probiotics, prebiotics, and syn biotics

PROBIOTICS, PREBIOTICS, AND SYN BIOTICS BIOACTIVE FOODS IN HEALTH PROMOTION

Probiotics, Prebiotics, and Synbiotics Bioactive Foods in Health Promotion

Edited by

Ronald Ross Watson

University of Arizona, Division of Health Promotion Sciences, Mel and Enid Zuckerman College of Public Health, and School of Medicine, Arizona Health Sciences Center, Tucson, AZ, USA

Victor R. Preedy

Department of Nutrition and Dietetics, Nutritional Sciences Division, School of Biomedical & Health Sciences, King’s College London, London, UK

AMSTERDAM • BOSTON • HEIDELBERG • LONDON NEW YORK • OXFORD • PARIS • SAN DIEGO SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO Academic Press is an imprint of Elsevier

Academic Press is an imprint of Elsevier 125 London Wall, London, EC2Y 5AS, UK 525 B Street, Suite 1800, San Diego, CA 92101-4495, USA 225 Wyman Street, Waltham, MA 02451, USA The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, UK © 2016 Elsevier Inc. All rights reserved No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress ISBN: 978-0-12-802189-7 For information on all Academic Press publications visit our website at http://store.elsevier.com/ Printed and bound in the United States of America Publisher: Nikki Levy Acquisition Editor: Andrea Topping Editorial Project Manager: Billie Jean Fernandez Production Project Manager: Caroline Johnson Designer: Ines Cruz

xii Contents

3 Prebiotics, Probiotics, and Synbiotics 4 Synbiotics and Immune Response 5 Conclusion Acknowledgment References

451 452 455 455 455

1.1 Definition of Acute Gastroenteritis 1.2 Incidence and Disease Burden 1.3 Causes 2 Intestinal Microfloria and Mucosal Barrier 2.1 Intestinal Microflora 2.2 Mucosal Barrier 3 Treatment and Synbiotics 4 Conclusions References

459 461

35. Symbiotics, Probiotics, and Fiber Diet in Diverticular Disease

31. Synbiotics and Immunization Against H9N2 Avian Influenza Virus Seyedeh Leila Poorbaghi and Masood Sepehrimanesh 1 Avian Immune System 2 Avian Influenza 3 Association of Probiotics, Prebiotics and Synbiotics with Immunity 4 Immunity Against AIVs 5 Conclusion References

462 463 465 466

32. Probiotics, Prebiotics, Synbiotics, and Foodborne Illness Eleni Likotrafiti and Jonathan Rhoades 1 Introduction 2 Inhibitory Mechanisms of Probiotics Against Pathogenic Bacteria 3 Reduction of Human Enteric Pathogen Carriage by Food Animals 3.1 Mammals 3.2 Poultry 3.3 Aquatic Animals 3.4 Concluding Comments 4 Inhibition of Pathogens in Food Products Prior to Consumption 5 Pathogen Inactivation in the Gut 6 Concluding Remarks References

469 469 471 471 471 471 472 472 473 473 474

33. In�Vitro Screening and Evaluation of Synbiotics Maria Lena Skalkam, Maria Wiese, Dennis Sandris Nielsen and Gabriella van Zanten 1 Introduction 2 Screening of Synbiotic Combinations 3 Models of the Human Gastrointestinal Tract 4 Cell Assays 5 Future Perspectives References

477 477 479 480 482 483

488 488 489 490 494 495

Edith Lahner and Bruno Annibale 1 Introduction 2 Diverticular Disease—Definition and Epidemiology 3 Which Options to Treat Diverticular Disease? 4 Diverticular Disease and ProbioticsSymbiotics 5 Diverticular Disease and Dietary Fiber/ Prebiotics 6 Conclusion References

501 501 502 503 507 511 511

36. Gut Microbiota: Impact of Probiotics, Prebiotics, Synbiotics, Pharmabiotics, and Postbiotics on Human Health Saikiran Chaluvadi, Arland T. Hotchkiss, Jr. and Kit L. Yam 1 Introduction 515 2 Gut Microbiota 516 3 Evolving Field of Probiotics 517 3.1 What is More Important, Survival or Efficacy? Does Survival also Guarantee Efficacy? 517 3.2 Beneficial Commensals or Traditional Probiotics 520 3.3 Pharmabiotics and Postbiotics 521 4 Conclusions 521 References 522

37. Potential Benefits of Probiotics, Prebiotics, and Synbiotics on the Intestinal Microbiota of the Elderly Raquel Bedani, Susana Marta Isay Saad and Katia Sivieri

34. Synbiotics and Infantile Acute Gastroenteritis Zuhal Gundogdu 1 Introduction

487 487 488

487

1 Introduction 2 Elderly Population 3 The Gut Microbiota

525 525 526

Chapter 36

Gut Microbiota: Impact of Probiotics, Prebiotics, Synbiotics, Pharmabiotics, and Postbiotics on Human Health Saikiran Chaluvadi*,†,‡, Arland T. Hotchkiss, Jr.† and Kit L. Yam‡ *Harris Tea Company, Moorestown, New Jersey, USA, †U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, Wyndmoor, Pennsylvania, USA, ‡Department of Food Science, Rutgers University, New Brunswick, New Jersey, USA

1 INTRODUCTION The “law of accelerating returns” is a theoretical concept proposed by Ray Kurzweil to explain the nature of advances in computing technology (Kurzweil, 2000). This concept directly or indirectly applies to many other fields of science that rely on advancing technology. There is an exponential growth in our ability to perform experiments; gather and analyze data; and develop new methods, products, and solutions, which suggests that we have exponentially reduced the time to find meaningful answers to challenging questions. The latest evidence on the role of gut microbes in several disease conditions (Clemente et al., 2012) and the effects of diet on the gut microbiota (David et al., 2014) are examples of technology-mediated advances that have potential ramifications in both food and medical sciences. However, so much data is produced from gut microbiome studies that it is challenging to interpret what it all means. We must be careful to ask the right questions and test hypotheses that relate data from exponentially advancing technology to the big picture of human health. In the food industry, most of the research and development during the past 60 years focused on producing great tasting products that look good, last long, and deliver value and convenience to consumers. The salt-sugar-fat bliss point was used to not only optimize food taste but also market-addictive foods without regard to rates of childhood obesity or type 2 diabetes (Moss, 2014). Wellness products were appreciated by a very small group of health aficionados and considered more of a transient trend. Over the years, specialty wellness products have gained significant traction in mainstream markets. Transient trends like reduced calorie, low sodium, low fat, all natural, whole grain, vegan, minimally processed, gluten-free, and GMO-free are constantly redefining modern food. Protein-rich Greek yogurt, electrolyte-dense coconut water, β-glucan- and omega-3-containing oats, antioxidants from tea and juice products, probiotic- and prebiotic-fortified foods are examples of products created to meet growing consumer demands for pure and convenient, but also meaningful functional foods. Increased regulatory oversight combined with a knowledgeable modern consumer is encouraging the food industry to think beyond traditional R&D and marketing methods. Answering questions such as “What is the bioavailability of an ingredient?”, “What will be the efficacy of a functional ingredient throughout the shelf life of the product?”, “How can the nutrients of a natural product be better preserved?”, “Is the ingredient safe below the detection limit of an analytical instrument?”, “How is the ingredient affecting gut microbiota?”, “How is a structure function claim on a label made?”, “How is the efficacy of a functional product defined?”, “How can we better educate the consumer without making unsubstantiated claims?”, are now a big part of research and development in the food industry. Questions like these have resulted in technologies like high hydrostatic pressure processing, in vitro digestion systems, ultrahigh performance liquid chromatography, and 16s rRNA-based qPCR. In the medical industry, growing evidence on the relationship between gut microbiota and chronic conditions such as obesity, diabetes, and inflammatory bowel disease is not only profound but also game changing. Human microbiome research had shown interindividual variations in gut microbiota composition, suggesting the need for personalized medicine to correct dysbiosis-related diseases. Understanding the role of several nondietary agents such as stress, sleep, antibiotic, and drug usage in dysbiosis of gut microbiota is now pivotal for finding effective therapies and cures. Nutraceutical

Probiotics, Prebiotics, and Synbiotics. http://dx.doi.org/10.1016/B978-0-12-802189-7.00036-8 © 2016 Elsevier Inc. All rights reserved.

515

516 PART | III Synbiotics: Production, Application, and Health Promotion

formulations, either supplements along with drugs or stand-alone therapeutics can be developed by combining probiotics and postbiotics to restore microbial balance in the gut. In this chapter, we attempt to raise and discuss relevant questions and also update the reader about the current status and future prospects in the field of probiotics.

2 GUT MICROBIOTA The NIH Human Microbiome Project (HMP) was commissioned to understand the role of bacteria in healthy and disease cohorts of the human population. The first phase (2007–12) of the HMP program focused on developing tools required to identify and classify microbiota from various sites in the human body. Advanced DNA sequencing methods including metagenomic analysis have eliminated the need for laborious cell culture techniques, sequencing vast amounts of genetic material that is harvested directly from microbial communities instead of individual genomes. Composition of microbiota from nasal passages, oral cavities, skin, and gastrointestinal and urogenital tracts was determined and classified into various phylogenetic and taxonomical groups using the traditional Sanger method and 16S ribosomal RNA gene sequencing. Sophisticated computational algorithms combined with bioinformatics tools were employed to interpret the massive amounts of data (Gevers et al., 2012; Methé, 2012). New innovative technologies are currently under development to improve isolation and analysis of unculturable and uncharacterized bacteria, differentiate species, and rapidly sort cells. For example, “FISH ‘N’ CHIPS” is a proposed microfluidic device that will utilize the concept of fluorescent in situ hybridization to identify, isolate, and encapsulate single cells from a sample containing diverse populations. “Multidimensional separation of bacteria” is an example of another technology aimed at mitigating the shortcomings of metagenomic approaches. The proposed microfluidic device attempts to determine the heterogeneity between and within species in a complex mixture (http://www.hmpdacc.org/tools_protocols/tools_protocols.php). In the second phase of the HMP (2013–16) project, along with genomic data, functional -omics such as proteomics, transcriptomics, and metabolomics will be utilized to study three models of microbiome-related human conditions: preterm birth, inflammatory bowel disease, and type 2 diabetes (Proctor, 2014). The gut microbiota composition obtained from metagenomic data of the HMP project showed staggering taxonomic-, phylogenetic-, and species-level diversity between healthy individuals of one community. However, functional data derived from metabolomics, transcriptomics, and proteomics studies showed about 70% similarity between these healthy individuals, suggesting the need to consider bacterial communities as an assembly of functional genes but not individual species-level diversity (Burke et al., 2011; Turnbaugh et al., 2009). Dietary changes were shown to alter the gut microbial composition of healthy individuals at an enterotype level (bacterial phyla level). While Wu et al. (2011) showed longterm protein and animal fat diets selected for Bacteroides of the Bacteriodetes phylum over Prevotella of the Firmicutes phylum, De Filippo et al. (2010) showed dominance of Bacteriodetes resulting from a plant-based diet in an African population and dominance of Firmicutes due to an animal-based diet of a European population. It was also suggested that the higher Firmicutes to Bacteriodetes ratio in EU children may predispose them to future obesity (De Filippo et al., 2010). Animal-based diets increased the amounts of bile-tolerant organisms belonging to the Bacteroides genus and decreased the level of plant polysaccharide metabolizing bacteria belonging to Roseburia sp., Eubacterium rectale, and Ruminococcus bromii (Clemente et al., 2012; David et al., 2014). A significant shift in gut microbiota was found in 24 h when diet in healthy individuals was shifted from high-fat, low-fiber to low-fat, high-fiber composition (Clemente et al., 2012; David et al., 2014). Due to interindividual variability within gut microbial composition of the healthy population, a healthy microbiota may not be defined without better understanding gene expression, metabolic profiles, and other functional aspects of the microbiome. However, behavior of healthy microbiota may be defined as its ability to resist changes induced by ecological stress and/or return to its native state after the stress is released (Bäckhed et al., 2012). Claesson et al. (2012) established a relationship between diet, diversity in gut microbiota, residence location in the community, and age. Elderly subjects living in the community who consumed a more diverse diet had more diverse gut microbiota compared to elderly long-stay subjects. Community dwellers who moved to a long-stay location and consumed a long-stay-type diet took a year to change their gut microbiota to lower diversity, indicating resistance to microbiota change in the elderly population (Claesson et al., 2012). The gut microbiota was found to be relatively stable in individuals with a consistent diverse diet and good health. Instability in the composition of microbial communities (reduced diversity and/or change in ratios of bacterial groups) is known as dysbiosis. Disruptive factors such as medication, chemotherapy, antibiotics, and chronic disease are major factors that cause dysbiosis (McFarland, 2014). Dysbiosis has been recently linked to diseases such as allergies, obesity, metabolic syndrome, Crohn’s disease, and irritable bowel syndrome. Dietary intervention, fecal transplantation (Wang et al., 2014), and probiotic and prebiotic supplementation (Bäckhed et al., 2012; McFarland, 2014) are a few methods that are showing promise in correcting dysbiosis.

-biotics and Gut Microbiota Chapter | 36 517

The HMP and its related studies have brought three important findings related to microbial behavior to light. i. Bacteria from different species can share similar metabolic pathways resulting in the same or similar physiological effects. This signifies that more than one microbe can function similarly in disease causation, prevention, and intervention mechanisms (Proctor, 2014; Bäckhed et al., 2012). ii. Bacteria, when present in a microbial community, may behave quite differently from how they behave when alone possibly due to quorum sensing. Hence, isolation methods for individual cells are being pursued to understand the extent of this behavior (http://www.hmpdacc.org/tools_protocols/tools_protocols.php). iii. In most diseases, like the ones described in the previous section, it is the microbial dysbiosis that causes a disease condition, not the presence or absence of one specific bacterial species (Clemente et al., 2012). These findings should encourage researchers to be more cautious before attributing merits or harm to one type of bacteria.

3 EVOLVING FIELD OF PROBIOTICS The definition “Live microorganisms that, when administered in adequate amounts, confer a health benefit on the host” was coined in 2001 by FAO/WHO and emphasizes the importance of survival and dosage of bacteria (FAO/WHO, 2001). Recent discoveries related to diversity, stability, interaction, and the role of gut microbiota in human health have uncovered several new factors that play a role in delivering health benefits. While survival and dosage of bacteria remain essential for a probiotic benefit, bacterial genetics, strain specificity, nature of the food matrix, and host factors are among a growing number of other influences on efficacy (Sanders et al., 2014). New knowledge about the gut microbiota will continue to shape the role and hence the future of probiotics.

3.1 What is More Important, Survival or Efficacy? Does Survival also Guarantee Efficacy? People working in the field of probiotics understand that the survival of bacteria is a fundamental requirement to manufacture, promote, and sell probiotic products. Industries using probiotics perform survival and dosage studies as a part of quality control and shelf life analysis. However, there is no established definition for probiotic efficacy, or are there standardized analytical tools and methods that measure efficacy. Regulations that enforce application-specific efficacy studies are also lacking. We recognize that efficacy depends on a number of factors discussed in this chapter and without multidisciplinary collaboration it is impractical to consider all of them. We defined probiotic efficacy as bacterial fitness, which is further defined as the ability of probiotic bacteria to exhibit stable anaerobic growth characteristics and produce consistent amounts of short-chain fatty acids (SCFAs) throughout aerobic storage at 4 °C (Chaluvadi et al., 2012). We developed synbiotic matrices, and compared the growth of the probiotics Lactobacillus acidophilus, Lactobacillus reuteri, Bifidobacterium breve, and Bifidobacterium longum that contained prebiotics including pectic oligosaccharides and inulin with high-viscosity alginic acid as a structural element in the matrix (Chaluvadi et al., 2012). The synbiotic matrix was used as a model system to test the survival and fitness of the probiotic bacteria. After each week of refrigerated aerobic storage, the inoculated synbiotic matrices were incubated anaerobically in Brain-Heart Infusion broth and turbidity changes in the broth indicated bacterial survival (Hotchkiss et al., 2008). Quantitative analysis using bacterial plate counts on de Man, Regosa and Sharpe agar (MRS agar) indicated >7 log CFU/ mL of bacteria survival throughout the 4-week storage period if calcium was not used to cross-link the alginate-based synbiotic matrix (Chaluvadi et al., 2012). This level of storage survival is considered good for commercial product shelf life. Large standard deviations in growth characteristics (lag time, maximum population density, growth rate, and growth time) and SCFA (lactic, acetic, propionic, and butyric acids) levels were observed (Chaluvadi et al., 2012) that may be attributed to stress conditions encountered by bacteria during aerobic storage. Figures 36.1–36.4 indicate the change in anaerobic growth lag time after each week of aerobic storage and using calcium cross-linked alginate-based synbiotic matrix. The anaerobic growth lag time fluctuated up or down compared to the control (bacterial strain without synbiotic storage) during the first 2 weeks in aerobic storage in a strain-dependent manner (Figures 36.1–36.4). By week 4, the anaerobic growth lag time recovered to the control value or was reduced (Figures 36.1–36.4). The presence of pectic oligosaccharides and inulin accentuated the anaerobic growth lag time fluctuation, but by week 4 of aerobic storage, synbiotics with and without prebiotic tended to have the same lag time (Figures 36.1–36.4). Figures 36.5 and 36.6 indicate the fluctuation in lactic acid production during storage. Lactic acid produced by L. acidophilus was significantly different for pectic oligosaccharide alginate (POSA) synbiotics after the first week of storage compared to alginate alone synbiotics (Figure 36.5). However, toward the end of the 4-week storage period, there was no difference in the lactic acid levels produced in the presence of POSA and alginate alone. There were no significant changes


16 14

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Weeks FIGURE 36.1 Anaerobic growth lag time of Lactobacillus acidophilus in synbiotics. Pectic oligosaccharides were included in synbiotics ( compared to synbiotics with only alginate ( ) and L. acidophilus grown anaerobically without synbiotic aerobic storage (--- ---).

) and

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Weeks FIGURE 36.2 Anaerobic growth lag time Lactobacillus reuteri in synbiotics. Inulin was included in synbiotics (X) and compared to synbiotics with only alginate ( ) and L. reuteri grown anaerobically without synbiotic aerobic storage (--- ---).

10 9 8 Lag time (h)

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Weeks FIGURE 36.3 Anaerobic growth lag time of Bifidobacterium breve in synbiotics. Inulin was included in synbiotics (X) and compared to synbiotics with only alginate ( ) and B. breve grown anaerobically without synbiotic aerobic storage (--- ---).


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Weeks FIGURE 36.4 Anaerobic growth lag time of Bifidobacterium longum in synbiotics. Pectic oligosaccharides were included in synbiotics ( compared to synbiotics with only alginate ( ) and B. longum grown anaerobically without synbiotic aerobic storage (--- ---).

) and

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Weeks FIGURE 36.5 Lactic acid production during anaerobic growth by Lactobacillus acidophilus in alginate-based synbiotics following aerobic storage. Pectic oligosaccharides were included in synbiotics ( ) and compared to synbiotics with only an alginate matrix ( ).

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Weeks FIGURE 36.6 Lactic acid production during anaerobic growth by Bifidobacterium longum in alginate-based synbiotics following aerobic storage. Inulin was included in synbiotics ( ) and compared to synbiotics with only an alginate matrix ( ).


in lactic acid levels produced when inulin was used as the prebiotic in alginate-based synbiotics (Figure 36.6). Lower levels of acetic acid and propionic acids were also produced by these synbiotics, and butyric acid was only produced by the synbiotics containing Lactobacilli with a significant variation in SCFA production levels throughout the storage period (Chaluvadi et al., 2012). Revival of anaerobic growth lag time and SCFA production after an initial perturbation suggests the involvement of a potential stress-adaptive mechanism that needs further investigation. Stress-adaptive mechanisms in bacteria may also be triggered by the following: 1. Environmental factors: Bifidobacterium strains exhibited an acid-tolerance response as a stress-adaptive mechanism (Sánchez et al., 2013; Sanz, 2007). This adaptive mechanism was also shown to provide cross-tolerance to bile, temperature, and sodium chloride. Sublethal exposures to stress factors have shown improved adaptive responses to subsequent stress conditions. This phenomenon may be utilized to help Bifidobacterium strains better adapt to the stress encountered during aerobic commercial processing, storage, and gastrointestinal transit (Sánchez et al., 2013; Sanz, 2007). Lactobacillus rhamnosus exhibited multiple stress-adaptive responses including upregulation of genes responsible for heat shock, osmolarity regulation, DNA repair, and starvation when different stresses were induced (Prasad et al., 2003). 2. Presence of prebiotics: Prebiotics are being pursued as candidates for preventing adhesion of pathogenic bacteria in different tissues (Blatchford et al., 2013). However, these oligosaccharides may also influence the attachment of probiotic and commensal bacteria in the gut. Evidence of extraintestinal interactions of prebiotic fibers with bacteria in the oral cavity and urinary and vaginal tracts has been reported (Hotchkiss and Buddington, 2011; Hotchkiss et al., 2013). Prebiotic oligosaccharide interactions with prokaryotic and eukaryotic cells result in lowering the colonic pH, modulating the immune system, and gene expression (Hotchkiss and Buddington, 2011). Prebiotics are defined as carbohydrates that selectively enhance the growth and/or activity of probiotic bacteria (Gibson and Roberfroid, 1995). However, the biological activity of many of these oligosaccharide mixtures is expanding beyond acting through probiotic bacteria to promote health. In some strains, we observed that high survival of bacteria does not necessarily correlate with fitness (Chaluvadi et al., 2012). Survival of bacteria is necessary in a commercial probiotic product, but it is not sufficient to guarantee efficacy. Based on these results, we strongly encourage defining and studying fitness along with the survival of bacteria before commercializing a probiotic product.

3.2 Beneficial Commensals or Traditional Probiotics Metagenome sequencing identified about 1000-1150 commensal bacterial species in the human gut. This microbial diversity discourages the ability of pathogenic bacteria to infect, colonize, and cause disease in the host. Even though the commensal bacteria are not completely characterized across varied populations, the mechanisms related to their dominance over pathogenic bacteria are much more understood. Colonization and resistance to pathogens is made possible by a range of mechanisms, including competition for nutrients and attachment sites, selective assimilation of compounds for energy, triggering host-mediated immune responses, upregulating virulence factors, and producing metabolic factors such as SCFAs that deter pathogen growth. For example, certain commensal bacteria possess a type 6 secretion system that release antimicrobial proteins against pathogenic bacteria, while other commensals interact with human gut innate immune receptors and restore intestinal homeostasis (Coulthurst, 2013; Abt and Pamer, 2014). Commensal bacteria also help the host in a variety of other ways such as metabolizing indigestible compounds and deriving nutrients from complex molecules (Martín et al., 2013). At least 90% of gut bacteria were identified to be dominated by two bacterial phyla, namely Bacteriodetes and Firmicutes (Qin et al., 2010). As discussed earlier, dysbiosis is observed in a number of debilitating chronic conditions. Fecal transplantation to re-establish the commensal microbiota represents the best therapy for opportunistic pathogen infection caused by Clostridium difficile (Wang et al., 2014). Probiotic bacteria strains such as L. rhamnosus GG, Lactobacillus casei Shirota, L. reuteri, a few Bifidobacterium, and Streptococcus spp. have demonstrated anti-inflammatory properties and alleviation of intestinal disorders like the ones mentioned above in mouse models and human clinical studies (Martín et al., 2013). The direct mechanism of action for probiotic bacteria in a disease condition has not been elucidated well enough to make clinical therapeutic claims. If dysbiosis can be confirmed as a single major factor responsible for a disease condition, then restoring balance in intestinal microflora with probiotics can be considered as a therapy. The classical prebiotic effect is usually confirmed by an increase in bifidobacteria or lactobacilli after consuming a nondigestible fiber. However, in a recent in vitro study focused on measuring the effects of sugar beet pectic oligosaccharides on human fecal microbiota composition, a 33-fold increase in Blautia spp., 10-fold increase in Coprococcus spp., and increases in Butyricicoccus spp. and Faecalibacterium spp. were observed after 24 h of fermentation (Leijdekkers et al., 2014). Lowered numbers of these species have been identified in


patients with colorectal cancer and inflammatory bowel diseases. Coprococcus spp. was previously identified to be a butyrate producer, which explained the increased production of butyrate despite no enhancement in the Bifidobacterium population (Leijdekkers et al., 2014). These findings along with others (Hentschel et al., 2003; Chassaing and Michaud, 2011; Erturk-Hasdemir and Kasper, 2013) are just a few examples that emphasize the need to include commensal bacteria in probiotic and prebiotic research. Depending on the situation, supplementing the host with beneficial commensals may also confer health benefits.

3.3 Pharmabiotics and Postbiotics Probiotics, by definition, must confer proven health benefits to the host, and these benefits should be strain specific. Commensal bacteria may also confer benefits similar to probiotics but mostly in a synergistic and collective manner. A new definition for the term probiotic had been suggested to include a growing number of agents, which include live or dead microbes or components of organisms, responsible for gut health. However, from a marketing standpoint, the term probiotic has a certain meaning to the consumer and any change to the definition may lead to confusion. Hence, the term pharmabiotic was coined in an effort to consider beneficial bacteria or their products with a proven pharmacological role in health or disease. Bacteriocins are one such pharmabiotic agent produced by beneficial commensals that can be detrimental to pathogenic bacteria (Hill, 2010; Klein et al., 2010). Postbiotics is a term coined more recently to include molecules depleted in an abnormal or a dysbiotic gut condition, which when supplemented in whole or precursor form will help restore the balance in the gut (Klemashevich et al., 2014). The idea behind postbiotics is to include all bioactive functional molecules that can be used or produced by the microbial community for promoting health. Postbiotics produced by gut microbiota could be metabolites such as SCFAs from carbohydrates, indole from amino acids, gamma-aminobutyric acid from glutamic acid, and polyphenolic acids and other functional compounds derived from the diet. Metabolomics has been suggested as a method to identify postbiotics from biological systems (Klemashevich et al., 2014). Understanding postbiotics will help develop dietary intervention methods and bioactive functional food products to alter dysbiosis in the human gut microbiota. If postbiotics can be identified using metabolomic approaches, foods can either be fortified or processed to include these compounds. There are several foods that are naturally abundant in postbiotics or their precursors such as acids, vitamins, and polyphenols. Fermented food products such as yogurt, sauerkraut, pickled vegetables, and kombucha are classic postbiotic-rich foods. There are more than 4000 unique flavonoids in nature that can be derived from the diet. Most of these phenolic compounds remain unabsorbed in the gut. Complex interaction between these polyphenols and intestinal microbiota result in microbial transformation products. These products have been shown to repress the growth of pathogenic strains of Clostridium spp. while commensal bacteria were either less or positively affected (Lee et al., 2006). Long-term consumption of tea polyphenols correlated with body weight reduction in obese individuals. Bacteriodetes produce more glycosidases required to metabolize polyphenols giving them a selective advantage over the Firmicutes (Rastmanesh, 2011). Hence, it has been hypothesized that weight loss may result from restoration of the Firmicutes:Bacteriodetes ratio to that found in healthy counterparts (Rastmanesh, 2011).

4 CONCLUSIONS The HMP has uncovered a staggering amount of interindividual variation in gut microbial composition but with very similar metabolomic data. Hence, comparing functional genes is much more important than comparing the type of microbial species between individuals. Dysbiosis in microbial communities as opposed to the presence or absence of a specific bacterial species was observed more prominently in disease conditions. The field of probiotics is rapidly evolving due to a better understanding of the gut microbiota. Efficacy and fitness of probiotic bacteria is as important as its survival for an intended health benefit. Based on the type of application, it is necessary for researchers to define efficacy of bacteria and monitor it throughout usage and shelf life conditions. Different Lactobacillus and Bifidobacterium spp. have demonstrated stress-adaptive responses that could be one of the important mechanisms of survival necessary to flourish in complex and diverse gut microbial communities. Understanding the relationship between commensal and probiotic bacteria will help tailor therapies specific for disease conditions. Pharmabiotics and postbiotics are necessary new -biotics to categorize different bioactive agents playing a role in modulating the gut microbiota. Understanding metabolic products of commensal bacteria and molecules that modulate them is necessary to create the next generation of food, supplements, and medical products that aims to restore and maintain the healthy balance in the gut microbiota. Multidisciplinary collaboration is necessary for understanding the interactions between gut microbiota, probiotic, prebiotic, pharmabiotic, and postbiotic agents.


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