bio_chapter_7_anaerobic_processes

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1、SEUSummerCourse2012Dr.FrancisL.delosReyesIIINorthCarolinaStateUniversityANAEROBICMETABOLISMOTHERELECTRONACCEPTORS3+2+1.Ferricreduction(Fe)Ferrous(Fe);ΔE˚’=+0.2Va.Electrontransportsystemterminateinaferricironreductasesystemb.GeneratesATPbyPMFc.Example:Shew

2、anellaputrefaciens,Geobactermetallireducenscanusetoluenease.d.2.+4+2ManganesereductionMnMna.ΔE˚’=0.798Vb.Shewanellaputrefaciens--3.ChloratereductionClO3Cl;ΔE˚’=1.03V4.ArsenateArsenite;ΔE˚’=0.139V5.Selenateselenite;+0.475V6.Organicsa.Dimethylsulfoxide

3、dimethylsulfide;+0.16Vb.Trimethylamine-N-oxide(TMAO)trimethylamine(TMA);+0.13Vc.FumarateSuccinate;+0.03VMethanogenesis4H2+CO2CH4+2H2OΔG°"=-32.5kcal/reaction+4H28H=>PMF--8euniqueecarriersCO2CH4+2H2O+42electronsatatime:CO2CH4+-1.CoenzymeF420:H22H+2e(fluore

4、scesat420nm)SEUSummercourse©F.L.delosReyesIII12.CoenzymeF430:highnickelrequirement-2eLaststep:-CH3CH4Methylreductase3.CoenzymeM(COM-SH)XCH3XCoMSHCOM–S–CH3(methylCoM)⇓-+CH4PMF2e+2HBottomline:PMFismadeinlaststep.NoCH4,noATP,nogrowth.Forcoenzymes,methanogensr

5、equire:Ni=>F430Fe=>ferredoxinCo=>VitaminB12ATPsynthesis:ΔG=ΔG°"+RTln[CH4]4-[H2][HCO3]ΔG=-32.5+0.592ln0.6-44(10)(0.01)ΔG=-8.3kcalbarelyenoughtoget1ATP/moleofCH4produced.SEUSummercourse©F.L.delosReyesIII2SEUSummercourse©F.L.delosReyesIII3SEUSummercourse©F.L.

6、delosReyesIII4SEUSummercourse©F.L.delosReyesIII5A.Overviewofanaerobicdigestiona.HydrolysisCarbohydratesProteinsLipidse.g.Lignocellulosicmaterialpeptides&Longchainfattyacidsaminoacidsgalactose&glycerolcellulosehemicelluloselignincellobiosepentoses,hexoses,&

7、glucoseb.Fermentationc.Acetogenesisd.MethanogenesisMainPoints:-differentgroupsofmicroorganisms-syntrophicassociation-methanogenesisisrate–limiting.Slowgrowthrates,pH-dependentSEUSummercourse©F.L.delosReyesIII6SEUSummercourse©F.L.delosReyesIII7Fermentation:

8、-metabolites(organiccompounds)areelectronsinksStartwithglycolysis:+Hexose+2NAD2pyruvate+2ATP+2NADHRequirements:+1.RegenerateNAD.2.MaygetadditionalATPMajorFermentations:-Homolacticacid-Aceticacid-Homoaceticaci