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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., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Chlorine dioxide (ClO2) is a disinfectant gas with strong antifungal, antibacterial, and antiviral activities. Applied on hard, non-porous surfaces as an aqueous solution or gas, the ClO2 exerts antimicrobial activity through its interaction and destabilization of cell membrane proteins, as well as through DNA/RNA oxidation, triggering cell death. As for viruses, the ClO2 promotes protein denaturalization mechanisms, preventing the union between the human cells and the viral envelope. Currently, ClO2 has been pointed out as a potential anti-SARS-CoV-2 clinical treatment for use in humans with the ability to oxidize the cysteine residues in the spike protein of SARS-CoV-2, inhibiting the subsequent binding with the Angiotensin-converting enzyme type 2 receptor, located in the alveolar cells. Orally administered ClO2 reaches the gut tract and exacerbates the symptoms of COVID-19, generating a dysbiosis with gut inflammation and diarrhea as side effects, and once absorbed, produces toxic effects including methemoglobinemia and hemoglobinuria, which can trigger respiratory diseases. These effects are dose-dependent and may not be entirely consistent between individuals since the gut microbiota composition is highly heterogeneous. However, to support the use of ClO2 as an anti-SARS-CoV-2 agent, further studies focused on its effectiveness and safety both in healthy and immunocompromised individuals, are needed., (© The Author(s) 2023. Published by Oxford University Press on behalf of Applied Microbiology International.)

Capsicum spp. fruits (CFs) are a basic ingredient in the diet and have been used as active ingredients in the pharmaceutical, cosmetic, and food products, due to their antioxidant, anti-inflammatory, antiseptic, and antimicrobial properties. The antimicrobial activity is the most studied property due to its effectiveness against pathogenic species, however, few studies have focused on the mechanisms of action involved. Therefore, this review discusses the effects generated by the CFs compounds on the viability and metabolism of microorganisms, highlighting the mechanisms by which these compounds exert their antimicrobial effects. The information provided shows that CFs are mainly source of capsaicinoids and phenolic compounds responsible for the inhibition of bacteria, yeasts, and fungi, through an increase in the permeabilization of the membrane and cell wall. Also, these compounds show an antiviral effect associated with the inactivation of virus binding proteins, preventing their replication and infection. Despite this, there is still a lack of information about the mechanisms that regulate the interactions between CFs compounds and food-important-microorganisms. Therefore, future research should focus on new antimicrobial compounds from CFs for their subsequent use against novel infectious agents, mainly virus of importance in health such as SARS-CoV-2., Competing Interests: Conflicts of interestThe authors declare that they have no Conflicts of interest., (© Association of Food Scientists & Technologists (India) 2022, Springer Nature or its licensor holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.)

Synthetic biology is employed for the study and design of engineered microbes with new and improved therapeutic functions. The main advantage of synthetic biology is the selective genetic manipulation of living organisms with desirable beneficial effects such as probiotics. Engineering technologies have contributed to the edition of metabolic processes involved in the mechanisms of action of probiotics, such as the generation of bioactive peptides. Hence, current information related to bioactive peptides, produced by different engineering probiotics, with antimicrobial, antiviral, antidiabetic, and antihypertensive activities, as well as their potential use as functional ingredients, is discussed here. Besides, the effectiveness and safety aspects of these bioactive peptides were also described., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2021 The Authors.)

The interest for food-derived bioactive peptides, either from common or unconventional sources, has increased due to their potential therapeutic effect against a wide range of diseases. The study of such bioactive peptides using conventional methods is a long journey, expensive and time-consuming. Hence, bioinformatic approaches, which can not only help to predict the formation of bioactive peptides from any known protein source, but also to analyze the protein structure/function relationship, have gained a new meaning in this scientific field. Therefore, this review aims to provides an overview of conventional characterization methods and the most recent advances in the field of in silico approaches for predicting and screening promising food-derived bioactive peptides., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2021 The Author(s).)

Human gut microbiota (HGM) is a microbial complex where dynamic mutualistic interactions related to digestion and absorption of dietary components take place. The consumption of specific food ingredients, such as prebiotics and dietary fibers, constituted mainly by carbohydrates polymers, can modulate the HGM composition and metabolism serving as a fermentable substrate to produce bacterial metabolites with beneficial effects on host health. Especially, bacterial short-chain fatty acids, tryptophan and organic acids have shown positive effects on pathogenic bacteria control, mineral absorption, weight control and obesity, immune response homeostasis, gut barrier improvement, brain modulation and anticancer activity. Despite the fact that these effects vary between individuals due to personal HGM richness, the information presented in this review contributes to understanding the effects of prebiotics and dietary fibers consumption on the generation of HGM metabolites and the mechanisms by which these metabolites interact with host cells improving host health., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

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.

Artisanal fermented beverages have been associated with beneficial effects for a long time. In Mexico, there are a wide variety of artisanal fermented beverages such as Tepache, where the fermentation is initiated by the addition of grains of a polysaccharide-containing biofilm matrix formed by a symbiotic association of bacteria and yeasts known as "Tibicos." These microorganisms can be responsible for the beneficial effect associated with fermented beverages inoculated with Tibicos. The probiotic potential of microorganisms has been widely studied, mainly in lactic acid bacteria, while despite the wide distribution of yeasts, these have not been so studied. Therefore, the aim of this study was to evaluate in vitro the probiotic potential properties of a yeast isolated from Tibicos. For this, the yeast was identified by molecular techniques as Saccharomyces cerevisiae, which showed a good resistance to pH 2.0, bile salts and in vitro digestion. The results also showed a good ability to form cellular aggregates as a result of having a hydrophobic surface. In addition, it can be considered as safe since it does not show hemolytic activity and is sensitive to nystatin. Additionally, the yeast presented an excellent antioxidant capacity to reduce the DPPH radical. The S. cerevisiae strain C41 isolated from Tibicos was successfully compared by means of in vitro tests with the only recognized probiotic yeast, S. boulardii. These findings point Saccharomyces cerevisiae C41 as a potentially probiotic yeast; nevertheless, it is necessary to consider further in vitro and in vivo studies that establish the benefits that this yeast could provide.