scholarly journals Lactate Metabolism and Microbiome Composition Are Affected by Nitrogen Gas Supply in Continuous Lactate-Based Chain Elongation

Fermentation ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 41
Author(s):  
Carlos A. Contreras-Dávila ◽  
Arielle Ali ◽  
Cees J. N. Buisman ◽  
David P. B. T. B. Strik
Keyword(s):  
Hydraulic Retention Time ◽  
Chain Elongation ◽  
Clostridium Tyrobutyricum ◽  
Lactate Metabolism ◽  
Nitrogen Gas ◽  
Microbiome Composition ◽  
Conversion Rates ◽  
Consumption Rates ◽  
Lactate Consumption ◽  
Gas Supply

Chain elongation reactor microbiomes produce valuable medium-chain carboxylates (MCC) from non-sterile residual substrates where lactate is a relevant intermediate. Gas supply has been shown to impact chain elongation performance. In the present study, the effect of nitrogen gas (N2) supply on lactate metabolism, conversion rates, biomass growth, and microbiome composition was evaluated in a lactate-fed upflow anaerobic reactor with continuous or intermittent N2 gas supply. Successful MCC production was achieved with continuous N2 gas supply at low superficial gas velocities (SGV) of 0.22 m∙h−1. Supplying N2 at high SGV (>2 m∙h−1) either continuously (2.2 m∙h−1) or intermittently (3.6 m∙h−1) disrupted chain elongation, resulting in production of short-chain carboxylates (SCC), i.e., acetate, propionate, and n-butyrate. Caproiciproducens-dominated chain-elongating microbiomes enriched at low SGV were washed out at high SGV where Clostridium tyrobutyricum-dominated microbiomes thrived, by displaying higher lactate consumption rates. Suspended growth seemed to be dominant regardless of SGV and gas supply regime applied with no measurable sludge bed formed. The highest MCC production from lactate of 10 g COD∙L−1∙d−1 with electron selectivities of 72 ± 5%was obtained without N2 gas supply at a hydraulic retention time (HRT) of 1 day. The addition of 5 g∙L−1 of propionate did not inhibit chain elongation, but rather boosted lactate conversion rates towards MCC with n-heptylate reaching 1.8 g COD∙L−1∙d−1. N2 gas supply can be used for mixing purposes and to steer lactate metabolism to MCC or SCC production.

scholarly journals nZVI Impacts Substrate Conversion and Microbiome Composition in Chain Elongation From D- and L-Lactate Substrates

2021 ◽  
Vol 9 ◽  
Author(s):  
Carlos A. Contreras-Dávila ◽  
Johan Esveld ◽  
Cees J. N. Buisman ◽  
David P. B. T. B. Strik
Keyword(s):  
Control Method ◽  
Reducing Power ◽  
Product Formation ◽  
Chain Elongation ◽  
Dependent Manner ◽  
Microbiome Composition ◽  
Conversion Rates ◽  
Substrate Conversion ◽  
Propionate Formation ◽  
Zero Valent Iron Nanoparticles

Medium-chain carboxylates (MCC) derived from biomass biorefining are attractive biochemicals to uncouple the production of a wide array of products from the use of non-renewable sources. Biological conversion of biomass-derived lactate during secondary fermentation can be steered to produce a variety of MCC through chain elongation. We explored the effects of zero-valent iron nanoparticles (nZVI) and lactate enantiomers on substrate consumption, product formation and microbiome composition in batch lactate-based chain elongation. In abiotic tests, nZVI supported chemical hydrolysis of lactate oligomers present in concentrated lactic acid. In fermentation experiments, nZVI created favorable conditions for either chain-elongating or propionate-producing microbiomes in a dose-dependent manner. Improved lactate conversion rates and n-caproate production were promoted at 0.5–2 g nZVI⋅L–1 while propionate formation became relevant at ≥ 3.5 g nZVI⋅L–1. Even-chain carboxylates (n-butyrate) were produced when using enantiopure and racemic lactate with lactate conversion rates increased in nZVI presence (1 g⋅L–1). Consumption of hydrogen and carbon dioxide was observed late in the incubations and correlated with acetate formation or substrate conversion to elongated products in the presence of nZVI. Lactate racemization was observed during chain elongation while isomerization to D-lactate was detected during propionate formation. Clostridium luticellarii, Caproiciproducens, and Ruminococcaceae related species were associated with n-valerate and n-caproate production while propionate was likely produced through the acrylate pathway by Clostridium novyi. The enrichment of different potential n-butyrate producers (Clostridium tyrobutyricum, Lachnospiraceae, Oscillibacter, Sedimentibacter) was affected by nZVI presence and concentrations. Possible theories and mechanisms underlying the effects of nZVI on substrate conversion and microbiome composition are discussed. An outlook is provided to integrate (bio)electrochemical systems to recycle (n)ZVI and provide an alternative reducing power agent as durable control method.

Effect of Varying Pco2 on Intracellular pH and Lactate Consumption in the Isolated Perfused Rat Liver

1978 ◽  
Vol 55 (2) ◽  
pp. 175-181 ◽  
Author(s):  
P. G. Baron ◽  
R. A. Iles ◽  
R. D. Cohen
Keyword(s):  
Intracellular Ph ◽  
Rat Liver ◽  
Isolated Perfused Rat Liver ◽  
Perfused Rat Liver ◽  
Lactate Metabolism ◽  
Isolated Rat Liver ◽  
Buffering Effect ◽  
Lactate Uptake ◽  
Lactate Consumption ◽  
Isolated Rat

1. The effects of varying Pco2 on lactate uptake and intracellular pH (pHl) were studied in the isolated rat liver perfused with differing concentrations of lactate. 2. In general, pHl and lactate uptake are inversely related to Pco2, and pHl and lactate uptake are directly related to each other, but the quantitative aspects and significance of these relationships vary with the availability of lactate. A model of hepatic lactate metabolism is proposed which may account for the quantitative variation. 3. The metabolism of lactate within the hepatocyte exerts a destabilizing effect on hepatocyte cell pH, in contrast to the buffering effect seen in predominantly glycolytic tissues. 4. An attempt is made to relate the findings to the disturbances of lactate metabolism in clinical respiratory failure.

Treatment of wastewaters from a formaldehyde-urea adhesives factory

2000 ◽  
Vol 42 (5-6) ◽  
pp. 293-300 ◽  
Author(s):  
J.M. Garrido ◽  
R. Méndez ◽  
J.M. Lema
Keyword(s):  
Activated Sludge ◽  
Organic Nitrogen ◽  
Hydraulic Retention Time ◽  
Loading Rate ◽  
Organic Matter Content ◽  
Matter Content ◽  
Organic Loading Rate ◽  
Nitrogen Gas ◽  
Laboratory Unit ◽  
Formaldehyde Removal

Wastewater from a formaldehyde-urea adhesives factory is characterised by a high organic matter content (COD between 460 and 3900 mg/L mostly due to formaldehyde 220–4000 mg/L) and organic nitrogen (TKN 110–805 mg/L). Besides, a fraction of COD is given by a formaldehyde-urea polymer with a relatively high molecular weight. In a lab-scale (2 L) activated sludge unit, a high formaldehyde removal (higher than 99%) was obtained while the total COD and TKN removal ranged between 70–85 % and 30–50%, respectively. Formaldehyde was used by microorganisms as carbon source and also for the conversion of nitrate to nitrogen gas. The Organic Loading Rate (OLR) was between 0.2 and 1.2 kg–COD/m3·d and the Hydraulic Retention Time (HRT) between 0.5 and 1.4 d. The non degraded TKN and COD, mostly corresponding to the polymeric fraction, was further treated in an ozonation unit, which increased very efficiently the bioavailability of TKN towards nitrification and allowed an additional COD removal. Results from lab-scale reactors were used for designing and operating an industrial scale activated sludge unit, being the efficiency attained at full-scale similar to the laboratory unit.

Universal crystal cooling device for precession cameras, rotation cameras and diffractometers

1985 ◽  
Vol 18 (6) ◽  
pp. 528-532 ◽  
Author(s):  
J. Hajdu ◽  
P. J. McLaughlin ◽  
J. R. Helliwell ◽  
J. Sheldon ◽  
A. W. Thompson
Keyword(s):  
Synchrotron Radiation ◽  
Radiation Source ◽  
Data Sets ◽  
Ball Joint ◽  
Cooling Device ◽  
Nitrogen Gas ◽  
Cooling Chamber ◽  
Set Up ◽  
Gas Supply ◽  
Goniometer Head

A versatile crystal cooling device is described for macromolecular crystallographic applications in the 290 to 80 K temperature range. It utilizes a fluctuation-free cold-nitrogen-gas supply, an insulated Mylar crystal cooling chamber and a universal ball joint, which connects the cooling chamber to the goniometer head and the crystal. The ball joint is a novel feature over all previous designs. As a result, the device can be used on various rotation cameras, precession cameras and diffractometers. The lubrication of the interconnecting parts with graphite allows the cooling chamber to remain stationary while the crystal and goniometer rotate. The construction allows for 360° rotation of the crystal around the goniometer axis and permits any settings on the arcs and slides of the goniometer head (even if working at 80 K). There are no blind regions associated with the frame holding the chamber. Alternatively, the interconnecting ball joint can be tightened and fixed. This results in a set up similar to the construction described by Bartunik & Schubert [J. Appl. Cryst. (1982), 15, 277–231], where the cooling chamber rotates with the crystal. The flexibility of the systems allows for the use of the device on most cameras or diffractometers. This device has been installed at the protein crystallographic stations of the Synchrotron Radiation Source at Daresbury Laboratory and in the Laboratory of Molecular Biophysics, Oxford. Several data sets have been collected with processing statistics typical of data collected without a cooling chamber. Tests using the full white beam of the synchrotron also look promising.

scholarly journals Machine Learning-assisted Identification of Bioindicators Predicts Medium-chain Carboxylate Production Performance of an Anaerobic Mixed Culture

2020 ◽  
Author(s):  
Bin Liu ◽  
Heike Sträuber ◽  
Joao Saraiva ◽  
Hauke Harms ◽  
Sandra Godinho Silva ◽  
...  
Keyword(s):  
Machine Learning ◽  
16S Rrna ◽  
Retention Time ◽  
Hydraulic Retention Time ◽  
Amplicon Sequencing ◽  
Production Performance ◽  
Chain Elongation ◽  
Sequencing Data ◽  
Medium Chain ◽  
16S Rrna Amplicon Sequencing

Abstract Background: The ability to quantitatively predict ecophysiological functions of microbial communities provides an important step to engineer microbiota for desired functions related to specific biochemical conversions. Here, we present the quantitative prediction of medium-chain carboxylate production in two continuous anaerobic bioreactors from 16S rRNA gene dynamics in enrichment cultures. Results: By progressively shortening the hydraulic retention time from 8 days to 2 days with different temporal schemes in both bioreactors operated for 211 days, we achieved higher productivities and yields of the target products n-caproate and n-caprylate. The datasets generated from each bioreactor were applied independently for training and testing in machine learning. A predictive model was generated by employing the random forest algorithm using 16S rRNA amplicon sequencing data. More than 90% accuracy in the prediction of n-caproate and n-caprylate productivities was achieved. Four inferred bioindicators belonging to the genera Olsenella, Lactobacillus, Syntrophococcus and Clostridium IV suggest their relevance to the higher carboxylate productivity at shorter hydraulic retention time. The recovery of metagenome-assembled genomes of these bioindicators confirmed their genetic potential to perform key steps of medium-chain carboxylate production.Conclusions: Shortening the hydraulic retention time of the continuous bioreactor systems allows to shape the communities with desired chain elongation functions. Using machine-learning, we demonstrated that 16S rRNA amplicon sequencing data can be used to predict bioreactor process performance quantitatively and accurately. Characterising and harnessing bioindicators holds promise to manage reactor microbiota towards selection of the target processes. Our mathematical framework is transferrable to other ecosystem processes and 3 microbial systems where community dynamics is linked to key functions. The general methodology can be adapted to data types of other functional categories such as genes, transcripts, proteins or metabolites.

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