Isoprene Production Research Articles

Occurance, emission and environmental effects of non-methane hydrocarbons in the Yellow Sea and the East China Sea.

The spatial distributions, fluxes, and environmental effects of non-methane hydrocarbons (NMHCs) were investigated in the Yellow Sea (YS) and the East China Sea (ECS) in spring. The average concentrations of ethane, propane, i-/n-butane, ethylene, propylene and isoprene in the seawater were 18.1±6.4, 15.4±4.7, 6.8±2.9, 6.4±3.2, 67.1±26.7, 20.5±8.7 and 17.1±11.1pmolL-1, respectively. The alkenes in the surface seawater were more abundant than their saturated homologs and NMHCs concentrations (with the exception of isoprene) decreased with carbon number. The spatial variations of isoprene were consistent with the distributions of chlorophyll a (Chl-a) and Chaetoceros, Skeletonema, Nitzschia mainly contributed to the production of isoprene, while the others' distributions might be related to their photochemical production. Observations in atmospheric NMHCs indicated alkanes in the marine atmosphere decreased from inshore to offshore due to influence of the continental emissions, while alkenes were largely derived from the oceanic source. In addition, no apparent diurnal discrepancy of atmospheric NMHCs (except for isoprene) were found between daytime and night. As the main sink of NMHCs in seawater, the average sea-to-air fluxes of ethane, propane, i-/n-butane, ethylene and propylene were 31.70, 29.75, 18.49, 15.89, 239.6, 67.94 and 52.41nmolm-2 d-1, respectively. The average annual emissions of isoprene accounted for 0.1-1.3% of the global ocean emissions, which indicated that the coastal and shelf areas might be significant sources of isoprene. Furthermore, this study represents the first effort to estimate the environmental effects caused by NMHCs over the YS and the ECS and the results demonstrated contributions of alkanes to ozone and secondary organic aerosol (SOA) formation were lower than those of the alkenes and the largest contributor was isoprene.

Evolution of isoprene emission in Arecaceae (palms).

Isoprene synthase (IspS) is the sole enzyme in plants responsible for the yearly emission in the atmosphere of thousands of tonnes of the natural hydrocarbon isoprene worldwide. Species of the monocotyledonous family Arecaceae (palms) are among the highest plant emitters, but to date no IspS gene from this family has been identified. Here, we screened with PTR‐ToF‐MS 18 genera of the Arecaceae for isoprene emission and found that the majority of the sampled species emits isoprene. Putative IspS genes from six different genera were sequenced and three of them were functionally characterized by heterologous overexpression in Arabidopsis thaliana, demonstrating that they encode functional IspS genes. Site‐directed mutagenesis and expression in Arabidopsis demonstrated the functional relevance of a novel IspS diagnostic tetrad from Arecaceae, whose most variable amino acids could not preserve catalytic function when substituted by a putatively dicotyledonous‐specific tetrad. In particular, mutation of threonine 479 likely impairs the open–closed transition of the enzyme by altering the network of hydrogen bonds between helices H1α, H, and I. These results shed new light on the evolution of IspS in monocots, suggesting that isoprene emission is an ancestral trait within the Arecaceae family. The identification of IspS from Arecaceae provides promising novel enzymes for the production of isoprene in heterologous systems and allows the screening and selection of commercially relevant palm varieties with lower environmental impact.

PATHcre8: A Tool That Facilitates the Searching for Heterologous Biosynthetic Routes.

Developing computational tools that can facilitate the rational design of cell factories producing desired products at increased yields is challenging, as the tool needs to take into account that the preferred host organism usually has compounds that are consumed by competing reactions that reduce the yield of the desired product. On the other hand, the preferred host organisms may not have the native metabolic reactions needed to produce the compound of interest; thus, the computational tool needs to identify the metabolic reactions that will most efficiently produce the desired product. In this regard, we developed the generic tool PATHcre8 to facilitate an optimized search for heterologous biosynthetic pathway routes. PATHcre8 finds and ranks biosynthesis routes in a large number of organisms, including Cyanobacteria. The tool ranks the pathways based on feature scores that reflect reaction thermodynamics, the potentially toxic products in the pathway (compound toxicity), intermediate products in the pathway consumed by competing reactions (product consumption), and host-specific information such as enzyme copy number. A comparison with several other similar tools shows that PATHcre8 is more efficient in ranking functional pathways. To illustrate the effectiveness of PATHcre8, we further provide case studies focused on isoprene production and the biodegradation of cocaine. PATHcre8 is free for academic and nonprofit users and can be accessed at https://www.cbrc.kaust.edu.sa/pathcre8/.

Alpine snowpit profiles of polar organic compounds from Mt. Tateyama central Japan: Atmospheric transport of organic pollutants with Asian dust

Snowpit samples (n = 10) were collected (19 April 2008) from the snowpit sequences (depth 6.60 m) at the Murodo-Daira site (36.58°N, 137.60°E, elevation of 2450 m a.s.l.) of Mt. Tateyama (3015 m a.s.l.), central Japan. The first time, low molecular weight diacids, ω-oxoacids, pyruvic acid, and α-dicarbonyls were measured for this snowpit sequence. Higher concentrations of short-chain diacids (C2–C5) are observed in dusty snow than non-dusty snow samples. Longer chain diacids (C7–C12) are significant in granular and dusty snow samples. Aromatic and aliphatic unsaturated diacids showed higher concentrations in the slightly dusty layer deposited in winter. Except for a clean layer, molecular distributions of diacids are characterized by the predominance of oxalic acid (C2, ave, 20 ± 22 ng/g-snow) followed by succinic (C4, 7.2 ± 5.9 ng/g -snow), and malonic acids (C3, 3.3 ± 2.9 ng/g -snow) for all the snow layers. Lower C3/C4 ratios (0.46) suggest that organic aerosols are rather fresh without serious photochemical aging during the long-range transport over central Japan. The higher concentrations of the secondary species in dusty snow than non-dusty samples were mainly attributed to the heterogeneous reaction. The strong correlations of incloud oxidation products of isoprene, aromatic acids, and fatty acids suggest that condensation, oxidation, and photolysis are important reaction mechanisms for the formation of diacids. Chinese Loess (Kosa particles) and Mongolian Gobi desert's dust provided the surface area for polar organic compounds, traveled to several thousand kilometers in the lower troposphere, and snow metamorphism altered the chemical composition of diacids and related compounds.

Paper Mill Sludge as a Source of Sugars for Use in the Production of Bioethanol and Isoprene

Paper mill sludge (PMS) solids are predominantly comprised of cellulosic fibers and fillers rejected during the pulping or paper making process. Most sludges are dewatered and discharged into landfills or land spread at a cost to the mill; creating large economic and environmental burdens. This lignocellulosic residual stream can be used as a source of sugars for microbial fermentation to renewable chemicals. The aim of this study was to determine the possibility of converting mill sludge to sugars and then fermentation to either isoprene or ethanol. Chemical analysis indicated that the cellulosic fiber composition between 28 to 68% and hemicellulose content ranged from 8.4 to 10.7%. Calcium carbonate concentration in the sludge ranged from 0.4 to 34%. Sludge samples were enzyme hydrolyzed to convert cellulose fibers to glucose, percent conversion ranged from 10.5 to 98%. Calcium carbonate present with the sludge resulted in low hydrolysis rates; washing of sludge with hydrochloric acid to neutralize the calcium carbonate, increased hydrolysis rates by 50 to 88%. The production of isoprene “very low” (190 to 470 nmol) because the isoprene yields were little. Using an industrial yeast strain for fermentation of the sludge sugars obtained from all sludge samples, the maximum conversion efficiency was achieved with productivity ranging from 0.18 to 1.64 g L−1 h−1. Our data demonstrates that PMS can be converted into sugars that can be fermented to renewable chemicals for industry.

Sources and Sinks of Isoprene in the Global Open Ocean: Simulated Patterns and Emissions to the Atmosphere

AbstractThe ocean is a source of isoprene to the atmosphere. Although their global estimates are relatively low compared with the terrestrial source, these emissions have an influence on atmospheric chemistry. The lack of knowledge about the sources and sinks of isoprene in the ocean has hitherto precluded a precise assessment of when and where these emissions might be significant. Here we use the general circulation and biogeochemistry model Nucleus for European Modelling of the Ocean, Pelagic Interaction Scheme for Carbon and Ecosystem Studies (NEMO‐PISCES) to explore different parameterizations of the 3D oceanic sources and sinks of isoprene. In addition, we investigate a representation of the isoprene emission due to photoproduction in the sea surface microlayer. Our model estimates are complemented by a new data compilation of laboratory isoprene production rates and in situ isoprene concentrations. This study constitutes the first attempt to simulate isoprene in a global 3D ocean biogeochemical model. We find that sea surface temperature is an important driver modulating phytoplankton isoprene production and that light levels only play a secondary role at the scale of the global ocean. Furthermore, the use of a variable biochemical consumption rate improves the model‐data comparison. We show the importance of isoprene production below the mixed layer and, as a consequence, demonstrate that models based on 2D surface satellite chlorophyll‐a could miss up to 18.5% of oceanic isoprene emissions. The oceanic isoprene emissions to the atmosphere are estimated to 0.66 (0.43–0.82) Tg C yr−1 in the low range of previous estimates.

Biocatalytic production of isoprene by fermentation of metabolically engineered Clostridium ljungdahlii on syngas

Biocatalytic production of isoprene by fermentation of metabolically engineered <i>Clostridium ljungdahlii</i> on syngas

Efficient Route for the Production of Isoprene via Decarboxylation of Bioderived Mevalonolactone

Isoprene production from biomass via solely biochemical processes is inherently limited by the low yields of the biological pathways. In this work, we demonstrate that isoprene can be efficiently produced via a hybrid bio/thermochemical process, combining the efficient fermentation of cellulosic sugars to mevalonolactone (MVL) with the acid-catalyzed MVL decarboxylation to isoprene. We report herein the thermochemical conversion of MVL to isoprene over inexpensive amorphous SiO2/Al2O3. A detailed investigation into the reaction conditions and the Si/Al ratio shows that isoprene formation is maximized over high-SiO2-content samples at mild temperatures (225–250 °C) that prevent its secondary oligomerization to alkylated aromatics and cyclic olefins. The highest isoprene yield is attained over SiO2/Al2O3 with 90 wt % SiO2 at 250 °C and 1.4 h–1, corresponding to ∼60% of the theoretical maximum. Acidity-performance correlations reveal the key role of Brønsted acidity in the reaction.

Converting formaldehyde-methylethylketone adduct to a nonlinear C5 1,3-diol over Pt-ceria catalysts for isoprene production

Isoprene has outmost importance in the manufacture of elastomer. Herein, an alternative approach for isoprene production from readily available chemicals is reported: condensation of methyl ethyl ketone and formaldehyde, followed by the hydrogenation and dehydration reaction. The focus was paid on the hydrogenation reaction over Pt-ceria catalysts giving 2-methyl-1,3-butanediol, where the influence of Ce species on the catalyst structure was studied, and the structure-activity relationship was established. It deduced that the presence of CeO2 appeared to be essential for the catalyst structure (e.g., dispersion, morphology) and the enhanced catalytic performance (e.g., activating H2, facilitating the reaction), these benefited from the presence of the oxygen vacancies on CeO2 surface. In addition, a relatively weak Pt-support interaction gave larger Pt particles which resulted in a higher yield. Finally, the application of the as-synthesized 2-methyl-1,3-butanediol in isoprene production was performed in the presence of the heteropolyacid catalysts, affording isoprene in ∼80 % yield.

Isoprene flux from permeable carbonate sediments on the Great Barrier Reef

Isoprene is the most abundant biogenic volatile organic compound (BVOC) on the planet, with annual emissions accounting for up to half of all BVOC emissions. Isoprene has been measured extensively in terrestrial habitats where it is highly abundant; however, there is limited knowledge on marine systems where it is found at lower concentrations. Here, we report for the first time isoprene fluxes from coral reef permeable carbonate sediments with a cover of microphytobenthos (MPB) from Heron and Lizard Islands, on the southern and northern ends of the Great Barrier Reef, respectively. Using advective and diffusive benthic chambers, we measured isoprene fluxes over full diel cycles on both islands. Net effluxes of isoprene from the sediment to the water column were observed at both Heron Island (mean: 10.0 ± 1.1 nmol m2 h−1) and Lizard Island (mean: 3.9 ± 0.9 nmol m2 h−1). Light isoprene fluxes were much higher on Heron Island than on Lizard Island and both islands had lower isoprene emissions in the dark. Higher isoprene fluxes during the day reflects the role of MPB photosynthesis in isoprene production. Lower isoprene fluxes at night is most likely due to isoprene consumption by microbial activity or less production in the absence of photosynthesis. The contribution of benthic isoprene emissions from coral reef carbonate sands worldwide (0.52 Gg C y−1) were estimated to represent less than 0.005% of the global marine atmospheric fluxes (11,600 Gg C y−1).

Efficient Synthesis of a Nonlinear C5 1,3-Diol from Butanone and Formalin under Mild Conditions for Isoprene Production

An alternative approach for isoprene production from readily available formaldehyde and 2-butanone under mild conditions is reported, where efficient synthesis of a nonlinear C5 1,3-diol was involv...

382-P: Exhaled Isoprene Products Change during Hypoglycemia in Type 1 Diabetes and Home Breath Capture Is Feasible as a Diagnostic Tool

Detection of hypoglycemia is important to reduce risk and optimize glucose in T1D. Noninvasive glucose detection methods have not been fully explored. Exhaled breath isoprene, a component of sterol metabolism, has been associated with hypoglycemia in controlled studies in a limited population in the laboratory setting. Home-monitoring of breath isoprene levels may permit noninvasive hypoglycemia detection. We conducted an exploratory study measuring exhaled volatile organic compounds (VOCs) in breath samples collected during hypoglycemia (CBG &amp;lt;70 mg/dL) compared to euglycemia (CBG 70-180 mg/dL) under free-living conditions in 10 subjects age 7-74 with T1D. Breath samples were collected using designated breath capture bags and processed 1-4 weeks later by proton-transfer-reaction time-of-flight (PTR TOF) mass spectrometry. Over 100 VOCs were identified in 52 breath samples (25 hypoglycemia, 27 euglycemia). During hypoglycemia, isoprene increased 37% (p&amp;lt;0.05) and its oxidation products methyl vinyl ketone (MVK) and methacrolein (MACR) decreased 59% (p&amp;lt;0.05). However, predictive modelling using metabolite concentration as the input could not reliably predict whether the breath sample was collected during hypoglycemia or euglycemia. All other measured VOCs were not statistically different. This is the first free-living study to evaluate exhaled VOCs in patients with T1D. We successfully replicated findings of a prior study done in a controlled laboratory setting suggesting isoprene concentration in human breath increases during hypoglycemia. We further describe decreased MVK and MACR during hypoglycemia and home breath capture may be feasible for diagnostics in medical conditions. In addition, the physiology of glucose changes on sterol metabolism is worthy of further study. Finally, identification of an exhaled marker of glucose levels hints at a possible mechanism of detection by so-called diabetes alert dogs. Disclosure E.A. Los: Advisory Panel; Self; Medtronic. W.L. Stone: None. G. Ford: None. Funding East Tennessee State University (18-025M)

Microbial metabolism of isoprene: a much-neglected climate-active gas.

The climate-active gas isoprene is the major volatile produced by a variety of trees and is released into the atmosphere in enormous quantities, on a par with global emissions of methane. While isoprene production in plants and its effect on atmospheric chemistry have received considerable attention, research into the biological isoprene sink has been neglected until recently. Here, we review current knowledge on the sources and sinks of isoprene and outline its environmental effects. Focusing on degradation by microbes, many of which are able to use isoprene as the sole source of carbon and energy, we review recent studies characterizing novel isoprene degraders isolated from soils, marine sediments and in association with plants. We describe the development and use of molecular methods to identify, quantify and genetically characterize isoprene-degrading strains in environmental samples. Finally, this review identifies research imperatives for the further study of the environmental impact, ecology, regulation and biochemistry of this interesting group of microbes.

Investigation of AISI 316 Stainless Steel Corrosion in Perchloric Acid

The synthesis of 4,4-dimethyl-1,3-dioxane for the production of isoprene in perchloric acid is carried out. The synthesis apparatus is made of AISI 316 stainless steel. Here, AISI 316 steel corrosion in pure perchloric acid and in the presence of benzotriazole as a corrosion inhibitor is investigated by the potentiodynamic method. Figure 1 shows the polarization curves in 1 M perchloric acid at various concentrations of benzotriazole. It is seen that with an increase in the inhibitor concentration, the curves shift to the cathode side and the cathode currents decrease more strongly than the anode currents. Therefore, benzotriazole in perchloric acid is an cathodic action inhibitor.The Tafel relation for the polarization curve can be represented as the equation (1) of a straight line, which is convenient for determining the corrosion currents icorr . Polarization curves at various inhibitor concentrations are shown in Figure 2 in the coordinates of this equation. Here icorr was defined as currents at (Е – Еcorr ) = 0.Corrosion currents, corrosion rates and inhibition efficiencies for various concentrations of benzotriazole are given in the Table. Figure 1

Engineered Escherichiacoli strains as platforms for biological production of isoprene.

Volatile compounds can be produced by fermentation from genetically engineered microorganisms. Escherichia coli strains are mainly used for isoprene production owing to their higher titers; however, this has thus far been confined to only strains BL21, BL21 (DE3), Rosetta, and BW25113. Here, we tested four groups of E. coli strains for improved isoprene production, including K‐12 (DH5α, BW25113, W3110, MG1655, XL1‐Blue, and JM109), B [Rosetta (DE3), BL21, and BL21 (DE3)], Crooks C, and Waksman W strains. The isoprene productivity of BL21 and MG1655 was remarkably higher than that of the others in 5‐L fermentation, and scale‐up fermentation (300 L) of BL21 was successfully performed. This system shows potential for biobased production of fuel and volatile compounds in industrial applications.

Depositing Different Carbon Species on MoP to Enhance Its Activity for Isoprene Production in Different Ways

To study the effects of aromatic and olefinic carbon on isoprene synthesis, different carbon sources were used to prepare a variety of carbon deposited MoP catalysts for the condensation of isobute...

The production of isoprene from cellulose using recombinant Clostridium cellulolyticum strains expressing isoprene synthase.

Isoprene is an important bulk chemical which is mostly derived from fossil fuels. It is used primarily for the production of synthetic rubber. Sustainable, biotechnology‐based alternatives for the production of isoprene rely on the fermentation of sugars from food and feed crops, creating an ethical dilemma due to the competition for agricultural land. This issue could be addressed by developing new approaches based on the production of isoprene from abundant renewable waste streams. Here, we describe a proof‐of‐principle approach for the production of isoprene from cellulosic biomass, the most abundant polymer on earth. We engineered the mesophilic prokaryote Clostridium cellulolyticum, which can degrade cellulosic biomass, to utilize the resulting glucose monomers as a feedstock for the production of isoprene. This was achieved by integrating the poplar gene encoding isoprene synthase. The presence of the enzyme was confirmed by targeted proteomics, and the accumulation of isoprene was confirmed by GC‐MS/MS. We have shown for the first time that engineered C. cellulolyticum can be used as a metabolic chassis for the sustainable production of isoprene.

Advanced Strategies for Production of Natural Products in Yeast.

Natural products account for more than 50% of all small-molecule pharmaceutical agents currently in clinical use. However, low availability often becomes problematic when a bioactive natural product is promising to become a pharmaceutical or leading compound. Advances in synthetic biology and metabolic engineering provide a feasible solution for sustainable supply of these compounds. In this review, we have summarized current progress in engineering yeast cell factories for production of natural products, including terpenoids, alkaloids, and phenylpropanoids. We then discuss advanced strategies in metabolic engineering at three different dimensions, including point, line, and plane (corresponding to the individual enzymes and cofactors, metabolic pathways, and the global cellular network). In particular, we comprehensively discuss how to engineer cofactor biosynthesis for enhancing the biosynthesis efficiency, other than the enzyme activity. Finally, current challenges and perspective are also discussed for future engineering direction.

Chemical Structure of Catalysts for Processing of High-Boiling By-Products of Isoprene Synthesis

Phase composition of catalysts for the processing of high-boiling by-products of isoprene production from isobutylene and formaldehyde was determined. A comparison of the chemical structure of the most effective K-97 and K-15 catalysts made it possible to find the role of boron oxide in the decrease in the coke formation.

Application of Stable Isotope Tracing to Elucidate Metabolic Dynamics During Yarrowia lipolytica α-Ionone Fermentation.

SummaryTargeted metabolite analysis in combination with 13C-tracing is a convenient strategy to determine pathway activity in biological systems; however, metabolite analysis is limited by challenges in separating and detecting pathway intermediates with current chromatographic methods. Here, a hydrophilic interaction chromatography tandem mass spectrometry approach was developed for improved metabolite separation, isotopologue analysis, and quantification. The physiological responses of a Yarrowia lipolytica strain engineered to produce ∼400 mg/L α-ionone and temporal changes in metabolism were quantified (e.g., mevalonate secretion, then uptake) indicating bottleneck shifts in the engineered pathway over the course of fermentation. Dynamic labeling results indicated limited tricarboxylic acid cycle label incorporation and, combined with a measurable ATP shortage during the high ionone production phase, suggested that electron transport and oxidative phosphorylation may limit energy supply and strain performance. The results provide insights into terpenoid pathway metabolic dynamics of non-model yeasts and offer guidelines for sensor development and modular engineering.