scholarly journals Fermentative Utilization of Glycerol by Escherichia coli and Its Implications for the Production of Fuels and Chemicals

2007 ◽  
Vol 74 (4) ◽  
pp. 1124-1135 ◽  
Author(s):  
Abhishek Murarka ◽  
Yandi Dharmadi ◽  
Syed Shams Yazdani ◽  
Ramon Gonzalez
Keyword(s):  
Escherichia Coli ◽  
Anaerobic Fermentation ◽  
Glycerol Metabolism ◽  
Nuclear Magnetic Resonance Analysis ◽  
Glycerol Fermentation ◽  
Glycerol Utilization ◽  
Negative Effect ◽  
Balance Analysis ◽  
Fuels And Chemicals ◽  
High Degree

ABSTRACT Availability, low prices, and a high degree of reduction make glycerol an ideal feedstock to produce reduced chemicals and fuels via anaerobic fermentation. Although glycerol metabolism in Escherichia coli had been thought to be restricted to respiratory conditions, we report here the utilization of this carbon source in the absence of electron acceptors. Cells grew fermentatively on glycerol and exhibited exponential growth at a maximum specific growth rate of 0.040 ± 0.003 h−1. The fermentative nature of glycerol metabolism was demonstrated through studies in which cell growth and glycerol utilization were observed despite blocking several respiratory processes. The incorporation of glycerol in cellular biomass was also investigated via nuclear magnetic resonance analysis of cultures in which either 50% U-13C-labeled or 100% unlabeled glycerol was used. These studies demonstrated that about 20% of the carbon incorporated into the protein fraction of biomass originated from glycerol. The use of U-13C-labeled glycerol also allowed the unambiguous identification of ethanol and succinic, acetic, and formic acids as the products of glycerol fermentation. The synthesis of ethanol was identified as a metabolic determinant of glycerol fermentation; this pathway fulfills energy requirements by generating, in a redox-balanced manner, 1 mol of ATP per mol of glycerol converted to ethanol. A fermentation balance analysis revealed an excellent closure of both carbon (∼95%) and redox (∼96%) balances. On the other hand, cultivation conditions that prevent H2 accumulation were shown to be an environmental determinant of glycerol fermentation. The negative effect of H2 is related to its metabolic recycling, which in turn generates an unfavorable internal redox state. The implications of our findings for the production of reduced chemicals and fuels were illustrated by coproducing ethanol plus formic acid and ethanol plus hydrogen from glycerol at yields approaching their theoretical maximum.

scholarly journals Anaerobic Fermentation of Glycerol in Paenibacillus macerans: Metabolic Pathways and Environmental Determinants

2009 ◽  
Vol 75 (18) ◽  
pp. 5871-5883 ◽  
Author(s):  
Ashutosh Gupta ◽  
Abhishek Murarka ◽  
Paul Campbell ◽  
Ramon Gonzalez
Keyword(s):  
Nmr Spectroscopy ◽  
Anaerobic Fermentation ◽  
Redox Balance ◽  
Glycerol Metabolism ◽  
Environmental Determinants ◽  
Glycerol Fermentation ◽  
Fermentation Products ◽  
Glycerol Utilization ◽  
Paenibacillus Macerans ◽  
Cellular Components

ABSTRACT Paenibacillus macerans is one of the species with the broadest metabolic capabilities in the genus Paenibacillus, able to ferment hexoses, deoxyhexoses, pentoses, cellulose, and hemicellulose. However, little is known about glycerol metabolism in this organism, and some studies have reported that glycerol is not fermented. Despite these reports, we found that several P. macerans strains are capable of anaerobic fermentation of glycerol. One of these strains, P. macerans N234A, grew fermentatively on glycerol at a maximum specific growth rate of 0.40 h−1 and was chosen for further characterization. The use of [U-13C]glycerol and further analysis of extracellular metabolites and proteinogenic amino acids via nuclear magnetic resonance (NMR) spectroscopy allowed identification of ethanol, formate, acetate, succinate, and 1,2-propanediol (1,2-PDO) as fermentation products and demonstrated that glycerol is incorporated into cellular components. A medium formulation with low concentrations of potassium and phosphate, cultivation at acidic pH, and the use of a CO2-enriched atmosphere stimulated glycerol fermentation and are proposed to be environmental determinants of this process. The pathways involved in glycerol utilization and synthesis of fermentation products were identified using NMR spectroscopy in combination with enzyme assays. Based on these studies, the synthesis of ethanol and 1,2-PDO is proposed to be a metabolic determinant of glycerol fermentation in P. macerans N234A. Conversion of glycerol to ethanol fulfills energy requirements by generating one molecule of ATP per molecule of ethanol synthesized. Conversion of glycerol to 1,2-PDO results in the consumption of reducing equivalents, thus facilitating redox balance. Given the availability, low price, and high degree of reduction of glycerol, the high metabolic rates exhibited by P. macerans N234A are of paramount importance for the production of fuels and chemicals.

scholarly journals Escherichia coli Strains Engineered for Homofermentative Production of d-Lactic Acid from Glycerol

2010 ◽  
Vol 76 (13) ◽  
pp. 4327-4336 ◽  
Author(s):  
Suman Mazumdar ◽  
James M. Clomburg ◽  
Ramon Gonzalez
Keyword(s):  
Escherichia Coli ◽  
Lactic Acid ◽  
Lactate Dehydrogenase ◽  
Cell Mass ◽  
Lactate Production ◽  
Fumarate Reductase ◽  
Glycerol Metabolism ◽  
E Coli ◽  
Fuels And Chemicals ◽  
Microaerobic Conditions

ABSTRACT Given its availability and low price, glycerol has become an ideal feedstock for the production of fuels and chemicals. We recently reported the pathways mediating the metabolism of glycerol in Escherichia coli under anaerobic and microaerobic conditions. In this work, we engineer E. coli for the efficient conversion of glycerol to d-lactic acid (d-lactate), a negligible product of glycerol metabolism in wild-type strains. A homofermentative route for d-lactate production was engineered by overexpressing pathways involved in the conversion of glycerol to this product and blocking those leading to the synthesis of competing by-products. The former included the overexpression of the enzymes involved in the conversion of glycerol to glycolytic intermediates (GlpK-GlpD and GldA-DHAK pathways) and the synthesis of d-lactate from pyruvate (d-lactate dehydrogenase). On the other hand, the synthesis of succinate, acetate, and ethanol was minimized through two strategies: (i) inactivation of pyruvate-formate lyase (ΔpflB) and fumarate reductase (ΔfrdA) (strain LA01) and (ii) inactivation of fumarate reductase (ΔfrdA), phosphate acetyltransferase (Δpta), and alcohol/acetaldehyde dehydrogenase (ΔadhE) (strain LA02). A mutation that blocked the aerobic d-lactate dehydrogenase (Δdld) also was introduced in both LA01 and LA02 to prevent the utilization of d-lactate. The most efficient strain (LA02Δdld, with GlpK-GlpD overexpressed) produced 32 g/liter of d-lactate from 40 g/liter of glycerol at a yield of 85% of the theoretical maximum and with a chiral purity higher than 99.9%. This strain exhibited maximum volumetric and specific productivities for d-lactate production of 1.5 g/liter/h and 1.25 g/g cell mass/h, respectively. The engineered homolactic route generates 1 to 2 mol of ATP per mol of d-lactate and is redox balanced, thus representing a viable metabolic pathway.

scholarly journals Methanol-dependent Escherichia coli strains with a complete ribulose monophosphate cycle

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Philipp Keller ◽  
Elad Noor ◽  
Fabian Meyer ◽  
Michael A. Reiter ◽  
Stanislav Anastassov ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Triosephosphate Isomerase ◽  
Methanol Conversion ◽  
Adaptive Laboratory Evolution ◽  
Fructose 1,6 Bisphosphatase ◽  
Food And Feed ◽  
Balance Analysis ◽  
Ribulose Monophosphate Cycle ◽  
High Degree ◽  
Rump Cycle

Abstract Methanol is a biotechnologically promising substitute for food and feed substrates since it can be produced renewably from electricity, water and CO2. Although progress has been made towards establishing Escherichia coli as a platform organism for methanol conversion via the energy efficient ribulose monophosphate (RuMP) cycle, engineering strains that rely solely on methanol as a carbon source remains challenging. Here, we apply flux balance analysis to comprehensively identify methanol-dependent strains with high potential for adaptive laboratory evolution. We further investigate two out of 1200 candidate strains, one with a deletion of fructose-1,6-bisphosphatase (fbp) and another with triosephosphate isomerase (tpiA) deleted. In contrast to previous reported methanol-dependent strains, both feature a complete RuMP cycle and incorporate methanol to a high degree, with up to 31 and 99% fractional incorporation into RuMP cycle metabolites. These strains represent ideal starting points for evolution towards a fully methylotrophic lifestyle.

Creation of Plasmidless and Markerless Escherichia coli Succinate Producing Strain and Evaluation of its Biosynthetic Potential during Utilization of Lignocellulosic Sugars

2020 ◽  
Vol 36 (2) ◽  
pp. 3-11
Author(s):  
O.A. Zhuravliova ◽  
Т.А. Voeikova ◽  
A.Yu. Gulevich ◽  
V.G. Debabov
Keyword(s):  
Escherichia Coli ◽  
Succinic Acid ◽  
Plant Biomass ◽  
Anaerobic Fermentation ◽  
Basic Research ◽  
Acid Fermentation ◽  
Mixed Acid ◽  
Gene Coding ◽  
Lignocellulosic Sugars ◽  
Basic Research Project

The plasmidless and markerless Escherichia coli succinate producing strain SGM2.0Pyc-int has been engineered and characterized. The strain has the inactivated main mixed-acid fermentation pathways due to the deletions of ldhA,poxB, ackA,pta, and adhE genes, constitutively expresses the genes of the aceEF-lpdA operon encoding components of pyravate dehydrogenase complex, and possesses the chromosomally integrated Bacillus subtilis pycA gene coding for pyruvate carboxylase. The capacity of the strain to synthesize succinic acid in course of dual-phase aerobic-anaerobic fermentation with lignocellulosic sugars as substrates was studied. The SGM2.0Pyc-int strain synthesized succinic acid from glucose, xylose, and arabinose with a molar yields of 1.41 mol/mol, 1.18 mol/mol, and 1.18 mol/mol, respectively, during the anaerobic production stage. The constructed strain has great potential for developing efficient processes for the succinic acid production from plant biomass-derived sugars. Escherichia coli, fermentation, arabinose, glucose, xylose, succinic acid. The work was supported by a Grant from the Russian Foundation for Basic Research (Project no. 18-29-14005).

Glycerol metabolism in rabbits

1968 ◽  
Vol 46 (9) ◽  
pp. 1107-1114 ◽  
Author(s):  
Jean Himms-Hagen
Keyword(s):  
Turnover Rate ◽  
Glycerol Kinase ◽  
Rabbit Liver ◽  
Constant Infusion ◽  
Glycerol Dehydrogenase ◽  
Glycerol Metabolism ◽  
Utilization Rate ◽  
Glycerol Concentration ◽  
Glycerol Utilization ◽  
Fractional Turnover

The endogenous rate of glycerol production in rabbits was measured by several techniques: constant infusion of 1,3-14C-glycerol or 2-3H-glycerol or unlabeled glycerol; single injection of 1,3-14C-glycerol or 2-3H-glycerol or unlabeled glycerol. The rate was 5.5–11.6 μmoles/kg per minute (9 rabbits). The mean fractional turnover rate was 0.0585 ± 0.0052. During infusion of noradrenaline together with 3H-glycerol, the fractional turnover rate was no different from that in the absence of noradrenaline. The maximum utilization rate of glycerol was 28.1 ± 1.40 μmoles/kg per minute. The glycerol space was 58.1% of body weight. The relationship of glycerol concentration to rate of glycerol utilization in the intact rabbit suggests the existence of an enzyme with a KM for glycerol of 0.33 × 10−3 M; the glycerol kinase of rabbit liver was found to have a KM for glycerol of 0.29 × 10−3 M. This enzyme could account for the disappearance of glycerol in the intact animal except that its Vmax is only 4% of that expected. Possible reasons for this are discussed. A glycerol dehydrogenase with a Vmax similar to that of the glycerol kinase also exists in rabbit liver; its KM for glycerol is so high (0.5 M) that it is unlikely to play a significant role in glycerol metabolism in the normal rabbit.

scholarly journals Can One Promote a Delegation of the Bilateral Aid to Multilateral Donors to Improve Foreign Aid Effect on Economic Growth in ECOWAS (Note 1) Countries?

2019 ◽  
Vol 2 (1) ◽  
pp. 51
Author(s):  
W. Jean Marie Kébré
Keyword(s):  
Economic Growth ◽  
Panel Data ◽  
Least Squares ◽  
Foreign Aid ◽  
Bilateral Aid ◽  
Multilateral Aid ◽  
Multilateral Institutions ◽  
Negative Effect ◽  
High Degree ◽  
The Relationship

<p><em>This article analyzes the relationship between external aid and economic growth in the ECOWAS region, with a focus on bilateral and multilateral aid effects. The key idea behind this analysis is an argument of Svensson</em><em> </em><em>(2000)</em><em> that multilateral aid is more effective than bilateral aid because of the high degree of altruism of bilateral donors. He therefore suggested a delegation of bilateral aid to multilateral institutions. To appreciate his suggestion, this analysis used panel data from the 16 ECOWAS countries from the period 1984 to 2014. The results of the estimates, based on the dynamic least squares estimator (DOLS), show a negative effect of foreign aid on economic growth. This negative effect on economic growth persists when the components of aid are introduced into the model. In addition, results highlight that governance is a channel through which foreign aid affect positively economic growth. In these conditions, bilateral aid is more effective on economic growth than multilateral aid. These results about foreign aid received by ECOWAS countries invalidates</em><em> </em><em>Svensson’s</em><em> </em><em>(</em><a title="Svensson, 2000 #5" href="#_ENREF_1"><em>2000</em></a><em>)</em><em> theory. Therefore, a delegation of bilateral aid to multilateral institutions is not relevant because bilateral aid contributes more to economic growth if governance is taken into account.</em></p>

scholarly journals Immigration, Wages and Employment under Informal Labor Markets

2021 ◽  
Author(s):  
Lukas Delgado-Prieto
Keyword(s):  
Labor Markets ◽  
Formal Sector ◽  
Informal Workers ◽  
Informal Labor ◽  
Wage Effect ◽  
Wage Effects ◽  
Market Impacts ◽  
Negative Effect ◽  
Informal Labor Markets ◽  
High Degree

This paper studies the labor market impacts of a massive inflow of Venezuelans in Colombia. By comparing areas that received different shares of migrants, I find a negative effect on wages and on local employment for natives. The negative wage effect is driven by a large drop of wages in the informal sector, where migrants are mostly employed, while the negative employment effect is driven by a reduction of employment in the formal sector, where the minimum wage is binding. To explain these results, I develop a model in which firms hire formal and informal workers with different costs. If these workers have a high degree of substitutability, and wages for formal workers are rigid, firms reallocate formal to informal employment as a response to lower informal wages. In settings with informal labor markets migration can therefore lead to asymmetric employment and wage effects across the informal and formal sectors.

scholarly journals The orientation of iron–sulphur clusters in membrane multilayers prepared from aerobically-grown Escherichia coli K12 and a cytochrome-deficient mutant

1980 ◽  
Vol 190 (2) ◽  
pp. 385-393 ◽  
Author(s):  
Haywood Blum ◽  
Robert K. Poole ◽  
Tomoko Ohnishi
Keyword(s):  
Magnetic Field ◽  
Escherichia Coli ◽  
Cytoplasmic Membrane ◽  
Deficient Mutant ◽  
E Coli ◽  
Membrane Particles ◽  
Degree Of Orientation ◽  
High Degree ◽  
Cytochrome Content ◽  
The Magnetic Field

1. Membrane particles prepared from ultrasonically-disrupted, aerobically-grown Escherichia coli were centrifuged on to a plastic film that was supported perpendicular to the centrifugal field to yield oriented membrane multilayers. In such preparations, there is a high degree of orientation of the planes of the membranes such that they lie parallel to each other and to the supporting film. 2. When dithionite- or succinate-reduced multilayers are rotated in the magnetic field of an e.p.r. spectrometer, about an axis lying in the membrane plane, angular-dependent signals from an iron–sulphur cluster at gx=1.92, gy=1.93 and gz=2.02 are seen. The g=1.93 signal has maximal amplitude when the plane of the multilayer is perpendicular to the magnetic field. Conversely, the g=2.02 signal is maximal when the plane of the multilayer is parallel with the magnetic field. 3. Computer simulations of the experimental data show that the cluster lies in the cytoplasmic membrane with the gy axis perpendicular to the membrane plane and with the gx and gz axes lying in the membrane plane. 4. In partially-oxidized multilayers, a signal resembling the mitochondrial high-potential iron–sulphur protein (Hipip) is seen whose gz=2.02 axis may be deduced as lying perpendicular to the membrane plane. 5. Appropriate choice of sample temperature and receiver gain reveals two further signals in partially-reduced multilayers: a g=2.09 signal arises from a cluster with its gz axis in the membrane plane, whereas a g=2.04 signal is from a cluster with the gz axis lying along the membrane normal. 6. Membrane particles from a glucose-grown, haem-deficient mutant contain dramatically-lowered levels of cytochromes and exhibit, in addition to the iron–sulphur clusters seen in the parental strain, a major signal at g=1.90. 7. Only the latter may be demonstrated to be oriented in multilayer preparations from the mutant. 8. Comparisons are drawn between the orientations of the iron–sulphur proteins in the cytoplasmic membrane of E. coli and those in mitochondrial membranes. The effects of diminished cytochrome content on the properties of the iron–sulphur proteins are discussed.

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