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Lactic Acid Bacteria

Lactic Acid Bacteria. Lactococcus lactis (L. lactis, Lc. Lactis). L. lactis subsp. lactis. L. lactis subsp. cremoris. L. lactis subsp. diacetylactis. + - - - - - - + - - - - -. + + - + - + + + + + + +. + + - + - + + + + - - + +. Growth at 10C

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Lactic Acid Bacteria

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  1. Lactic Acid Bacteria

  2. Lactococcus lactis(L. lactis, Lc. Lactis) L. lactis subsp. lactis L. lactis subsp. cremoris L. lactis subsp. diacetylactis + - - - - - - + - - - - - + + - + - + + + + + + + + + - + - + + + + - - + + Growth at 10C Growth at 40C Growth at 45C Growth in 4% NaCl Growth in 6.5% NaCl Growth at pH 9.2 Growth with methylene blue (0.1% milk) Growth in the presence of bile (40%) NH3 from arginine CO2 from citrate Diacetyl and acetoin Ferment of maltose Ferment ribose

  3. Lactococci as components of starter cultures for fermented dairy products Type of product Composition of starter culture 1. Cheese types without eye formation (Cheddar, Camembert, Tilsit) 2. Cottage cheese, quarg, fermented milks, cheese types with few or small eyes (e.g. Edam) 3. Cultured butter, fermented milk, buttermilk, cheese types with round eyes (e.g. Gouda) 4. Taette (Scandinavian ropey milk) Lc. lactis subsp. cremoris, 95-98%, Lc. lactis subsp lactis, 2-5% Lc. lactis subsp. cremoris, 95%, Leuc. Mesenteroides subsp. cremoris, 5%; or Lc. lactis subsp. cremoris, 85-90%, Lc. lactis subsp. lactis 3%; Leuc. mesenteroides subsp. cremoris 5% Lc. lactis subsp. cremoris, 70-75%, Lc. lactis subsp. diacetylactis, 15-20%; Leuc. Mesenteroides subsp. cremoris, 2-5%. Lc. lactis subsp. cremoris (ropey strain) From Teuber, in The Genera of Lactic Acid Bacteria

  4. Lactobacillus spp. • Group A • Obligately homofermentative lactobacilli • 6C to LA by glycolysis (EMP), possess fructose-1,6-bisphosphate-aldolase (FDP), but lack phosphoketolase (PK) • Group B • Facultative heterofermentative • EMP most, also possess FDP and PK • Group C • Obligately heterofermentative Lactobacillus delbrueckii subsp. Bulgaricus, by Broadbent

  5. Lactobacillus spp. • G+ • Non-spore forming • Rods or coccobacilli • G+C usually below 50% • Strictly fermentative, aero-tolerant or anaerobic • Aciduric or acidophilic • Complex nutritional requirements (carb, aa, peptides, FA, salts, nucleic acid derivatives, vit) • Homo or heterofermentative

  6. Lb. casei, by Broadbent Group I obligately homofermentative Group II facultatively heterofermentative Group III obligately heterofermentative Character Arrangement of the Genus Lactobacillus - - - + - Lb. acidophilus Lb. delbruckii Lb. helveticus Lb. salivarius + - + + + Lb. casei Lb. curvatus Lb. plantarum Lb. sake + + + - + Lb. brevis Lb. buchneri Lb. fermentum Lb. reuteri Pentose fermentation CO2 from glucose CO2 from gluconate FDP aldolase present Phosphoketolase present

  7. Streptococcus thermophilus • Also mentioned as S. salivarius subsp. Thermophilus • Grow at 45C, and some even grow at 50C • No growth in 0.1% methylene blue or at pH9.6 • Used in yogurt fermentation with Lb. delbrueckii subsp. Bulgaricus • Also used in cheese making S. thermophilus, by Broadbent

  8. Pediococccus spp. • Tetrads via cell division in two perpendicular directions in a single plane • Acid tolerant, cannot synthesize porphyrins, lactic acid as major metabolic end product • Strictly fermentative (homo) facultative anaerobic • Need rich media (N, aa, nicotinic acid, pantothenic acid, biotin, some require other Vit) • Catalase- (some Pseudo+) • G+C 34-44% • Surface of plants and fruits • Become predominant microflora in fermenting plant materials (silage, sauerkraut, olives, etc.) • Diversified, some grow in beer, soy sause • BeerAlso found in cured meat, raw sausages, and marinated fish, and used in biotechnological processing and preservation of foods By Broadbent, USU, NCBI microbial genome

  9. Leuconostoc spp. • G+, non-motile, shape vary with growth condition • Complex nutrient requirement • Facultative heterofermentative anaerobes, • Optimal growth pH 6-7 except acidophilic species • L. mesenteroides stops around pH 5.4-5.7 • L. mesenteroides subsp. mesenteroides associated with sauerkraut (pickled cabbage) and dill pickle fermentation • It also produces exopolysaccharides such as dextran (polymer production) applications in cosmetics, medical, and creation of sephadex gels and beads DOE JGI

  10. Industry Applications of LAB • Mesophilic and thermophilic starters used by dairy industry • Mesophilic: acid-forming lactococci and often flavor producers • Thermophlic: yogurt and cheese varieties with high cooking temperatures • Starter functions • Acid production • Proteolytic activity • Aroma formation • Exopolysaccharide formation • Production of inhibitory compounds

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