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George N. Bennett - One of the best experts on this subject based on the ideXlab platform.
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production of succinic acid by engineered e coli strains using soybean carbohydrates as feedstock under aerobic fermentation conditions
Bioresource Technology, 2013Co-Authors: Chandresh Thakker, George N. BennettAbstract:Abstract Escherichia coli strains HL2765 and HL27659k harboring pRU600 and pKK313 were examined for Succinate production under aerobic conditions using galactose, sucrose, raffinose, stachyose, and mixtures of these sugars extracted from soybean meal and soy solubles. HL2765(pKK313)(pRU600) and HL27659k(pKK313)(pRU600) consumed 87 mM and 98 mM hexose of soybean meal extract and produced 83 mM and 95 mM Succinate, respectively. While using soy solubles extract, HL2765(pKK313)(pRU600) and HL27659k(pKK313)(pRU600) consumed 160 mM and 187 mM hexose and produced 158 mM and 183 mM Succinate, respectively. Succinate yield of HL2765(pKK313)(pRU600) was low as compared to that of HL27659k(pKK313)(pRU600) while using acid hydrolysate of soybean meal or soy solubles extracts. Maximum Succinate production of 312 mM with a molar yield of 0.82 mol/mol hexose was obtained using soy solubles hydrolysate by HL27659k(pKK313)(pRU600). This study demonstrated the use of soluble carbohydrates of the renewable feedstock, soybean as an inexpensive carbon source to produce Succinate by fermentation.
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Culture conditions' impact on Succinate production by a high Succinate producing Escherichia coli strain
Biotechnology Progress, 2011Co-Authors: Irene Martínez, George N. Bennett, Amanda Lee, Ka-yiu SanAbstract:This work aimed to identify the key operational factors that significantly affect Succinate production by the high Succinate producing Escherichia coli strain SBS550MG (pHL413), which bears mutations inactivating genes adhE ldhA iclRackpta::CmR and overexpresses the pyruvate carboxylase from Lactococcus lactis. The considered factors included glucose concentration, cell density, CO2 concentration in the gas stream, pH, and temperature. The results showed that high glucose concentrations inhibited Succinate production and that there is a compromise between the total Succinate productivity and Succinate specific productivity, where the total productivity increased with the increase in cell density and the specific productivity decreased with cell density, probably due to mass transfer limitation. On the other hand, a CO2 concentration of 100% in the gas stream showed the highest specific Succinate productivity, probably by favoring pyruvate carboxylation, increasing the OAA pool that later is converted into Succinate. A full factorial design of experiments was applied to analyze the pH and temperature effects on Succinate production in batch bioreactors, where Succinate yield was not significantly affected by either temperature (37 to 43°C) or pH (6.5 to 7.5). Additionally, the temperature effect on Succinate productivity and titer was not significant, in the range tested. On the other hand, a pH of 6.5 showed very low productivity, whereas pH values of 7.0 and 7.5 resulted in significantly higher specific productivities and higher titers. The increase on pH value from 7.0 to 7.5 did not show significant improvement. Then, pH 7.0 should be chosen because it involves a lower cost in base addition. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011
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efficient succinic acid production from glucose through overexpression of pyruvate carboxylase in an escherichia coli alcohol dehydrogenase and lactate dehydrogenase mutant
Biotechnology Progress, 2008Co-Authors: Ailen Sanchez, George N. Bennett, Ka-yiu SanAbstract:An adhE, ldhA double mutant Escherichia coli strain, SBS110MG, has been constructed to produce succinic acid in the presence of heterologous pyruvate carboxylase (PYC). The strategic design aims at diverting maximum quantities of NADH for Succinate synthesis by inactivation of NADH competing pathways to increase Succinate yield and productivity. Additionally an operational PFL enzyme allows formation of acetyl-CoA for biosynthesis and formate as a potential source of reducing equivalents. Furthermore, PYC diverts pyruvate toward OAA to favor Succinate generation. SBS110MG harboring plasmid pHL413, which encodes the heterologous pyruvate carboxylase from Lactococcus lactis, produced 15.6 g/L (132 mM) of Succinate from 18.7 g/L (104 mM) of glucose after 24 h of culture in an atmosphere of CO(2) yielding 1.3 mol of Succinate per mole of glucose. This molar yield exceeded the maximum theoretical yield of Succinate that can be achieved from glucose (1 mol/mol) under anaerobic conditions in terms of NADH balance. The current work further explores the importance of the presence of formate as a source of reducing equivalents in SBS110MG(pHL413). Inactivation of the native formate dehydrogenase pathway (FDH) in this strain significantly reduced Succinate yield, suggesting that reducing power was lost in the form of formate. Additionally we investigated the effect of ptsG inactivation in SBS110MG(pHL413) to evaluate the possibility of a further increase in Succinate yield. Elimination of the ptsG system increased the Succinate yield to 1.4 mol/mol at the expense of a reduction in glucose consumption of 33%. In the presence of PYC and an efficient conversion of glucose to products, the ptsG mutation is not indispensable since PEP converted to pyruvate as a result of glucose phosphorylation by the glucose specific PTS permease EIICB(glu) can be rediverted toward OAA favoring Succinate production.
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novel pathway engineering design of the anaerobic central metabolic pathway in escherichia coli to increase Succinate yield and productivity
Metabolic Engineering, 2005Co-Authors: Ailen Sanchez, George N. BennettAbstract:Abstract A novel in vivo method of producing Succinate has been developed. A genetically engineered Escherichia coli strain has been constructed to meet the NADH requirement and carbon demand to produce high quantities and yield of Succinate by strategically implementing metabolic pathway alterations. Currently, the maximum theoretical Succinate yield under strictly anaerobic conditions through the fermentative Succinate biosynthesis pathway is limited to one mole per mole of glucose due to NADH limitation. The implemented strategic design involves the construction of a dual Succinate synthesis route, which diverts required quantities of NADH through the traditional fermentative pathway and maximizes the carbon converted to Succinate by balancing the carbon flux through the fermentative pathway and the glyoxylate pathway (which has less NADH requirement). The synthesis of Succinate uses a combination of the two pathways to balance the NADH. Consequently, experimental results indicated that these combined pathways gave the most efficient conversion of glucose to Succinate with the highest yield using only 1.25 moles of NADH per mole of Succinate in contrast to the sole fermentative pathway, which uses 2 moles of NADH per mole of Succinate. A recombinant E. coli strain, SBS550MG, was created by deactivating adhE, ldhA and ack-pta from the central metabolic pathway and by activating the glyoxylate pathway through the inactivation of iclR, which encodes a transcriptional repressor protein of the glyoxylate bypass. The inactivation of these genes in SBS550MG increased the Succinate yield from glucose to about 1.6 mol/mol with an average anaerobic productivity rate of 10 mM/h(∼0.64 mM/h-OD600). This strain is capable of fermenting high concentrations of glucose in less than 24 h. Additional derepression of the glyxoylate pathway by inactivation of arcA, leading to a strain designated as SBS660MG, did not signicantly increase the Succinate yield and it decreased glucose consumption by 80%. It was also observed that an adhE, ldhA and ack-pta mutant designated as SBS990MG, was able to achieve a high Succinate yield similar to SBS550MG when expressing a Bacillus subtilis NADH-insensitive citrate synthase from a plasmid.
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Effect of carbon sources differing in oxidation state and transport route on Succinate production in metabolically engineered Escherichia coli
Journal of Industrial Microbiology and Biotechnology, 2005Co-Authors: George N. BennettAbstract:In mixed-acid fermentation, Succinate synthesis requires one mole of phosphoenolpyruvate (PEP), one mole of CO_2, and two moles of NADH for every mole of Succinate to be formed. Different carbon sources with different properties were used to address these requirements. Sorbitol generates one more mole of NADH than glucose. Fermentation of sorbitol was shown in this study (and by others) to produce significantly more Succinate than fermentation of glucose, due to increased NADH availability. Xylose fermentation conserves the intracellular PEP pool, since its transport does not require the phosphotransferase system normally used for glucose transport. The extra PEP can then be assimilated in the Succinate pathway to improve production. In this study, fermentation of xylose did yield higher Succinate production than glucose fermentation. Subsequent inactivation of the acetate and lactate pathways was performed to study metabolite redistribution and the effect on Succinate production. With the acetate pathway inactivated, significant carbon flux shifted toward lactate rather than Succinate. When both acetate and lactate pathways were inactivated, Succinate yield ultimately increased with a concomitant increase in ethanol yield.
Anthony L Moore - One of the best experts on this subject based on the ideXlab platform.
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new insights in the regulation of the plant Succinate dehydrogenase on the role of the protonmotive force
Journal of Biological Chemistry, 2001Co-Authors: Charles Affourtit, Graeme R Leach, David G Whitehouse, Klaas Krab, Anthony L MooreAbstract:Regulation of Succinate dehydrogenase was investigated using tightly coupled potato tuber mitochondria in a novel fashion by simultaneously measuring the oxygen uptake rate and the ubiquinone (Q) reduction level. We found that the activation level of the enzyme is unambiguously reflected by the kinetic dependence of the Succinate oxidation rate upon the Q-redox poise. Kinetic results indicated that Succinate dehydrogenase is activated by both ATP (K ½ ~ 3 µm) and ADP. The carboxyatractyloside insensitivity of these stimulatory effects indicated that they occur at the cytoplasmic side of the mitochondrial inner membrane. Importantly, our novel approach revealed that the enzyme is also activated by oligomycin (K ½~ 16 nm). Time-resolved kinetic measurements of Succinate dehydrogenase activation by Succinate furthermore revealed that the activity of the enzyme is negatively affected by potassium. The Succinate-induced activation (±K +) is prevented by the presence of an uncoupler. Together these results demonstrate that in vitro activity of Succinate dehydrogenase is modulated by the protonmotive force. We speculate that the widely recognized activation of the enzyme by adenine nucleotides in plants is mediated in this manner. A mechanism that could account for such regulation is suggested and ramifications for its in vivo relevance are discussed.
Changan Yu - One of the best experts on this subject based on the ideXlab platform.
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involvement of a histidine residue in the interaction between membrane anchoring protein qps and Succinate dehydrogenase in mitochondrial Succinate ubiquinone reductase
Biochimica et Biophysica Acta, 1991Co-Authors: Hemant K Paudel, Linda Yu, Changan YuAbstract:The involvement of a histidine residue of the membrane-anchoring protein (QPs) fraction in reconstitution of Succinate dehydrogenase to form Succinate-ubiquinone reductase is studied by using a histidine-modifying reagent, diethylpyrocarbonate (DEPC). A maximum inactivation of 80% of reconstitutive activity is obtained when QPs is treated with 1 mM DEPC at 0°C for 30 min in 50 mM Tris-HCl (pH 7.0). DEPC also inactivates about 85% of intact Succinate-ubiquinone reductase. The inactivation of Succinate-ubiquinone reductase by DEPC is a result of the modification of essential histidine residues of Succinate dehydrogenase. The inactivation is not a result of the modification of the histidine residue in QPs which is essential for interaction with Succinate dehyrogenase because the QPs dissociated from the inactivated Succinate-ubiquinone reductase is active in reconstitution with active Succinate-dehydrogenase. Apparently, the essential histidine in QPs is shielded by Succinate dehydrogenase and thus inaccessible to DEPC modification in Succinate-ubiquinone reductase. The involvement of a histidine residue of QPs in interaction with Succinate dehydrogenase is further evident by the presence of 553 nm shoulder on the α-absorption peak of reduced cytochrome b-560 (a characteristic of physical association of QPs with Succinate dehydrogenase) in the DEPC-inactivated Succinate-ubiquinone reductase. This shoulder disappears from a mixture of Succinate dehydrogenase and DEPC-treated QPs when reduced with dithionite. About one histidine residue per molecule of QPs is modified in the DEPC-treated sample, suggesting that only one histidine residue is essential for interaction with Succinate dehyrogenase. This essential histidine group is located in the smaller subunit (Mr 13 000) of QPs.
Charles Affourtit - One of the best experts on this subject based on the ideXlab platform.
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new insights in the regulation of the plant Succinate dehydrogenase on the role of the protonmotive force
Journal of Biological Chemistry, 2001Co-Authors: Charles Affourtit, Graeme R Leach, David G Whitehouse, Klaas Krab, Anthony L MooreAbstract:Regulation of Succinate dehydrogenase was investigated using tightly coupled potato tuber mitochondria in a novel fashion by simultaneously measuring the oxygen uptake rate and the ubiquinone (Q) reduction level. We found that the activation level of the enzyme is unambiguously reflected by the kinetic dependence of the Succinate oxidation rate upon the Q-redox poise. Kinetic results indicated that Succinate dehydrogenase is activated by both ATP (K ½ ~ 3 µm) and ADP. The carboxyatractyloside insensitivity of these stimulatory effects indicated that they occur at the cytoplasmic side of the mitochondrial inner membrane. Importantly, our novel approach revealed that the enzyme is also activated by oligomycin (K ½~ 16 nm). Time-resolved kinetic measurements of Succinate dehydrogenase activation by Succinate furthermore revealed that the activity of the enzyme is negatively affected by potassium. The Succinate-induced activation (±K +) is prevented by the presence of an uncoupler. Together these results demonstrate that in vitro activity of Succinate dehydrogenase is modulated by the protonmotive force. We speculate that the widely recognized activation of the enzyme by adenine nucleotides in plants is mediated in this manner. A mechanism that could account for such regulation is suggested and ramifications for its in vivo relevance are discussed.
J B Russell - One of the best experts on this subject based on the ideXlab platform.
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Succinate transport by a ruminal selenomonad and its regulation by carbohydrate availability and osmotic strength
Applied and Environmental Microbiology, 1991Co-Authors: H J Strobel, J B RussellAbstract:Washed cells of strain H18, a newly isolated ruminal selenomonad, decarboxylated Succinate 25-fold faster than Selenomonas ruminantium HD4 (130 versus 5 nmol min-1 mg of protein-1, respectively). Batch cultures of strain H18 which were fermenting glucose did not utilize Succinate, and glucose-limited continuous cultures were only able to decarboxylate significant amounts of Succinate at slow (less than 0.1 h-1) dilution rates. Strain H18 grew more slowly on lactate than glucose (0.2 versus 0.4 h-1, respectively), and more than half of the lactate was initially converted to Succinate. Succinate was only utilized after growth on lactate had ceased. Although nonenergized and glucose-energized cells had similar proton motive forces and ATP levels, glucose-energized cells were unable to transport Succinate. Transport by nonenergized cells was decreased by small increases in osmotic strength, and it is possible that energy-dependent inhibition of Succinate transport was related to changes in cell turgor. Since cells which were deenergized with 2-deoxyglucose or iodoacetate did not transport Succinate, it appeared that glycogen metabolism was providing the driving force for Succinate uptake. An artificial delta pH drove Succinate transport in deenergized cells, but an artificial membrane potential (delta psi) could not serve as a driving force. Because Succinate is nearly fully dissociated at pH 7.0 and the transport process was electroneutral, it appeared that Succinate was taken up in symport with two protons. An Eadie-Hofstee plot indicated that the rate of uptake was unusually rapid at high substrate concentrations, but the low-velocity, high-affinity component could account for Succinate utilization by stationary cultures.(ABSTRACT TRUNCATED AT 250 WORDS)