CEE 370 Environmental Engineering Principles Lecture #13 - - PowerPoint PPT Presentation

David Reckhow CEE 370 L#13 1

CEE 370 Environmental Engineering Principles

Lecture #13 Environmental Biology II

Metabolism Reading: Mihelcic & Zimmerman, Chapter 5

Davis & Masten, Chapter 3

Updated: 16 October 2019

Print version

David Reckhow

CEE 370 L#13

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Environmental Microbiology

 Types of Microorganisms

 Bacteria  Viruses  Protozoa  Rotifers  Fungi

 Metabolism  Microbial Disease  Microbial Growth

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Metabolism

Metabolites (wastes)

Biosynthesis (Anabolism) Energy Production (Catabolism)

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An overview of metabolism

From: Sawyer, McCarty & Parkin, 1994; also: Sawyer & McCarty, 1978

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Energy

• Source
• Light
• Chemicals (e.g., glucose)
• Storage
• ATP
• NAD+
• Advantages of oxygen as a terminal electron acceptor
• aerobic
• anaerobic
• facultative

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ATP

7.3 kcal per mole

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Nicotinamide Adenine Dinucleotide

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Embden-Meyerhof Pathway

Glucose Fructose-1,6-diphosphate 2 Pyruvate

2 ATP 2 ADP 4 ADP 4 ATP 2 NAD+ 2 NADH

Investment Pay-back

Net result: 2 ATPs

• r 14.6 kcal/mole

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Advantages of Aerobic Systems

If we have aerobic metabolism, rather than fermentation, energy from NADH may be harvested.

NADH + H + 3 PO + 3ADP + O NAD+ + 3ATP + H O

+ 4 3- 2 2 12

→

This gives us 6 more ATPs. Then the pyruvate may be further

• xidized to carbon dioxide and water, producing 30 more
• ATPs. The final tally is 38 ATPs or 277 kcal/mole of glucose.

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Pathways

 Generalized

view of both aerobic and fermentative pathways

 Also showing

energy transfer

 ATP  NAD

From: Sawyer, McCarty & Parkin, 1994; also: Sawyer & McCarty, 1978

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Metabolic Classification

Carbon Source

Heterotrophic: other organic matter Autotrophic: inorganic carbon (CO2)

Energy Source (electron donor)

Chemosynthetic: chemical oxidation Photosynthetic: light energy

Terminal Electron Acceptor

Aerobic: oxygen Anaerobic: nitrate, sulfate Fermentative: organic compounds

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Energy Flow

 Storage of Energy

 Photosynthesis

 Release of Energy

 Respiration

 Energy transfers by organisms are

inherently inefficient

 5-50% capture

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Aerobic Respiration

 A Redox reaction

 Oxidation of Carbon  Reduction of oxygen or some other

terminal electron acceptor

− + +

+ → + e H CO O H O H C 4 4 ) (

2 2 2

O H e H O

2 2

2 4 4 → + +

− +

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Other TEA: Anaerobic Respiration

 Nitrate  Manganese  Iron  Sulfate  Fermentation

O H HCO CO N NO O H C

2 3 2 2 3 2 )

( + + + → +

− −

O H CO Mn Mn O H C

2 2 2 4 2 )

( + + → +

+ +

O H CO Fe Fe O H C

2 2 2 3 2 )

( + + → +

+ +

O H CO S H SO O H C

2 2 2 2 4 2 )

( + + → +

− 2 4 2 )

( CO CH O H C + →

Ecological Redox Sequence

methanogenesis

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Terminal Electron Acceptors

 Contribution to

the oxidation of

• rganic matter

 Bottom waters of

Onondaga Lake, NY

 (Effler, 1997) Aerobic 39% Nitrate Reduction 10% Sulfate Reduction 27% Iron Reduction 1% Methano- genesis 23%

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Energetics

 Principles of Gibbs

Free Energy and Energy Balance can be applied to microbial growth

From: Sawyer, McCarty & Parkin, 1994; also: Sawyer & McCarty, 1978

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Energetics Cont.

 Energy Balance

 Cell synthesis (Rc)  Energy (Ra)  Electron acceptor

(Rd)

From: Sawyer, McCarty & Parkin, 1994; also: Sawyer & McCarty, 1978

d a e c s

R R f R f R − + =

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f-values and Yield

 Portions of electron

donor used for:

 Synthesis (fs)  Energy (fe)

 Values are for

rapidly growing cells

From: Sawyer, McCarty & Parkin, 1994; also: Sawyer & McCarty, 1978

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Novel Biotransformations

 Oxidation

 Toluene dioxygenase (TDO)

From: Sawyer, McCarty & Parkin, 1994; also: Sawyer & McCarty, 1978

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Overall Types

Carbon Source

Heterotrophic Autotrophic

Energy Source

Chemosynthetic Photosynthetic

Photoheterotrophs (rare) Photoautotrophs (primary producers) Chemoheterotrophs (organotrophs) Chemoautotrophs (lithotrophs)

Nitrifying, hydrogen , iron and sulfur bacteria Most bacteria, fungi, protozoa & animals Cyanobacteria, algae & Plants Purple and green non- sulfur bacteria

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Enzyme Chemistry

 Highly dependent on:

 Temperature  pH

From: Sawyer, McCarty & Parkin, 1994; also: Sawyer & McCarty, 1978

Enzymatic Reactions

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 Many ways of illustrating the steps

 Substrate(s) bond to active site  Product(s) form via transition state  Product(s) are released

Basic Enzyme Kinetics

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 Irreversible

 Single intermediate

 The overall rate is determined by the RLS, k2  But we don’t know [ES], so we can get it by the SS mass

balance

 Again, we only know [Eo] or [Etot], not free [E], so:

] [ ] [ ] ][ [ ] [

2 1 1

ES k ES k S E k dt ES d − − = =

−

E + S ES → E + P

→ ←

k1 k-1 k2

] [ ] [ ] [

2 ES

k dt P d dt S d r = = − ≡

( )

] [ ] [ ] [ ] [ ] [

2 1 1

ES k ES k S ES E k

• −

− − =

−

Note that some references use k2 for k-1, and k3 for k2

Reactants, products and Intermediates

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24  Simple Progression of

components for simple single intermediate enzyme reaction

 Shaded block shows steady

state intermediates

 Assumes [S]>>[E]t  From Segel, 1975; Enzyme

Kinetics

Basic Enzyme Kinetics II

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 And solving for [ES],

] ][ [ ] [ ] [ ] ][ [

1 2 1 1

S E k ES k ES k S ES k

• =

+ +

− 2 1 1 1

] [ ] ][ [ ] [ k k S k S E k ES

• +

+ =

−

1 2 1

] [ ] ][ [ ] [

k k k

• S

S E ES

+

−

+ =

Michaelis-Menten

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 Irreversible

 Single intermediate

] [ ] [ ] [ ] ][ [ ] [

max 2

1 2 1

S K S r S S E k dt P d r

s k k k

• +

= + = ≡

+

−

E + S ES → E + P

→ ←

k1 k-1 k2

] [ ] [

2 ES

k dt P d r = ≡

1 2 1

] [ ] ][ [ ] [

k k k

• S

S E ES

+

−

+ =

Michaelis Menten Kinetics

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Substrate Concentration

20 40 60 80 100 120

Reaction Rate

20 40 60 80 100

rmax

0.5rmax

Ks

 Classical substrate plot

] [ ] [ ] [

max

S K S r dt P d r

s +

= ≡

Maud Menten

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Substrate and growth

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29  If we consider Y  We can define a microorganism-specific substrate

utilization rate, U

 And the maximum rates are then

] [ ] [ ] [ 1

max

S K S dt X d X

s +

= ≡ µ µ dt dX Y dt S d dt P d r 1 ] [ ] [ = − = ≡

Y YX dt dX X r U µ ≡ = ≡ Y k U

max max

µ ≡ ≡

] [ ] [ ] [ 1 S K S k dt S d X U

s +

= ≡

and

Linearizations

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 Lineweaver-Burke

 Double reciprocal plot

Wikipedia version Voet & Voet version

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