Bacteria in Food and Beverage Production

Abstract

Foods typically contain a variety of bacteria of which some may be beneficial, such as those preserving foods through products of fermentation, and others may be harmful by causing human illness or food spoilage. Lactic acid bacteria are among the most important groups of microorganisms used in food fermentations and are largely included in the genera Carnobacterium, Enterococcus, Lactobacillus, Lactococcus , Leuconostoc, Oenococcus, Pediococcus, Streptococcus, Tetragenococcus, Vagococcus, and Weissella. The essential feature of lactic acid bacteria metabolism is efficient carbohydrate fermentation coupled to substrate-level phosphorylation. These bacteria can degrade a variety of carbohydrates, with lactic acid being the predominant end product. Many lactic acid bacteria also produce bacteriocins that have antimicrobial activity that is antagonistic to other bacteria, especially toward bacteria closely related to the bacteriocin-producing strain. Bacteriocins are peptides that are produced ribosomally by bacteria and released extracellularly.

Starter cultures, which are largely comprised of lactic acid bacteria, are food-grade microorganisms that are used to produce fermented foods of desirable appearance, body, texture, and flavor. Types of fermented foods for which commercial starter cultures are currently used include dairy products (cheese, sour cream, yogurt), meat products (sausages), and vegetable products (pickles, sauerkraut, olives). For starter cultures to be effective during food fermentations, they must dominate over naturally occurring microflora and produce the desired end products of fermentation. Many of the activities essential for food fermentations, including lactose metabolism, proteinase activity, oligopeptide transport, bacteriophage-resistance mechanisms, bacteriocin production and immunity, bacteriocin resistance, exopolysaccharide production, and citrate utilization, are encoded on plasmids harbored by lactic acid bacteria. Advances in molecular technology have enabled the construction of superior strains of starter cultures for food fermentations. Improved features of these strains include bacteriophage resistance, genetic stability, and reduced variation and unpredictability in performance.

Another application for beneficial microbes used in foods is adding probiotic microorganisms to provide a health benefit to consumers. Many beneficial health effects for probiotics have been reported and include protection against enteric pathogens, improved digestion by means of enzymes to metabolize otherwise indigestible food nutrients (e.g., lactase to hydrolyze lactose in lactose intolerant consumers), stimulation of the intestinal immune system, and improvement of intestinal peristaltic activity. Lactic acid bacteria are the most common types of probiotic microbes being used. Probiotics have been largely delivered in fermented foods such as yogurt and fermented milk products; however, growing consumer interest in probiotics is leading to using other types of foods such as fruit and vegetable juices, cereal-based products, and even ice cream, as delivery vehicles.

Fermented foods are an important part of the food processing industry and of many consumers’ diets and are largely produced by lactic acid bacteria that have been selected for their ability to produce desired products or changes in the food. Many advances have been made during the past decade in developing improved bacterial strains for starter culture application, which largely have been made possible through advances in molecular technology. The use of lactic acid bacteria to enhance the quality and safety of foods is a rapidly evolving field. With the discovery of new bacteriocins and the development of more efficient approaches to deliver them to foods, the importance of lactic acid bacteria in preserving and providing enhanced safety of food will continue to increase for the foreseeable future.