Document Type
Article
Publication Date
9-20-1989
Publication Title
Applied and Environmental Microbiology
Department
Thayer School of Engineering
Abstract
Fermentation of dilute-acid-pretreated mixed hardwood and Avicel by Clostridium thermocellum was comparedinbatchandcontinuouscultures.Maximumspecificgrowthratesper hourobtainedon cellulosic substrateswere 0.1inbatchcultureand>0.13incontinuousculture.Cellyields(gramsofcellsper gram of substrate)inbatchculturewere 0.17forpretreatedwoodand0.15forAvicel.Ethanolandacetatewere the mainproductsobservedunderalconditions.Ethanol:acetateratios(ingrams)were approximately1.8:1in batchcultureand generallyslightlylessthan 1:1incontinuousculture.Utilizationofcellulosicsubstrateswas essentially complete in batch culture. A prolonged lag phase was initialy observed in batch culture on pretreated wood; the length of the lag phase could be shortened by addition of cell-free spent medium. In continuousculturewith-5g ofglucoseequivalentper literinthefeed,substrateconversionrelativeto theoreticalrangedfrom0.86ata dilutionrate(D)of0.05/hto0.48ata D of0.167/hforAvicelandfrom0.75 ata D of0.05/hto0.43ata D of0.11/hforpretreatedwood.Atfeedconcentrationsof<4.5g ofglucose equivalentperliter,conversionofpretreatedwoodwas80to90%atD= 0.083/h.Lowerconversionwas obtainedathigherfeedsubstrateconcentrations,consistentwitha limitingfactorotherthancellulose.Free Avicelaseactivitiesof12to84mU/mlwere observed,withactivityincreasinginthisorder:batchceliobiose, batchpretreatedwood< batchAvicel,continuouspretreatedwood< continuousAvicel.Freecellulaseactivity was higheratincreasingextentsofsubstrateutilizationforbothpretreatedwoodandAvicelunderal conditions tested. The results indicate that fermentation parameters, with the exception of free cellulase activity,are essentiallythesame forpretreatedmixedhardwoodandAvicelundera varietyofconditions. HydrolysisyieldsobtainedwithC.thermocellumcellulaseactingeitherinvitroor invivowere comparableto thosepreviouslyreportedforTrichodermareeseion thesame substrates.
Fermentation of dilute-acid-pretreated mixed hardwood and Avicel by Clostridium thermocellum was comparedinbatchandcontinuouscultures.Maximumspecificgrowthratesper hourobtainedon cellulosic substrateswere 0.1inbatchcultureand>0.13incontinuousculture.Cellyields(gramsofcellsper gram of substrate)inbatchculturewere 0.17forpretreatedwoodand0.15forAvicel.Ethanolandacetatewere the mainproductsobservedunderalconditions.Ethanol:acetateratios(ingrams)were approximately1.8:1in batchcultureand generallyslightlylessthan 1:1incontinuousculture.Utilizationofcellulosicsubstrateswas essentially complete in batch culture. A prolonged lag phase was initialy observed in batch culture on pretreated wood; the length of the lag phase could be shortened by addition of cell-free spent medium. In continuousculturewith-5g ofglucoseequivalentper literinthefeed,substrateconversionrelativeto theoreticalrangedfrom0.86ata dilutionrate(D)of0.05/hto0.48ata D of0.167/hforAvicelandfrom0.75 ata D of0.05/hto0.43ata D of0.11/hforpretreatedwood.Atfeedconcentrationsof<4.5g ofglucose equivalentperliter,conversionofpretreatedwoodwas80to90%atD= 0.083/h.Lowerconversionwas obtainedathigherfeedsubstrateconcentrations,consistentwitha limitingfactorotherthancellulose.Free Avicelaseactivitiesof12to84mU/mlwere observed,withactivityincreasinginthisorder:batchceliobiose, batchpretreatedwood< batchAvicel,continuouspretreatedwood< continuousAvicel.Freecellulaseactivity was higheratincreasingextentsofsubstrateutilizationforbothpretreatedwoodandAvicelunderal conditions tested. The results indicate that fermentation parameters, with the exception of free cellulase activity,are essentiallythesame forpretreatedmixedhardwoodandAvicelundera varietyofconditions. HydrolysisyieldsobtainedwithC.thermocellumcellulaseactingeitherinvitroor invivowere comparableto thosepreviouslyreportedforTrichodermareeseion thesame substrates.
Original Citation
Lynd LR, Grethlein HE, Wolkin RH. Fermentation of Cellulosic Substrates in Batch and Continuous Culture by Clostridium thermocellum. Appl Environ Microbiol. 1989;55(12):3131-3139. doi:10.1128/AEM.55.12.3131-3139.1989
Dartmouth Digital Commons Citation
Lynd, Lee R.; Grethlein, Hans E.; and Wolkin, Richard H., "Fermentation of Cellulosic Substrates in Batch and Continuous Culture by Clostridium thermocellum" (1989). Dartmouth Scholarship. 502.
https://digitalcommons.dartmouth.edu/facoa/502
