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Full-Text Articles in Microbiology
Both Adhe And A Separate Nadph-Dependent Alcohol Dehydrogenase Gene, Adha, Are Necessary For High Ethanol Production In Thermoanaerobacterium Saccharolyticum, Tianyong Zheng, Daniel G. Olson, Sean J. Murphy, Xiongjun Shao, Liang Tian, Lee Lynd
Both Adhe And A Separate Nadph-Dependent Alcohol Dehydrogenase Gene, Adha, Are Necessary For High Ethanol Production In Thermoanaerobacterium Saccharolyticum, Tianyong Zheng, Daniel G. Olson, Sean J. Murphy, Xiongjun Shao, Liang Tian, Lee Lynd
Dartmouth Scholarship
Thermoanaerobacterium saccharolyticum has been engineered to produce ethanol at ∼90% theoretical yield and titer of 70 g/L. Its ethanol-producing ability has drawn attention to its metabolic pathways, which could potentially be transferred to other organisms of interest. Here we report that the iron-containing AdhA is important for ethanol production in the high-ethanol strain of T. saccharolyticum (LL1049). A single-gene deletion of adhA in LL1049 reduced ethanol production by ∼50%, whereas multiple gene deletions of all annotated alcohol dehydrogenases except adhA and adhE did not affect ethanol production. Deletion of adhA in wild-type T. saccharolyticum reduced NADPH-linked ADH activity (acetaldehyde-reducing) by …
Deletion Of Nfnab In Thermoanaerobacterium Saccharolyticum And Its Effect On Metabolism, Jonathan Lo, Tianyong Zheng, Daniel G. Olson, Natalie Ruppertsberger, Shital Tripathi, Adam Guss, Lee Lynd
Deletion Of Nfnab In Thermoanaerobacterium Saccharolyticum And Its Effect On Metabolism, Jonathan Lo, Tianyong Zheng, Daniel G. Olson, Natalie Ruppertsberger, Shital Tripathi, Adam Guss, Lee Lynd
Dartmouth Scholarship
NfnAB catalyzes the reversible transfer of electrons from reduced ferredoxin and NADH to 2 NADP+. The NfnAB complex has been hypothesized to be the main enzyme for ferredoxin oxidization in strains of Thermoanaerobacterium saccharolyticum engineered for increased ethanol production. NfnAB complex activity was detectable in crude cell extracts of T. saccharolyticum. Activity was also detected using activity staining of native PAGE gels. The nfnAB gene was deleted in different strains of T. saccharolyticum to determine its effect on end product formation. In wild-type T. saccharolyticum, deletion of nfnAB resulted in a 46% increase in H2 formation but …
The Bifunctional Alcohol And Aldehyde Dehydrogenase Gene, Adhe, Is Necessary For Ethanol Production In Clostridium Thermocellum And Thermoanaerobacterium Saccharolyticum, Jonathan Lo, Tianyong Zheng, Shuen Hon, Daniel G. Olson, Lee Lynd
The Bifunctional Alcohol And Aldehyde Dehydrogenase Gene, Adhe, Is Necessary For Ethanol Production In Clostridium Thermocellum And Thermoanaerobacterium Saccharolyticum, Jonathan Lo, Tianyong Zheng, Shuen Hon, Daniel G. Olson, Lee Lynd
Dartmouth Scholarship
Thermoanaerobacterium saccharolyticum and Clostridium thermocellum are anaerobic thermophilic bacteria being investigated for their ability to produce biofuels from plant biomass. The bifunctional alcohol and aldehyde dehydrogenase gene, adhE, is present in these bacteria and has been known to be important for ethanol formation in other anaerobic alcohol producers. This study explores the inactivation of the adhE gene in C. thermocellum and T. saccharolyticum. Deletion of adhE reduced ethanol production by >95% in both T. saccharolyticum and C. thermocellum, confirming that adhE is necessary for ethanol formation in both organisms. In both adhE deletion strains, fermentation products shifted from ethanol …
High Ethanol Titers From Cellulose By Using Metabolically Engineered Thermophilic, Anaerobic Microbes, D. Aaron Argyros, Shital A. Tripathi, Trisha F. Barrett, Stephen R. Rogers, Lawrence F. Feinberg, Daniel G. Olson, Justin M. Foden, Bethany B. Miller, Lee R. Lynd, David A. Hogsett, Nicky C. Caiazza
High Ethanol Titers From Cellulose By Using Metabolically Engineered Thermophilic, Anaerobic Microbes, D. Aaron Argyros, Shital A. Tripathi, Trisha F. Barrett, Stephen R. Rogers, Lawrence F. Feinberg, Daniel G. Olson, Justin M. Foden, Bethany B. Miller, Lee R. Lynd, David A. Hogsett, Nicky C. Caiazza
Dartmouth Scholarship
This work describes novel genetic tools for use in Clostridium thermocellum that allow creation of unmarked mutations while using a replicating plasmid. The strategy employed counter-selections developed from the native C. thermocellum hpt gene and the Thermoanaerobacterium saccharolyticum tdk gene and was used to delete the genes for both lactate dehydrogenase (Ldh) and phosphotransacetylase (Pta). The Δldh Δpta mutant was evolved for 2,000 h, resulting in a stable strain with 40:1 ethanol selectivity and a 4.2-fold increase in ethanol yield over the wild-type strain. Ethanol production from cellulose was investigated with an engineered coculture of organic acid-deficient engineered strains of …
Identification Of The [Fefe]-Hydrogenase Responsible For Hydrogen Generation In Thermoanaerobacterium Saccharolyticum And Demonstration Of Increased Ethanol Yield Via Hydrogenase Knockout, A. Joe Shaw, David A. Hogsett, Lee R. Lynd
Identification Of The [Fefe]-Hydrogenase Responsible For Hydrogen Generation In Thermoanaerobacterium Saccharolyticum And Demonstration Of Increased Ethanol Yield Via Hydrogenase Knockout, A. Joe Shaw, David A. Hogsett, Lee R. Lynd
Dartmouth Scholarship
Three putative hydrogenase enzyme systems in Thermoanaerobacterium saccharolyticum were investigated at the genetic, mRNA, enzymatic, and phenotypic levels. A four-gene operon containing two [FeFe]-hydrogenase genes, provisionally termed hfs (hydrogenase-Fe-S), was found to be the main enzymatic catalyst of hydrogen production. hfsB, perhaps the most interesting gene of the operon, contains an [FeFe]-hydrogenase and a PAS sensory domain and has several conserved homologues among clostridial saccharolytic, cellulolytic, and pathogenic bacteria. A second hydrogenase gene cluster, hyd, exhibited methyl viologen-linked hydrogenase enzymatic activity, but hyd gene knockouts did not influence the hydrogen yield of …
Temperature Influence And Heat Management Requirements Of Microalgae Cultivation In Photobioreactors, Thomas Hagen Mehlitz
Temperature Influence And Heat Management Requirements Of Microalgae Cultivation In Photobioreactors, Thomas Hagen Mehlitz
Master's Theses
Microalgae are considered one of the most promising feedstocks for biofuel production for the future. The most efficient way to produce vast amounts of algal biomass is the use of closed tubular photobioreactors (PBR). The heat requirement for a given system is a major concern since the best algae growth rates are obtained between 25-30 °C, depending on the specific strain. A procedure to determine temperature influence on algal growth rates was developed for a lab-scale PBR system using the species Chlorella. A maximum growth rate of 1.44 doublings per day at 29 °C (optimal temperature) was determined. In addition, …
Metabolic Engineering Of A Thermophilic Bacterium To Produce Ethanol At High Yield, A. Joe Shaw, Kara K. Podkaminer, Sunil G. Desai, John S. Bardsley, Stephen R. Rogers, Philip G. Thorne, David A. Hogsett, Lee R. Lynd
Metabolic Engineering Of A Thermophilic Bacterium To Produce Ethanol At High Yield, A. Joe Shaw, Kara K. Podkaminer, Sunil G. Desai, John S. Bardsley, Stephen R. Rogers, Philip G. Thorne, David A. Hogsett, Lee R. Lynd
Dartmouth Scholarship
We report engineering Thermoanaerobacterium saccharolyticum, a thermophilic anaerobic bacterium that ferments xylan and biomass-derived sugars, to produce ethanol at high yield. Knockout of genes involved in organic acid formation (acetate kinase, phosphate acetyltransferase, and L-lactate dehydrogenase) resulted in a strain able to produce ethanol as the only detectable organic product and substantial changes in electron flow relative to the wild type. Ethanol formation in the engineered strain (ALK2) utilizes pyruvate:ferredoxin oxidoreductase with electrons transferred from ferredoxin to NAD(P), a pathway different from that in previously described microbes with a homoethanol fermentation. The homoethanologenic phenotype was stable for >150 generations …