alkane biodegradation

15
Alkane Biodegradation R. A. Kerr Science 329, 734-735 (2010)

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Page 1: Alkane Biodegradation

Alkane Biodegradation

R. A. Kerr Science 329, 734-735 (2010)

Page 2: Alkane Biodegradation

Alkanes

Alkane Formula Boiling point [°C]

Melting point [°C] Solubility at 20 °C

Methane CH4 -162 -182 gas

Ethane C2H6 -89 -183 63.7 gas

Propane C3H8 -42 -188 gas

Butane C4H10 0 -138 gas

Hexane C6H14 69 -95 12.3 liquid

Octane C8H18 126 -57 liquid

Nonane C9H20 151 -54 liquid

Decane C10H22 174 -30 0.05 liquid

Dodecane C12H26 216 -10 liquid

Hexadecane C16H34 287 19 5.2 x 10 -5 liquid

Icosane C20H42 343 37 3.1 x 10 -7 solid

Triacontane C30H62 450 66 solid

Tetracontane C40H82 525 82 solid

Pentacontane

C50H102 575 91 solid

Hexacontane C60H122 625 100 solid

• Saturated hydrocarbons• Large fraction of crude oil• Solubility decreases with chain

length (straight chains)• Can also be branched chains or

rings• Branched chains are more

difficult to degrade than straight chains

Page 3: Alkane Biodegradation

n-alkane aerobic degradation pathways

Callaghan 2006, Biodegradation 1990 1:79-92-oxidation

-oxidation

OH

H

O

OH

O

OHOH

O

OHH

O

O

OHOH

O

O

OH

O

H

OOH

OH

O

O

O

O

O

OH

O

OH+

Diterminal oxidation Terminal oxidation Subterminal oxidation

Page 4: Alkane Biodegradation

Aerobic degradation

http://2010.igem.org/Image:TUDelft_Alkane_degradation_route.png

• Oxygen-dependent reactions• Formation of fatty acids, followed by β-oxidation• Biosurfactants may be required before degradation can begin

Page 5: Alkane Biodegradation

Branched alkanes

• More difficult to degrade than n-alkanes

Appl. Environ. Microbiol. 2000;66:4462-4467

Page 6: Alkane Biodegradation

Alkane biodegradation-anaerobic

Environ. Microbiol. 2009 11(10):2477-2490

Page 7: Alkane Biodegradation

β-oxidation

http://nutrition.jbpub.com/resources/animations.cfm?id=23&debug=0

Page 8: Alkane Biodegradation

Bioremediation

http://www.nies.go.jp/kenko/biotech/bioehp/Topics1.html

Bioremediation – using biological systems to treat contaminated sites

Biodegradation – biological activity that results in the break down of a specific contaminant

Bioaugmentation – adding biodegrading organisms to the contaminated site (not genetically manipulated)

Biostimulation – adding nutrients like nitrogen or phosphorus in order to stimulate microbial activity

Page 9: Alkane Biodegradation

Case study: Deepwater Horizon

• Louisiana crude oil• Predominantly alkanes, lower

concentrations of aromatics• Oil in a large plume near the

wellhead, 1 km depth• Also surface oil, mobilized oil,

reaching shoreline/sensitive wetland areas

http://en.wikipedia.org/wiki/File:Deepwater_Horizon_offshore_drilling_unit_on_fire_2010.jpg April 21, 2010

http://1.bp.blogspot.com/_1p20WdeXKKs/TD-VPBQ7NuI/AAAAAAAAJao/7a_bs38l5jE/s200/GulfOilSpillCap1.jpg

Page 10: Alkane Biodegradation

Deepwater Horizon-physical/chemical remediation

• Burning – not environmentally smart – greenhouse gases, toxic chemicals released into the atmosphere

• Physical removal-does not remove all of the oil; there is water recovered as well, would need to be separated from the oil

• Chemical dispersion

http://advocacy.britannica.com/blog/advocacy/2010/06/catastrophe-in-the-gulf-2/

http://www.csmonitor.com/USA/2010/0530/BP-oil-spill-top-kill-failure-means-well-may-gush-until-August

http://beforeitsnews.com/story/99/939/What_Is_The_Corexit_Dispersant.html

Page 11: Alkane Biodegradation

E. Kintisch Science 329, 735-736 (2010)

Adding dispersant to gushing oil

Oil washing up in wetland area

Page 12: Alkane Biodegradation

Studying the spill

http://oceanexplorer.noaa.gov/explorations/03windows/logs/jul24/media/pushcorealvin.html

Sample collection

http://www.whoi.edu/dwhresponse/page.do?pid=43715&tid=201&cid=44272&ct=362#

http://www.whoi.edu/oceanus/viewSlideshow.do?clid=58913&aid=105249&mainid=159855&p=157273&n=159853

Page 13: Alkane Biodegradation

http://www.mpg.de/257961/Oil_degrading_bacteria?print=yes

• Bioavailability:– Bacteria are located at the oil-water interface, not inside the oil droplets– Smaller droplets (dispersed oil) give more surface area to increase

biodegradation. • Explosions in bacterial growth would deplete available

nutrients and ultimately slow degradation• Oxygen consumption – possible dead zones?• Sedimentation – deposition in anaerobic zones in sediment

Biodegradation concerns

Page 14: Alkane Biodegradation

Oil-degrading microbes• Hazen et al. (2010) found 2-fold higher cell

densities within the plume.• Enrichment in plume for Oceanospirillales• Some oxygen depletion in the plume, not

enough to create anoxic “dead zones”• Enough oxygen loss to indicate aerobic

activity• Increased degradation genes in plume

• Valentine et al. (2010) found oxygen depletion in the plume to be driven by ethane and propane metabolism

Image from Hoi-Ying Holman group)

Oil consuming bacteria on oil droplets, 1500x magnification © Johannes Zedelius, MPI Bremen

Page 15: Alkane Biodegradation

Results

http://www.msnbc.msn.com/id/21134540/vp/38853793#38853793