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Lactic Acid Bacteria. Carbohydrate and Protein Metabolism. Cell Wall. Cell Membrane. Cytoplasm. Milk. Amino Acid Transport System. Amino Acids. Amino Acids. Di- and Tri- Peptidases. ?. Di/Tri Peptide Transport System. Di/Tri peptides. Di/Tri Peptides. ?. Smaller Oligo-

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Lactic Acid Bacteria

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Lactic acid bacteria l.jpg

Lactic Acid Bacteria

Carbohydrate and Protein Metabolism


Slide2 l.jpg

Cell Wall

Cell Membrane

Cytoplasm

Milk

Amino Acid

Transport

System

Amino Acids

Amino Acids

Di- and Tri-

Peptidases

?

Di/Tri

Peptide

Transport

System

Di/Tri

peptides

Di/Tri Peptides

?

SmallerOligo-

peptides

Peptidases

?

Oligopeptide

Transport

System

Oligopeptides

Large Oligo-

peptides

Proteinase

Casein


Lab proteolytic system l.jpg

LAB proteolytic system

  • Fastidious, cannot synthesize some amino acids

  • Utilize exogenous N source

  • Involves at least a cell wall/membrane associated proteinase

  • Amino acid, di, tri-peptide and oligopeptide transport systems

  • Di-, tri-peptidase, oligopeptase


Lab amino acid metabolism l.jpg

LAB amino acid metabolism

  • 20 basic amino acids

  • Amino acids can further be used as building blocks

  • Or going through metabolism, converting into other intermediates such as pyruvate (C3), oxaloacetic acid (C4), acetyl (C2)

  • The % of amino acids vary in casein and some insufficient for proper growth, so still rely on biosynthesis


Polysaccharide pectin cellulose starch glycogen cp l.jpg

Carbohydrate metabolism

Polysaccharide(pectin, cellulose, starch, glycogen, Cp)

Enzymes

Enzymes

PEP-PTS system

Disaccharide (C12)

Enzymes

Monosaccharide (C6)

Monosaccharide (C6)

PEP-PTS system

Enzymes

lactate (lactic acid), acetate (acetic acid), formate, CO2, diacetyl,


C6 monosaccharide metabolism glucose galactose fructose etc l.jpg

C6 monosaccharide metabolismGlucose, galactose, fructose, etc.


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C6

C5

FDP aldolase

PK

C2

LDH

2C3

C3


Homolactic fermentation of glucose embden meyerhof pathway glycolysis ldh l.jpg

Homolactic fermentation of Glucose(Embden-Meyerhof Pathway, Glycolysis+LDH)

Glucose

G-P

F-6-P

F-1,6-P

Dihydroxyacetone-P Glyceraldehyde (C3)

PEP

(2) Pyruvate

(2) Lactate

FDP aldolase

Products:

2ATP

2Lactate

Key enzymes

FDP aldolase

Lactate dehydrogenase

(C3)

Lactata dehydrogenase (LDH)

(C3)


Mixed acid fermentation alternative end products for pyruvate l.jpg

Mixed Acid Fermentation: Alternative end products for pyruvate

Glucose

FDP aldolase

Dihydroxyacetone-phosphate

Glyceralderhyde-3-phosphate

NAD+

NADH+H+

(2) ADP

(2) ATP

LDH

(2) ADP

(2) ATP

(2) Lactate

(2)Pyruvate

(2)CoA

(2)NAD+

(2)NADH+(2)H+

PFL

(2) Formate

(2) Acetyl-CoA

NADH+H+

NAD+

Acetaldehyde

Products:

3ATP

2 Formate

1 Ethanol

1 Acetate

Key enzymes

FDP aldolase

Pyruvate formate lyase (PFL)

Acetyl-phosphate

NADH+H+

NAD+

ADP

ATP

Ethanol

Acetate


Heterolactic fermentation of glucose pentose phosphate pathway l.jpg

Heterolactic Fermentation of Glucose (Pentose Phosphate Pathway)

Glucose

facultative anaerobic

Anaerobic, aero-tolerant

CO2

Ribulose-5-phosphate

Xylulose-5-phosphate

PK

Glyceralderhyde-3-phosphate

Acetyl-phosphate

Ethanol

Acetaldehyde

Acetate

Pyruvate

Products:

2ATP

2 CO2

1 Lactate

1 Acetate

Key enzymes

PK

LDH

(NADH oxidase)

LDH

Lactate


Slide11 l.jpg

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


Lactose utilization in lab l.jpg

Lactose utilization in LAB

  • Transport of lactose into cell

  • Hydrolysis of lactose

  • Metabolism of the monosaccharides

  • Efflux of lactic acid and protons from the cell

  • Unstable


Disaccharide metabolism lactose l.jpg

Disaccharide Metabolism(Lactose)


Sugar transport in lab l.jpg

Sugar

Sugar

Sugar1

H+

Sugar2

H+

F1F0

ATPase

Permease

Permease

EIIS

EIIIS

HPr

H+

Sugar

Sugar2

Sugar

EI

Sugar1

H+

Pyruvate

PEP

Sugar Transport in LAB

Symport

Antiport

PEP-PTS

Out

In

Energy

Source:

Proton Motive Force

(PMF:∆pH+∆ψ )

Concentration Gradient

(∆S1&∆S2 )

PEP


Transport hydrolysis systems l.jpg

Transport hydrolysis systems

  • The PEP-PTS system

    • PEP: phosphoenolpyruvate H2C=COPO32-COO-

    • PTS: phosphotransferase

    • Substrate specific system

      • EII, EIII induced synthesis by the specific sugar

      • EI, HPr soluble components


Transport hydrolysis systems17 l.jpg

Transport hydrolysis systems

  • The PEP-PTS system

    • Lactose phosphorylated during transport

    • Multicomponent group translocation system

      • Two cytoplasmic proteins: Enz I and HPr

      • Two lactose-specific components: the membrane-located LacE and the soluble phosphocarrier LacF (or Enz IIlac and Enz IIIlac)


Slide18 l.jpg

LACTOSE PEP-PTS SYSTEM

membrane

Medium

E-I

PEP

P-HPr

out

in

pyruvate

P-EI

HPr

LACTOSE

P-EIII-lac

EII-Lac

E-III-lac

Lactose-P

P-beta-Galactosidase

Galactose-6P

Glucose


Slide19 l.jpg

Pathways for Galactose and Lactose Catabolism

Galactose

Lactose

Galactose

PEP-PTS

Permease

PEP-PTS

Lactose-P

Galactose

Galactose-6P

P-beta-Gal

Gal-1P

Glucose

Tagatose-6P

Glu-1P

Glucose-6P

Glyceraldehyde-3P +DHAP

Tagatose 1,6-diP

Glycolysis


Primary and secondary transport systems l.jpg

Primary and secondary transport systems

  • Lactose translocated unmodified

  • Disaccharide hydrolysed by beta–galactosidase (lacz)

  • Primary-involve a sugar transport ATPase

    • Agrobacterium radiobacter, Strep. mutans

  • Secondary-couples with ions or other solutes

    • L. lactis ATCC 7962 (proton), E.coli (LacY)


Secondary transport systems l.jpg

Secondary transport systems

  • Secondary-couples with ions or other solutes

    • L. lactis ATCC 7962 (proton-coupled), E.coli (LacY)

    • LacS in Strep. thermophilus

      • Proton symport or lactose-galactose antiporter


Slide22 l.jpg

lactose

galactose

lactose

galactose

Bata-Gal

S. thermophilus

Lb. bulgaricus

Lb. acidophilus

Lb. lactis- don’t have the

ability to ferment galactose

glucose

glycolysis


Slide23 l.jpg

LACTOSE

Beta-Gal

LACTOSE

Gal

Glu

Gal-1-P

Glu-6-P

Glu-1-P

Glycolysis

Lb. helveticus


Proton pump l.jpg

Proton pump

  • Acid tolerant

    • Inside: pH ~5.3

    • Outside: pH~4.2


Summary l.jpg

Summary

  • Glucose fermentation

    • Homo- heterolactic fermentation

  • Lactose utilization trait unstable

  • Strain dependent diversified pathways

    • Transport, hydrolysis

  • Select for proper starters for specific application


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