and one L. plantarum (Q3C4) were able to grow in the presence of 10% (w/v) of NaCl. Except for 2 L. plantarum (Q1C6 and Q3C4), all strains showed low or medium acidifying activity and good proteolytic features. Furthermore, lipolytic activity was revealed in none of the strains, while the production of EPS and diacetyl was widespread and variable among the tested strains. Finally, regarding aminopeptidase activities, 1 L. delbrueckii (P10), 1 L. rhamnosus (P50), and 1 L. lactis (Q5C6) were considered as the better performing, showing high values of both Pep N and Pep X. Based on data presented here, the aforementioned strains could be suggested as promising adjunct cultures in cheesemaking. [ABSTRACT FROM AUTHOR]

Lactic acid bacteria (LAB) are industrially important bacteria that are widely used in the fermented food industry, especially in the manufacture of yogurt. The fermentation characteristics of LAB are an important factor affecting the physicochemical properties of yogurts. Here, different ratios of L. delbrueckii subsp. bulgaricus IMAU20312 and S. thermophilus IMAU80809 were compared with a commercial starter JD (control) for their effects on viable cell counts, pH values, titratable acidity (TA), viscosity and water holding capacity (WHC) of milk during fermentation. Sensory evaluation and flavour profiles were also determined at the end of fermentation. All samples had a viable cell count above 5.59 × 107 CFU/mL at the end of fermentation, and a significant increase in TA and decrease in pH were observed. Viscosity, WHC and the sensory evaluation results of one treatment ratio (A3) were closer to the commercial starter control than the others. A total of 63 volatile flavour compounds and 10 odour-active (OAVs) compounds were detected in all treatment ratios and the control according to the results from solid-phase micro-extraction–gas chromatography–mass spectrometry (SPME–GC–MS). Principal components analysis (PCA) also indicated that the flavour characteristics of the A3 treatment ratio were closer to the control. These results help us understand how the fermentation characteristics of yogurts are affected by the ratio of L. delbrueckii subsp. bulgaricus to S. thermophilus in starter cultures; this is useful for the development of value-added fermented dairy products. [ABSTRACT FROM AUTHOR]

This article presents the study of the morpho-cultural properties and biofilm formation of lactobacilli isolated from lactic acid products (irimchik, suzbe, cheese, ashygan kozhe) produced in different districts of the Karaganda region. The species of the isolated lactic acid bacillus isolates were identified by using a MALDI-TOF mass spectrometer. The evaluation of the resistance of the isolates to various stress factors, such as the ability to survive at low acidic pH values and in the presence of bile, made it possible to identify some promising isolates – Lactobacillus helveticus -13 (Lh-13) and Lactiplantibacillus plantarum – 5 (Lpl-5), for studying antimicrobial and biofilm-forming activity. The antimicrobial activity of Lh-13, Lpl-5 was closely studied. They have a certain level of antibacterial and fungicidal activities, which indicates their pronounced inhibition against indicator microorganisms. Using a laboratory robot, TecanEVolizer100 (Tecan), the optical density of Lh-13, Lpl-5 was studied in the wells of polystyrene plates, reflecting the intensity of biofilm formation along their surface. Using laser capture microdissection, the images of cell morphology in biofilm of Lh-13 isolates included in the matrix were obtained. The atomic force microscopy made it possible to study the two and three-dimensional morphological images of biofilm-forming isolates of Lh-13. [ABSTRACT FROM AUTHOR]

Over the years, probiotics have been extensively studied within the medical, pharmaceutical, and food fields, as it has been revealed that these microorganisms can provide health benefits from their consumption. Bacterial probiotics comprise species derived from lactic acid bacteria (LAB) (genus Lactobacillus, Leuconostoc, and Streptococcus), the genus Bifidobacterium, and strains of Bacillus and Escherichia coli, among others. The consumption of probiotic products is increasing due to the current situation derived from the pandemic caused by COVID-19. Foods with bacterial probiotics and postbiotics are premised on being healthier than those not incorporated with them. This review aims to present a bibliographic compilation related to the incorporation of bacterial probiotics in food and to demonstrate through in vitro and in vivo studies or clinical trials the health benefits obtained with their metabolites and the consumption of foods with bacterial probiotics/postbiotics. The health benefits that have been reported include effects on the digestive tract, metabolism, antioxidant, anti-inflammatory, anticancer, and psychobiotic properties, among others. Therefore, developing food products with bacterial probiotics and postbiotics is a great opportunity for research in food science, medicine, and nutrition, as well as in the food industry. [ABSTRACT FROM AUTHOR]

Pediococci are lactic acid bacteria (LAB) which have been used for centuries in the production of traditional fermented foods. There fermentative abilities were explored by the modern food processing industry in use of pediococci as starter cultures, enabling the production of fermented foods with distinct characteristics. Furthermore, some pediococci strains can produce bacteriocins and other antimicrobial metabolites (AMM), such as pediocins, which are increasingly being explored as bio-preservatives in various food matrices. Due to their versatility and inhibitory spectrum, pediococci bacteriocins and AMM are being extensively researched not only in the food industry, but also in veterinary and human medicine. Some of the pediococci were evaluated as potential probiotics with different beneficial areas of application associated with human and other animals' health. The main taxonomic characteristics of pediococci species are presented here, as well as and their potential roles and applications as starter cultures, as bio-preservatives and as probiotic candidates. [ABSTRACT FROM AUTHOR]

To fulfil the growing interest in investigating microbial interactions in co-cultures, a novel two-compartment bioreactor system was developed, characterised, and implemented. The system allowed for the exchange of amino acids and peptides via a polyethersulfone membrane that retained biomass. Further system characterisation revealed a Bodenstein number of 18, which hints at backmixing. Together with other physical settings, the existence of unwanted inner-compartment substrate gradients could be ruled out. Furthermore, the study of Damkoehler numbers indicated that a proper metabolite supply between compartments was enabled. Implementing the two-compartment system (2cs) for growing Streptococcus thermophilus and Lactobacillus delbrueckii subs. bulgaricus, which are microorganisms commonly used in yogurt starter cultures, revealed only a small variance between the one-compartment and two-compartment approaches. The 2cs enabled the quantification of the strain-specific production and consumption rates of amino acids in an interacting S. thermophilus–L. bulgaricus co-culture. Therefore, comparisons between mono- and co-culture performance could be achieved. Both species produce and release amino acids. Only alanine was produced de novo from glucose through potential transaminase activity by L. bulgaricus and consumed by S. thermophilus. Arginine availability in peptides was limited to S. thermophilus' growth, indicating active biosynthesis and dependency on the proteolytic activity of L. bulgaricus. The application of the 2cs not only opens the door for the quantification of exchange fluxes between microbes but also enables continuous production modes, for example, for targeted evolution studies. [ABSTRACT FROM AUTHOR]

The market of probiotic foods and supplements is growing rapidly but frequently the commercialized products are not compliant with their labels in terms of claimed probiotic strain(s) and labeled number of viable probiotic cells, thus mining the authenticity of these probiotic products. In this review, we provide an up-to-date overview of: (i) the current regulatory aspects, (ii) the consistency of probiotic foods and supplements with their labels, (iii) the implications of mislabeling on the quality, safety and functionality of these products and (iv) the available and most promising methods to assess the authenticity of these products, taking into account the need to discriminate among the different physiological states probiotics might be in the carrier matrices. It arises that authenticity of probiotic foods and supplements is an urgent issue, of industrial and legislation relevance, that need to be addressed. A plethora of methods are available to reach this goal, each with its own advantages and disadvantages. Protocols that combine the use of propidium monoazide (PMA) with metagenomics or polyphasic approaches including the PMA real time PCR or flow cytometry (for the viability assessment) and the whole genome sequence analysis (for the identification and typing of the probiotic strain) are the most promising that should be standardized and used by producers and regulators. [ABSTRACT FROM AUTHOR]

High-moisture mozzarella cheese (HMMC) is a highly perishable cheese with a short shelf life. In this study, the effects of UF cheese whey containing postbiotics from Lactobacillus acidophilus LA-5 (P-LA-5), Bifidobacterium animalis BB-12 (P-BB-12), and their combination on the microbial (i.e., psychrophiles, mesophiles, lactic acid bacteria, and mold-yeast population) and sensory properties of HMMC were investigated. Postbiotics were prepared in a cheese whey model medium as a novel growth media and used as a preserving liquid in HMMC. The results demonstrate that postbiotics reduced the growth of all microorganisms (1.5–2 log CFU/g reduction) and P-LA5 and P-BB12 had the highest antibacterial performance on mesophiles and psychrophiles, respectively. Mold and yeast had the highest susceptibility to the postbiotics. Postbiotics showed a significant effect on maintaining the microbial quality of HMMC during storage, proposing postbiotics as a new preserving liquid for HMMC. [ABSTRACT FROM AUTHOR]

Summary: Lactic acid bacteria (LAB) are ubiquitous and integral members of the heterogeneous class of bacteria employed for fermented food and dairy applications such as yoghurt products. LAB are gram‐positive, non‐spore‐forming, non‐respiring but aerotolerant microorganisms that are generally characterised by the production of lactic acid as a key fermentation product. LAB, specifically Lb. bulgaricus, are essential dairy starter cultures for the manufacture of several fermented dairy products such as yoghurt and cheese. In this review, we discuss the importance of LAB as starter cultures and a probiotic for yoghurt production, its mode of metabolism, acidification characteristic, synthesis of lactase (β‐galactosidase) and a perspective on LAB's growth medium for dairy fermentations. [ABSTRACT FROM AUTHOR]

Postbiotics are non-viable bacterial products or metabolic byproducts produced by probiotic microorganisms that have biologic activity in the host. Postbiotics are functional bioactive compounds, generated in a matrix during anaerobic fermentation of organic nutrients like prebiotics, for the generation of energy in the form of adenosine triphosphate. The byproducts of this metabolic sequence are called postbiotics, these are low molecular weight soluble compounds either secreted by live microflora or released after microbial cell lysis. A few examples of widely studied postbiotics are short-chain fatty acids, microbial cell fragments, extracellular polysaccharides, cell lysates, teichoic acid, vitamins, etc. Presently, prebiotics and probiotics are the products on the market; however, postbiotics are also gaining a great deal of attention. The numerous health advantages of postbiotic components may soon lead to an increase in consumer demand for postbiotic supplements. The most recent research aspects of postbiotics in the food and pharmaceutical industries are included in this review. The review encompasses a brief introduction, classification, production technologies, characterization, biological activities, and potential applications of postbiotics. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the antimicrobial activity of both cells, and cell-free supernatants (CFS) of 7 selected lactic acid bacteria (LAB) strains belonging to Limosilactobacillus fermentum (4 strains), Lacticaseibacillus paracasei (1 strain), Lacticaseibacillus rhamnosus (1 strain), and Enterococcus faecium (1 strain) species, against Listeria monocytogenes, Escherichia coli, Salmonella Typhimurium, Pseudomonas aeruginosa and Staphylococcus aureus, by both the agar-well diffusion and co-culture methods. In addition, probiotic and safety traits were also detected. Great variability was detected on antimicrobial effects, whereas all tested strains were found sensitive to most of the tested antibiotics, and without any DNase, gelatinase, or hemolytic activity. Moreover, strains showed excellent survival in acidic conditions and exhibited tolerance to pepsin and bile salts. Based on the in vitro results, the CFSs of two selected L. fermentum strains were applied, in a mixed solution, as bio-preservative into minimally processed pomegranate arils, inoculated with a cocktail of L. monocytogenes and E. coli. Samples, packaged in an ordinary atmosphere, were analyzed during refrigerated storage, for up to 12 days, for physicochemical (as weight loss, texture, color, pH, total soluble solids and organic acid content) and for microbiological traits. Results revealed the effectiveness of CFS, up to 12 days, in reducing weight loss and microbial growth, without any significant effect on texture, total soluble solid content and color, found comparable to the acid citric treatment, highlighting the multi-functional potential of selected probiotic strains. [ABSTRACT FROM AUTHOR]

Lactic acid bacteria (LAB) are widely used in fermentation processes for the preparation of various foodstuffs, including dairy, meat and vegetable products. In the course of industrial biotechnological processes, lactobacilli are often exposed to oxidative stress, which occurs due to accumulation of reactive oxygen species (ROS) inside the cells. ROS are formed as a result of incomplete reduction of molecular oxygen to superoxide radical hydrogen peroxide (H2O2), or hydroxyl radical (OH•) and cause serious damage to all cellular macromolecules. Since LAB do not possess a complete electron transport chain, it was previously believed that they are incapable of existence under oxic conditions. Nevertheless, a number of LAB strains were found to possess the principal antioxidant defense enzymes with high specific activity. These include two types of catalases and NADH peroxidase. Heme-containing catalase is synthesized in many species of lactobacilli if heme or hematin is present in the culture medium. Both monofunctional catalase and bifunctional catalase-peroxidase were found in the cells of many LAB. Catalases of the second type (Mn-containing), which do not require the presence of heme, are also present in the cells of some lactobacilli species. Many LAB strains are characterized by high intracellular levels of Mn(II). Probiotic LAB cultures with pronounced antioxidant activity are in high demand, since they are potentially able to protect the host organism from the toxic effects of ROS and contribute to the prevention of cardiovascular, inflammatory, and oncologic diseases. In this review, antioxidant defense systems in LAB cells are described based on a thorough analysis of the current scientific data. In particular, the review describes the effect of oxidative stress on the metabolism of lactobacilli, their main antioxidant enzymes (NADH oxidase, NADH peroxidase, catalase, superoxide dismutase, and thioredoxin reductase), as well as the key regulatory proteins and the genes responsible for oxygen uptake as one of the mechanisms for decreasing the ROS concentration. [ABSTRACT FROM AUTHOR]

Lacticaseibacillus rhamnosus CM MSU 529 was grown in a batch culture under intensive aeration in the presence of 38 µM hemin and 18 µM vitamin K2 as a source of menaquinone to activate respiratory metabolism. Unsupplemented aerobic culture served as a control. Supplementation of the growth medium with hemin or menaquinone alone had no significant effect on the culture growth. In respiratory conditions (hemin + K2), a biomass production was 2.86 ± 0.05 g dw cells/L for a 24-h culture; the molar growth yield coefficient YP/S after 18 h of cultivation was 25.6 ± 1.5 g dw cells/mol of glucose consumed. Both values were 27% higher compared to those for the aerobic conditions. Spectral analysis revealed the presence of cytochromes b- and d-types in membranes of L. rhamnosus CM MSU 529. The activity of the bacterial electron transport chain was investigated using polarography. Membrane preparations of cells grown aerobically in a hemin-supplemented medium intensively consumed oxygen in the presence of 1 mM NADH. The addition of 0.2 mM menaquinone to the reaction mixture was accompanied by a 4.6-fold increase in NADH oxidation rate. Enzymes presumably involved in NADH oxidation by membranes and identified using MALDI-TOF MS/MS included pyridine nucleotide-disulfide oxidoreductase (Nox-2), NADH dehydrogenase 2 (Ndh-2), and ubiquinol oxidase bd subunit I (CydA). Therefore, in NADH oxidation, 80% of electron transport from NADH to oxygen occurred via Ndh-2, menaquinone, and bd-type quinol oxidase; as little as 20% were transfered via Nox-2. The study reports experimental evidence to support an electron transport chain functioning in L. rhamnosus CM MSU 529 under aerobic cultivation in the presence of hemin and menaquinone. The NADH oxidation rates of membrane preparations of lactic acid bacteria were measured for the first time. Additionally, this is the first time when the property of exogenous menaquinone to transfer electrons from Ndh-2 to bd-type quinol oxidase was demonstrated in vitro in lactic acid bacteria. [ABSTRACT FROM AUTHOR]

Probiotic milk is a class of fermented milk that possesses health-promoting effects, not only due to the lactic acid bacteria (LAB) presence but potentially also to yeast activity. Hence, the aim of this work was to isolate and select yeasts from spontaneous milk fermentations to be used as inoculum, together with LAB, for manufacturing a potentially probiotic acidic low-alcohol fermented milk. Six yeast species were detected from the spontaneous milk fermentation. A screening of 13 yeast strains and 14 previously isolated LAB strains, based on the resistance to bile salts and to acidic conditions, was carried out. The best performing strains were successively tested for in vitro gastrointestinal tolerance. A strain of Kluyveromyces marxianus and a strain of Lactococcus lactis were selected for the manufacturing of two different fermented milk. The values of the main technological and microbiological parameters (pH, organic acids, ethanol, and microbial concentrations) of the experimental milk were in the range of those reported for this category of products. The evaluation of microorganism survival in fermented milk samples subjected to simulated gastrointestinal conditions highlighted a high resistance of both strains. In conclusion, the selected microbial starter culture enabled the setting up of potential probiotic fermented milk. [ABSTRACT FROM AUTHOR]

Preparations containing probiotic strains of bacteria have a beneficial effect on human and animal health. The benefits of probiotics translate into an increased interest in techniques for the preservation of microorganisms. This review compares different drying methods and their improvements, with specific reference to processing conditions, microorganisms, and protective substances. It also highlights some factors that may influence the quality and stability of the final probiotic preparations, including thermal, osmotic, oxidative, and acidic stresses, as well as dehydration and shear forces. Processing and storage result in the loss of viability and stability in probiotic formulations. Herein, the addition of protective substances, the optimization of process parameters, and the adaptation of cells to stress factors before drying are described as countermeasures to these challenges. The latest trends and developments in the fields of drying technologies and probiotic production are also discussed. These developments include novel application methods, controlled release, the use of food matrices, and the use of analytical methods to determine the viability of probiotic bacteria. [ABSTRACT FROM AUTHOR]

Traditional fermented foods are a significant source of starter and/or non‐starter lactic acid bacteria (nsLAB). Moreover, these microorganisms are also known for their role as probiotics. The potential of nsLAB is huge; however, there are still challenges to be overcome with respect to characterization and application. In the present review, the most important steps that autochthonous lactic acid bacteria isolated from fermented foods need to overcome, to qualify as novel starter cultures, or as probiotics, in food technology and biotechnology, are considered. These different characterization steps include precise identification, detection of health‐promoting properties, and safety evaluation. Each of these features is strain specific and needs to be accurately determined. This review highlights the advantages and disadvantages of nsLAB, isolated from traditional fermented foods, discussing safety aspects and sensory impact. [ABSTRACT FROM AUTHOR]

The interest in probiotics has increased rapidly the latest years together with the global market for probiotic products. Consequently, establishing reliable microbiological methods for assuring the presence of a certain number of viable microorganisms in probiotic products has become increasingly important. To assure adequate numbers of viable cells, authorities are enquiring for information on viability rates within a certain shelf-life in colony forming units (CFU). This information is obtained from plate count enumeration, a method that enables detection of bacterial cells based on their ability to replicate. Although performing plate count enumeration is one manner of assessing viability, cells can still be viable without possessing the ability to replicate. Thus, to properly assess probiotic viability, further analysis of a broader group of characteristics using several types of methods is proposed. In addition to viability, it is crucial to identify how well the cells in a probiotic product can survive in the gastrointestinal tract (GIT) and thus be able to mediate the desired health benefit while passing through the human body. A broad spectrum of different assay designs for assessing probiotic gastric tolerance have been used in research and quality control. However, the absence of any consensus on how to assess these qualities makes it difficult to compare between laboratories and to translate the results into in vivo tolerance. This review presents and discusses the complexity of assuring that a probiotic is suitable for beneficial consumption. It summarizes the information that can be subtracted from the currently available methods for assessment of viability and stress tolerance of a probiotic, hereby altogether defined as "activity." Strengths and limitations of the different methods are presented together with favorable method combinations. Finally, the importance of choosing a set of analyses that reveals the necessary aspects of probiotic activity for a certain product or application is emphasized. [ABSTRACT FROM AUTHOR]

Colonization of intestinal tract with the potential to exclude, displace, and inhibit enteric pathogens is principally dependent on the adhesion ability of probiotics. Therefore, probiotic efficacy is considered to be mainly determined by their adhesion ability. The current study reports the antagonistic effect of four lactic acid bacteria (LAB) on the adhesion profile of four diarrhoeagenic and one non‐diarrhoeagenic enteroaggregative Escherichia coli (EAEC). All the bacterial strains investigated adhered to the Caco‐2 cells. All the LAB tested competitively excluded, displaced, and inhibited at least three (non‐) diarrhoeagenic EAEC strains from adhesion (p < 0.05). In all, Lactobacillus plantarum, FS2 exhibited the strongest adhesion to the Caco‐2 cells, competitive exclusion (CE), displacement, and inhibition against most of the EAEC strains. Additionally, the competence to exclude, displace, and inhibit the EAEC from adhesion depended on both the pathogens and the LAB strains tested; signifying the participation of several mechanisms. Contrary to all the EAEC strains, gastro‐intestinal stress factors such as low pH (2.5) had no effect on the adhesion of the LAB. Unlike the gastro‐intestinal acidic conditions, bile salt conditioning (at pH 6.5) had no effect on the adhesion of both EAEC and LAB. In conclusion, all the LAB tested showed specific anti‐adherence effects including CE, displacement, and inhibition against the selected EAEC. The results indicate that all the LAB, particularly, the L. plantarum, FS2 had a good ability for exerting antagonistic effects against the selected EAEC for the prevention of gastrointestinal infection. [ABSTRACT FROM AUTHOR]

β-galactosidases, commonly referred to as lactases, are used for producing lactose-free dairy products. Lactases are usually purified from microbial sources, which is a costly process. Here, we explored the potential that lies in using whole cells of a food-grade dairy lactic acid bacterium, Streptococcus thermophilus, as a substitute for purified lactase. We found that S. thermophilus cells, when treated with the antimicrobial peptide nisin, were able to hydrolyze lactose efficiently. The rate of hydrolysis increased with temperature; however, above 50 °C, stability was compromised. Different S. thermophilus strains were tested, and the best candidate was able to hydrolyze 80% of the lactose in a 50 g/L solution in 4 h at 50 °C, using only 0.1 g/L cells (dry weight basis). We demonstrated that it was possible to grow the cell catalyst on dairy waste, and furthermore, that a cell-free supernatant of a culture of a nisin-producing Lactococcus lactis strain could be used instead of purified nisin, which reduced cost of use significantly. Finally, we tested the cell catalysts in milk, where lactose also was efficiently hydrolyzed. The method presented is natural and low-cost, and allows for production of clean-label and lactose-free dairy products without using commercial enzymes from recombinant microorganisms. Key points: • Nisin-permeabilized Streptococcus thermophilus cells can hydrolyze lactose efficiently. • A low-cost and more sustainable alternative to purified lactase enzymes. • Reduction of overall sugar content. • Clean-label production of lactose-free dairy products. [ABSTRACT FROM AUTHOR]

The cell surface is the primary recognition site between the bacterium and the host. An operon of three genes, LSEI_0219 (cwaR), LSEI_0220 (cwaS), and LSEI_0221 (ldcA), has been previously identified as required for the establishment of Lactobacillus paracasei in the gut. The genes cwaR and cwaS encode a predicted two-component system (TCS) and ldcA a predicted D-alanyl-D-alanine carboxypeptidase which is a peptidoglycan (PG) biosynthesis enzyme. We explored the functionality and the physiological role of these three genes, particularly their impact on the bacterial cell wall architecture and on the bacterial adaptation to environmental perturbations in the gut. The functionality of CwaS/R proteins as a TCS has been demonstrated by biochemical analysis. It is involved in the transcriptional regulation of several genes of the PG biosynthesis. Analysis of the muropeptides of PG in mutants allowed us to re-annotate LSEI_0221 as a putative L,D-carboxypeptidase (LdcA). The absence of this protein coincided with a decrease of two surface antigens: LSEI_0020, corresponding to p40 or msp2 whose implication in the host epithelial homeostasis has been recently studied, and LSEI_2029 which has never been functionally characterized. The inactivation of each of these three genes induces susceptibility to antimicrobial peptides (hBD1, hBD2, and CCL20), which could be the main cause of the gut establishment deficiency. Thus, this operon is necessary for the presence of two surface antigens and for a suitable cell wall architecture. [ABSTRACT FROM AUTHOR]

Antimicrobial peptides that contribute to innate immunity are among the most important protective measures against infection in many organisms. Several substances are known to regulate the expression of antimicrobial peptides. In this study, we investigated the factors in lactic acid bacteria (LAB) that induce antimicrobial peptide expression in the host. We found that Lactobacillus helveticus SBT2171 (LH2171) induced the expression of human β-defensin (hBD)2 in Caco-2 human colonic epithelial cells. Specifically, surface layer protein (SLP) of LH2171 stimulated hBD2 expression by activating c-Jun N-terminal kinase (JNK) signaling via Toll-like receptor (TLR)2 in Caco-2 cells. SLPs extracted from other lactobacilli similarly increased hBD2 expression, suggesting that this stimulatory effect is common feature of Lactobacillus SLPs. Interestingly, Lactobacillus strains that strongly induced hBD2 expression also potently activated JNK signaling. Thus, upregulation of hBD2 induced by TLR2–JNK signaling contributes to protection of the host against infection. [ABSTRACT FROM AUTHOR]

Lactobacillus helveticus belongs to the large group of lactic acid bacteria (LAB), which are the major players in the fermentation of a wide range of foods. LAB are also present in the human gut, which has often been exploited as a reservoir of potential novel probiotic strains, but several parameters need to be assessed before establishing their safety and potential use for human consumption. In the present study, six L. helveticus strains isolated from natural whey cultures were analyzed for their phenotype and genotype in exopolysaccharide (EPS) production, low pH and bile salt tolerance, bile salt hydrolase (BSH) activity, and antibiotic resistance profile. In addition, a comparative genomic investigation was performed between the six newly sequenced strains and the 51 publicly available genomes of L. helveticus to define the pangenome structure. The results indicate that the newly sequenced strain UC1267 and the deposited strain DSM 20075 can be considered good candidates for gut-adapted strains due to their ability to survive in the presence of 0.2% glycocholic acid (GCA) and 1% taurocholic and taurodeoxycholic acid (TDCA). Moreover, these strains had the highest bile salt deconjugation activity among the tested L. helveticus strains. Considering the safety profile, none of these strains presented antibiotic resistance phenotypically and/or at the genome level. The pangenome analysis revealed genes specific to the new isolates, such as enzymes related to folate biosynthesis in strains UC1266 and UC1267 and an integrated phage in strain UC1035. Finally, the presence of maltose-degrading enzymes and multiple copies of 6-phospho-β-glucosidase genes in our strains indicates the capability to metabolize sugars other than lactose, which is related solely to dairy niches. [ABSTRACT FROM AUTHOR]

This study aimed at isolating and identifying lactic acid bacteria (LAB) with probiotic potential from fermented flour of selected banana varieties grown in Sri Lanka and evaluating their probiotic and safety attributes in vitro. Ten lactic acid bacteria were isolated from six varieties of fermented banana flour, kolikuttu, seeni parakum, ambul nadee, ambum, seeni and anamalu. The isolates were screened for phenotypical and biochemical characteristics. The selected isolates were identified by 16 S rRNA sequencing as Enterococcus durans (two strains), E. gallinarum, E. hirae, E. faecium (two strains), Lactobacillus plantarum, L. curieae, Weissella cibaria and Pediococcus acidilactici and their partial sequences were deposited in NCBI. Among them, six isolates were selected based on the results of in vitro safety attributes and evaluated for their probiotic attributes. Three isolates, namely, E. durans MF405179.1, E. faecium MF574466.1 and L. curieae MF405178.1 isolated from kolikuttu, seeni parakum and ambul nadee, respectively demonstrated tolerance to acid, gastric juice, bile, salt, phenol and temperature under gastric conditions, and also showed susceptibility to tested antibiotics. Among the selected isolates, E. durans MF405179.1 demonstrated the highest hydrophobicity and auto-aggregation of 69.91% and 76.53%, respectively. Further, it exhibited highest adhesion to both HCT116 and HT29 cell lines demonstrating 72.5% and 74.16% adhesion, respectively. This is the first report of isolation and characterisation of LAB strains with probiotic potential from flour of banana varieties kolikuttu, seeni parakum, ambul nadee, ambum, seeni and anamalu grown in Sri Lanka. [ABSTRACT FROM AUTHOR]

Several probiotic-marketed formulations available for the consumers contain live lactic acid bacteria and/or bifidobacteria. The multispecies product commercialized as VSL#3 has been used for treating various gastro-intestinal disorders. However, like many other products, the bacterial strains present in VSL#3 have only been characterized to a limited extent and their efficacy as well as their predicted mode of action remain unclear, preventing further applications or comparative studies. In this work, the genomes of all eight bacterial strains present in VSL#3 were sequenced and characterized, to advance insights into the possible mode of action of this product and also to serve as a basis for future work and trials. Phylogenetic and genomic data analysis allowed us to identify the 7 species present in the VSL#3 product as specified by the manufacturer. The 8 strains present belong to the species Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus plantarum, Lactobacillus helveticus, Bifidobacterium breve and B. animalis subsp. lactis (two distinct strains). Comparative genomics revealed that the draft genomes of the S. thermophilus and L. helveticus strains were predicted to encode most of the defence systems such as restriction modification and CRISPR-Cas systems. Genes associated with a variety of potential probiotic functions were also identified. Thus, in the three Bifidobacterium spp., gene clusters were predicted to encode tight adherence pili, known to promote bacteria-host interaction and intestinal barrier integrity, and to impact host cell development. Various repertoires of putative signalling proteins were predicted to be encoded by the genomes of the Lactobacillus spp., i.e. surface layer proteins, LPXTG-containing proteins, or sortase-dependent pili that may interact with the intestinal mucosa and dendritic cells. Taken altogether, the individual genomic characterization of the strains present in the VSL#3 product confirmed the product specifications, determined its coding capacity as well as identified potential probiotic functions. [ABSTRACT FROM AUTHOR]

Control and quantification of effector molecules such as heavy metals, toxins or other target molecules is of great biotechnological, social and economic interest. Microorganisms have regulatory proteins that recognize and modify the gene expression in the presence or absence of these compounds (effector molecules) by means of binding to gene sequences. The association of these recognizing gene sequences to reporter genes will allow the detection of effector molecules of interest with high sensitivity. Once investigators have these two elements--recognizing gene sequences and reporter genes that emit signals--we need a suitable vehicle to introduce both elements. Here, we suggest lactic acid bacteria (LAB) and bifidobacteria as promising carrier microorganisms for these molecular biosensors. The use of fluorescent proteins as well as food-grade vectors and clustered regularly interspaced short palindromic repeats (CRISPR) are indispensable tools for introducing biosensors into these microorganisms. The use of these LAB and bifidobacteria would be of special interest for studying the intestinal environment or other complex ecosystems. The great variety of species adapted to many environments, as well as the possibility of applying several protocols for their transformation with recognizing gene sequences and reporter genes are considerable advantages. Finally, an effort must be made to find recognizable gene sequences. [ABSTRACT FROM AUTHOR]

The human gastrointestinal tract (GIT) is highly colonized by bacterial communities, which live in a symbiotic relationship with the host in normal conditions. It has been shown that a dysfunctional interaction between the intestinal microbiota and the host immune system, known as dysbiosis, is a very important factor responsible for the development of different inflammatory conditions of the GIT, such as the idiopathic inflammatory bowel diseases (IBD), a complex and multifactorial disorder of the GIT. Dysbiosis has also been implicated in the pathogenesis of other GIT inflammatory diseases such as mucositis usually caused as an adverse effect of chemotherapy. As both diseases have become a great clinical problem, many research groups have been focusing on developing new strategies for the treatment of IBD and mucositis. In this review, we show that lactic acid bacteria (LAB) have been capable in preventing and treating both disorders in animal models, suggesting they may be ready for clinical trials. In addition, we present the most current studies on the use of wild type or genetically engineered LAB strains designed to express anti-inflammatory proteins as a promising strategy in the treatment of IBD and mucositis. [ABSTRACT FROM AUTHOR]

Aims The population of the Himalayan region is known to consume a variety of fermented and nonfermented foods and as a result they have been benefited in terms of overall health, because of the associated beneficial microbes. Therefore, the focus of the present study was to identify new strains of lactic acid bacteria ( LAB) from dairy products such as milk (cow, goat, buffalo) and fermented products (curd and buttermilk) with properties suitable for use as probiotic cultures. Methods and Results A total of 75 isolates tentatively identified as LAB from 100 samples were initially screened for production of β-haemolysin as indicators of virulence which resulted in 38 isolates with no haemolytic activity. Further subtractive screening based on resistance to gastrointestinal tract barriers (acid and bile salts) resulted in the selection of the eight most promising strains. All these eight strains were resistant to pH 2·0, 1% bile concentration and pancreatin (1 mg l−1). Among the eight isolates, three isolates were identified as Brevibacillus thermoruber and the others as Brevibacillus aydinogluensis, Lactobacillus gastricus, L. paracasei, Enterococcus sp. Weisella confusa based on 16S rDNA region. Among these isolates, L. paracasei CD4 and L. gastricus BTM7 indicated maximum tolerance to simulated gastric environment. Both the isolates possessed highest score for cell surface hydrophobicity, cell autoaggregation, adherence to Caco-2 cell lines and antimicrobial activity against clinical isolates of Escherichia coli and Shigella sp. comparable to standard strain of Lactobacillus rhamnosus GG. Further principal component analysis and clustering analysis based on Euclidean Similarity index of probiotic characters revealed that L. paracasei strain CD4 and L. gastricus strain BTM7 were placed closest to reference strain L. rhamnosus GG and were therefore identified as most promising probiotic candidate cultures. Conclusions These characteristics suggest that these strains could be excellent candidates for probiotics. Significance and Impact of the Study Milk-based products serve as reservoir for bacterial species with probiotic attributes. [ABSTRACT FROM AUTHOR]

Aerobic and respiratory cultivations provide benefits for some lactic acid bacteria (LAB). Growth, metabolites, enzymatic activities (lactate dehydrogenase; pyruvate and NADH oxidases, NADH peroxidase; catalase), antioxidant capability and stress tolerance of Lactobacillus casei N87 were evaluated in anaerobic, aerobic and respiratory (aerobiosis with heme and menaquinone supplementation) batch cultivations with different dissolved oxygen (DO) concentrations. The expression of pox (pyruvate oxidase) and cydABCD operon (cytochrome bd oxidase complex) was quantified by quantitative Real Time polymerase chain reaction. Respiration increased biomass production compared to anaerobiosis and unsupplemented aerobiosis, and altered the central metabolism rerouting pyruvate away from lactate accumulation. All enzymatic activities, except lactate dehydrogenase, were higher in respiratory cultures, while unsupplemented aerobiosis with 60% of DO promoted H2O2 and free radical accumulation. Respiration improved the survival to oxidative and freeze-drying stresses, while significant numbers of dead, damaged and viable but not cultivable cells were found in unsupplemented aerobic cultures (60% DO). Analysis of gene expression suggested that the activation of aerobic and respiratory pathways occurred during the exponential growth phase, and that O2 and hemin induced, respectively, the transcription of pox and cydABCD genes. Respiratory cultivation might be a natural strategy to improve functional and technological properties of L. casei. [ABSTRACT FROM AUTHOR]

Impedance microbiology is a method that enables tracing microbial growth by measuring the change in the electrical conductivity. Different systems, able to perform this measurement, are available in commerce and are commonly used for food control analysis by mean of measuring a point of the impedance curve, defined "time of detection." With this work we wanted to find an objective way to interpret the metabolic significance of impedance curves and propose it as a valid approach to evaluate the potential acidifying performances of starter lactic acid bacteria to be employed in milk transformation. To do this it was firstly investigated the possibility to use the Gompertz equation to describe the data coming from the impedance curve obtained by mean of BacTrac 4300®. Lag time (λ), maximum specific M% rate (μmax), and maximum value of M% (Yend) have been calculated and, given the similarity of the impedance fitted curve to the bacterial growth curve, their meaning has been interpreted. Potential acidifying performances of eighty strains belonging to Lactobacillus helveticus, Lactobacillus delbrueckii subsp. bulgaricus, Lactococcus lactis, and Streptococcus thermophilus species have been evaluated by using the kinetics parameters, obtained from Excel add-in DMFit version 2.1. The novelty and importance of our findings, obtained by means of BacTrac 4300®, is that they can also be applied to data obtained from other devices. Moreover, the meaning of λ, μmax, and Yend that we have extrapolated from Modified Gompertz equation and discussed for lactic acid bacteria in milk, can be exploited also to other food environment or other bacteria, assuming that they can give a curve and that curve is properly fitted with Gompertz equation. [ABSTRACT FROM AUTHOR]

Twenty-five strains of ciprofloxacin-resistant lactic acid bacteria (LAB; 14 Lactobacillus spp. and 11 Streptococcus thermophiles spp.) isolated from commercial yogurts in China were analyzed in this study. For each of these strains, amino acid changes associated with quinolone resistance-determining regions (QRDRs) were investigated using PCR-based detection methods. The same methodology was used to identify the presence of plasmid-mediated quinolone resistance (PMQR) genes in LAB. Sequencing analyses and an efflux pump inhibition test (using reserpine) were also performed as part of the analysis. Our results showed that typical mutations corresponding to quinolone resistance were found in the QRDRs of LAB strains. Detected mutations included Ser80Leu in parC, and Ser83Leu and Glu87Asp in gyrA. In addition, a Tyr74Phe substitution in parC, which had not previously been reported to be associated with quinolone resistance, was observed in two Lactobacillus delbrueckii subsp. bulgaricus strains. For each of the tested strains, the presence of the efflux pump inhibitor, reserpine, resulted in a two- to eightfold reduction in the minimum inhibitory concentrations (MICs) of ciprofloxacin. However, PMQR genes were not observed in any of the strains analyzed. Our results suggest that mutations in the QRDRs or efflux pump could be involved in ciprofloxacin resistance, and that a combination of these mechanisms may lead to increased ciprofloxacin resistance in LAB strains. [ABSTRACT FROM AUTHOR]

Lactic acid bacteria (LAB) and propionic acid bacteria (PAB) are widely used in the manufacture of cheeses and other fermented dairy products. Bacterial species used as starters are mainly chosen according to their intrinsic properties: the milk acidifying capacity for LAB starters and the aromatizing properties of PAB, for example. Beyond the general characteristics of a bacterial species, many key phenotypic traits determining their interest for dairy applications depend on the strain within a given species. Through some examples, this review illustrates how the choice of a bacterial strain with specific technological characteristics, within a given species of LAB or PAB, can determine the final properties in the end product. This concerns the technological properties of cheeses, such as flavour, texture, and opening formation, and their functional properties, such as inhibition of undesirable microorganisms and health properties. When known, the genetic determinants of the diversity are presented. This review emphasizes the importance of preserving and exploring microbial resources at the intraspecific level, as an unending source of diversity for innovation in food fermentation. [ABSTRACT FROM AUTHOR]

Efflux pumps are membrane proteins involved in the active extrusion of a wide range of structurally dissimilar substrates from cells. A multidrug efflux pump named TetA belonging to the major facilitator superfamily ( MFS) of transporters was identified in the Streptococcus thermophilus DSM 20617T genome. The tetA-like gene was found in the genomes of a number of S. thermophilus strains sequenced to date and in Streptococcus macedonicus ACA- DC 198, suggesting a possible horizontal gene transfer event between these two Streptococcus species, which are both adapted to the milk environment. Flow cytometry (single-cell) analysis revealed bistable TetA activity in the S. thermophilus population, and tetA-like gene over-expression resulted in a reduced susceptibility to ethidium bromide, tetracycline, and other toxic compounds even when the efflux pump was over-expressed in a strain naturally lacking tetA-like gene. [ABSTRACT FROM AUTHOR]

Background Lactic acid bacteria (LAB) has been considered a beneficial bacterial group, found as part of the microbiota of diverse hosts, including humans and various animals. However, the mechanisms of how hosts and LAB interact are still poorly understood. Previous work demonstrates that 13 species of Lactobacillus and Bifidobacterium from the honey crop in bees function symbiotically with the honeybee. They protect each other, their hosts, and the surrounding environment against severe bee pathogens, bacteria, and yeasts. Therefore, we hypothesized that these LAB under stress, i.e. in their natural niche in the honey crop, are likely to produce bioactive substances with antimicrobial activity. Results The genomic analysis of the LAB demonstrated varying genome sizes ranging from 1.5 to 2.2 mega-base pairs (Mbps) which points out a clear difference within the protein gene content, as well as specialized functions in the honeybee microbiota and their adaptation to their host. We demonstrate a clear variation between the secreted proteins of the symbiotic LAB when subjected to microbial stressors. We have identified that 10 of the 13 LAB produced extracellular proteins of known or unknown function in which some are arranged in interesting putative operons that may be involved in antimicrobial action, host interaction, or biofilm formation. The most common known extra-cellular proteins secreted were enzymes, DNA chaperones, S-layer proteins, bacteriocins, and lysozymes. A new bacteriocin may have been identified in one of the LAB symbionts while many proteins with unknown functions were produced which must be investigated further. Conclusions The 13 LAB symbionts likely play different roles in their natural environment defending their niche and their host and participating in the honeybee's food production. These roles are partly played through producing extracellular proteins on exposure to microbial stressors widely found in natural occurring flowers. Many of these secreted proteins may have a putative antimicrobial function. In the future, understanding these processes in this complicated environment may lead to novel applications of honey crop LAB proteins. [ABSTRACT FROM AUTHOR]

Background: How to maintain "gut health" is a goal for scientists throughout the world. Therefore, microbiota management models for testing probiotics, prebiotics, and synbiotics have been developed. Methods: The SHIME® model was used to study the effect of Lactobacillus acidophilus 1014 on the fermentation pattern of the colon microbiota. Initially, an inoculum prepared from human feces was introduced into the reactor vessels and stabilized over 2-wk using a culture medium. This stabilization period was followed by a 2-wk control period during which the microbiota was monitored. The microbiota was then subjected to a 4-wk treatment period by adding 5 mL of sterile peptone water with L. acidophilus CRL1014 at the concentration of 108 CFU/mL to vessel one (the stomach compartment). Plate counts, Denaturing Gradient Gel Electrophoresis (DGGE), short-chain fatty acid (SCFA) and ammonium analyses were carried out for monitoring of the microbial community from the colon compartments. Results: A significant increase (p < 0.01) in the Lactobacillus spp. and Bifidobacterium spp. populations was observed during the treatment period. The DGGE obtained showed changes in the lactobacilli community from the colon compartments of the SHIME® reactor. The (SCFA) concentration increased (p < 0.01) during the treatment period, due mainly to significant increased levels of acetic, butyric, and propionic acids. However, ammonium concentrations decreased during the same period (p < 0.01). Conclusions: This study showed the beneficial influence of L. acidophilus CRL 1014 on microbial metabolism and lactobacilli community composition for improving human health. [ABSTRACT FROM AUTHOR]