lactic acid

lactic acid

اسلاید 1: Lactic Acid BacteriaTaxonomy and energy metabolism

اسلاید 2: LABLactic acid bacteria (LAB) - “milk-souring organisms.” Gram positive NonsporulatingCatalase negativeAnaerobic but aerotolerant (facultative anaerobes)FastidiousLow mol% G+CAcid tolerantStrictly fermentative with lactic acid as the major end product during sugar fermentationSome other G+ also produce lactic acid (Bacillus, Listeria, Bifidobacterium)

اسلاید 3: Functions in the food chain Dairy starter culture Vegetable fermentationAlcoholic beverage fermentation (3/4)Meat fermentationCereal fermentationProbiotics

اسلاید 4: LAB Classification and IdentificationPhenotypic/biochemical charactersMorphologyMode of glucose fermentationGrowth at different temperaturesConfiguration of the LA producedAbility to grow at high salt concentrationsAcid or alkaline tolerance

اسلاید 5: Lactic Acid Bacteria: ClassificationChemotaxonomic markers Fatty acid composition, constituents of the cell wall etc.Phylogenetic clusters do not correlate with classification based on phenotypic charactersNew tools for classification and identification of LABNucleic acid probing techniquesPartial rRNA-gene sequencing using PCR (16S, 23S rRNA gene)Soluble protein patterns

اسلاید 6: Lactic Acid Bacteria: ClassificationBased on 16S rRNA gene sequence12 genera (Fig. 2-2)Streptococcus-Lactococcus branchLactobacillus branchLactobacillus-Pediococcus branchOenococcus-Leuconostoc-Weisella branchCarnobacterium-Aerococcus-Enterocccus-Tetragenococcus-Vagococcus The genus Bifidobacterium (G+C55-67%), often considered as LAB, is phylogenetically unrelated and has a unique mode of sugar fermentationBifidus pathway, fructose-6-phosphate shunt

اسلاید 7: Lactic Acid Bacteria: ClassificationAerococcus, Carnobacterium, Vagococcus, Enterococcus, Tetragenococcus, Leuconostoc, Oenococcus, Weissella, Lactobacillus, Lactococcus, Pediococcus, Streptococcus (Table 2-2)