Fermented milks with specific Lactobacillus spp. with potential cardioprotective effects.

In vitro and in vivo studies have reported the potential cardioprotective effects of fermented milks (FM). The aim of the present study was to evaluate the inhibitory activities of angiotensin converting enzyme (ACE), thrombin enzyme (TI) and micellar solubility of cholesterol of FM after 24 and 48 h of fermentation with Limosilactobacillus fermentum (J20, J23, J28 and J38), Lactiplantibacillus plantarum (J25) or Lactiplantibacillus pentosus (J34 and J37) exposed to simulated gastrointestinal digestion. Results showed that FM with J20 and J23 at 48 h of fermentation presented significantly (p < 0.05) higher degree of hydrolysis than other FM, and were not significantly different (p > 0.05) between them. Conversely, peptide relative abundance was significantly (p < 0.05) higher in FM with J20 than FM with J23. Moreover, IC50 (protein concentration necessary to inhibit enzyme activity by 50%) for ACE inhibition were 0.33 and 0.5 mg/mL for FM with J20 and J23, respectively. For TI inhibition, the IC50 were 0.3 and 0.24 mg/mL for FM with J20 and J23, respectively. Results exhibited 51 and 74% inhibition of micellar solubility cholesterol for FM with J20 and J23, respectively. Therefore, these results showed that not only peptide abundance, but also specific peptides might be responsible for these potential cardioprotective effects.

Peptides, Exopolysaccharides, and Short-Chain Fatty Acids from Fermented Milk and Perspectives on Inflammatory Bowel Diseases.

Crohn's disease and ulcerative colitis are characterized by chronic inflammatory processes and an imbalanced immune response along the gastrointestinal (GI) tract. Pharmacological treatments have been widely used, although their long-term application has adverse side effects. On the other hand, milks fermented with specific lactic acid bacteria (LAB) have been shown to be useful as alternative or complementary aids. Many metabolites such as peptides, exopolysaccharides, and short-chain fatty acids are produced during milk fermentation. These components have been shown to change the pH of the gastrointestinal lumen, aid intestine mucosal recovery, modulate the microbiota, and reduce the inflammatory response (innate and adaptive immune system), both in vitro and in vivo. Therefore, the objective of the present review is to describe how these bioactive compounds from fermented milk by specific LAB can decrease the deleterious symptoms of inflammatory bowel disease.

Current trends and perspectives on bioaccessibility and bioavailability of food bioactive peptides: in vitro and ex vivo studies.

The bioaccessibility and bioavailability of food-derived bioactive compounds are important issues when assessing their in vivo physiological health-promoting effects. Food components such as proteins and peptides are exposed to different proteases and peptidases during gastrointestinal digestion and absorption. Different in vitro approaches have therefore been developed to evaluate the bioaccessibility and stability of bioactive peptides. The static simulated gastrointestinal digestion model (SGD) was widely reported to assess the bioaccessibility of bioactive peptides. On the other hand, although the dynamic SGD model may better simulate human digestion, it has rarely been explored in bioaccessibility studies of food bioactive peptides due to its high cost and lack of standardization. For bioavailability studies, the Caco-2 cell monolayer model has been used extensively for the assessment of food bioactive peptides. In fact, very few reports using alternative methods for determining transepithelial transport of bioactive peptides have been employed. In this sense, ex vivo tissue-based models such as the Ussing chamber and the everted sac gut have been used. Current evidence supports the fact that using SGD with cell-based models for evaluating the bioaccessibility, absorption, and bioavailability of food-derived bioactive peptides, is the most commonly used approach. Nevertheless, SGD with ex vivo tissue-based models such as the everted sac, remains to be further explored because it seems to be the model that better mimics the physiological process - it is also fast and inexpensive, and several compounds may be tested simultaneously. In the present review, we discuss information available on the different in vitro approaches for the determination of bioaccessibility and bioavailability of food-derived bioactive peptides with special emphasis on ex vivo tissue-based models such as the everted sac and the Ussing chamber models. © 2022 Society of Chemical Industry.

Invited review: Potential antiobesity effect of fermented dairy products.

The growing prevalence of obesity affects millions of people around the world and has gained increased attention over the years because it is associated with the development of other chronic degenerative diseases. Different organizations recommend lifestyle changes to treat obesity; nevertheless, other strategies in addition to lifestyle changes have recently been suggested. One of these strategies is the use of probiotics in fermented dairy products; however, a need exists to review the different studies available related to the potential antiobesity effect of these products. Because probiotic fermented dairy products that support weight management are not available in the market, there is a great opportunity for the development of functional dairy products with new lactic acid bacteria that may present this added health benefit. Thus, the purpose of this overview is to highlight the importance of probiotic fermented dairy products as potential antiobesogenic functional foods and present in vitro and in vivo studies required before this kind of product may be introduced to the market. Overall, most studies attributed the antiobesity effect of fermented dairy foods to the probiotic strains present; however, bioactive peptides released during milk fermentation may also be responsible for this effect.

Invited review: Effect of antihypertensive fermented milks on gut microbiota.

Hypertension is a risk factor for the development of other cardiovascular diseases and remains one of the leading causes of death worldwide. Although genetic and environmental factors are associated with the development of hypertension, it has been recently recognized that gut microbiota (GM) may also have an effect on human health. In this sense, gut dysbiosis (a marked decrease in richness and diversity of GM) has been linked to different metabolic diseases, such as hypertension. Therefore, different studies have been pursued to reduce gut dysbiosis and diminish hypertension. Different strategies to maintain a balanced GM, particularly through diet and the use of probiotics, are being evaluated. Most recently, the effect of antihypertensive fermented milks on GM has been addressed. New evidence suggests that antihypertensive fermented milks may modulate GM. Thus, the aim of this review is to present available information related to the effect of antihypertensive fermented milks on gut microbiota.

Novel bacteriocins produced by Lactobacillus fermentum strains with bacteriostatic effects in milk against selected indicator microorganisms.

The aim of this work was to isolate and characterize bacteriocins produced by 2 Lactobacillus fermentum strains isolated from artisanal Mexican Cocido cheese. Fractions (F ≤3 kDa) obtained from cell-free supernatants of Lb. fermentum strains J23 and J32 were further fractionated by reversed-phase HPLC on a C18 column. Antimicrobial activities of F ≤3 kDa and bacteriocin-containing fractions (BCF), obtained from fractionation of F ≤3 kDa against 4 indicator microorganisms, were determined by the disk diffusion method and growth inhibition in milk. Subsequently, isolated BCF were analyzed by reversed-phase HPLC tandem mass spectrometry. Results showed that BCF presented antimicrobial activity against the 4 indicator microorganisms tested. For J23, one of the fractions (F3) presented the highest activity against Escherichia coli and was also inhibitory against Staphylococcus aureus, Listeria innocua, Salmonella Typhimurium, and Salmonella Choleraesuis. Similarly, fractions F3 and F4 produced by J32 presented antimicrobial activity against all indicator microorganisms. Furthermore, generation time and growth rate showed that F3 from J23 presented significantly higher antimicrobial activity against the 4 indicator microorganisms (2 gram-positive and 2 gram-negative) when inoculated in milk compared with F3 from J32. Interestingly, this fraction presented a broader antimicrobial spectrum in milk than nisin (control). Reversed-phase HPLC tandem mass spectrometry analysis revealed the presence of several peptides in BCF; however, F3 from J23 that was the most active fraction of all presented only 1 bacteriocin. The chemical characterization of this bacteriocin suggested that it was a novel peptide with 10 hydrophobic AA residues in its sequence and a molecular weight of 2,056 Da. This bacteriocin and its producing strain, J23, may find application as a biopreservative against these indicator microorganisms in dairy products.

Evaluation of acrylamide-removing properties of bacterial consortia under simulated gastrointestinal conditions.

BACKGROUND: Previous studies have demonstrated the acrylamide-removing properties of probiotic monocultures; however, potential advantages of consortia over monocultures in reducing the dietary exposure to acrylamide have not been proven. Hence this work aims to assess the acrylamide (AA)-binding properties of bacterial consortia, consisting of either probiotic strains and / or representative bacteria of duodenal microbiota, exposed to simulated gastrointestinal conditions (SGC). The AA binding capacity of ten probiotic strains (PS) and six duodenal strains (NDS) was evaluated under different conditions; then, three different consortia (PS, NDS, and PS + NDS) were assessed under SGC. RESULTS: Among individual PS, Bacillus coagulans GBI-30, Lactobacillus fermentum J23, L. pentosus J37 and J24, and L. casei Shirota, exhibited the highest AA-binding capacity (80-87%), while Bifidobacterium catenulatun ATCC27676, Streptococcus salivarius subsp. thermophilus ATCC19258, and S. gallolyticus ATCC9809 were the best (ca. 68%) NDS monocultures. Probiotic strain consortia showed higher (P < 0.05) AA binding capacity (> 90%) than monoculture bacteria. Conversely, individual NDS cultures displayed higher (P < 0.05) binding capacity than NDS consortia (60%). A significant reduction (P < 0.05) in AA removal capacity was observed when consortia were exposed to SGC, PS consortia being the most effective (> 60% removal). CONCLUSION: These results suggest that consortia of specific PS could play an important role in reducing the intestinal availability of acrylamide. © 2021 Society of Chemical Industry.

Probiotic Potential of Lactobacillus paracasei CT12 Isolated from Water Kefir Grains (Tibicos).

The water kefir grains are a multi-species starter culture used to produce fermented beverages of sucrose solution with or without fruit extracts. The water kefir grains are known in Mexico as Tibicos, which are mainly used to produce Tepache, a traditional Mexican drink made by fermenting pineapple peel. The microbiota of Tibicos mainly include lactic acid bacteria (LAB) and since most probiotics belong to this group, Tibicos may represent a potential source of probiotic bacteria. Moreover, several bacteria isolated from kefir samples have been recognized as probiotics. Hence, the aim of this study was to assess the probiotic properties of a Lactobacillus strain isolated from Tibicos. The isolated, designed as CT12, was identified as Lactobacillus paracasei by sequencing 16S RNA gene. L. paracasei CT12 showed a survival rate of ca. 57% and 40% following simulated gastric and intestinal digestion, respectively. Besides, the strain was sensitive to ampicillin and erythromycin, and exhibited hydrophobicity (97-99%), autoaggregation (ca. 70%) and mucin adhesion properties (up to 90%), while no possessed haemolytic capacity. Furthermore, its cell-free supernatant displayed relevant antimicrobial, antifungal and antioxidant capacity. Hence, L. paracasei CT12 appears to possess a potential probiotic value.

Poro de Tabasco cheese: Chemical composition and microbiological quality during its artisanal manufacturing process.

Poro de Tabasco cheese (PTC) is one of the most popular cheeses in southern Mexico. It has been made by traditional, nonstandardized artisanal techniques dating back more than 50 yr. These techniques result in the cheese having a heterogeneous chemical and microbiological composition and, consequently, distinct organoleptic characteristics. Scientific interest in artisanal cheese is growing because it represents a source of bacteria with potential health benefits. However, the quality of raw-milk cheeses often does not comply with official sanitary standards. The objective of the present study was to explore the chemical composition and microbiological quality of PTC and to describe its production process. Based on chemical composition, this cheese can be classified as a hard, full-fat, fresh cheese, with moisture on a fat-free basis and fat in dry matter ranging from 41 to 55% and from 49 to 57%, respectively. The chemical and microbiological composition of PTC varied among the evaluated dairies due to the lack of standardization in the production process. Microbial populations decreased during production, which may be associated with high acidity and high salt and low moisture contents, the presence of lactic acid bacteria or antimicrobial substances, and the drainage of whey. However, despite the absence of Escherichia coli, Salmonella spp., and Listeria monocytogenes in final cheeses for all dairies, Staphylococcus aureus and its toxins were found in some samples from one dairy. Therefore, heat treatment for milk and good manufacturing practices should be implemented throughout the entire production process to ensure a safe product.

Obtaining glycoconjugates of marine origin via Maillard reaction and their cytotoxic effect: an alternative for the use of animal byproducts.

BACKGROUND: Protein glycation by Maillard reaction is commonly used to improve the functional and bioactive properties of food proteins. It is also known that this glycation method can be accelerated by heat without the need for chemical reagents that could be harmful to health. In this study, glycoconjugates were obtained from a mixture of connective tissue proteins (CTP) from jumbo squid (Dosidicus gigas) and two different sugars, dextran (DEX; 10 kDa) and glucose (GLU), using protein-to-carbohydrate ratios of 1:2 and 1:3, in solution at 50 °C for 6 h. The glycation products were characterized by means of their physicochemical properties and cytotoxic effect. RESULTS: The intensity of the browning measured at A420nm and A294nm in glycoconjugates showed no significant difference (P < 0.05). CTP-DEX (1:2) and CTP-DEX (1:3) were those products with the greatest fluorescence related to the intermediate stage in the Maillard reaction, and also with the highest degree of glycation, which was confirmed using o-phthaldialdehyde assay and Fourier transform infrared analysis. The values of cellular viability for CTP-GLU (1:3), CTP-DEX (1:2, 1:3) as well as CTP (0, 6 h) were around 92-103%. CONCLUSIONS: The operational parameters used in the glycation process achieved the formation of glycoconjugates from proteins of D. gigas, showing no cytotoxic effect on the HaCaT cell line. This research proposes an alternative for the modification of proteins and opens the way to future investigations regarding the bioactivity of these macromolecules to have applications for the use of byproducts in food science and technology. © 2020 Society of Chemical Industry.

Invited review: Bioactive compounds produced during cheese ripening and health effects associated with aged cheese consumption.

Traditionally, cheese is manufactured by converting fluid milk to a semisolid mass through the use of a coagulating agent, such as rennet, acid, heat plus acid, or a combination thereof. Cheese can vary widely in its characteristics, including color, aroma, texture, flavor, and firmness, which can generally be attributed to the production technology, source of the milk, moisture content, and length of aging, in addition to the presence of specific molds, yeast, and bacteria. Among the most important bacteria, lactic acid bacteria (LAB) play a critical role during the cheese-making process. In general, LAB contain cell-envelope proteinases that contribute to the proteolysis of cheese proteins, breaking them down into oligopeptides that can be subsequently taken up by cells via specific peptide transport systems or further degraded into shorter peptides and amino acids through the collaborative action of various intracellular peptidases. Such peptides, amino acids, and their derivatives contribute to the development of texture and flavor in the final cheese. In vitro and in vivo assays have demonstrated that specific sequences of released peptides exhibit biological properties including antioxidant, antimicrobial, anti-inflammatory, immunomodulatory, and analgesic/opioid activity, in addition to angiotensin-converting enzyme inhibition and antiproliferative activity. Some LAB also produce functional lipids (e.g., conjugated linoleic acid) with anti-inflammatory and anticarcinogenic activity, synthesize vitamins and antimicrobial peptides (bacteriocins), or release γ-aminobutyric acid, a nonprotein amino acid that participates in physiological functions, such as neurotransmission and hypotension induction, with diuretic effects. This review provides an overview of the main bioactive components present or released during the ripening process of different types of cheese.

Randomized double-blind controlled clinical trial of the blood pressure-lowering effect of fermented milk with Lactococcus lactis: A pilot study.

The blood pressure-lowering effect of fermented milk with Lactococcus lactis NRRL B-50571 was evaluated in a double-blind randomized controlled clinical trial with prehypertensive subjects. Participants were randomized into 2 groups (n = 18 each group): one group treated with fermented milk with Lactococcus lactis NRRL B-50571 and a control group treated with artificially acidified milk. Results revealed that during daily consumption of fermented milk for 5 wk, systolic [(116.55 ± 12.26 mmHg vs. 124.77 ± 11.04 mmHg) and diastolic blood pressure (80.7 ± 9 vs. 84.5 ± 8.5 mmHg)] from the fermented milk group was lower than the control group. Additionally, triglyceride, total cholesterol, and low-density lipoprotein in blood serum were lower in the fermented milk group than in the control group. Results demonstrated that daily consumption of fermented milk with Lactococcus lactis (NRRL B-50571) had a blood pressure-lowering effect on prehypertensive subjects. Regular consumption of this product may be used as a potential functional food.

Artisanal Sonoran cheese (Cocido cheese): an exploration of its production process, chemical composition and microbiological quality.

BACKGROUND: The objective of this study was to explore and document the production process of artisanal Cocido cheese and to determine its chemical composition and microbiological quality, considering samples from six dairies and four retailers. RESULTS: Cocido cheese is a semi-hard (506-555 g kg-1 of moisture), medium fat (178.3-219.1 g kg-1 ), pasta filata-type cheese made from raw whole cow's milk. The production process is not standardized and therefore the chemical and microbiological components of the sampled cheeses varied. Indicator microorganisms significantly decreased (P < 0.05) during the processing of Cocido cheese. Salmonella spp. were not found during the production process, and both Listeria monocytogenes and staphylococcal enterotoxin were absent in the final cheeses. CONCLUSION: This study provides more information on one of the most popular artisanal cheeses with high cultural value and economic impact in northwestern Mexico. In view of the foregoing, good manufacturing practices need to be implemented for the manufacture of Cocido cheese. Also, it is of utmost importance to make sure that the heat treatment applied for cooking the curd ensures a phosphatase-negative test, otherwise it would be necessary to pasteurize milk. Nevertheless, since Cocido cheese is a non-ripened, high-moisture product, it is a highly perishable product that could present a health risk if not properly handled. © 2017 Society of Chemical Industry.

Invited review: Artisanal Mexican cheeses.

The objective of this review is to present an overview of some of the most commonly consumed artisanal Mexican cheeses, as well as those cheeses that show potential for a protected designation of origin. A description is given for each of these cheeses, including information on their distinguishing characteristics that makes some of them potential candidates for achieving a protected designation of origin status. This distinction could help to expand their frontiers and allow them to become better known and appreciated in other parts of the world. Due to the scarcity of scientific studies concerning artisanal Mexican cheeses, which would ultimately aid in the standardization of manufacturing processes and in the establishment of regulations related to their production, more than 40 varieties of artisanal cheese are in danger of disappearing. To preserve these cheeses, it is necessary to address this challenge by working jointly with government, artisanal cheesemaking organizations, industry, academics, and commercial partners on the implementation of strategies to protect and preserve their artisanal means of production. With sufficient information, official Mexican regulations could be established that would encompass and regulate the manufacture of Mexican artisanal cheeses. Finally, as many Mexican artisanal cheeses are produced from raw milk, more scientific studies are required to show the role of the lactic acid bacteria and their antagonistic effect on pathogenic microorganisms during aging following cheese making.

Food-derived immunomodulatory peptides.

Food proteins contain specific amino acid sequences within their structures that may positively impact bodily functions and have multiple immunomodulatory effects. The functional properties of these specific sequences, also referred to as bioactive peptides, are revealed only after the degradation of native proteins during digestion processes. Currently, milk proteins have been the most explored source of bioactive peptides, which presents an interesting opportunity for the dairy industry. However, plant- and animal-derived proteins have also been shown to be important sources of bioactive peptides. This review summarizes the in vitro and in vivo evidence of the role of various food proteins as sources of immunomodulatory peptides and discusses the possible pathways involving these properties. © 2016 Society of Chemical Industry.

Antimicrobial activity and partial characterization of bacteriocin-like inhibitory substances produced by Lactobacillus spp. isolated from artisanal Mexican cheese.

Lactobacillus spp. from Mexican Cocido cheese were shown to produce bacteriocin-like substances (BLS) active against Staphylococcus aureus,Listeria innocua,Escherichia coli, andSalmonella typhimurium by using the disk diffusion method. Crude extracts of Lactobacillus fermentum showed strong inhibitory activity against Staph. aureus, L. innocua, E. coli, and Salmonella cholerae. Complete inactivation of antimicrobial activity was observed after treatment of crude extracts with proteinase K, pronase, papain, trypsin, and lysozyme, confirming their proteinaceous nature. However, antimicrobial activity was partly lost for some of the crude extracts when treated with α-amylase, indicating that carbohydrate moieties were involved. The antimicrobial activity of the crude extracts was stable at 65°C for 30min over a wide pH range (2-8), and addition of potassium chloride, sodium citrate, ethanol, and butanol did not affect antibacterial activity. However, antimicrobial activity was lost after heating at 121°C for 15min, addition of methanol or Tween 80. Fourteen out of 18 Lactobacillus spp. showed antimicrobial activity against different test microorganisms, and 12 presented bacteriocin-like substances. Generation time and growth rate parameters indicated that the antimicrobial activity of crude extracts from 3 different strains was effective against the 4 indicator microorganisms. One of the crude extracts showed inhibition not only against gram-positive but also against gram-negative bacteria. Bacteriocin-like substances produced by this specific Lactobacillus strain showed potential for application as a food biopreservative.

Microbiological quality and native lactic acid bacteria diversity of artisanal Mexican cheeses: A review.

This review aims to provide an overview of artisanal Mexican cheeses microbiota focused on microbiological quality and safety, as well as native Lactic acid Bacteria (LAB) diversity. For the search, key words of artisanal Mexican cheeses varieties was carried out through several online databases and original articles were screened and data about populations of indicator microorganisms, presence of pathogens, and native LAB identified were extracted. Several artisanal Mexican cheeses exceeded the permissible limit established in Mexican regulation (NOM-243-SSA1-2010) for indicator microorganisms, as well as in some types of cheese, the presence of pathogens was confirmed. However, other varieties of artisanal Mexican cheeses possess unique physicochemical characteristics, and during their manufacturing particular steps are used that contribute to ensuring their quality and safety. Additionally, strains able to control the growth of pathogenic and spoilage bacteria are part of the microbiota of some artisanal Mexican cheeses. About native LAB diversity, it is composed by species of Lactobacillus, Enterococcus, Streptococcus, Leuconostoc, Weisella, Lactococcus, Pediococus, Aerococus, Carnobacterium, Tetragenococus, among others genera. Otherwise, artisanal Mexican cheeses represent an important source of specific LAB with several approaches within human health because they showed potential for the development of functional foods, nutraceutical, and bioprotective cultures.

Angiotensin converting enzyme inhibitory hydrolysate and peptide fractions from chicken skin collagen, as modulators of lipid accumulation in adipocytes 3 T3-L1, after in vitro gastrointestinal digestion.

Inhibitory activity against angiotensin-converting enzyme (IAACE) by chicken skin collagen hydrolysate (CSCH) and their peptide fractions before and after in-vitro gastrointestinal digestion, were evaluated; as well as their ability to modulate lipid accumulation in 3 T3-L1 adipocytes. Before digestion, peptide fraction <1 kDa (F4) showed the highest IAACE (p < 0.05) followed by CSCH. After these samples were digested, F4 presented an IAACE with IC50 similar to its digest (DF4) (188.84 and 220.03 µg/mL, respectively), which was 2-fold lower (p < 0.05) than IC50 of fraction <1 kDa from post-digested hydrolysate (FDH) (388.57 µg/mL). Nine peptides were identified as the potential ACE inhibitors in F4 and DF4. Addition of DF4 (800 µg/mL) reduced(p < 0.05) lipid accumulation by 83% within preadipocytes. A 45-60% reduction of lipid accumulation within differentiated adipocytes was obtained by adding FDH and DF4 (regardless the concentration). These results, digested CSCH and F4 with IAACE may be considered as potential adjuvants for obesity treatment.

Potential probiotic lactobacilli strains isolated from artisanal Mexican Cocido cheese: evidence-based biosafety and probiotic action-related traits on in vitro tests.

The biosafety of four potentially probiotic lactobacilli strains, isolated from artisanal Mexican Cocido cheese, was assessed through in vitro tests aimed to determine (1) the antibiotic susceptibility profile by broth microdilution, (2) the transferability of antibiotic resistance determinants by filter-mating, and (3) the phenotypic and genotypic stability during serial batch sub-culture (100-day period) by evaluating physiological and probiotic features and RAPD-PCR fingerprinting. Lactobacilli strains exhibited multidrug-resistance; however, resistance determinants were not transferred in the filter-mating assay. Significant (p < 0.05) differences were observed in bacterial morphology and some functional and technological properties when strains were serially sub-cultured over 50 generations (G50), compared to the initial cultures (G0). Conversely, the strains did not show mucinolytic and hemolytic activities either at G0 or after 100 generations (G100). Genetic polymorphism and genomic template instability on selected strains were detected, which suggest possible evolutionary arrangements that may occur when these bacteria are largely cultured. Our findings suggest that the assessed strains did not raise in vitro biosafety concerns; however, complementary studies are still needed to establish the safe potential applications in humans and animals.

Key Stress Response Mechanisms of Probiotics During Their Journey Through the Digestive System: A Review.

The survival of probiotic microorganisms during their exposure to harsh environments plays a critical role in the fulfillment of their functional properties. In particular, transit through the human gastrointestinal tract (GIT) is considered one of the most challenging habitats that probiotics must endure, because of the particularly stressful conditions (e.g., oxygen level, pH variations, nutrient limitations, high osmolarity, oxidation, peristalsis) prevailing in the different sections of the GIT, which in turn can affect the growth, viability, physiological status, and functionality of microbial cells. Consequently, probiotics have developed a series of strategies, called "mechanisms of stress response," to protect themselves from these adverse conditions. Such mechanisms may include but are not limited to the induction of new metabolic pathways, formation/production of particular metabolites, and changes of transcription rates. It should be highlighted that some of such mechanisms can be conserved across several different strains or can be unique for specific genera. Hence, this review attempts to review the state-of-the-art knowledge of mechanisms of stress response displayed by potential probiotic strains during their transit through the GIT. In addition, evidence whether stress responses can compromise the biosafety of such strains is also discussed.