Chemical Composition and Evaluation of the Biological Properties of the Essential Oil of the Dietary Phytochemical Lippia citriodora.

The aim of the study was to characterize the chemical composition and biological properties of the essential oil from the plant Lippia citriodora grown in Greece. The essential oil volatiles were analyzed by gas chromatography-mass spectrometry GC-MS indicating citral as the major component. Τhe antimicrobial properties were assayed using the disk diffusion method and the minimum inhibitory and non-inhibitory concentration values were determined. Listeria monocytogenes, Staphylococcus epidermidis, Staphylococcus aureus, Saccharomyces cerevisiae, and Aspergillus niger were sensitive to Lippia citriodora oil, but not Escherichia coli, Salmonella Enteritidis, Salmonella typhimurium, and Pseudomonas fragi. Adversely, all microbes tested were sensitive to citral. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays were used to assess direct antioxidant activity, which proved to be weak for both agents, while comet assay was utilized to study the cytoprotective effects against H2O2-induced oxidative damage in Jurkat cells. Interestingly, the oil showed a more profound cytoprotective effect compared to citral. The antiproliferative activity was evaluated in a panel of cancer cell lines using the sulforhodamine B (SRB) and 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-S-(phenylamino) carbonyl-2-tetrazolium hydroxide (XTT) assays and both agents demonstrated potent antiproliferative activity with citral being more cytotoxic than the oil. Taken together, the essential oil of Lippia citriodora and its major component, citral, exert diverse biological properties worthy of further investigation.

Phytochemical Profile and Evaluation of the Biological Activities of Essential Oils Derived from the Greek Aromatic Plant Species Ocimum basilicum, Mentha spicata, Pimpinella anisum and Fortunella margarita.

Natural products, known for their medicinal properties since antiquity, are continuously being studied for their biological properties. In the present study, we analyzed the composition of the volatile preparations of essential oils of the Greek plants Ocimum basilicum (sweet basil), Mentha spicata (spearmint), Pimpinella anisum (anise) and Fortunella margarita (kumquat). GC/MS analyses revealed that the major components in the essential oil fractions, were carvone (85.4%) in spearmint, methyl chavicol (74.9%) in sweet basil, trans-anethole (88.1%) in anise, and limonene (93.8%) in kumquat. We further explored their biological potential by studying their antimicrobial, antioxidant and antiproliferative activities. Only the essential oils from spearmint and sweet basil demonstrated cytotoxicity against common foodborne bacteria, while all preparations were active against the fungi Saccharomyces cerevisiae and Aspergillus niger. Antioxidant evaluation by DPPH and ABTS radical scavenging activity assays revealed a variable degree of antioxidant potency. Finally, their antiproliferative potential was tested against a panel of human cancer cell lines and evaluated by using the sulforhodamine B (SRB) assay. All essential oil preparations exhibited a variable degree of antiproliferative activity, depending on the cancer model used, with the most potent one being sweet basil against an in vitro model of human colon carcinoma.

Composition, antimicrobial, antioxidant, and antiproliferative activity of Origanum dictamnus (dittany) essential oil.

BACKGROUND: Nowadays, there has been an increased interest in essential oils from various plant origins as potential antimicrobial, antioxidant, and antiproliferative agents. This trend can be mainly attributed to the rising number and severity of food poisoning outbreaks worldwide along with the recent negative consumer perception against artificial food additives and the demand for novel functional foods with possible health benefits. Origanum dictamnus (dittany) is an aromatic, tender perennial plant that only grows wild on the mountainsides and gorges of the island of Crete in Greece. OBJECTIVE: The aim of the present study was to investigate the antimicrobial, antioxidant, and antiproliferative properties of O. dictamnus essential oil and its main components and assess its commercial potential in the food industry. DESIGN: O. dictamnus essential oil was initially analyzed by gas chromatography-mass spectrometry (GC-MS) to determine semi-quantitative chemical composition of the essential oils. Subsequently, the antimicrobial properties were assayed and the minimum inhibitory and non-inhibitory concentration values were determined. The antioxidant activity and cytotoxic action against the hepatoma adenocarcinoma cell line HepG2 of the essential oil and its main components were further evaluated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and by the sulforhodamine B (SRB) assay, respectively. RESULTS: The main constituents of O. dictamnus essential oil identified by GC-MS analysis were carvacrol (52.2%), γ-terpinene (8.4%), p-cymene (6.1%), linalool (1.4%), and caryophyllene (1.3%). O. dictamnus essential oil and its main components were effective against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Listeria monocytogenes, Salmonella Enteritidis, Salmonella typhimurium, Saccharomyces cerevisiae, and Aspergillus niger. In addition, the estimated IC50 value for the DPPH radical scavenging activity for O. dictamnus essential oil was 0.045±0.0042% (v/v) and was mainly attributed to carvacrol. The EC50 value for the essential oil in the 72h SRB assay in HepG2 cells was estimated to be 0.0069±0.00014% (v/v). Among the individual constituents tested, carvacrol was the most bioactive compound and accounted for the observed antiproliferative activity of the essential oil. CONCLUSIONS: The results revealed that O. dictamnus essential oil is a noteworthy growth inhibitor against the microbes studied. It also possesses significant antioxidant activity and demonstrated excellent cytotoxicity against HepG2 cells. Taken together, O. dictamnus essential oil may represent an effective and inexpensive source of potent natural antimicrobial agents with health-promoting properties, which may be incorporated in food systems.

Exploiting the beneficial effects of Salvia officinalis L. extracts in human health and assessing their activity as potent functional regulators of food microbiota.

Salvia officinalis L. has attracted scientific and industrial interest due to its pharmacological properties. However, its detailed phytochemical profile and its correlation with beneficial effects in the human microbiome and oxidative stress remained elusive. To unveil this, S. officinalis was collected from the region of Epirus and its molecular identity was verified with DNA barcoding. Phytochemical profile for both aqueous and ethanol-based extracts was determined by high-pressure liquid chromatography-tandem mass spectrometry and 103 phytochemicals were determined. The effect of S. officinalis extracts as functional regulators of food microbiota by stimulating the growth of Lacticaseibacillus rhamnosus strains and by suppressing evolution of pathogenic bacteria was verified. Furthermore, we recorded that both extracts exhibited a significant cellular protection against H2O2-induced DNA damage. Finally, both extracts exhibited strong inhibitory effect towards LDL oxidation. This study provides a comprehensive characterization of S. officinalis on its phytochemical components as also its potential impact in human microbiome and oxidative stress.

Novel Functional Grape Juices Fortified with Free or Immobilized Lacticaseibacillus rhamnosus OLXAL-1.

During the last decade, a rising interest in novel functional products containing probiotic microorganisms has been witnessed. As food processing and storage usually lead to a reduction of cell viability, freeze-dried cultures and immobilization are usually recommended in order to maintain adequate loads and deliver health benefits. In this study, freeze-dried (free and immobilized on apple pieces) Lacticaseibacillus rhamnosus OLXAL-1 cells were used to fortify grape juice. Juice storage at ambient temperature resulted in significantly higher (>7 log cfu/g) levels of immobilized L. rhamnosus cells compared to free cells after 4 days. On the other hand, refrigerated storage resulted in cell loads > 7 log cfu/g for both free and immobilized cells for up to 10 days, achieving populations > 109 cfu per share, with no spoilage noticed. The possible resistance of the novel fortified juice products to microbial spoilage (after deliberate spiking with Saccharomyces cerevisiae or Aspergillus niger) was also investigated. Significant growth limitation of both food-spoilage microorganisms was observed (both at 20 and 4 °C) when immobilized cells were contained compared to the unfortified juice. Keynote volatile compounds derived from the juice and the immobilization carrier were detected in all products by HS-SPME GC/MS analysis. PCA revealed that both the nature of the freeze-dried cells (free or immobilized), as well as storage temperature affected significantly the content of minor volatiles detected and resulted in significant differences in the total volatile concentration. Juices with freeze-dried immobilized cells were distinguished by the tasters and perceived as highly novel. Notably, all fortified juice products were accepted during the preliminary sensory evaluation.

Pathogenic Biofilm Removal Potential of Wild-Type Lacticaseibacillus rhamnosus Strains.

The emergence of antimicrobial resistance remains one of the greatest public health concerns. Biofilm formation has been postulated as a mechanism of microbial pathogens to resist antimicrobial agents. Lactic Acid Bacteria (LAB) and their metabolites have been proposed to combat bacterial biofilms due to their antimicrobial activity. In this vein, the aim of the present study was to investigate the biofilm removal potential of cell-free supernatants (CFSs) of five wild-type Lacticaseibacillus rhamnosus strains, isolated from Greek natural products, in comparison to the commercially available L. rhamnosus GG strain, against biofilms formed by common foodborne pathogens (Salmonella Enteritidis, Salmonella Typhimurium, Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus). The biofilm removal activity of LAB was assessed on a two-day-old mature biofilm using a microtiter plate-based procedure. Both non-neutralized and neutralized CFSs removed biofilms in a concentration-dependent manner. The biofilm removal activity of the non-neutralized CFSs was significantly higher compared to the neutralized CFSs, as expected, with ranges of 60-89% and 30-80%, respectively. The biofilm removal efficiency of L. rhamnosus OLXAL-3 was significantly higher among the wild-type L. rhamnosus strains tested (20-100% v/v). In conclusion, our results suggest the great potential of the application of wild-type L. rhamnosus strain' CFSs as effective natural agents against pathogenic bacterial biofilms.

Insights into Antimicrobial and Anti-Inflammatory Applications of Plant Bioactive Compounds.

Plants have long been thought to contribute to health promotion due to their fiber and phenolic content, as well as their inherent biological potential. The bioactive derivatives of medicinal plants are a valuable resource in the fight against serious diseases all around the world. The present review focuses on the current state of knowledge on the usage and medicinal applications of plant bioactives. Issues concerning the effect of aromatic plant derivatives on human gut microbiota and their antimicrobial and anti-inflammatory potentials are discussed and worth further exploring.

Corinthian Currants Supplementation Restores Serum Polar Phenolic Compounds, Reduces IL-1beta, and Exerts Beneficial Effects on Gut Microbiota in the Streptozotocin-Induced Type-1 Diabetic Rat.

The present study aimed at investigating the possible benefits of a dietary intervention with Corinthian currants, a rich source of phenolic compounds, on type 1 diabetes (T1D) using the animal model of the streptozotocin-(STZ)-induced diabetic rat. Male Wistar rats were randomly assigned into four groups: control animals, which received a control diet (CD) or a diet supplemented with 10% w/w Corinthian currants (CCD), and diabetic animals, which received a control diet (DCD) or a currant diet (DCCD) for 4 weeks. Plasma biochemical parameters, insulin, polar phenolic compounds, and inflammatory factors were determined. Microbiota populations in tissue and intestinal fluid of the caecum, as well as fecal microbiota populations and short-chain fatty acids (SCFAs), were measured. Fecal microbiota was further analyzed by 16S rRNA sequencing. The results of the study showed that a Corinthian currant-supplemented diet restored serum polar phenolic compounds and decreased interleukin-1b (IL-1b) (p < 0.05) both in control and diabetic animals. Increased caecal lactobacilli counts (p < 0.05) and maintenance of enterococci levels within normal range were observed in the intestinal fluid of the DCCD group (p < 0.05 compared to DCD). Higher acetic acid levels were detected in the feces of diabetic rats that received the currant diet compared to the animals that received the control diet (p < 0.05). Corinthian currant could serve as a beneficial dietary component in the condition of T1D based on the results coming from the animal model of the STZ-induced T1D rat.

Biotechnological potential of Zymotis-2 bioreactor for the cultivation of filamentous fungi.

BACKGROUND/AIM: A new prototype of Solid-State Fermentation Bioreactor, namely "Zymotis-2 ", was developed to produce fungal spores. MAIN METHODS AND MAJOR RESULTS: A fermentation process for fungal spores, and hydrolase enzymes (endo and exoglucanases, amylases) production by Trichoderma asperellum DWG3, Aspergillus niger G131 and Beauveria bassiana was scaled-up from flasks and glass Raimbault column packed with 20 g of solid substrates (dry weight) to 5 kg of solid substrate by using the new Zymotis-2 bioreactor. Fungi strains growth using a mix of vine shoots, wheat bran, and olive pomace was tested under similar experimental conditions in Zymotis-2 bioreactor, column bioreactor and flasks in a parallel fermentation system. Overall, significant spore production on Zymotis-2 bioreactor was obtained, achieving 22.01 ± 0.01×109 spores/g DM 16.30 ± 0.07 × 109 spores/g DM, and 3.30 ± 0.07 × 109 spores/g DM for B. bassiana, T. asperellum DWG3, and A. niger G131, respectively. Forced aeration increased the endoglucanases, exoglucanases and amylases activities for T. asperellum DWG3 but B. bassiana and A. niger G131 were affected negatively by the aerated process, showing the lowest enzyme activities. CONCLUSIONS AND IMPLICATIONS: In conclusion, a high yield of spores was obtained at 137 h of cultivation time, confirming the validity of the new Zymotis-2 bioreactor to produce virulent spores at low cost by T. asperellum, B. bassiana and A. niger G131.

Effect of Free or Immobilized Lactiplantibacillus plantarum T571 on Feta-Type Cheese Microbiome.

BACKGROUND: Cheese microbiome plays a key role in determining the organoleptic and physico-chemical properties and may be also used as an authenticity tool for distinguishing probiotic cultures. Due to significant reduction of cell viability often witnessed during food production processes and storage, immobilization is proposed to ascertain high probiotic cell loads required to confer the potential health benefits. Hence, the aim of the present study was to investigate the effect of free or immobilized Lactiplantibacillus plantarum T571 on whey protein on feta cheese microbiome. METHODS: Next-Generation Sequencing technology was used to investigate cheese microbiome. Cheese samples containing free or immobilized Lactiplantibacillus plantarum T571 (a wild type strain isolated from Feta cheese brine) on whey protein, along with products containing commercial starter culture, were analyzed. RESULTS: The results showed a great diversity of bacteria and fungi genera among the samples. An increased presence of Lactobacillus OTUs in cheese with immobilized cells on whey protein was witnessed, highlighting the survival of the strain in the final product. The immobilized culture had also a significant impact on other genera, such as Lactococcus, Leuconostoc and Debaryomyces, which are associated with improved technological characteristics and health benefits. CONCLUSIONS: Enrichment of feta cheese with immobilized potential probiotics to secure cell viability consists of an industrial challenge and leads to distinct microbiome composition that may be used as a valuable food authenticity tool.

Maintaining Digestive Health in Diabetes: The Role of the Gut Microbiome and the Challenge of Functional Foods.

Over the last decades, the incidence of diabetes has increased in developed countries and beyond the genetic impact, environmental factors, which can trigger the activation of the gut immune system, seem to affect the induction of the disease process. Since the composition of the gut microbiome might disturb the normal interaction with the immune system and contribute to altered immune responses, the restoration of normal microbiota composition constitutes a new target for the prevention and treatment of diabetes. Thus, the interaction of gut microbiome and diabetes, focusing on mechanisms connecting gut microbiota with the occurrence of the disorder, is discussed in the present review. Finally, the challenge of functional food diet on maintaining intestinal health and microbial flora diversity and functionality, as a potential tool for the onset inhibition and management of the disease, is highlighted by reporting key animal studies and clinical trials. Early onset of the disease in the oral cavity is an important factor for the incorporation of a functional food diet in daily routine.

Charting the structural and thermodynamic determinants in phenolic acid natural product - cyclodextrin encapsulations.

Cyclodextrins are pliable platforms that have served to optimize the pharmaceutic profile of numerous compounds and to enhance the stability of natural food additives. Caffeic and rosmarinic acid are natural products with proven health benefits, though their full therapeutic potential has not been exploited. To enhance their pharmaceutic profile, we developed cyclodextrin-based formulates and unveiled their thermodynamic and structural principles. The complexes' stoichiometry was determined by ESI-MS. Solid-state and liquid NMR spectroscopy revealed the interactions and the topographical location of the caffeic and rosmarinic acid inside the cyclodextrin cavity. The theoretically analyzed HP-ß-CD's degree of substitution (DS) of caffeic and rosmarinic acids can explain the intensities obtained by 2D NOESY experiments. The thermodynamics and the affinity of the complexes were evaluated through isothermal titration calorimetry. In addition, the rosmarinic and caffeic acids as, also, their complexes showed considerable antimicrobial activity against common food spoilage and pathogenic bacteria. The generated data could provide the basis to understand the structural and thermodynamic determinants implicated in natural products - CD recognition and to develop platforms for the optimization of their pharmaceutical and stability profiles in order to be utilized as safe and stable natural antimicrobial food additives.Communicated by Ramaswamy H. Sarma.

Citrus medica and Cinnamomum zeylanicum Essential Oils as Potential Biopreservatives against Spoilage in Low Alcohol Wine Products.

Low alcohol wine is a new entry in the global wine market, due to the increase in consumers' concern for health, economic and modern lifestyle issues. As low alcohol products are prone to spoilage, the adoption of natural-derived products with antimicrobial activity as biopreservatives seems to be an intriguing alternative. Thus, the aim of the present study was to investigate the possible antimicrobial properties of Citrus medica and Cinnamomum zeylanicum essential oils (EOs) and assess their commercial prospective in the wine industry. The main constituents identified by GC/MS analysis were limonene (38.46%) and linalool (35.44%) in C. medica EO, whereas trans-cinnamic-aldehyde (63.58%) was the dominant compound in C. zeylanicum EO. The minimum inhibitory (MIC), non-inhibitory (NIC) and minimum lethal concentration (MLC) values against common wine spoilage microbes were initially determined. Subsequently, their efficiency was further validated in low alcohol (~6% vol) wines, either separately or in combination at 0.010% (v/v), as well as in wines deliberately inoculated with Gluconobacter cerinus, Oenococcus oeni, Pediococcus pentosaceus, Dekkera bruxellensis, Candida zemplinina, Hanseniaspora uvarum, Pichia guilliermondii or Zygosaccharomyces bailii. EO addition led to considerable spoilage and microbial growth delay during storage at room or refrigerated temperature, suggesting their potential use as wine biopreservatives.

Freeze-Dried Immobilized Kefir Culture in Low Alcohol Winemaking.

Low alcohol wines represent a rising trend in the global market. Since for ethanol removal, certain physicochemical methods that negatively affect wine quality are applied, the aim of this present study was to evaluate the efficiency of freeze-dried, immobilized kefir culture on natural supports (apple pieces, grape skins and delignified cellulosic material) in low alcohol winemaking at various temperatures (5-30 °C). Initially, genetic analysis of kefir culture was performed by Next Generation Sequencing. There was an immobilization of kefir culture on grape skins-enhanced cell survival during freeze-drying in most cases, even when no cryoprotectant was used. Simultaneous alcoholic and malolactic fermentations were performed in repeated batch fermentations for >12 months, using freeze-dried free or immobilized cells produced with no cryoprotectant, suggesting the high operational stability of the systems. Values of great industrial interest for daily ethanol productivity and malic acid conversion [up to 39.5 g/(Ld) and 67.3%, respectively] were recorded. Principal Component Analysis (PCA) showed that freeze-drying rather than the fermentation temperature affected significantly minor volatiles. All low alcohol wines produced were accepted during the preliminary sensory evaluation.

Functional modulation of gut microbiota in diabetic rats following dietary intervention with pistachio nuts (Pistacia vera L.).

BACKGROUND: Gut microbiota holds a key-role in numerous biological functions and has emerged as a driving force for the development of diabetes. Diet contributes to gut microbiota diversity and functionality providing a tool for the prevention and management of the disease. The study aimed to investigate the effect of a dietary intervention with pistachio nuts, a rich source of monounsaturated fatty acids, dietary fibers and phytochemicals on gut microbiota composition in the rat model of Type 1 Diabetes. METHODS: Male Wistar rats were randomly assigned into four groups: healthy animals which received control diet (CD) or pistachio diet (PD), and diabetic animals which received control diet (DCD) or pistachio diet (DPD) for 4 weeks. Plasma biochemical parameters were determined and histological examination of liver and pancreas was performed at the end of the dietary intervention. Adherent intestinal microbiota populations in jejunum, ileum, caecum and colon were analyzed. Fecal microbiota populations at the beginning and the end of the study were determined by microbiological analysis and 16S rRNA sequencing. RESULTS: Diabetic animals of both groups exhibited high plasma glucose and low insulin concentrations, as well as characteristic pancreatic lesions. Pistachio supplementation significantly increased lactobacilli and bifidobacteria populations in jejunum, ileum and caecum (p < 0.05) and normalized microbial flora in all examined intestinal regions of diabetic animals. After 4 weeks of supplementation, populations of bifidobacteria and lactobacilli were increased in feces of both healthy and diabetic animals, while enterococci levels were decreased (p < 0.05). Next Generation Sequencing of fecal samples revealed increased and decreased counts of Firmicutes and Bacteroidetes, respectively, in healthy animals that received the pistachio diet. Actinobacteria OTUs were higher in diabetic animals and increased over time in the pistachio treated groups, along with increased abundance of Bifidobacterium. Lactobacillus, Turicibacter and Romboutsia populations were elevated in healthy animals administered the pistachio nuts. Of note, relative abundance of Bacteroides was higher in healthy than in diabetic rats (p < 0.05). CONCLUSION: Dietary pistachio restored normal flora and enhanced the presence of beneficial microbes in the rat model of streptozotocin-induced diabetes.

Assessment of the Antimicrobial, Antioxidant, and Antiproliferative Potential of Sideritis raeseri subps. raeseri Essential Oil.

The aim of the present study was to investigate the antimicrobial potential of Sideritis raeseri subps. raeseri essential oil (EO) against common food spoilage and pathogenic microorganisms and evaluate its antioxidant and antiproliferative activity. The EO was isolated by steam distillation and analyzed by GC/MS. The main constituents identified were geranyl-p-cymene (25.08%), geranyl-γ-terpinene (15.17%), and geranyl-linalool (14.04%). Initially, its activity against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Listeria monocytogenes, Salmonella Enteritidis, Salmonella Typhimurium, Pseudomonas fragi, Saccharomyces cerevisiae, and Aspergillus niger was screened by the disk diffusion method. Subsequently, minimum inhibitory concentration (MIC), non-inhibitory concentration (NIC), and minimum lethal concentration (MLC) values were determined. Growth inhibition of all microorganisms tested was documented, although it was significantly lower compared to gentamycin, ciproxin, and voriconazole, which were used as positive controls. In a next step, its direct antioxidant properties were examined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays, and the IC50 values were determined. The potential cytoprotective activity of the oil against H2O2-induced oxidative stress and DNA damage was studied in human immortalized keratinocyte (HaCaT) cells using the comet assay. Finally, the antiproliferative activity of the oil was evaluated against a panel of cancer cell lines including A375, Caco2, PC3, and DU145 and the non-cancerous HaCaT cell line using the sulforhodamine B (SRB) assay, and the EC50 values were determined. The oil demonstrated weak radical scavenging activity, noteworthy cytoprotective activity against H2O2-induced oxidative stress and DNA damage in HaCaT cells, and antiproliferative activity against all cell lines tested, being more sensitive against the in vitro model of skin melanoma.

Effect of Sugar Content on Quality Characteristics and Shelf-Life of Probiotic Dry-Fermented Sausages Produced by Free or Immobilized Lactobacillus casei ATCC 393.

The aim of the present study was to investigate the effect of sugar content (0, 0.30, and 0.60%) on quality attributes and shelf-life of dry-fermented sausages stored for 66 days containing free or immobilized Lactobacillus casei ATCC 393 on wheat. For comparison, dry-fermented sausages with no starter culture were also produced. Physicochemical characteristics ranged within the levels usually observed in fermented sausages, while a drastic decrease was recorded in numbers of enterobacteria, staphylococci, and pseudomonads during ripening in all cases. Noticeably, sugar addition and the probiotic culture resulted in significant increase of shelf-life, whereas levels of L. casei ATCC 393 after 66 days of ripening persisted above 6 log cfu/g. Sugar addition had a positive effect on sensory attributes; although all products were of high quality, the immobilized cells provided a distinctive characteristic aroma and a fine taste.

Disinfection efficiencies of sage and spearmint essential oils against planktonic and biofilm Staphylococcus aureus cells in comparison with sodium hypochlorite.

Staphylococcus aureus causes human infections and foodborne intoxications. This study explored the potential antibacterial actions of sage and spearmint essential oils (EOs) against both its planktonic and biofilm cells, in comparison with sodium hypochlorite (NaOCl), a commonly applied chemical sanitizer. Initially, the minimum inhibitory and bactericidal concentrations (MICs, MBCs) of each plant mixture were determined against planktonic cultures, following growth at 30°C for 24h. Stationary phase planktonic bacteria were then individually exposed for 6min to either each EO (applied at 1-2×MBC; 2.5-5%), or NaOCl (250-450ppm). These were also left to form biofilms on 96-well polystyrene microplates, at 30°C for 96h, with medium renewal at 48h, in the presence of 10 different concentrations of each EO, expanding from sub- to super-inhibitory for planktonic growth, and the minimum biofilm inhibitory concentrations (MBICs; >90% inhibition) of each plant mixture were calculated. Formed biofilms were finally exposed for 6min to either each EO (applied at 2-6×MBC; 5-15%), or NaOCl (7500-25,000ppm; applied either alone or in combination with each EO at 5%). Results showed that both EOs presented MIC and MBC equal to 1.25 and 2.5%, respectively. As expected, their application at their MIC and above significantly inhibited biofilm formation, while spearmint EO was still able to cause this at ½ of its MIC, with MBICs equal to 1.25 and 0.63% for sage and spearmint EOs, respectively. Alarmingly, the application of both EOs at 1/8 to 1/16 of their MIC further increased biofilm formation. Regarding biofilm disinfection experiments, the individual application of each EO against the pre-established sessile communities resulted in log decrease ranges of 0.8-3logCFU/cm2, while in the case of NaOCl application (either alone or combined with each EO), the observed reductions never exceeded 1.7logCFU/cm2. These last results highlight the great antimicrobial recalcitrance of biofilm communities, found here to be ca. 100 times more resistant to NaOCl compared to planktonic ones, and stress the urgent need for further research on alternative, adequate and safe disinfection strategies to control them in food processing and other environments.

Immobilization technologies in probiotic food production.

Various supports and immobilization/encapsulation techniques have been proposed and tested for application in functional food production. In the present review, the use of probiotic microorganisms for the production of novel foods is discussed, while the benefits and criteria of using probiotic cultures are analyzed. Subsequently, immobilization/encapsulation applications in the food industry aiming at the prolongation of cell viability are described together with an evaluation of their potential future impact, which is also highlighted and assessed.