Bioenergetics Lecture of May 28, 2009

Introduction to bioenergetics.

The thermodynamics of biological energy production

Kinetic aspects of bioenergetic processes

The molecular and cellular organization of bioenergetic systems

Photosynthesis

Respiration and ATP synthesis

Haber-Bosch process and biological nitrogen fixation

Bi i

Biomass conversion

The Nitrogen Cycle

Rhizobiumrootroot

nodulesBlue-green

algaealgae

Soil bacteria

http://web.ead.anl.gov/ecorisk/fundamentals/html/ch1/fig1.7.htm

Biological Nitrogen Cycle

ANAMMOX Process: anaerobic ammonia oxidation

NH4 + NO2- N2 + H2O

Di d i t t t t t l t• Discovered in wastewater treatment plants• Developed as a new low-cost method for

N-removal in wastewater treatment

• Largest single source of dinitrogen gas on Earth• Brocadia anammoxidans, Kuenenia stuttgartiensis and Scalindua sorokinii.Brocadia anammoxidans, Kuenenia stuttgartiensis and Scalindua sorokinii.

l dd li id f d iladderane lipids found inlipid bilayer of anammoxosome

www.anammox.com

atmospheric N2 reservoir - 4 x 109 Mt

magnitudes of nitrogen fixation processes

i d t i l (H b B h ) 80 Mt N/industrial (Haber-Bosch process) ~80 Mt N/year

biological nitrogen fixation ~140 Mt N/year

Thermodynamics of NH3 synthesis

1/2 N2 + 3/2 H2 NH3/ 2 3/ 2 3

∆G˚ = -16.5 kJ/mole 298 K, 1 atm

∆H˚ = 46 1 kJ/mole∆H = -46.1 kJ/mole

K decreases as T increases lnK( / )

H

0(1/T) R

0˚)ln(

VP

KRTPG

K increases as P increasesPP

Haber - Bosch process - industrial synthesis of ammonia

although the equilibrium favors ammonia synthesis at low T, 1/2 N2 + 3/2 H2 NH3 ∆G˚ = -16.5 kJ/mole

g ythe reaction rate with non-biological catalysts is quite low

high temperatures are required to get reasonable rates high temperatures are required to get reasonable rates

but, at high temperatures, the equilibrium favors reactants

high pressures are required to shift the equilibrium to NH3

t i l diti l d i th H b B htypical conditions employed in the Haber-Bosch processare T ~ 450˚C, P ~ several 100 atm

[see V. Smil “Enriching the Earth: Fritz Haber, Carl Bosch and the Transformation of World Food Production” MIT Press (2001)]

P, T dependence of NH3 synthesis

brief history of nitrogen fixation and the Haber-Bosch process

• traditional sources of fixed nitrogen - agriculturally derivedtraditional sources of fixed nitrogen agriculturally derived

• 1800’s guano and sodium nitrate from South America

b 1900’ d d• by 1900’s - new sources needed

synthesis of ammonia from Nsynthesis of ammonia from N2

Fritz Haber 1904 - study of the N2/H2/NH3 equilibrium

W lt N t bli l iti i d H b ’ ltWalter Nernst - publicly criticized Haber’s results as strongly inaccurate; states conditions are much less favorable for NH3 synthesis3 y

Haber, determined to vindicate himself, on July 2, 1909 perfected his bench-top apparatus and demonstrated the potential of high-pressure synthesis of ammonia

Osmium metal catalyst

Carl Bosch Solved the engineering challenges of handling large volumes of corrosive gases under both high temperature and high pressure -developments that opened up a new field of large-scale, high pressure synthesis.

Alwin Mittasch identified the optimum catalysts that are till ti ll i t dstill essentially in use today:

Catalyst: iron (II / III)-oxide Fe3O4, plus % O % C O % O % S O

1910, pilot plant operational at BASF

0.5-1.2% K2O, 2-3.5% CaO, 2-4% Al2O3 and 0.2-0.5% SiO2

1914, production plant in operation

with the outbreak of World War I the role of ammonia synthesiswith the outbreak of World War I, the role of ammonia synthesis changed from fertilizer to munitions

Nobel Prizes in Chemistry

1918 - Haber - “an exceedingly important means of improving 9 8 abe a e ceed g y po ta t ea s o p o gthe standards of agriculture and the well-being of mankind”

1931- Bosch - “for originating and developing chemical high-pressure methods”

Ammonia Plant, Modderfontein, South Africaproduction 100 000 metric tons NH3/year

Principal stages of natural gas-based NH3 synthesis

Synthetic steps reflects requirement for pure reactants to

Reforming reaction:

Synthetic steps reflects requirement for pure reactants to prevent catalyst poisoning.

CH4 + H2O CO + 3H2 ∆H˚ = +206 kJ/mole

this step is the single largest consumer of energyp g g gy

secondary reforming - reduces amount of unconverted CH4(5-15% of the gas) CH4 + 2O2 CO2 + 2H2O

Shift reaction - converts CO (catalyst poison)

CO + H2O CO2 + H2

(remove CO )(remove CO2)

methanation - the reverse of reforming;methanation the reverse of reforming;

converts residual CO and CO2 to CH4

synthesis gas: 74% H2, 24% N2, 0.8% CH4, 0.3% Ar

compressed, stripped of H2O and fed to converter

conversion to NH utilizes a metallic iron catalyst plusconversion to NH3 utilizes a metallic iron catalyst, plus additives

exit gas (12-18% NH3) is cooled to -33˚C (boiling pt)

unreacted synthesis gas is recompressed and recycled

Annual production of NH3 by the Haber-Bosch process:

100 x 106 metric tons NH3/year (1 metric ton = 1000 kg)

one of very top volume chemical industries

Energy cost ~ 40 GJ/metric ton NH3gy 3

(theoretical minimum ~ 20 GJ/metric ton)

consumes ~ 1.3% of all energy derived from fossil fuels

(if all the energy for nitrogen fixation came from natural gas, ( gy g gthis would represent 5% of the annual global consumption)

K ll B & R t d i dKellogg, Brown & Root designed plants account for more than half the worlds NH3 capacity added 3since the mid-1960’s

Bi l f Nit Fi tiBiology of Nitrogen Fixation

• Reduced N is an essential component of proteins, nucleic acids and other biomolecules

• Atmospheric N2 provides an abundant reservoir of nitrogen

• But, most organisms are unable to access this source; the gexceptions are: diazotrophic bacteria that can

reduce N2 to ammonia.

• These bacteria contain the nitrogenase enzyme system

Nitrogenase and Biological Nitrogen Fixation

+2 ATPreduced

oxidized+ 2 ADP

reducedN2H+

reduced

ferredoxinFe protein

-2 ADPoxidized

reduced+ 2 ATP

Fe-proteinMoFe-protein

oxidized NH3oxidized + 2 ATP H2

N + 10H+ + 8 Fdred + 16ATP 2NH + + H + 16ADP + 8 FdoxN2 + 10H+ + 8 Fdred + 16ATP 2NH4+ + H2 + 16ADP + 8 Fdox

(Mg2+)

Nitrogenase molybdenum-iron (MoFe-) protein

pdb id 1M1N

[]2 MoFe Protein has two independent active sites

[8Fe:7S]

• electron transfer betweenelectron transfer betweenthe Fe protein and the FeMocofactor

• rearrangement of two Featoms upon oxidation

Nit t i l d i llNitrogenase system is a large drain on cell resources:Requires iron, and reaction uses 16 ATP and 8e- per dinitrogen

molecule

FeMo-cofactor7Fe:9S:1Mo:homocitrate and central (nitrogen?) ligand

…Nitrogenase also produces hydrogen

Biological Hydrogen Production: HydrogenasesBiological Hydrogen Production: Hydrogenases

Three types: [FeS], [NiFe] and [FeFe] hydrogenasesyp [ ], [ ] [ ] y gOxygen sensitive!! NiFe is fastestRequire biogenic proteins to make active site

Recently, can be expressed in E. coli : only three proteins necessary develop system to produce

f ( )hydrogen from waste (anaerobically)

Improve Hydrogenases for hydrogen production:1. Engineer enzymes to be less sensitive to oxygen2. Directly connect hydrogenase to photosystem I (e- source)2. Directly connect hydrogenase to photosystem I (e source)3. Increase rate of enzyme

Nitrogen fixation + Carbon fixation

Plant growthCarbon Storage

Starches, Oils Cellulose / Lignin

Pre-treatment of lignocellulose

( l ) $

almost all renewable fuels and chemicals are usually based on food resources such as starch,

(costly) $sugars, and oils

Sugars for fermentation,Chemicals

Dry-milling of Corn

Wet-milling of Corn

Examples of chemicalsproduced by fermentationsproduced by fermentations

Fermentation productsFermentation productsFermentation products considered commodityChemicals:

Fermentation products considered commodityChemicals:

ethanolmonosodium glutamateethanolmonosodium glutamatecitric acidlysinegluconic acid

citric acidlysinegluconic acidg uco c ac dg uco c ac d

New developments in fractionation of lignocellulose tosimple sugars may increase production of

lactic acidlactic acid2,3 butanediolbutanolitaconic aciditaconic acidpropanediol…

…any molecule that you can engineer microbes to produce

Biodiesel from vegetable oils and algae

• For industrial biodiesel production, homogeneous basic catalysts, including KOH, NaOH, potassium and sodium alkoxides, are commonly used for the transesterification of vegetable oils with methanol toused for the transesterification of vegetable oils with methanol to produce fatty acid methyl esters (better known as biodiesel).

• Base-catalyzed process has drawbacks, such as difficulty in recycling

• Lipases can also catalyze the transesterification of oil with methanol toproduce fatty acid methyl esters

Base catalyzed process has drawbacks, such as difficulty in recycling catalyst and environmental pollution.

produce fatty acid methyl esters

• Biodiesel production produces glycerol as a by-product

• Some naturally occurring algae produce an excess of lipids and thus can produce oil at near-theoretical limitsand thus can produce oil at near theoretical limits.

• Algae small size (less than 30 microns) • Ideal for a large-scale, closed production system called a photobioreactor

Chemical Transformation of LignocellulosicBiomass into Furans for Fuels and ChemicalsBiomass into Furans for Fuels and Chemicals

5-hydroxymethylfurfural (HMF)• HMF is a hexose dehydration product• HMF can be converted into a variety of useful acids, aldehydes,

alcohols, amines, and the promising fuel 2,5-dimethylfuran (DMF)

J. Am. Chem. Soc., 2009, 131 (5) 1979-1985

The Tragedy of Fritz HaberNobel Laureate Transformed World Food Production, Warhttp://www.npr.org/programs/morning/features/2002/jul/fritzhaber/

industrial ammonia synthesis l ti i d i lt i th 20threvolutionized agriculture in the 20th

century

responsible for the huge explosion in the earth’s population

responsible for prolonging World War I by providing a synthetic route to the production of ammonia for the

nobel e-museumproduction of ammonia for the manufacturing of explosives

“Haber earned a Nobel prize for his work with nitrogen. But it's not his only legacy. He pioneered the use of chemical warfare in World y g y pWar I.

Like Einstein, Haber was Jewish and German; unlike Einstein, he converted to Christianity and was a German patriot. When the war y pturned into a stalemate, with both sides stuck in trenches, Haber tried to break the deadlock with chemistry. His idea: to use poison gas to destroy enemy trenches.

"Haber actually insisted on this," says biographer Margit Szöllösi-Janze. "He said, if you want to win the war, then please, wage chemical warfare with conviction.”

On April 22, 1915, Haber was at the front lines directing the first gas attack in military history. About 150 tons of chlorine blew across the fields of Flanders, Belgium, spreading panic and death among the British and French soldiers opposing the German forces.”

http://www.npr.org/programs/morning/features/2002/jul/fritzhaber/

ti t d lti f h i l f i W ldestimated casualties of chemical warfare in World War I were 1.3 million

Haber continuedHaber, continued

April 22, 1915 first use of Cl2 in chemical warfare

1919 received Nobel Prize for 1918 (awarded 1920)

May 2, 1915 wife Clara Haber committed suicide

1919 received Nobel Prize for 1918 (awarded 1920)

Haber suffered from chronic depression

resigned from Kaiser Wilhelm Institute in 1933 as an employee of “non-Aryan descent”

died 1934 “his spirit broken by his rejection by the

went into exile in Paris and Cambridge

died 1934 his spirit broken by his rejection by the Germany he had served so well” (Nobel biography)

Haber Nobel Lecture

New forms of Photosynthesis: a oxidize arsenica. oxidize arsenic b. oxidize nitrite to nitrate

See: Science 316: 1870 (2007)Science 321: 967 (2008)( )

Microbial Mediated Iron Redox Cycle

Inorganic electron donersInorganic electron doners

Banded Iron Formations (BIF)

Nature Reviews Microbiology 4: 752-764

120˚ steps = 90˚ (ATP binding) +120 steps = 90 (ATP binding) + 30˚ (product release?) steps

( ibl 80˚ 40˚)

Nature 410, 898 (2001)

(possibly 80˚ + 40˚)