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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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Lactococcus lactis l lactis lc lactis l.jpg
Lactococcus lactis(L. lactis, Lc. Lactis)

L. lactis subsp.

lactis

L. lactis subsp.

cremoris

L. lactis subsp.

diacetylactis

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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


Lactococci as components of starter cultures for fermented dairy products l.jpg
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


Lactobacillus spp l.jpg
Lactobacillus dairy products 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


Lactobacillus spp5 l.jpg
Lactobacillus dairy productsspp.

  • 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


Slide6 l.jpg

Lb. casei dairy products, by Broadbent

Group I

obligately

homofermentative

Group II

facultatively

heterofermentative

Group III

obligately

heterofermentative

Character

Arrangement of the Genus Lactobacillus

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Lb. acidophilus

Lb. delbruckii

Lb. helveticus

Lb. salivarius

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Lb. casei

Lb. curvatus

Lb. plantarum

Lb. sake

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Lb. brevis

Lb. buchneri

Lb. fermentum

Lb. reuteri

Pentose fermentation

CO2 from glucose

CO2 from gluconate

FDP aldolase present

Phosphoketolase present


Streptococcus thermophilus l.jpg
Streptococcus thermophilus dairy products

  • 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


Pediococccus spp l.jpg
Pediococccus dairy products 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


Leuconostoc spp l.jpg
Leuconostoc dairy products 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


Industry applications of lab l.jpg
Industry Applications of LAB dairy products

  • 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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