Probiotic Activity Research Articles

Exopolysaccharide production by Lactobacillus plantarum T10 is responsible for the probiotic activity in enhancing intestinal barrier function in vitro and in vivo.

Lactobacillus probiotics exert their effects in a strain-specific and metabolite-specific manner. This study aims to identify lactobacilli that can effectively enhance the intestinal barrier function both in vitro and in vivo and to investigate the underlying metabolite and molecular mechanisms involved. Nine Lactobacillus isolates were evaluated for their ability to enhance the IPEC-J2 cellular barrier function and for their anti-inflammatory and anti-apoptotic effects in IPEC-J2 cells after an enterotoxigenic Escherichia coli challenge. Of the nine isolates, L. plantarum T10 demonstrated significant advantages in enhancing the cellular barrier function and displayed anti-inflammatory and anti-apoptotic activities in vitro. The bioactivities of L. plantarum T10 were primarily attributed to the production of exopolysaccharides, which exerted their effects through the TLR-mediated p38 MAPK pathway in ETEC-challenged IPEC-J2 cells. Furthermore, the production of EPS by L. plantarum T10 led to the alleviation of dextran sulfate sodium-induced colitis by reducing intestinal damage and enhancing the intestinal barrier function in mice. The EPS is classified as a heteropolysaccharide with an average molecular weight of 23.0 kDa. It is primarily composed of mannose, glucose, and ribose. These findings have practical implications for the targeted screening of lactobacilli used in the production of probiotics and postbiotics with strain-specific features of exopolysaccharides.

Antibacterial and Anti Diabetic Activities of Ethyl Acetate Fractions of Lactobacillus Isolated from Cow and Goat Milk

ABSTRACT: Antibiotics are one of our most important weapons in fighting with bacterial infections and diabetics. Drugs were derived from natural sources that play an important role in the treatment and prevention of human diseases. Traditional fermented foods containing lactic acid bacteria such as milk, yogurt, curd, etc., have historically been consumed by human. Lactobacilli are well known friendly bacteria for their probiotic activities against pathogens. In this investigation cow and goat milk samples were selected and collected for the study. The gram stain was used for morphological identification of Lactobacillus sp. in the two samples. The two isolated Lactobacillus sp. from goat and cow milk samples were subjected to the extraction of secondary metabolites using the solvent ethyl acetate. The two extracts of Lactobacillus spp. those were isolated from cow and goat milk samples, showed antibacterial activity against Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Pseudomonas aeruginosa. The zone of inhibition was assessed by mm. The good results of zones were observed at 1000 and 2000 µg in cow milk and 2000 µg in goat milk extraction. These metabolites were also showed good results in antidiabetic activity using the alpha amylase inhibition activity. The IC50 value has showed moderate activity in the two crude extractions when compared to acarbose standard drug. Therefore, in this investigation the Lactobacillus sp. producing secondary metabolites was good source for the activity of antibacterial and antidiabetic activity.

Tri-cultured lactic-acetic acid co-fermentation improves stored jujube puree functionality, physicochemical, volatile compounds, and sensory characteristics

Jujubes, known for their bioactive compounds, are underutilized due to their unappealing dry qualities with lingering bitterness, and short shelf-life when fresh. Co-fermented jujube puree storage could enhance its functional food potential. For the first time, the impact of storage on 8-day tri-cultured Junzao jujube puree experimented with commercial and indigenous Chinese lactic and acetic acid bacteria on the functionality, physicochemical, volatile compounds, and sensory characteristics was investigated. Despite a decline in microbial loads, the stored purees exhibited excellent viability, with specific tricultures showing promising probiotic activity of more than 6-log CFU/mL of viable counts. Stored purees demonstrated improved acidification, increased total acid content, and reduced pH. Fourier-transform infrared spectroscopic analysis indicated structural changes in polysaccharides, and total flavonoid content quintupled (31.05%), with the highest observed in tri-culture: Lactobacillus casei, Lactobacillus plantarum and Acetobacter pasteurianus (98.74 mg rutin equivalent/100 g) with peculiar formation of l-methionine (1.93 mg/100 g). Antioxidant capacity varied among stored tri-cultured purees, and sensory analysis showed sourness, fruity, floral, thickness, intense yellowish color was associated with the stored tricultures compared to the unfermented sample. Headspace solid-phase microextraction gas chromatography-mass spectrometry analysis identified 80 volatile compounds, with esters (38%) being predominant. Overall, the results demonstrated that lactic-acetic acid tri-culture storage could bio-valorize Junzao jujube puree, improving its organoleptic appeal and shelf-life.

Systematic Review of Probiotics and Their Potential for Developing Functional Nondairy Foods

The gastrointestinal tract is an environment that hosts various microorganisms, including pathogens. Generally, pathogenic bacteria enter the host body through food and the gastrointestinal tract. These pathogenic bacteria can colonize or infiltrate host cells and tissues, causing various infectious diseases. In recent years, the protective role of probiotic bacteria against gastrointestinal pathogens has been carefully investigated. Probiotics have been found to modulate intestinal microbial flora and play a significant role in the gastrointestinal tract’s function, especially by inhibiting the growth of pathogenic bacteria. However, the mechanism of action of probiotics has yet to be sufficiently proven and recognized. Several important mechanisms support the antagonistic effects of probiotics on various microorganisms, which is achieved, for example, through the production of different antimicrobial compounds, such as bacteriocins, various organic acids, antibiotics, antimicrobial proteins, and exopolysaccharides; mucosal barriers with mucosa and bacteria binding blockers; competition for nutrient uptake; and strengthening of the immune system. Accordingly, this review summarizes the recent studies that have examined the mechanism of action of probiotic bacteria and their beneficial effects in preventing pathogenic bacterial growth and improving gastrointestinal functions. Comprehending their mechanisms of action allows the selection of appropriate probiotic strains for specific applications in gastrointestinal dysfunction.

Adjuvant Pluronic F68 Is Compatible with a Plant Root-Colonizing Probiotic, Pseudomonas chlororaphis O6

Plant probiotic bacteria are being increasingly used to maximize both the productivity and quality of field crops. Pseudomonas chlororaphis O6 (PcO6) is a plant root colonizer with probiotic activities. This bacterium produces an array of metabolites, including a group of phenazines that are functional in plant protection. The paper reports responses of PcO6 to a nonionic triblock copolymer surfactant, Pluronic F68. This Pluronic exhibits membrane “healing” activity and improves cryopreservation recovery in eukaryotic cells. The product is FDA-approved and is applied as an adjuvant in formulations used in agriculture, medicine, and biotechnology. Growth of PcO6 on lysogeny broth at 25 °C was unhindered by 0.1 and 1.0 g/L F68, reduced at 10 g/L, and with significant inhibition at 100 g/L F68; micelle formation could account for inhibited growth at higher doses. Phenazine production was not changed by F68, whereas the surfactant activity of F68 induced the spread of bacterial colonization on 0.5% agar. Exposure of cells to fluorescein-labeled F68 resulted in intense fluorescence, stable to washing, showing a direct association of the Pluronic with the bacterium. However, neither protection nor harm was found for PcO6 cells suspended in either 0.1% or 1% F68 after three freeze (−20 °C)/thaw cycles. These findings suggest that F68 could be compatible for use in agricultural formulations with little effect on probiotics such as PcO6.

Functional Cheeses: Updates on Probiotic Preservation Methods

The consumption of natural products, especially those that promote some health benefit, has become a choice for consumers. Foods that improve health when ingested are called functional foods. Among them, the most consumed are probiotics, which are defined as microorganisms that, when administered in adequate quantities, can promote a health benefit for consumers. Probiotic dairy products, especially cheese, are the most appreciated and have been produced to possess the properties that favor the viability of these microorganisms after passing through the gastrointestinal tract. They provide benefits such as antibacterial activity, prevention of cancer and cardiovascular diseases, anti-obesity effects, anti-diabetic effects, improved immune systems, and prodiseases, among others. Despite cheeses being a viable matrix for the survival of these probiotics, the development and adoption of technologies with the aim of increasing the viability of probiotic bacteria are necessary, which presents a research trend to be increasingly explored, as well as studies about the complex mechanisms of health benefits resulting from the actions of probiotics. Thus, this review aims to address the most recent innovations regarding the incorporation of probiotics in cheeses and their functional potential.

Comparison of Bioconversion Ability and Biological Activities of Single and Multi-Strain Probiotics for an Active Molecule in Roasted Tartary Buckwheat

Comparison of Bioconversion Ability and Biological Activities of Single and Multi-Strain Probiotics for an Active Molecule in Roasted Tartary Buckwheat

Development of technology for obtaining encapsulated probiotics

One of the priority areas of the modern food industry is the development of functional food products that have a regulatory effect on physiological functions, biochemical reactions and psychosocial behavior of a person through the normalization of his microecological status. Scientists assign a special role in functional nutrition to fermented milk products with probiotics, which have a more pronounced functional effect on the human body, due to the complex action of probiotics. However today traditional production technologies face some problems, in particular, the problem of preserving and delivering viable probiotic cells to the gastrointestinal tract in order to display therapeutic properties. In this regard, the use of methods for encapsulating probiotics to obtain capsules and their application in the technology of fermented milk products for functional purposes is relevant. This article discusses the technology for obtaining encapsulated probiotics. To obtain encapsulated probiotics, several types of biopolymers were used: amidated pectin, sodium alginate, and gelatin. To substantiate the selected encapsulating materials, experimental studies were carried out to determine the possibility of capsule formation of amidated pectin, sodium alginate and gelatin at a concentration of 1 %, 2 %, 3 %, as well as the ratio of gelatin and sodium alginate 1/1 %, 2/1 %, 3/1 %, 4/1 %.

Encapsulated Probiotic Microorganisms in Functional Food Products

Alterations in the composition of the gut microbiota are associated with a wide range of pathologies, including not only inflammatory diseases of the gastrointestinal tract, but also diabetes, obesity, cancer, and diseases of the cardiovascular and central nervous systems. With an imbalance of the microbiota (dysbiosis), there is increased intestinal permeability and a violation of local or systemic immune responses. One of the possible ways to improve intestinal microbiota is the use of dietary supplements and functional food products enriched with highly effective encapsulated probiotic microorganisms, as well as prebiotic compounds. Such products contribute to the restoration of normal intestinal microflora and its integrity, and also indirectly affect the positive outcome in the treatment of many pathological conditions mediated by an imbalance in the intestinal microbiota. Maintaining the activity of probiotics in food carriers or functional food products designed for the prevention and complex therapy of various pathological conditions is important both for the normalization of the intestinal microflora and the health of the body as a whole. In this context, encapsulation is an effective approach to maintain the viability and stability of probiotics under adverse conditions in the gastrointestinal tract and also an effective way to protect from processing conditions, temperature, and transportation. The development of functional nutrition products enriched with highly effective encapsulated probiotic microorganisms is a priority for new research in the field of prevention and treatment in microbiota-targeted therapy. The use of such products is based on the conception of 3p — pathophysiology-based individualized use of probiotics and prebiotics in various pathological conditions mediated by a violation of the qualitative and/or quantitative composition of the intestinal microbiota: implementing a predictive, preventive, and personalized medical approach.

Probiotic Development: Research Gaps and Opportunities

Abstract Probiotics are live microbes, that when administered in adequate amounts, confer a health benefit on the host. Various health benefits have been documented for different strains/combinations of probiotics; mostly related to digestive and immune health. Because the gut is also linked to many other organ systems, health benefits outside the gut have been reported. Further, new strains from species not previously used in food and dietary supplements are being investigated as so-called next generation probiotics (NGPs). These NGPs are often intended to become drugs rather than dietary supplements or functional foods. The future may also bring new delivery formats that are not consumed but otherwise applied to the body. To develop these NGPs and better understand the mechanism of action of current probiotics, the so-called omics techniques are helpful. For a layperson, it is difficult to identify a good quality probiotic. However, careful reading of the product label can help to identify the strains and counts at the end of a product’s shelf life. Information © The Authors 2023

Au‐Modified Carbon Electrodes Produced by Laser Scribing for Electrochemical Analysis of Probiotic Activity

AbstractA simple and fast (<15 min), two‐step laser scribing of cardboard substrates is described as a method for fabricating carbon electrodes modified with metallic nanoparticles. The first scribing step patterned a cardboard substrate (promoting the formation of porous carbon electrodes). The second step was included to produce metallic nanoparticles via a chemical reduction process of cations from an aqueous solution. For these experiments, the effects of copper, silver, nickel, cobalt, zinc, and gold were evaluated considering their effect on the electrical properties and the composition of the carbon materials produced. These experiments revealed that, despite significant changes in resistance (from 138±7 Ω for plain electrodes to just 53±3 Ω for Au‐modified electrodes), only marginal changes were observed in the morphology or composition of the material produced (IG/ID ranged from 1.2±0.3 for the plain cardboard to 1.8±0.3 for the cobalt‐modified electrodes). To demonstrate the applicability of the proposed strategy, Au‐modified electrodes were assembled into electrochemical sensors and applied to measure the metabolic activity of live microorganisms in various commercial samples, requiring only 100 μL of sample and 10 min of incubation time.

Grafting chlorogenic acid enhanced the antioxidant activity of curdlan oligosaccharides and modulated gut microbiota

In this study, the effects of grafting chlorogenic acid (CA) on the antioxidant and probiotic activities of curdlan oligosaccharides (CDOS) were investigated. CDOS with degrees of polymerization of 3–6 was first obtained by degradation of curdlan with hydrogen peroxide and then grafted with CA using a free radical-mediated method under an ultrasonication-assisted Fenton system. The thermal stability and antioxidant ability of CDOS were enhanced after grafting with CA. In vitro fermentation, supplementation of CDOS-CA stimulated the proliferation of Prevotella and Faecalibacterium while inhibiting the growth of harmful microbiota. Notably, the concentration of total short-chain fatty acids and the relative abundance of beneficial bacteria markedly increased after fermentation of CDOS-CA, indicating that CA grafting could improve the probiotic activity of CDOS. Overall, the covalent binding of CDOS and CA could enhance the antioxidant and probiotic activities of CDOS, suggesting potential improvements in gastrointestinal and colonic health.

Therapeutic effects of orally administration of viable and inactivated probiotic strains against murine urinary tract infection.

Urinary tract infections (UTIs) are highly prevalent bacterial infections that pose significant health risks. Specific probiotic strains have been recommended for UTI control and management of antibiotic resistance. Otherwise, para-probiotics, defined as inactivated probiotic cells, offer potential advantages by minimizing risks associated with live microorganisms. However, the effectiveness of heat-killed probiotic strains against UTIs remains uncertain. Additionally, lactoferrin (LF), an iron-binding glycoprotein, exhibits immunomodulatory, antimicrobial, and anti-inflammatory properties. Recently, we had developed recombinant LF-expression probiotics, which can display considerate antibacterial activities against select food-borne pathogens in vitro. Thus, the present study aimed to evaluate the antibacterial activities of heat-killed natural and recombinant LF-expressing probiotics against UTIs in vitro and in vivo. Firstly, using in vitro assays, we assessed the antibacterial activity of heat-killed natural and recombinant LF-expressing probiotics against uropathogenic Escherichia coli and Klebsiella pneumoniae. Among the tested probiotics, 10 heat-killed LF-expressing strains displayed superior antibacterial efficacy compared to 12 natural probiotics. Based on their potent in vitro activity, selected probiotics were formulated into three probiotic mixtures: viable probiotic mixture (LAB), heat-killed probiotic mixture (HK-LAB), and heat-killed LF-expressing probiotic mixture (HK-LAB/LF). To further evaluate the therapeutic potential of these probiotic mixtures in vivo, we established a murine model of UTIs by intraurethral administration of E. coli to 40 female C57BL/6JNarl mice on day 0. Subsequently, mice received oral gavage of placebo, LAB, HK-LAB, or HK-LAB/LF for 21 consecutive days (n = 8 per group). An additional control group (n = 8) received ampicillin treatment for 7 days. To assess protective effects against re-infection or UTI relapse, all mice were challenged with E. coli on day 22 and E. coli plus K. pneumoniae on day 25. Results from the murine UTI model demonstrated that placebo administration did not reduce bacteriuria throughout the experiment. Conversely, supplementation with ampicillin, HK-LAB/LF, HK-LAB, or LAB significantly (p < 0.05) reduced daily bacteriuria by 103 to 104-fold on days 1, 3, 5, and 14, respectively. Furthermore, all four therapeutic treatments improved the bacteriological cure rate (BCR) with varying levels of efficacy. For the 7-day treatment course, the BCR was 25% (placebo), 62.5% (ampicillin), 37.5% (LAB), 37.5% (HK-LAB), and 62.5% (HK-LAB/LF). For the 21-day treatment course, the BCR was 25% (placebo), 75% (ampicillin), 37.5% (LAB), 37.5% (HK-LAB), and 75% (HK-LAB/LF). Notably, HK-LAB and HK-LAB/LF demonstrated superior therapeutic efficacy compared to viable LAB in treating UTIs. Overall, regarding BCR, the three probiotic mixtures can provide benefits against UTI in mice, but ampicillin therapy remains the most efficient among the four treatments. Furthermore, there was no significant difference between pre- and post-challenge courses for the two instances of re-challenging uropathogens in all mice groups, as bacteriuria levels remained below 103 CFU/mL, implying that adaptive responses of mice may help reduce the risk of recurrent UTIs. In conclusion, our results provide new evidence that oral administration of heat-killed probiotic mixtures can confer significant therapeutic efficacy against UTIs in a murine model.

Lactobacillus paracasei R3 Alleviates Tumor Progression in Mice with Colorectal Cancer.

Lactobacillus paracasei (L. paracasei), a common probiotic lactobacillus, has important functions in the food industry and human health. However, different strains of L. paracasei inevitably show differences in activity and colonization resistance, leading to differentiation in their functions, as well as their physical or chemical properties. The purpose of this study was to evaluate the characteristics of L. paracasei R3 (L.p R3) isolated from healthy human feces and determine whether the criteria for edible probiotics is met. The hemolysis type, biofilm-forming ability, antibiotic susceptibility, toxicity, and effective activity of L.p R3 were determined by establishing its probiotic activity traits in vitro and in vivo. The results showed that L.p R3 had a moderate biofilm formation ability, was sensitive to 11 antibiotics, was resistant to eight antibiotics, and was not hemolytic. The culture characteristics, morphology, and biochemical responses of the strain were consistent with the seed batch characteristics. In toxicity assays, L.p R3-fed mice showed no abnormalities in body weight, growth, or various organs. Additionally, L.p R3 was found to be effective in the prevention and treatment of colorectal cancer. In conclusion, our results revealed that L.p R3 has potential value as an edible probiotic without toxic side effects and alleviated the tumor progression of colorectal cancer in mice.

Osteopontin enhances the probiotic viability of Bifidobacteria in pectin-based microencapsulation subjected to in vitro infant gastrointestinal digestion

Encapsulation is usually adapted to improve probiotic viability under adverse environmental conditions, and used to ensure adequate amount of probiotics reach the distal gastrointestinal tract and achieve probiotic action. In the present study, sub-species of Bifidobacterium were encapsulated with pectin or alginate by an emulsification/internal gelation method. Bovine milk osteopontin (OPN) was used as an excipient with potential to improve the protection of the probiotics during processing and/or gastrointestinal digestion. Here, we reported that the use of OPN significantly improved probiotic viability during freeze drying and simulated infant gastrointestinal digestion. The viability of Bifidobacterium bifidum R0071 and Bifidobacterium breve M-16V loaded in pectin-based freeze-dried microcapsules with 0.5% OPN addition remained at over 106 CFU g−1 after simulated infant digestion. In comparison, the microcapsules without OPN had a probiotic viability of only 103 CFU g−1. The protective effect of OPN was proven to be dose dependent. For example, the B. bifidum R0071 viability was 6.1 log CFU·g−1 after the gastrointestinal digestion for the pectin-based microencapsulation without OPN addition, while the value remained at 8.4 log CFU·g−1 when OPN concentration reached 5%. In this study, we also demonstrated that extracellular calcium ions could chelate with OPN molecules which could be attributed to preventing damage of the probiotic cell wall and the improved protective effective of microencapsulation. Overall, these results provide new insight into the use of OPN as a microencapsulation excipient to promote probiotic viability and its potential future application in functional foods such as infant formula with enhanced gut health.

Unveiling strain-level dynamics in probiotic activity

Divergent gene content among distinct probiotic strains contributes to varied or conflicting clinical efficacies. Zhang et al. unveils a novel bacterial gene signature, particularly the abfA gene cluster, offering a promising avenue for screening probiotics and advancing our understanding of strain-level activities in the context of gastrointestinal health.

Unveiling the Probiotic Potential of the Anaerobic Bacterium Cetobacterium sp. nov. C33 for Enhancing Nile Tilapia (Oreochromis niloticus) Cultures.

The bacterium strain Cetobacterium sp. C33 was isolated from the intestinal microbial content of Nile tilapia (O. niloticus) under anaerobic conditions. Given that Cetobacterium species are recognized as primary constituents of the intestinal microbiota in cultured Nile tilapia by culture-independent techniques, the adaptability of the C33 strain to the host gastrointestinal conditions, its antibacterial activity against aquaculture bacterial and its antibiotic susceptibility were assessed. The genome of C33 was sequenced, assembled, annotated, and subjected to functional inference, particularly regarding pinpointed probiotic activities. Furthermore, phylogenomic comparative analyses were performed including closely reported strains/species relatives. Comparative genomics with closely related species disclosed that the isolate is not phylogenetically identical to other Cetobacterium species, displaying an approximately 5% sequence divergence from C. somerae and a 13% sequence divergence from Cetobacterium ceti. It can be distinguished from other species through physiological and biochemical criteria. Whole-genome annotation highlighted that Cetobacterium sp. nov. C33 possesses a set of genes that may contribute to antagonism against competing bacteria and has specific symbiotic adaptations in fish. Additional in vivo experiments should be carried out to verify favorable features, reinforcing its potential as a probiotic bacterium.

Bacillus mojavensis isolated from aguamiel and its potential as a probiotic bacterium

BackgroundMillenary fermented beverages are a source of industrially important microorganisms. Aguamiel and pulque are traditional Mexican beverages of pre-Hispanic origin, with a microbial diversity that contributes to the different fermentations (lactic, alcoholic and acetic). The aim of this research was to characterize the Bacillus mojavensis (BF2A1) strain isolated from aguamiel and determine its probiotic potential. The strain was identified through Mass Spectrometry (MS), molecular techniques, as well as morphological and biochemical profiling. The probiotic activity of the BF2A1 strain and its response during the gastric simulation was determined. ResultsThe strain BF2A1 is a Gram-positive, spore-forming bacillus, positive for catalase, gamma-hemolysis, citrate, ornithine, grows at 7.5% NaCl, and acetoin, but negative for motility, indole, and methyl red. Its taxonomic identity was determined as B. mojavensis both by MALDI-TOF MS and sequencing of 16S rDNA. Its probiotic potential was demonstrated as BF2A1 was tolerant to pH 2 (OD620nm 0.289 ± 0.012), 0.3% bile salts (OD620nm 0.103 ± 0.089), 8% NaCl (OD620nm 0.254 ± 0.096), and 1% lysozyme (OD620nm 1.342 ± 0.078) compared to the probiotic strain Lactobacillus leichmannii ATCC 7830TM (Laclei). The antagonistic effect of BF2A1 against Escherichia coli (ATCC25922), Staphylococcus aureus (ATCC25923), and Candida albicans (ATCC60193) showed 25.5%, 8% and, 65% inhibitory growing effect, respectively. BF2A1 in the gastric simulation showed only a reduction of 1–2 log CFU/mL and showed after the intestinal phase a survival rate of 84.4% as compared to the control strains. ConclusionsThis study shows that BF2A1 isolated from aguamiel is a bacterium with probiotic properties that can be used in different areas of Biotechnology.How to cite: Martínez-Ortiz V, Trujillo-López MA, El-Kassis EG, et al. Bacillus mojavensis isolated from aguamiel and its potential as a probiotic bacterium. Electron J Biotechnol 2024;67. https://doi.org/10.1016/j.ejbt.2023.11.002.

Comparative characteristics of the effect of probiotics Vetom 2 and Liquafed in growing rainbow trout in ST “Romanov” (Leningrad region)

In the conditions of modern industrial fish farms of various types, the risk of bacterial diseases increases. Various probiotic and immunomodulatory preparations are actively used in modern aquaculture. Especially popular are probiotics based on Bacillus subtilus, which are used in the cultivation of carp, sturgeon and salmon fish. Recently, a large positive experience has been accumulated in the use of Vetom 1.1 in fish farming (manufactured by the Scientific and Production Company Research Center, Novosibirsk). At the same time, fish farms actively use Vetom 2, created on the basis of dried spore biomass of Bacillus subtilis and Bacillus licheniformis bacteria. For use in aquaculture, LikvaFid seems to be promising, containing as active ingredients live cultures of the bacteria Bacillus megaterium and Bacillus subtilis (manufactured by LLC BIOTROF, St. Petersburg). Experimental work on the use of probiotics of domestic production LikvaFid and Vetom 2 was carried out at the fish-breeding enterprise Sole Trader Romanov (Leningrad region, Lopukhinka village). A one-year-old rainbow trout was chosen as the object of research. Vetom 2 and LikVafid were administered orally with food by irrigation at a dosage of 5 g/kg and 2 g/kg, respectively, in two courses, the duration of each course was 10 days, the interval between them was 40 days. An analysis of the results of the experimental work showed a statistically significant increase in body weight and length in the experimental groups, as well as a significant increase in the growth rate. The absolute increase in the experiment is 1.4–1.7 times higher than in the control. At the same time, the maximum indicators for almost all significant morpho-biological indicators were found in fish treated with the LiquaFeed probiotic. The relative growth rate in this group is 1.2 times higher than in the control. Research work confirms the beneficial effect of these preparations on the processes of fish digestion. Strains of Bacillus subtilis, Bacillus licheniformis and Bacillus megaterium, due to their probiotic activity, stimulate the growth of normal intestinal microflora. Improving the absorption of nutrients in the gastrointestinal tract, inhibiting the development of pathogenic and opportunistic microorganisms, and stimulating the immune system contribute to a more active growth of rainbow trout.

Biosurfactant potential and antiviral activity of multistrain probiotics

The COVID-19 caused by the SARS-CoV-2 has become a great threat to humans. However, there is no recommendation for an effective and safe drug to treat the disease. The strategy developed in this study is to utilize biosurfactant potential activity of Lactobacillus spp. and Rhodopseudomonas palustris probiotics to prevent the virus from entering human body. The outer membrane of the virus is comprising of phospholipid compounds. Biosurfactants, are known to have detergent-like properties (able to dissolve lipids) that are safe for in vivo use. Thus, the biosurfactant potential activity of the multistrain probiotics extract is expected to be able to disrupt the phospholipid membrane, resulting in the inactivity of the virus to infect human body. The biosurfactant potential activity of the probiotics extract was evaluated using oil spreading, drop collapse, and emulsification methods. The virus infectivity was evaluated on the SARS-CoV-2 of delta variant as a virus model. The results indicated that the probiotics extract has biosurfactant potential activity, able to inhibit virus growth up to 99.9 % within 48 h in the prevention platform, and up to 99.6 % within 48 h in the treatment platform. Therefore, the multistrain probiotics extract was identified to have potential as a promising antiviral agent.