Updates in the Metabolism of Lactic Acid Bacteria

Abstract

Lactic acid bacteria (LAB) are fermentative bacteria naturally dwelling in or intentionally added to nutrient -rich environments where carbohydrates and proteins are usually abundant. The effi cient use of nutrients and the concomitant production of lactic acid during growth endow LAB with remarkable selective advantages in the diverse ecological niches they inhabit. Besides lactic acid, LAB metabolism produces a variety of compounds, such as diacetyl, acetoin and 2 -3 -butanediol from the utilization of citrate, and a vast array of volatile compounds and bioactive peptides from the catabolism of amino acids. The enzymatic reactions of LAB metabolism further modify the organoleptic, rheological, and nutritive properties of the raw materials, giving rise to fi nal fermented products. Last decade witnessed an impressive amount of data on several aspects of LAB physiology and genetics. The latest knowledge was gathered through sequencing and analysis of LAB genomes, and the subsequent use of post -genomic techniques, such as proteomics, comparative genome hybridization, transcriptomics, and metabolomics. Manipulation of the metabolic pathways of LAB to improve their effi ciency in various industrial applications (as starters, adjunct cultures, and probiotics) was undertaken soon after the development of early engineering tools. The availability of complete genome sequences of different LAB species and strains has expanded our ability to further study LAB metabolism from a global perspective, strengthening a full exploitation of LAB ' s metabolic potential.

Lactic Acid Bacteria and Their Bacteriocins: A Promising Approach to Seafood Biopreservation

“…LAB are Gram (+), usually nonmotile, nonsporulating, catalase -negative, acid -tolerant, facultative anaerobic organisms and have less than 55 mol% G+C content in their DNA [60][61][62]. Except for a few species, LAB members are nonpathogenic organisms with a reputed generally recognized as safe status (GRAS).…”

“…An important characteristic used in the differentiation of the LAB genera is the mode of glucose fermentation under standard conditions. In this regard, the accepted definition is that given by Hommes and Vogel [64]: obligately homofermentative LAB are able to ferment hexoses almost exclusively to lactic acid by the Embden-Meyerhof-Parnas (EMP) pathway while pentoses and gluconate are not fermented as they lack phosphoketolase; facultatively heterofermentative LAB degrade hexoses to lactic acid by the EMP pathway and are also able to degrade pentoses and often gluconate as they possess both aldolase and phosphoketolase; finally, obligately heterofermentative degrade hexoses by the phosphogluconate pathway producing lactate, ethanol or acetic acid and carbon dioxide; moreover, pentoses are fermented by this pathway [62]. Several strains of groups 1 and 2 and some of the hetero fermentative group 3 are either used in fermented foods, but group 3 are also commonly associated with food spoilage.…”

“…However, from a practical, food-technology point of view, the following genera are considered the principal LAB: Aerococcus, Carnobacterium, Enterococcus, Lactobacillus, Lactococcus, Leuconostoc, Oenococcus, Pediococcus, Streptococcus, Tetragenococcus, Vagococcus, and Weissella [61]. The classification of lactic acid bacteria into different genera is largely based on morphology, mode of glucose fermentation, growth at different temperatures, configuration of the lactic acid produced, ability to grow at high salt concentrations, and acid or alkaline tolerance [62,63]. An important characteristic used in the differentiation of the LAB genera is the mode of glucose fermentation under standard conditions.…”

Exopolysaccharides of Lactic Acid Bacteria for Food and Colon Health Applications

“…EPS are classified into two groups: homo-EPS, consisting of a single type of monosaccharide ( -D-glucans, -D-glucans, fructans, and others represented by polygalactan) and hetero-EPS, composed of different types of monosaccharides, mainly D-glucose, D-galactose, L-rhamnose, and their derivatives [16].…”

Produção de bacteriocina por Bifidobacterium lactis a partir de soro de leite

“…Because of their high growth rate and productivity, microorganisms belonging to this genus are used in important industrial productions (Kyl€ a-Nikkil€ a, Hujanen, Leisola, & Palva, 2000) and make use of two main routes to ferment glucose (Gao et al, 2011;Mayo, Piekarczyk, Kowalczyk, Pablo, & Bardowski, 2010).…”