Effect of tannic acid on Lactobacillus hilgardii analysed by a proteomic approach

Comparative Proteomics of Bacteria Under Stress Conditions

Bacteria are unicellular organisms with the ability to exist in the harshest of climate and cope with sub-optimal fluctuating environmental conditions. They accomplish this by modification of their internal cellular environment. When external conditions are varied, change in the cell is triggered at the transcriptional level, which usually leads to proteolysis and rewiring of the proteome. Changes in cellular homeostasis, modifications in proteome, and dynamics of such survival mechanisms can be studied using various scientific techniques. Our focus in this chapter would be on comparative proteomics of bacteria under stress conditions using approaches like 2D electrophoresis accompanied by N-terminal sequencing and recently, mass spectrometry. More than 170 such studies on bacteria have been accomplished till to date and involve analysis of whole cells as well as that of cellular fractions, i.e., outer membrane, inner membrane, cell envelope, cytoplasm, thylakoid, lipid bodies, etc. Similar studies conducted on gram-negative and gram-positive model organism, i.e., Escherichia coli and Bacillus subtilis, respectively, have been summarized. Vital information, hypothesis about conservation of stress-specific proteome, and conclusions are also presented in the light of research conducted over the last decades.

Antimicrobial Compounds in Wine

Ipsum vinum est potestas et possession (wine itself is power and possession). Wine is a complex system that triggers multisensory cognitive stimuli. Wine and its consumption are thoroughly intertwined with the development of human society. The beverage was appreciated in many ancient mythologies and plays an essential part in Christianity and rituals to this day. Wine has been said to enlighten and inspire artists and has even been prohibited by law and some religions, but has nevertheless played a role in human civilizations since the beginning. Winemaking is also a prospering and economically important industry and a longtime symbol of status and luxury. In winemaking, the formation of the final product is influenced by several factors that contribute to the chemical and sensory complexity often associated with quality vintages. Factors such as terroir, climatic conditions, variety of the grape, all aspects of the winemaking process to the smallest details, including metabolic processes carried out by yeast and malolactic bacteria, and the conditions for the maturation and storage of the final product, up to, and even beyond the point of deciding to open the bottle and enjoy the wine. In conjunction with the empiric and scientific process of winemaking, different molecules with antibacterial activity can be identified in wine during the production process, and several of them are clearly present in the final product. Some of these antibacterial components are phytochemicals, such as flavonoids and phenolic compounds, that may be delivered to the final product (wine) as a part of the grape, a variety of potential additive compounds, or from the oak barrels or clay amphoras used during the maturation process. Others are produced by yeasts and malolactic bacteria and play a role not only in the moderation of the fermentation process but contributing to the microbiological safety and beneficial properties spectra of the final product. Lactic acid bacteria, responsible for conducting malolactic fermentation, contribute to the final balance of the wine but are also directly involved in the production of different compounds exhibiting antibacterial activity. Some examples of these compounds include bacteriocins (antibacterial peptides), diacetyl, organic acids, reuterin, hydrogen peroxide, and carbon dioxide. Major aspects of these different beneficial metabolites are the subject of discussion in this review with the aim of highlighting their beneficial functions.

Interaction between plants and epiphytic lactic acid bacteria that affect plant silage fermentation

Lactic acid bacteria (LAB) have the ability to ferment water-soluble carbohydrates, resulting in the production of significant amounts of lactic acid. When utilized as additives in silage fermentation and feed, they have been shown to enhance the quality of these products. Epiphytic LAB of plants play a major role in the fermentation of silage plants. Plant species in turn affect the community structure of epiphytic LAB. In recent years, an increasing number of studies have suggested that epiphytic LAB are more effective than exogenous LAB when applied to silage. Inoculating silage plants with epiphytic LAB has attracted extensive attention because of the potential to improve the fermentation quality of silages. This review discusses the interaction of epiphytic LAB with plants during silage fermentation and compares the effects of exogenous and epiphytic LAB on plant fermentation. Overall, this review provides insight into the potential benefits of using epiphytic LAB as an inoculant and proposes a theoretical basis for improving silage quality.

Characterizing Selected Sorghum Grain Varieties and Evaluating the Suitability of Their Malt Extracts for Cultivating Microbial Biomass

Microbial biomass is cultivated for different technological applications including food processing, medicine, waste management, and research. The conventional growth media used are generally expensive thus necessitating the development of more affordable alternatives. In this study, four sorghum grain varieties, SESO 1, SESO 3, Epuripur, and Eyera, and their malt extracts were characterized which is aimed at determining their suitability for growing microbial biomass. The varieties had kernel length, kernel width, kernel thickness, and thousand kernel weigh equivalent to 3.8-4.3 mm, 3.2-4.5 mm, 2.4-2.8 mm, and 12.4-20.2 g, respectively. SESO 1 and Epuripur had corneous endosperm textures whereas those of SESO 3 and Eyera were intermediate and floury, respectively. Varieties had germinative energies > 90% and total defects < 8%. SESO 3 had the highest (p < 0.05) crude protein (10.8 ± 0.3%) and dietary fiber (22.5 ± 0.4%) whereas Epuripur had the highest (p < 0.05) starch (81.6 ± 0.0%) and crude fat (2.9 ± 0.1%). There was no significant difference (p > 0.05) in the ash contents (2.1 ± 0.0%). The total sugars, free amino nitrogen, condensed tannins, and pH of the malt extracts were 106-116 g/L, 70-78 mg/L, 0.1-0.6 mg/mL, and 5.5-5.7, respectively. The composition of the sorghum malt extracts suggests their potential for use in cultivating microbial biomass.

Molecular Responses of Lactobacilli to Plant Phenolic Compounds: A Comparative Review of the Mechanisms Involved

Lactobacilli are well-studied bacteria that can undergo oxidative selective pressures by plant phenolic compounds (PPCs) in plants, during some food fermentations or in the gastrointestinal tract of animals via dietary inputs. Lactobacilli are known to be more tolerant to PPCs than other bacterial groups and, therefore, must have mechanisms to cope with the effects of these metabolites. In this review, we intend to present what is currently known about the basics beyond the responses of Lactobacillus spp. to individual PPCs. We review the molecular mechanisms that are engaged in the PPC-modulated responses studied to date in these bacteria that have been mainly characterized by system-based strategies, and we discuss their differences and similarities. A wide variety of mechanisms are induced to increase the oxidative stress response highlighting the antimicrobial nature of PPCs. However other uncovered mechanisms that are involved in the response to these compounds are reviewed, including the capacity of PPCs to modulate the expression of molecular functions used by lactobacilli to adapt to host environments. This shows that these phytochemicals can act as more than just antimicrobial agents in the dual interaction with lactobacilli.

Thermosonication as an alternative method for processing, extending the shelf life, and conserving the quality of pulque: A non-dairy Mexican fermented beverage

The aim of this study was to evaluate thermosonication as an alternative method for the pasteurization of pulque in order to improve its shelf life and retain its quality parameters. Thermosonication was carried out at 50 °C using amplitudes of 75% (for 6 and for 9 min), 85% (for 4 and for 6 min), and 95% (for 3 and for 5 min). These were the optimal conditions found for processing pulque by thermosonication. Physicochemical (acidity, color, alcohol content, and sensory analysis) and microbiological (lactic acid bacteria and yeasts) parameters were determined during 30 days for storage at 4 ± 1 °C. Conventional pasteurization (63 °C, 30 min) and raw pulque were used as controls. According to the results, the shelf life of pulque was extended up to 24 days storage at 4 °C. After this time, the quality of beverage decreased, due that the microbial load increases. Thermosonication treatments at 75% and 85% showed a higher content of LAB (6.58-6.77 log CFU/mL) and yeasts (7.08-7.27 log CFU/mL) than conventional pasteurization (3.64 log CFU/mL of LAB and 3.97 log CFU/mL of yeasts) at 24 days of storage. Raw pulque demonstrated up to 7.77 log CFU/mL of yeasts and 7.51 log CFU/mL of LAB. Pulque processed by thermosonication exhibited greater lightness, sensory acceptance, a maximal acidity of 0.83 g/lactic acid, and an alcohol content of 4.48-4.95% v/v. The thermosonication process preserves sensory and physicochemical properties better than conventional pasteurization. Lactic acid bacteria such as Lactobacillus kefiri, Lactobacillus acidophilus, and Lactobacillus hilgardii and yeasts such as Saccharomyces cereviasiae were identified in thermosonicated pulque.

Updates on understanding of probiotic lactic acid bacteria responses to environmental stresses and highlights on proteomic analyses

Probiotics are defined as live microorganisms that improve the health of the host when administered in adequate quantities. Nonetheless, probiotics encounter extreme environmental conditions during food processing or along the gastrointestinal tract. This review discusses different environmental stresses that affect probiotics during food preparation, storage, and along the alimentary canal, including high temperature, low temperature, low and alkaline pH, oxidative stress, high hydrostatic pressure, osmotic pressure, and starvation. The understanding of how probiotics deal with environmental stress and thrive provides useful information to guide the selection of the strains with enhanced performance in specific situations, in food processing or during gastrointestinal transit. In most cases, multiple biological functions are affected upon exposure of the cell to environmental stress. Sensing of sublethal environmental stress can allow for adaptation processes to occur, which can include alterations in the expression of specific proteins.

Plant Polyphenols Stimulate Adhesion to Intestinal Mucosa and Induce Proteome Changes in the Probiotic Lactobacillus acidophilus NCFM

SCOPE

Plant phenolics, known to exert beneficial effects on human health, were supplemented to cultures of the probiotic bacterium Lactobacillus acidophilus NCFM (NCFM) to assess their effect on its adhesive capacity and the abundancy of individual proteins.

METHODS AND RESULTS

The presence of resveratrol and ferulic acid during bacterial growth stimulated adhesion of NCFM to mucin and human intestinal HT-29 cells, while tannic acid improved adhesion only to HT-29 cells and caffeic acid had very modest effect overall. Some dosage dependence was found for the four phenolics supplemented at 100, 250, and 500 μg mL^-1 to the cultures. Notably, 500 μg mL^-1 ferulic acid only stimulated adhesion to mucin. Analyses of differential whole-cell as well as surface proteomes revealed relative abundancy changes for a total of 27 and 22 NCFM proteins, respectively. These changes include enzymes acting in metabolic pathways, such as glycolysis, nucleotide metabolism, and stress response, as well as known moonlighting or surface-associated proteins.

CONCLUSION

The five plant phenolics found in various foods stimulate the adhesive capacity of NCFM in diverse ways and elicit relative abundancy changes of specific proteins, providing molecular level insight into the mechanism of the putative beneficial effects of the polyphenols.

Functional proteomics within the genus Lactobacillus

Lactobacillus are mainly used for the manufacture of fermented dairy, sourdough, meat, and vegetable foods or used as probiotics. Under optimal processing conditions, Lactobacillus strains contribute to food functionality through their enzyme portfolio and the release of metabolites. An extensive genomic diversity analysis was conducted to elucidate the core features of the genus Lactobacillus, and to provide a better comprehension of niche adaptation of the strains. However, proteomics is an indispensable "omics" science to elucidate the proteome diversity, and the mechanisms of regulation and adaptation of Lactobacillus strains. This review focuses on the novel and comprehensive knowledge of functional proteomics and metaproteomics of Lactobacillus species. A large list of proteomic case studies of different Lactobacillus species is provided to illustrate the adaptability of the main metabolic pathways (e.g., carbohydrate transport and metabolism, pyruvate metabolism, proteolytic system, amino acid metabolism, and protein synthesis) to various life conditions. These investigations have highlighted that lactobacilli modulate the level of a complex panel of proteins to growth/survive in different ecological niches. In addition to the general regulation and stress response, specific metabolic pathways can be switched on and off, modifying the behavior of the strains.

Lactobacillus acidophilus-Rutin Interplay Investigated by Proteomics

Dietary polyphenols are bioactive molecules that beneficially affect human health, due to their anti-oxidant, anti-inflammatory, cardio-protective and chemopreventive properties. They are absorbed in a very low percentage in the small intestine and reach intact the colon, where they are metabolized by the gut microbiota. Although it is well documented a key role of microbial metabolism in the absorption of polyphenols and modulation of their biological activity, molecular mechanisms at the basis of the bacteria-polyphenols interplay are still poorly understood. In this context, differential proteomics was applied to reveal adaptive response mechanisms that enabled a potential probiotic Lactobacillus acidophilus strain to survive in the presence of the dietary polyphenol rutin. The response to rutin mainly modulated the expression level of proteins involved in general stress response mechanisms and, in particular, induced the activation of protein quality control systems, and affected carbohydrate and amino acid metabolism, protein synthesis and cell wall integrity. Moreover, rutin triggered the expression of proteins involved in oxidation-reduction processes.This study provides a first general view of the impact of dietary polyphenols on metabolic and biological processes of L. acidophilus.

Influence of fresh date palm co-products on the ripening of a paprika added dry-cured sausage model system

Date palm co-products are a source of bioactive compounds that could be used as a new ingredient for the meat industry. An intermediate food product (IFP) from date palm co-products (5%) was incorporated into a paprika added dry-cured sausage (PADS) model system and was analysed for physicochemical parameters, lipid oxidation and sensory attributes during ripening. Addition of 5% IFP yielded a product with physicochemical properties similar to the traditional one. Instrumental colour differences were found, but were not detected visually by panellists, who also evaluated positively the sensory properties of the PADS with IFP. Therefore, the IFP from date palm co-products could be used as a natural ingredient in the formulation of PADS.

Effectiveness of sal deoiled seed cake as an inducer for protease production from Aeromonas sp. S1 for its application in kitchen wastewater treatment

The present study is an attempt to demonstrate the feasibility of sal (Shorea robusta) deoiled cake--a forest-based industrial by-product--as a cheaper media supplement for augmented protease production from Aeromonas sp. S1 and application of protease in the treatment of kitchen wastewater. Under optimized conditions, protease production could successfully be enhanced to 5.13-fold (527.5 U mL(-1)) on using sal deoiled seed cake extract (SDOCE), as medium additive, compared to an initial production of 102.7 U mL(-1) in its absence. The culture parameters for optimum production of protease were determined to be incubation time (48 h), pH (7.0), SDOCE concentration (3 % (v/v)), inoculum size (0.3-0.6 % (v/v)), and agitation rate (100 rpm). The enzyme was found to have an optimum pH and temperature of 8.0 and 60 °C, respectively. The protease preparation was tested for treatment of organic-laden kitchen wastewater. After 96 h of wastewater treatment under static condition, enzyme preparation was able to reduce 74 % biological oxygen demand, 37 % total suspended solids, and 41 % oil and grease. The higher and improved level of protease obtained using sal deoiled seed cake-based media hence offers a new approach for value addition to this underutilized biomass through industrial enzyme production. The protease produced using this biomass could also be used as pretreatment tool for remediation of organic-rich food wastewater.

Tannic acid-dependent modulation of selected Lactobacillus plantarum traits linked to gastrointestinal survival

BACKGROUND

Owing to its antimicrobial properties dietary tannins may alter the functional efficacy of probiotic lactobacilli in the gastrointestinal (GI)-tract influencing their growth, viability and molecular adaptation to the intestinal environment.

METHODS AND FINDINGS

The effects of tannic acid on Lactobacillus plantarum WCFS1 were studied by in vitro growth monitoring and visualizing the morphological alteration on the cell wall using transmission electron microscopy. Growth upon tannic acid was characterized by dose-dependent reductions of initial viable counts and extended lag phases. Lag phase-cells growing upon 0.5 mM tannic acid were abnormally shaped and experienced disturbance on the cell wall such as roughness, occasional leakage and release of cell debris, but resumed growth later at tannic acid concentrations high as 2.5 mM. To gain insight on how the response to tannic acid influenced the molecular adaptation of L. plantarum to the GI-tract conditions, gene expression of selected biomarkers for GI-survival was assessed by RT-qPCR on cDNA templates synthetized from mRNA samples obtained from cells treated with 0.5 or 2 mM tannic acid. Tannic acid-dependent gene induction was confirmed for selected genes highly expressed in the gut or with confirmed roles in GI-survival. No differential expression was observed for the pbp2A gene, a biomarker negatively related with GI-survival. However PBP2A was not labeled by Bocillin FL, a fluorescent dye-labeled penicillin V derivative, in the presence of tannic acid which suggests for enhanced GI-survival reportedly associated with the inactivation of this function.

CONCLUSIONS

Probiotic L. plantarum WCFS1 is able to overcome the toxic effects of tannic acid. This dietary constituent modulates molecular traits linked to the adaptation to intestinal environment in ways previously shown to enhance GI-survival.

Nanomaterial transformation and association with fresh and freeze-dried wastewater activated sludge: implications for testing protocol and environmental fate

Engineered nanomaterials (ENMs) are an emerging class of contaminants entering wastewater treatment plants (WWTPs), and standardized testing protocols are needed by industry and regulators to assess the potential removal of ENMs during wastewater treatment. A United States Environmental Protection Agency (USEPA) standard method (OPPTS 835.1110) for estimating soluble pollutant removal during wastewater treatment using freeze-dried, heat-treated (FDH) activated sludge (AS) has been recently proposed for predicting ENM fate in WWTPs. This study is the first to evaluate the use of FDH AS in batch experiments for quantifying ENM removal from wastewater. While soluble pollutants sorbed equally to fresh and FDH AS, fullerene, silver, gold, and polystyrene nanoparticles' removals with FDH AS were approximately 60-100% less than their removals with fresh AS. Unlike fresh AS, FDH AS had a high concentration of proteins and other soluble organics in the liquid phase, an indication of bacterial membrane disintegration due to freeze-drying and heat exposure. This cellular matter stabilized ENMs such that they were poorly removed by FDH AS. Therefore, FDH AS is not a suitable sorbent for estimating nanoparticle removal in WWTPs, whereas fresh AS has been shown to reasonably predict full-scale performance for titanium removal. This study indicates that natural or engineered processes (e.g., anaerobic digestion, biosolids decomposition in soils) that result in cellular degradation and matrices rich in surfactant-like materials (natural organic matter, proteins, phospholipids, etc.) may transform nanoparticle surfaces and significantly alter their fate in the environment.

Effect of yeast mannoproteins and grape polysaccharides on the growth of wine lactic acid and acetic acid bacteria

Polysaccharides constitute one of the main groups of wine macromolecules, and the difficulty in separating and purifying them has resulted in them being less studied than other wine macromolecules. In this study, the biological activity of a number of polysaccharide fractions obtained from yeast lees, must, and wine has been analyzed against a large collection of both lactic acid bacteria (LAB) and acetic acid bacteria (AAB) of enological origin. Results showed that a high proportion of AAB strains (60-88%) was inhibited by concentrations lower than 50 mg/L polysaccharide fractions containing intermediate- (6-22 kD) and small-molecular-weight (<6 kD) mannoproteins and oligosaccharide fragments derived from cellulose and hemicelluloses. Results also showed that, in contrast, yeast mannoproteins in concentrations up to 200 mg/L activated the growth of 23-48% of the studied LAB strains when ethanol was present in the culture broth. Specially, yeast commercial mannoproteins of intermediate molecular weight (6-22 kD) were active in increasing Oenococcus oeni growth (81.5% of the studied O. oeni strains) in the presence of ethanol in the culture broth. These effects of wine polysaccharides on bacterial growth provide novel and useful information for microbiological control of wines and winemaking biotechnology.

Effect of tannic acid on Lactobacillus plantarum wine strain during starvation: A proteomic study

The molecular mechanisms involved in tannic-acid (TA)-mediated cell growth retardation and viability prolongation of Lactobacillus plantarum VP08 strain were evaluated by a proteomic analysis of starved cells grown in the presence of TA or glucose as carbon source. The tannase activity and the cell growth retardation as well as viability prolongation were confirmed by enzymatic assay and growing tests, respectively. In order to gain information about the effect triggered at the molecular level by TA, total proteins (extracted from starved cells grown in 250 mg/L TA, or 2 g/L glucose) were analyzed by a 2D-PAGE/MS approach to detect differentially expressed proteins. A total of 15 spots were found to be down-regulated and 21 up-regulated in TA-grown cells. The results indicate an overall impact of TA on proteins involved in some cellular and metabolic pathways: glycolysis, amino acid metabolism, translation and protein folding. The modulation of specific proteins correlates with the positive effect of TA on the survival of tannase-positive L. plantarum.

Food phenolics and lactic acid bacteria

Phenolic compounds are important constituents of food products of plant origin. These compounds are directly related to sensory characteristics of foods such as flavour, astringency, and colour. In addition, the presence of phenolic compounds on the diet is beneficial to health due to their chemopreventive activities against carcinogenesis and mutagenesis, mainly due to their antioxidant activities. Lactic acid bacteria (LAB) are autochthonous microbiota of raw vegetables. To get desirable properties on fermented plant-derived food products, LAB has to be adapted to the characteristics of the plant raw materials where phenolic compounds are abundant. Lactobacillus plantarum is the commercial starter most frequently used in the fermentation of food products of plant origin. However, scarce information is still available on the influence of phenolic compounds on the growth and viability of L. plantarum and other LAB species. Moreover, metabolic pathways of biosynthesis or degradation of phenolic compounds in LAB have not been completely described. Results obtained in L. plantarum showed that L. plantarum was able to degrade some food phenolic compounds giving compounds influencing food aroma as well as compounds presenting increased antioxidant activity. Recently, several L. plantarum proteins involved in the metabolism of phenolic compounds have been genetically and biochemically characterized. The aim of this review is to give a complete and updated overview of the current knowledge among LAB and food phenolics interaction, which could facilitate the possible application of selected bacteria or their enzymes in the elaboration of food products with improved characteristics.