Probiotic lactic acid bacteria vs. bacilli: pros and cons ARTHUR C. OUWEHAND1*, SOFIA FORSSTEN1, MARKUS LEHTINEN1, ELIZABETH GALBRAITH2, ELLEN DAVIS2 *Corresponding author 1. Active Nutrition, DuPont Nutrition & Health, Sokeritehtaantie 20, 02460 Kantvik, Finland Arthur C. Ouwehand 2. Animal and Environmental Applications, DuPont Nutrition & Health, W227 N752 Westmound Drive, Waukesha, WI 53186, USA KEYWORDS: probiotic, lactic acid bacteria, Lactobacillus, Bifidobacterium, Bacillus, spores ABSTRACT: Both lactic acid bacteria (LAB) and bacilli are commercialised as probiotics; LAB are mainly utilised as live and active or dormant cells, while bacilli are utilised as spores. Belonging to very different genera, they have different technological properties. LAB have a longer history of use as probiotics and therefore have a broader base as far as health efficacy documentation is concerned. The question therefore sometimes arises; strains from which of these groups make better probiotics? Considering the fact that probiotics, by definition, have to be viable in sufficient numbers and have to have documented health benefits, this is not a relevant question. Any microbial strain has to fulfil these criteria in order to qualify as a probiotic. The current paper reviews and compares the available data for both groups of organisms. Pre - Probiotics INTRODUCTION In order to supply consumers with products that provide meaningful levels of probiotics, several requirements have There is no legal description of probiotics. However, the most to be fulfilled by probiotic strains selected for industrial commonly accepted definition is from a FAO/WHO working production. Quality-control must be vigilantly performed, group: “Live microorganisms which when administered in assuring identity, viability and absence of contaminants. adequate amounts confer a health benefit on the host”. This Other properties, that are related to the physiological state implies that probiotics must be alive in sufficient number at of the strain, such as adhesion; bile and acid resistance; the time of use and must have documented health benefits. effects on carbohydrate, protein, and fat utilisation; and, The most commonly used probiotics for human use are especially, colonisation properties (usually as faecal strains that belong to the genera Lactobacillus and recovery) and immunogenicity (e.g. in vitro as cytokine Bifidobacterium, although the latter are genetically distinct induction in peripheral blood mononuclear cells) may also from the former, for convenience they will be grouped need to be assessed (1). Long-term industrial processing and here as lactic acid bacteria (LAB). An emerging group of storage conditions may influence probiotic properties. Thus, probiotics are strains that belong to the genus Bacillus. An in addition to technological properties, functional properties often arising question is which one makes a ‘better’ probiotic should be considered in quality-control measures. as both groups have pros and cons. The present review compares the characteristics for both probiotic groups. The production of probiotics follows a general process LACTIC ACID BACTERIA consisting of several steps, starting with fermentation. Ingredient choice is a crucial step in the fermentation Taxonomy process; final product form and allergen potential are Lactic acid bacteria (LAB) are Gram-positive organisms factors that must be considered. Growth conditions exhibiting a DNA G+C content of less than 50 %. have to be optimised with the right oxygen tension, pH, Phylogenetically they belong to the Clostridium-Bacillus and temperature. For organisms belonging to the genus subdivision of Gram-positive eubacteria. Lactobacilli are Bacillus, induction of spores is promoted near the end of the facultative anaerobes. The genus Bifidobacterium belongs fermentation process, typically through nutrient depletion. to the Actinomycetes subdivision of the Gram-positive After fermentation, the large biomass of probiotics produced is concentrated either by centrifugation or membrane filtration. As spore formers, bacilli are more robust and resist the downstream processing better then LAB, and therefore traditional spray drying is commonly utilised in their production. To preserve LAB viability, maintaining biological membrane integrity and associated proteins through the drying process, is critical in order to maximise cell recovery following rehydration. Cryoprotectants, such as e.g. lactose or sucrose, are used to stabilise the membrane and to minimise the degrading effects caused during the freezing and drying steps. The stabilised material can then be frozen for the freeze-drying process. Formation of ice crystals is minimised during freeze- drying. Solid water is removed via sublimation. The chosen residual moisture content and the stabiliser components have an important impact upon shelf-life. For both LAB and bacilli, the dry material is milled to appropriate particle size, 30-100 µm, for blending and packaging. 13 eubacteria and has a high G+C content of approximately but-non-culturable state, with 60%. Although bifidobacteria are taxonomically distant possible beneficial effects from LAB, they are commonly grouped together as they all such as immune modulation produce lactic acid as a major metabolic end product and and carcinogen binding share habitats such as the intestinal tract and dairy. For the in the host (3). Thus, for purposes of this review, we will consider bifidobacteria to be some probiotics it might part of the LAB group. be sufficient that they grow well during the initial Application in food production steps in order LAB have traditionally been used in the fermentation of to obtain high enough various foods. Since the beginning of the 20th century, they numbers in the product, have also been recognised as providers of health benefits while good viability during and are included for this purpose primarily in fermented storage and/or passage dairy products and dietary supplements. In foods, LAB will through the GI tract may not usually be present as active organisms; limiting their shelf be required. life to about a month. In dietary supplements, however, the microbes will be in a dormant desiccated state expanding Health effects their shelf life to up to 24 months, provided a low water Sequencing technologies have activity (Aw<0.20) is maintained. Application of probiotics increased our understanding of the role in food and feed is limited by water activity, temperature of microorganisms on health and disease. and pH and to a lesser extend oxygen. Of course, all these Function and composition of the gut microbiota may factors combined and the time they are exposed to stressful be modulated by introducing beneficial bacteria, opening conditions influences the level of live microbes, Figure 1. intriguing possibilities for improving health. Gastrointestinal health benefits The impact of LAB has been studied extensively on prevention and treatment of gastrointestinal diseases. Irritable bowel syndrome (IBS) manifests itself as a combination of functional gut problems, like diarrhoea, constipation, intestinal pain, and bloating. It has been estimated that ~10% of the western population have Pre - Probiotics indications of IBS. The underlying cause of IBS is still unclear, but a meta-analysis has shown that LAB consumption improves symptoms of IBS in a species specific manner (4). Infectious diarrhoea is a global problem and frequent cause of mortality especially in children. Diarrhoea may also be caused by outgrowth of opportunistic pathogens in the gut or when antibiotic treatment disturbs the balance of the microbiota. A recent meta-analyses has shown convincingly that prophylactic consumption of LAB reduce the risk of antibiotic associated diarrhoea, Clostridium difficile Figure 1. Schematic representation of the effect of temperature and water activity (Aw) associated diarrhoea (5), infectious diarrhoea (6), and on viability of LAB probiotics necrotising enterocolitis (7). Effects of LAB consumption in the treatment of chronic diarrhoea are not yet conclusive but indications of some benefit in children have been found (8). Feed applications with long shelf lives at ambient Inflammatory bowel disease (IBD) is a condition vol 24(6) - November/December 2013 - temperatures, relatively high processing temperatures characterised by dysbalance in gut microbiota and and high water activity are especially challenging for LAB impaired recognition of gut microbiota by the immune formulations. Combination of LAB with prebiotics to create system, and IBD occurs in two forms: Crohn’s disease and a synbiotic is sometimes suggested but there is currently ulcerative colitis (UC). LAB consumption may reduce the insufficient data available to substantiate a performance relapse rate in UC but the evidence is far from clear (9). benefit with such combination. Also the effect of LAB on Crohn’s disease is still inconclusive Industry Hi Tech and it has been suggested that LAB could potentially Viability/activity (in product and intestine) increase relapse rate (10). In the light of the current research FOOD Probiotic strains must retain their characteristics and viability on Crohn’s disease it is not surprising that consumption during the production processes and storage in different of supplemental LAB probiotics may not be effective in Agro surroundings as well as transit through the GI tract. For ameliorating symptoms. Crohn’s disease has a genetic products where the probiotic is