Branchings indicate phylogenies; phylogenetic distances are not shown to scale. B.C. Specifically, lactic acid bacteria can reduce levels of the enzymes β-glucuronidase, nitroreductase, and azoreductase (28). Lactic acid bacteria, or LAB, are found on grape surfaces and in must during wine fermentations and include both lactobacilli (e.g., Lactobacillus brevis) and lactococci (e.g., Oenococcus oeni). Dillon, in Encyclopedia of Food Microbiology (Second Edition), 2014. Lactic acid bacteria associated with foods include species of Lactobacillus, Lactococcus, Enterococcus, Pediococcus, Leuconostoc, Streptococcus, Carnobacterium, Fructobacillus, Oenococcus, and Weissella. In: Salminen S and von Wright A (eds) Lactic Acid Bacteria. This lactic acid bacterium is now called Lactococcus lactis and is used for fermenting milk to produce hundreds of different dairy products. Within each genus, classical division of LABs into species relies heavily on carbohydrate fermentation profiles and some other simple physiological tests such as growth at particular temperatures and tolerance of salt and extremes of pH. Science and Technology (see ‘Further Reading’). From: Comprehensive Biotechnology (Second Edition), 2011, F. Mozzi, in Encyclopedia of Food and Health, 2016. Among genera of LAB, both Lactobacillus (hereto- and homo-lactic) is the most dominant genus in fermented foods, mostly followed by the species of Pediococcus. ), Table 1. Lactic acid bacteria have a very limited capacity to synthesize amino acids using inorganic nitrogen sources. J.M. Schematic, unrooted phylogenetic tree of the lactic acid bacteria, including some aerobic and facultative anaerobic Gram-positives of the low G+C subdivision. However, bifidobacteria are phylogenetically unrelated to LAB and also differ physiologically in that they utilize a sugar fermentation pathway unique to the genus. Figure 2. Today, many traditional fermentation technologies have been industrialized and form large commercial enterprises. Typical LAB are nonsporing and nonrespiring, aero- and acid tolerant, and fastidious. However, the development of genotyping techniques has to a certain extent revolutionized our understanding of the relationships within the group. For this reason, studies of the metabolic properties of LAB, especially with relation to food product characteristics, are also receiving increasing attention. An example of the beneficial aspects is the malolactic fermentation that occurs after the main yeast fermentation and results in the decarboxylation of l-malic acid to l-lactic acid, catalyzed by the malolactic enzyme in LAB. Nevertheless, the allocation of most LAB isolates to the correct genus should be possible by the use of the characterization tests shown in the table. Examples of these are the production of cheese and other fermented dairy products, fermented sausages such as salami, and fermented cabbage – sauerkraut. This enzyme complex is capable of hydrolyzing oligopeptides produced by chymosin and plasmin activity on caseins to small peptides and amino acids. This trait has, throughout history, linked LAB with food fermentations, as acidification inhibits the growth of spoilage ag… The requirement for amino acids differs among species and strains within species. However, some species are pathogenic and the recent developments in the field of probiotics have brought safety aspects of LAB into focus. Figure 2 shows a schematic, unrooted phylogenetic tree of the lactic acid bacteria. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. URL: https://www.sciencedirect.com/science/article/pii/B9780123849472004141, URL: https://www.sciencedirect.com/science/article/pii/B012227055X006738, URL: https://www.sciencedirect.com/science/article/pii/B9780123847300000380, URL: https://www.sciencedirect.com/science/article/pii/B978012384730000238X, URL: https://www.sciencedirect.com/science/article/pii/B9780123744074002557, URL: https://www.sciencedirect.com/science/article/pii/B9780123847300003566, URL: https://www.sciencedirect.com/science/article/pii/B9780123744074002715, URL: https://www.sciencedirect.com/science/article/pii/B9780123744074000844, URL: https://www.sciencedirect.com/science/article/pii/B9780123744074002582, Comprehensive Biotechnology (Second Edition), 2011, Encyclopedia of Food Sciences and Nutrition (Second Edition), FERMENTED FOODS | Origins and Applications, CHEESES | Starter Cultures Employed in Cheese-making, FERMENTED MILKS | Types of Fermented Milks.
Lactic acid bacteria can tolerate low pH, high concentrations of salt, and heat treatments. The genera Lactococcus and Lactobacillus are commonly associated with milk and milk products, but none of the genera, with the exception of the wine-bound Oenococcus, are associated with only one habitat. Lactic acid bacteria (LAB) are usually employed as starter cultures in the production of fermented food such as cheese and yogurts or probiotics. Bifidobacteria are used in treatment as so-called "probiotics," the opposite of antibiotics.
The stringent response along with the SOS response seems to be common among LAB. Under conditions of limiting carbohydrate, fermentation by homofermentative strains may become mixed. In addition, certain strains of bifidobacteria are used in probiotic applications, much in the same way as some LAB. Related terms:
Production includes both artificial synthesis as well as natural sources. However, LAB were soon discovered in other habitats and a broader view of the group developed.
J.A. Orla Jensen described seven genera in 1919, but only the name of one of them, Streptococcus, remains valid today. They contribute to the taste and texture of fermented products and inhibit food spoilage bacteria by producing growth-inhibiting substances and large amounts of lactic acid.
Aside from the known pathogens, LAB are rarely isolated from disease and in almost all cases are associated with underlying illness which increases the susceptibility of the host. Walker, in Encyclopedia of Food Microbiology (Second Edition), 2014. The lactic acid bacteria are weakly proteolytic, but release a complex well-characterized proteinase/peptidase system into the curd that contributes to flavor development. While in liquid state (dissolved state) it is a colorless solution. Reproduced from Axelsson L (1998) Lactic acid bacteria: classification and physiology. By continuing you agree to the use of cookies. LAB were amongst the very first bacteria studied. Note: evolutionary distances are approximate. In addition, citric acid and many other wine substrates are metabolized into compounds that contribute to the final flavors and aromas. The phylogenetic tree of LAB is presented in Figure 1. They are strictly fermentative, the principal end product of carbohydrate metabolism being lactic acid. Some of these techniques can also be used to identify and characterize isolates down to species and even strain level. LAB are only weakly proteolytic and lipolytic, which is also important since breakdown products from protein and fat are often organoleptically unpleasant in high concentrations. Application of LAB has changed from traditionally fermented foods and beverages to rationally controlled food fermentation, in situ production of industrially relevant metabolites, and use as probiotics or as efficient microbial cell factories. Genera of lactic acid bacteria important in food, showing changes in nomenclature from 1980 to 2000. Early work on LAB was mainly concentrated on those associated with dairy products and, with time, many commercial starter cultures were developed. O. oeni is the dominant bacterial species responsible for the malolactic fermentation that may occur spontaneously, or may be controlled by the addition of pure malolactic starter cultures of O. oeni. LAB are nonsporeforming, Gram-positive, catalase-negative without cytochromes, nonaerobic or aerotolerant, fastidious, acid tolerant, and strictly fermentative bacteria with lactic acid as the major end-product during sugar fermentation. Figure 1. As more genome sequences are characterized, additional systems and their regulation are being uncovered. Overlapping stress responses provide protection against multiple stress conditions. It is used as a synthetic intermediate in many organic synthesis industries and in various biochemical industries. Such variations bring substantial complexity and challenges to understanding the entire stress response of LAB. G.M.
New York: Marcel Dekker with permission from Marcel Dekker. Lactic acid bacteria (LAB) play a crucial role in the development of flavor (taste, retronasal odor, and orthonasal aroma) of several dairy systems, but because of the time frame over which ripening occurs, aged cheese presents by far the most complex system in terms of both flavor pathways and range of flavor outcomes. This reduces acidity and results in a smoother tasting wine. Lactic acid bacteria are found in fermented foods like yogurt and cheese. Many species of LAB, such as probiotics and antimicrobial, can also exert biopreservers and have functional properties. Lactic Acid Bacteria. We use cookies to help provide and enhance our service and tailor content and ads. Low-resolution dendrogram showing phylogenetic relationships between bacteria of the high- and low-G+C subdivisions of the Gram-positive division, based primarily on 16S rRNA sequence data. Despite the beneficial status of LAB, some psychrotrophic species may cause detrimental effects in packaged foods. The separation of the various genera of LAB from each other using conventional biochemical tests has always been problematic, since a certain overlapping of properties exists (Table 1). Nowadays, LAB comprise around 20 genera, of which Aerococcus, Carnobacterium, Enterococcus, Lactobacillus, Lactococcus, Leuconostoc, Oenococcus, Pediococcus, Streptococcus, Tetragenococcus, Vagococcus, and Weissella are considered as the principal LAB. They are therefore dependent on preformed amino acids being present in the growth medium as a source of nitrogen. Narvhus, L. Axelsson, in Encyclopedia of Food Sciences and Nutrition (Second Edition), 2003, Lactic acid bacteria (LAB) are responsible for a great diversification in the flavor and texture of food products due to their fermentation of food raw materials. J.P. Tamang, in Encyclopedia of Food Microbiology (Second Edition), 2014. This enzyme complex is capable of hydrolyzing oligopeptides produced by chymosin and plasmin activity on caseins to small peptides and amino acids. LAB are a metabolically and physiologically related group of Gram-positive, catalase-negative bacteria, which consist of both cocci and bacilliforms. Lactic Acid Bacteria. In: Salminen S and von Wright A (eds) Lactic Acid Bacteria. From concentrating on the reactions of the organisms in milk, interest was diverted into more diverse attributes and the taxonomy of the group was gradually mapped. Configuration of lactic acid produced from glucose. +, positive; −, negative; ±, response varies between species; ND, not determined. Some species of lactic acid bacteria also will produce metabolic compounds with antifungal properties that could be used to control fungal spoilage of food during storage. Lactic acid bacteria may also be involved in the direct reduction of procarcinogens, for example, by taking up nitrites and by reducing the levels of secondary bile salts (28).
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