Minimal Inhibitory Concentrations of Thymol and Carvacrol: Toward a Unified Statistical Approach to Find Common Trends.

Thymol and carvacrol are some of the most important and used components of Essential oils (EOs); they are widely studied, and there are much data available in the literature. Their Minimal Inhibitory Concentration (MIC) values found in the literature from 2005 to present were used to assess the bioactivity toward yeasts, molds, Gram-positive bacteria, and Gram-negative bacteria, as well as on some bacterial species/serotypes (Salmonella sp., Escherichia coli, E. coli O157:H7, lactic acid bacteria, Listeria monocytogenes, Staphylococcus aureus, S. epidermidis, etc.) to find possible common trends or differences between the two compounds and among the tested species. The results were quite interesting and pointed out that there is a common range for the MIC of thymol and carvacrol for some bacterial species (150-400 mg/L), with some exceptions to this generalized statement. In addition, the statistics pointed out that bacteria could experience homogeneous (S. epidermidis, E. coli O157:H7) or heterogeneous trends (for example, Salmonella sp.) depending on the existence of possible sub-species or different experimental set-ups. Moreover, this paper suggests that there are some drawbacks and issues that should be solved for the effective use of EOs, which are the strong variability among the microorganisms and the lack of standard protocols and reference strains.

Ultrasound can increase biofilm formation by Lactiplantibacillus plantarum and Bifidobacterium spp.

The main goal of this research was to study the effect of an Ultrasound (US) treatment on biofilm formation of Lactiplantibacillus plantarum (strains c19 and DSM 1055), Bifidobacterium animalis subsp. lactis DSM 10140, Bifidobacterium longum subsp. longum DSM 20219, and Bifidobacterium longum subsp. infantis DSM 20088. From a methodological point of view, each microorganism was treated through six US treatments, different for the power (10, 30, or 50% of the net power, 130 W), the duration (2, 6, or 10 min) and the application of pulses (0 or 10 s). After the treatment, a biofilm of the strains was let to form on glass slides and the concentration of sessile cells was analyzed for 16 days. Biofilms formed by untreated microorganisms were used as controls. As a first result, it was found that US significantly increased the concentration of sessile cells of B. longum subsp. infantis, while for some other strains US treatment could not affect the formation of biofilm while improving its stability, as found for L. plantarum DSM1055 after 16 days. The variable mainly involved in this positive effect of US was the duration of the treatment, as biofilm formation and stability were improved only for 2 min-treatments; on the other hand, the effect of power and pulses were strain-dependent. In conclusion, the results suggest practical implication of a US pre-treatment for various fields (improvement of adhesion of microorganisms useful in food or in the gut, biomedical and environmental industries), although further investigations are required to elucidate the mode of action.

Gut-Microbiota, and Multiple Sclerosis: Background, Evidence, and Perspectives.

Many scientific studies reveal a significant connection between human intestinal microbiota, eating habits, and the development of chronic-degenerative diseases; therefore, alterations in the composition and function of the microbiota may be accompanied by different chronic inflammatory mechanisms. Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS), in which autoreactive immune cells attack the myelin sheaths of the neurons. The purpose of this paper was to describe the main changes that occur in the gut microbiota of MS patients, with a focus on both microbiota and its implications for health and disease, as well as the variables that influence it. Another point stressed by this paper is the role of microbiota as a triggering factor to modulate the responses of the innate and adaptive immune systems, both in the intestine and in the brain. In addition, a comprehensive overview of the taxa modified by the disease is presented, with some points on microbiota modulation as a therapeutic approach for MS. Finally, the significance of gastro-intestinal pains (indirectly related to dysbiosis) was assessed using a case study (questionnaire for MS patients), as was the willingness of MS patients to modulate gut microbiota with probiotics.

Psycho-Microbiology, a New Frontier for Probiotics: An Exploratory Overview.

Probiotics are gradually gaining importance in the field of psychiatry in the form of psychobiotics. Psychobiotics' studies examine the existing relationship between gut microbiota and mental phenomena; the intake of certain strains of probiotics, such as Bifidobacterium and Lactobacillus, for example, allow the gut microbial system to be modified in order to provide benefits at the psychic, immune, hormonal, and mental levels. Those who suffer from forms of depression, anxiety disorders, chronic stress, low mood, but also people who do not suffer from such disorders, can therefore benefit from the use of psychobiotics. Thanks to probiotics, neurochemicals can in fact be produced within the gut microbiota and interact with receptors of the enteric nervous system that innervate the entire gastrointestinal tract. Once they enter the portal circulation, these substances go on to influence components of the nervous system and ultimately the brain, through what is called the gut-brain axis. This article proposes an exploratory overview of the proven effects of probiotics on brain activity and psycho-related diseases, focusing on clinical studies and measurable outcomes. The search was conducted using two different online tools: ClinicalTrials.gov and PubMed.

How Diet and Physical Activity Modulate Gut Microbiota: Evidence, and Perspectives.

Gut microbiota plays a significant role in the maintenance of physiological homeostasis, contributing to human health. Nevertheless, some factors (sex, age, lifestyle, physical activity, drug-based therapies, diet, etc.) affect its composition and functionality, linked to pathologies and immunological diseases. Concerning diet, it interacts with microorganisms, leading to beneficial or detrimental outcomes for the health of host. On the other hand, physical activity is known to be useful for preventing and, sometimes, treating several diseases of cardiovascular, neuroendocrine, respiratory, and muscular systems. This paper focuses on diet and physical activity presenting the current knowledge about how different diets (Western, ketogenic, vegan, gluten free, Mediterranean) as well as different types of exercise (intensive, endurance, aerobic) could shape gut microbiota.

Wine Microbiology and Predictive Microbiology: A Short Overview on Application, and Perspectives.

Predictive microbiology (PM) is an essential element in food microbiology; its aims are the determination of the responses of a given microorganism combining mathematical models with experimental data under certain environmental conditions, and the simulation a priori of the growth/inactivation of a population based on the known traits of a food matrix. Today, a great variety of models exist to describe the behaviour of several pathogenic and spoilage microorganisms in foods. In winemaking, many mathematical models have been used for monitoring yeast growth in alcoholic fermentation as well as to predict the risk of contamination of grapes and grape products by mycotoxin producing fungi over the last years, but the potentialities of PM in wine microbiology are underestimated. Thus, the goals of this review are to show some applications and perspectives in the following fields: (1) kinetics of alcoholic and malolactic fermentation; (2) models and approaches for yeasts and bacteria growth/inactivation; (3) toxin production and removal.

Viability, Sublethal Injury, and Release of Cellular Components From Alicyclobacillus acidoterrestris Spores and Cells After the Application of Physical Treatments, Natural Extracts, or Their Components.

Alicyclobacillus acidoterrestris is a spoiling microorganism regarded as one of the most important causes of spoilage of fruit juices and acidic products. In this paper, four strains of A. acidoterrestris (type strain-DSM 3922; two wild strains isolated from soil-C8 and C24; wild strain isolated from a spoiled pear juice CB1) were treated through natural extracts/active compounds from essential oils (EOs), and physical treatments were used to assess their susceptibility and the presence of sublethal injury. The characterization of damage was also performed. The results suggest that it is possible to control A. acidoterrestris through alternative approaches, although the effect relied upon the age of spores. In addition to the mere antimicrobial effect, some treatments could cause a sublethal injury on spores. Lemon extract was the most effective treatment for both the antimicrobial effect and the sublethal injury, as evidenced by the release of proteins, and calcium dipicolinate [dipicolinic acid (DPA)] by fresh spores and only DPA (with an exception for C8) by old spores. A sublethal injury with protein release was also found for physical treatments [US (ultrasound) or heating]. For the first time, this paper reports on the existence of a sublethal injury for A. acidoterrestris, and this evidence could also be a challenge, because injured microorganisms could restore their metabolism, or an opportunity to design new preserving treatments.

Removal of Phenols in Table Olive Processing Wastewater by Using a Mixed Inoculum of Candida boidinii and Bacillus pumilus: Effects of Inoculation Dynamics, Temperature, pH, and Effluent Age on the Abatement Efficiency.

The main goal of this paper was to assess the ability of a combination of Candida boidinii and Bacillus pumilus to remove phenol in table olive processing water, as a function of some variables, like temperature, pH, a dilution of waste and the order of inoculation of the two microorganisms. At this purpose C. boidinii and B. pumilus were sequentially inoculated in two types of table olive processing water (fresh wastewater, FTOPW and wastewater stored for 3 months-aged wastewater, ATOPW). pH (6 and 9), temperature (10 and 35 °C) and dilution ratio (0, 1:1) were combined through a 2k fractional design. Data were modeled using two different approaches: Multifactorial Analysis of Variance (MANOVA) and multiple regression. A higher removal yield was achieved by inoculating B. pumilus prior to the yeast (192 vs. 127 mg/L); moreover, an increased efficiency was gained at 35 °C (mean removal of 200 mg/L). The use of two statistic approach suggested a different weight of variables; temperature was a global variable, that is a factor able to affect the yield of the process in all conditions. On the other hand, an alkaline pH could increase the removal of phenol at 10 °C (25-43%).

Increase of acidification of synthetic brines by ultrasound-treated Lactiplantibacillus plantarum strains isolated from olives.

This paper focused on the evaluation of Ultrasound effect on the growth patterns (3-6% of salt and 45 °C), acidification (pH-decrease), interactions with microorganisms, and membrane permeability of nine strains of Lactiplantibacillus plantarum. Ultrasound treatment was applied at 20% of net power by modulating duration (2-10 min) and pulses (2-10 s). Viable count (7.15-8.16 log CFU/mL) was never affected by Ultrasound, while the treatment increased the extent of pH decrease of at least three strains (109, 162 and c19). L. plantarum c19 was the best performer, as a low intensity treatment was able to increase its acidification, without affecting its growth. The effects could be attributed to an increased permeability of the cellular membrane, as suggested by the increase of released intracellular components. Other factors should be further assessed (e.g. possible changes in the metabolism) and the performances of Ultrasound-treated strains in real brines.

Use of Autochthonous Lactiplantibacillus plantarum Strains to Produce Fermented Fish Products.

The present research was aimed to the optimization of the production of a fish fermented salami-like product using autochthonous Lactiplantibacillus plantarum starters. The activity was performed through two phases: (1) Optimization of fermented fish product composition by using a 2k-p Fractional Factorial Design: the variables tested were nitrites (0-150 ppm), salt (2.5-7.5%), sucrose (0-4%), white pepper (0-0.10%), and fermentation temperature (10-30°C); (2) Product realization and evaluation of its microbiological profile [aerobic microbiota (APC), Pseudomonadaceae (PSE), Enterobacteriaceae (E), and lactic acid bacteria (LAB) populations], chemico-physical parameters (pH and aw), and sensorial quality (odor, texture, color, and overall acceptability) during its storage at 4°C for 21 days. In the first step, the fish pulp was mixed with the appropriate amounts of ingredients, according to the experimental design; each batch was individually inoculated with the studied starter (L. plantarum 11, L. plantarum 69, and L. plantarum DSM1055) at 107 cfu/g and incubated at 10, 20, or 30°C for 7 days. The lowest fermentation time (time to reach pH 4.4) was obtained with 4% sucrose, 100 ppm nitrite and a process temperature of 30°C. In the second step, salami-like were produced according to the individuated formulation and inoculated with the studied starters (107 cfu/g); the fish mixture was stuffed into a natural casing and left to ferment at 30°C for 7 days. The use of the selected strains not only assured a correct fermentation but reduced the process time at only 2 days; during refrigerated storage, a good microbiological, chemico-physical and sensorial quality of the final product was recorded for at least 21 days.

Ultrasonic Modulation of the Technological and Functional Properties of Yeast Strains.

This research was aimed at studying the effects of low intensity ultrasound (US) on some technological and functional properties of eight strains of Saccharomyces cerevisiae; namely, growth patterns (growth at 2-5% of NaCl or at 37 °C), autoaggregation and tolerance to simulated gastrointestinal conditions were evaluated. A US treatment was applied at 20% of net power (130 W) by a modulating duration (2-10 min) and pulses (2-10 s). The viable count (4.81-6.33 log CFU/mL) was not affected by US, while in terms of technological traits the effect was strain specific; in particular, for some strains a positive effect of US was found with a significant growth enhancement (growth index > 120%). The treatment was also able to increase the autoaggregation of some strains, thus suggesting that US could represent a promising way to treat and select nonconventional functional yeasts for food applications.

Microencapsulation of Saccharomyces cerevisiae into Alginate Beads: A Focus on Functional Properties of Released Cells.

Five yeast strains (four wild Saccharomyces cerevisiae strains and a collection strain-S. cerevisiae var. boulardii) were encapsulated in alginate beads. Encapsulation yield was at least 60% (100% for some strains) and yeasts survived in beads for 30 days at 4 °C, although the viability was strongly affected during storage at 25 °C (3 log reduction after 7 days). The kinetic of cell release was studied under static and dynamic conditions, but the results suggest that, after 48 h, beads contained a high number of yeasts. Thus, their use is advisable as re-usable carriers of starter cultures or as a vehicle of probiotics into the gut. Finally, some functional properties (biofilm formation, hydrophobicity, auto-aggregation, survival during the transit into the gut) were evaluated on yeasts released by beads to assess if microencapsulation could negatively affect these traits. The results showed that yeasts' entrapment in beads did not affect probiotic properties.

Industrial Validation of a Promising Functional Strain of Lactobacillus plantarum to Improve the Quality of Italian Sausages.

This paper proposes the industrial validation of a functional strain of Lactobacillus plantarum (strain 178). First, acidification in a meat model medium and bioactivity towards Staphylococcus aureus, Salmonella sp., Listeria monocytogenes, and Escherichia coli were assessed; the performances of Lb. plantarum 178 were compared to those of a commercial Lb. sakei and a probiotic Lb. casei. Lb. plantarum 178 inhibited the pathogens and experienced a higher acidification at 15 °C. Lb. casei and Lb. plantarum were used for an industrial fermentation of traditional Italian sausages. The strains assured the correct course of fermentation and inhibited pathogens and enterobacteria. This study represents the scaling up and the validation of a promising strain at industrial level and shows the possibility of performing the fermentation of traditional Italian sausage through functional starter cultures, combining the benefit of a controlled fermentation and possible health benefits.

Biofilm formation by potentially probiotic Saccharomyces cerevisiae strains.

Four wild strains of Saccharomyces cerevisiae and the collection strain S. cerevisiae var. boulardii ATCC MYA-796 were used as test organisms to study the effect of some environmental conditions on the formation of biofilm by potentially probiotic yeasts. In a first step, the formation of biofilm was studied in four different media (YPD-Yeast Peptone Glucose; diluted YPD; 2% BP, a medium containing only bacteriological peptone; 2% GLC, a medium containing only glucose). Then, the dilution of YPD was combined with pH and temperature through a mixture design to assess the weight of the interaction of the variables; the experiments were done on S. boulardii and on S. cerevisiae strain 4. The dilution of nutrients generally determined an increased biofilm formation, whereas the effect of pH relied upon the strain. For S. cerevisiae strain 4, the highest level of sessile cells was found at pH 4-5, while S. boulardii experienced an enhanced biofilm formation at pH 6.0. Concerning temperature, the highest biofilm formation was found at 25-30 °C for both strains. The importance of this work lies in its extension of our knowledge of the effect of different environmental conditions on biofilm formation by potentially probiotic S. cerevisiae strains, as a better understanding of this trait could be an important screening tool into the selection of new multifunctional yeasts.

Two Nonthermal Technologies for Food Safety and Quality-Ultrasound and High Pressure Homogenization: Effects on Microorganisms, Advances, and Possibilities: A Review.

Some nonthermal technologies have gained special interest as alternative approaches to thermal treatments. High pressure homogenization (HPH) and ultrasound (US) are two of the most promising approaches. They rely upon two different modes of action, although they share some mechanisms or ways of actions (mechanic burden against cells, cavitation and micronization, primary targets being the cell wall and the membrane, temperature and pressure playing important roles for their antimicrobial potential, and their effect on cells can be either positive or negative). HPH is generally used in milk and dairy products to break lipid micelles, whereas US is used for mixing and/or to obtain active compounds of food. HPH and US have been tested on pathogens and spoilers with different effects; thus, the main goal of this article is to describe how US and HPH act on biological systems, with a focus on antimicrobial activity, mode of action, positive effects, and equipment. The article is composed of three main parts: (i) an overview of US and HPH, with a focus on some results covered by other reviews (mode of action toward microorganisms and effect on enzymes) and some new data (positive effect and modulation of metabolism); (ii) a tentative approach for a comparative resistance of microorganisms; and (iii) future perspectives.

A case study on the use of ultrasound for the inhibition of Escherichia coli O157:H7 and Listeria monocytogenes in almond milk.

The interest towards not-dairy beverages is increasing and almond milk is widespread diffused. The main topic of this paper was a focus on Ultrasound (US) to inhibit Escherichia coli O157:H7 and Listeria monocytogenes. The variables of the treatment (power, duration, and pulse) were combined through a randomized design; the use of DoE theory (Design of Experiments) and its outputs (Pareto chart, 3D plots, desirability profiles) pointed out that the effect of the treatment relies upon the total energy distributed into the system on E. coli O157:H7, as suggested by the significance of interactions of power, pulse and time, while power was the most important factor for L. monocytogenes. A final challenge test was done by using two combinations (H-80% of power, 8 min and pulse at 6 s- for E. coli and F-80%; 2 min; 6 s- for L. monocytogenes) and storing the samples at 4 °C for 2 weeks. This experiment suggests that the treatment could exert a sub-lethal injury on the pathogens, which, combined with the storage under refrigeration, could contribute to increase the shelf life.

Viability of Lactobacillus plantarum on Fresh-Cut Chitosan and Alginate-Coated Apple and Melon Pieces.

There is an increasing trend toward foods with probiotics; the awareness of healthy diet and wellbeing is the leading cause of this increase. As a result, food producers and stakeholders require new probiotic products. The increased incidence of lactose intolerance and the new lifestyles (vegan and vegetarian styles) have led to a renewed interest in non-dairy probiotic carriers. The use of biopolymeric matrices to develop active food packaging carrying probiotics has been studied and proposed as an alternative method to design new solutions. The main topic of this paper was the design of fresh-cut fruits (apples and melons) as carriers for a promising Lactobacillus plantarum; fruit pieces were coated with either alginate or chitosan. Apple (Granny Smith) and melon pieces (Cucumis melo, var. Cantalupensis) were preliminary treated with an anti-browning solution (citric and ascorbic acids). Then, fruit pieces were dipped in a solution containing L. plantarum c19 (9 log cfu/ml) and coated with alginate or chitosan. Samples without probiotic and/or coatings were used as controls. All samples were stored at 4°C for 14 days under air or modified atmosphere (65% N2, 30% CO2, and 5% O2); the following analyses were done: pH, color, O2, and CO2 in the head space, microbiology (mesophilic bacteria, lactic acid bacteria, yeasts, and molds). The most important results can be summarized as follows: (a) Alginate coating showed better performances than chitosan-coating, as it did not affect the viability of L. plantarum. (b) The inoculation of probiotics in the controls negatively affected the color, but the coating was able to counteract this effect. This paper supports the combination of edible coatings and probiotic as a promising way to design new fruit-based functional foods; further investigations are required to study the effect of this combination on the sensory scores.

Dairy propionibacteria as probiotics: recent evidences.

Nowdays there is evidence that dairy propionibacteria display probiotic properties, which as yet have been underestimated. The aim of this paper is to review the recent highlights of data representing the probiotic potential of dairy propionibacteria, studied both by general selection criteria (useful for all probiotic potentials), and by more specific and innovative approach. Dairy propionibacteria show a robust nature, that makes them able to overcome technological hurdles, allowing their future use in various fermented probiotic foods. In addition to the general selection criteria for probiotics in areas such as food safety, technological and digestive stress tolerance, many potential health benefits have been recently described for dairy propionibacteria, including, production of several active molecules and adhesion capability, that can mean a steady action in modulation of microbiota and of metabolic activity in the gut; their impact on intestinal inflammation, modulation of the immune system, potential modulation of risk factors for cancer development modulation of intestinal absorption.

Influence of prebiotics on Lactobacillus reuteri death kinetics under sub-optimal temperatures and pH.

Eaten foodstuffs are usually fortified with prebiotic ingredients, such as inulin and oligofructose (FOS). The main goal of this study was to evaluate the combined effects of inulin and FOS with either suboptimal pH or storage temperature on the viability of Lactobacillus reuteri DSM 20016. Data were modeled through Weibull equation for the evaluation of the microbiological shelf life and the survival time. Prebiotics enhanced the microbiological shelf life and enhanced the survival time of the target bacterium. The use of the factorial ANOVA highlighted that inulin and FOS exerted a different effect as a function of pH and temperature. Inulin prolonged survival time under acidic conditions, while the effect of glucose + FOS was significant at pH 8. Finally, temperature could act by increasing or decreasing the effect of prebiotics, as they could exert a protective effect at 30 °C but not at 44 °C. As the main output of this research, we could suggest that the effect of prebiotics on L. reuteri could be significantly affected by pH and temperature, thus pinpointing that the design of a symbiotic food should also rely on these factors.

Screening of Propionibacterium spp. for potential probiotic properties.

The main topic of this paper is the evaluation of adhesion of propionibacteria to IPEC-J2 cells and the survival at pH 2.5 and with 0.3% bile salts added, bioactivity towards pathogens and antibiotic resistance of Propionibacterium freudenreichii subsp. shermanii, Propionibacterium jensenii, Propionibacterium acidipropionici and Propionibacterium thoenii. Adhesion to IPEC-J2 cell lines was ca. 25-35% and significantly increased with CaCl2. Moreover, propionibacteria showed a reduction of cell count of ca. 0.5% at pH 2.5 after 3 h, whereas cell count increased after 24 h with bile salts; finally, they significantly inhibited Escherichia coli O157:H7.