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Home » Archives for May 2021

May 2021

Archives for May 2021

Bailey Published in The Conversation

May 26, 2021 by Kayla Benson

Oil companies are going all-in on petrochemicals – and green chemistry needs help to compete

A Chevron oil refinery in Richmond, California.
AP Photo/Paul Sakuma

Constance B. Bailey, University of Tennessee

Global oil consumption declined by roughly 9% in 2020 as the pandemic reduced business and pleasure travel, factory production and transportation of goods. This abrupt drop accelerated an ongoing shift from fossil fuels to renewable energy.

U.S. government forecasts show that oil use for transportation, industry, construction, heating and electricity is declining and will continue to drop in the coming years. This trend has enormous implications for the oil industry: As the International Energy Agency observed in 2020, “No oil and gas company will be unaffected by clean energy transitions.”

About 80% of every barrel of oil refined in the U.S. today is used to make gasoline, distillate (diesel) and jet fuel, with the rest going into petrochemical products. EIA

Many of these companies are trying to make up losses by boosting production of petrochemicals derived from oil and natural gas. Today roughly 80% of every barrel of oil is used to make gasoline, diesel and jet fuel, with the rest going into petrochemical products. As demand for petroleum fuels gradually declines, the amount of oil used for that “other” share will grow.

This makes sense as a business strategy, but here’s the problem: Researchers are working to develop more sustainable replacements for petrochemical products, including bio-based plastics and specialty chemicals. However, petrochemicals can be manufactured at a fraction of the cost. As a biochemist working to develop environmentally benign versions of valuable chemicals, I’m concerned that without adequate support, pioneering green chemistry research will struggle to compete with fossil-based products.

This video from Austrian oil and gas company OMV shows how petrochemicals serve as building blocks for goods from pharmaceuticals to bike helmets.

Pivoting toward petrochemicals

Petrochemicals are used in millions of products, from plastics, detergents, shampoos and makeup to industrial solvents, lubricants, pharmaceuticals, fertilizer and carpeting. Over the next 20 years, oil company BP projects that this market will grow by 16% to 20%.

Oil companies are ramping up to increase petrochemical production. In the Saudi Arabian town of Yanbu, for example, two state-owned companies, Saudi Aramco and Sabic, are planning a new complex that will produce 9 million metric tons of petrochemicals each year, transforming Arabian light crude oil into lubricants, solvents and other products.

These changes are happening across the global industry. Several Chinese companies are constructing factories that will convert about 40% of their oil into chemicals such as p-Xylene, a building block for industrial chemicals. Exxon-Mobil began expanding research and development on petrochemicals as far back as 2014.

The International Energy Agency projects that petrochemicals will account for one-third of growth in global oil demand through 2030 and half of growth in demand through 2050.

The promise of green chemistry

At the same time, in the U.S. and other industrialized countries, health, environmental and security issues are driving a quest to produce sustainable alternatives for petroleum-based chemicals. Drilling for oil and natural gas, using petrochemicals and burning fossil fuels have widespread environmental and human health impacts. High oil consumption also raises national security concerns.

The Department of Energy has led basic research on bioproducts through its national laboratories and funding for university BioEnergy Research Centers. These labs are developing plant-based, sustainable domestic biofuels and bioproducts, including petrochemical replacements, through a process called “metabolic engineering.”

Researchers like me are using enzymes to transform leafy waste matter from crops and other sources into sugars that can be consumed by microorganisms – typically, bacteria and fungi such as yeast. These microorganisms then transform the sugars into molecules, similar to the way that yeast converts sugar to ethanol, fermenting it into beer.

In the creation of bioproducts, instead of creating ethanol the sugar is transformed into other molecules. We can design these metabolic pathways to create solvents; components in widely used polymers like nylon; perfumes; and many other products.

My laboratory is exploring ways to engineer enzymes – catalysts produced by living cells that cause or speed up biochemical reactions. We want to produce enzymes that can be put into engineered bacteria, in order to make structurally complex natural products.

The overall goal is to put carbon and oxygen together in a predictable fashion, similar to the chemical structures created through petroleum-based chemistry. But the green approach uses natural substances instead of oil or natural gas as building blocks.

This isn’t a new concept. Enzymes in bacteria are used to make an important antibiotic, erythromycin, which was first discovered in 1952.

All of this takes place in a biorefinery – a facility that takes natural inputs like algae, crop waste or specially grown energy crops like switchgrass and converts them into commercially valuable substances, as oil refineries do with petroleum. After fermenting sugars with engineered microorganisms, a biorefinery separates and purifies microbial cells to produce a spectrum of bio-based products, including food additives, animal feed, fragrances, chemicals and plastics.

In response to the global plastic pollution crisis, one research priority is “polymer upcycling.” Using bio-based feedstocks can transform single-use water bottles into materials that are more recyclable than petroleum-based versions because they are easier to heat and remold.

Heaps of debris spill out of shipping containers.

Thousands of pounds of marine debris, much of it plastic, collects on Midway Atoll in the northern Pacific Ocean.
Holly Richards, USFWS

Reducing the cost gap

To replace polluting goods and practices, sustainable alternatives have to be cost-competitive. For example, many plastics currently end up in landfills because they’re cheaper to manufacture than to recycle.

High costs are also slowing progress toward a bioeconomy. Today research, development and manufacturing are more costly for bioproducts than for established petrochemical versions.

Governments can use laws and regulations to drive change. In 2018 the European Union set an ambitious goal of sourcing 30% of all plastics from renewable sources by 2030. In addition to reducing plastic pollution, this step will save energy: Petroleum-based plastics production ranks third in energy consumption worldwide, after energy production and transport.

Promoting bio-based products is compatible with President Biden’s all-of-government approach to climate change. Biomanufacturing investments could also help bring modern manufacturing jobs to rural areas, a goal of Biden’s American Jobs Plan.

But oil company investments in the design of novel chemicals are growing, and the chasm between the cost of petroleum-based products and those produced through emerging green technologies continues to widen. More efficient technologies could eventually flood existing petrochemical markets, further driving down the cost of petrochemicals and making it even harder to compete.

In my view, the growing climate crisis and increasing plastic pollution make it urgent to wean the global economy from petroleum. I believe that finding replacements for petroleum-based chemicals in many products we use daily can help move the world toward that goal.

[You’re smart and curious about the world. So are The Conversation’s authors and editors. You can read us daily by subscribing to our newsletter.]The Conversation

Constance B. Bailey, Assistant Professor of Chemistry, University of Tennessee

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Filed Under: Bailey, News

Heberle Lab Published in Data in Brief

May 25, 2021 by Kayla Benson

Heberle Lab Published their research “Dataset of asymmetric giant unilamellar vesicles prepared via hemifusion: Observation of anti-alignment of domains and modulated phases in asymmetric bilayers” in Data in Brief.

The data provided with this paper are confocal fluorescence images of symmetric giant unilamellar vesicles (GUVs) and asymmetric giant unilamellar vesicles (aGUVs). In this work, aGUVs were prepared using the hemifusion method and are labelled with two different fluorescent dyes, named TFPC and DiD. Both dyes show strong preference for the liquid-disordered (Ld) phase instead of the liquid-ordered (Lo) phase. The partition of these dyes favoring the Ld phase leads to bright Ld phase and dark Lo phase domains in symmetric GUVs observed by fluorescence microscopy. In symmetric vesicles, the bright and the dark domains of the inner and the outer leaflets are aligned. In aGUVs, the fluorescent probe TFPC exclusively labels the aGUV outer leaflet.

Here, they show a dataset of fluorescence micrographs obtained using scanning fluorescence confocal microscopy. For the system chosen, the fluorescence signal of TFPC and DiD show anti-alignment of the brighter domains on aGUVs. Important for this dataset, TFPC and DiD have fluorescence emission centered in the green and far-red region of the visible spectra, respectively, and the dyes’ fluorescence emission bands do not overlap. This dataset were collected in the same conditions of the dataset reported in the co-submitted work (Enoki, et al. 2021) where most of aGUVs show domains alignment. In addition, they show micrographs of GUVs displaying modulated phases and macrodomains. They also compare the modulated phases observed in GUVs and aGUVs. For these datasets, they collected a sequence of micrographs using confocal microscopy varying the z-position, termed a z-stack. Images were collected in a scanning microscope Nikon Eclipse C2+ (Nikon Instruments, Melville, NY). Additional samples used to measure the lipid concentrations and to prepare GUVs with accurate lipid fractions are also provided with this paper.

Filed Under: Heberle

Campagna Lab published in Frontiers In Microbiology

May 20, 2021 by Kayla Benson

The Campagna lab published their work “Comparative Decomposition of Humans and Pigs: Soil Biogeochemistry, Microbial Activity and Metabolomic Profiles” in Frontiers In Microbiology.

Vertebrate decomposition processes have important ecological implications and, in the case of human decomposition, forensic applications. Animals, especially domestic pigs (Sus scrofa), are frequently used as human analogs in forensic decomposition studies. However, recent research shows that humans and pigs do not necessarily decompose in the same manner, with differences in decomposition rates, patterns, and scavenging.

The objective of this study was to extend these observations and determine if human and pig decomposition in terrestrial settings have different local impacts on soil biogeochemistry and microbial activity. In two seasonal trials (summer and winter), we simultaneously placed replicate human donors and pig carcasses on the soil surface and allowed them to decompose. In both human and pig decomposition-impacted soils, they observed elevated microbial respiration, protease activity, and ammonium, indicative of enhanced microbial ammonification and limited nitrification in soil during soft tissue decomposition. Soil respiration was comparable between summer and winter, indicating similar microbial activity; however, the magnitude of the pulse of decomposition products was greater in the summer.

Using untargeted metabolomics and lipidomics approaches, they identified 38 metabolites and 54 lipids that were elevated in both human and pig decomposition-impacted soils. The most frequently detected metabolites were anthranilate, creatine, 5-hydroxyindoleacetic acid, taurine, xanthine, N-acetylglutamine, acetyllysine, and sedoheptulose 1/7-phosphate; the most frequently detected lipids were phosphatidylethanolamine and monogalactosyldiacylglycerol. Decomposition soils were also significantly enriched in metabolites belonging to amino acid metabolic pathways and the TCA cycle.

Comparing humans and pigs, they noted several differences in soil biogeochemical responses. Soils under humans decreased in pH as decomposition progressed, while under pigs, soil pH increased. Additionally, under pigs we observed significantly higher ammonium and protease activities compared to humans. We identified several metabolites that were elevated in human decomposition soil compared to pig decomposition soil, including 2-oxo-4-methylthiobutanoate, sn-glycerol 3-phosphate, and tryptophan, suggesting different decomposition chemistries and timing between the two species.

Together, this work shows that human and pig decomposition differ in terms of their impacts on soil biogeochemistry and microbial decomposer activities, adding to our understanding of decomposition ecology and informing the use of non-human models in forensic research.

The group also published their work “Enterococcus faecalis Readily Adapts Membrane Phospholipid Composition to Environmental and Genetic Perturbation” in Frontiers In Microbiology. 

The bacterial lipid membrane, consisting both of fatty acid (acyl) tails and polar head groups, responds to changing conditions through alteration of either the acyl tails and/or head groups. This plasticity is critical for cell survival as it allows maintenance of both the protective nature of the membrane as well as functioning membrane protein complexes. Bacteria that live in fatty-acid rich environments, such as those found in the human host, can exploit host fatty acids to synthesize their own membranes, in turn, altering their physiology. Enterococcus faecalis is such an organism: it is a commensal of the mammalian intestine where it is exposed to fatty-acid rich bile, as well as a major cause of hospital infections during which it is exposed to fatty acid containing-serum. Within, the group employed an untargeted approach to detect the most common phospholipid species of E. faecalis OG1RF via ultra-high performance liquid chromatography high-resolution mass spectrometry (UHPLC-HRMS).

The group examined not only how the composition responds upon exposure to host fatty acids but also how deletion of genes predicted to synthesize major polar head groups impact lipid composition. Regardless of genetic background and differing basal lipid composition, all strains were able to alter their lipid composition upon exposure to individual host fatty acids. Specific gene deletion strains, however, had altered survival to membrane damaging agents. Combined, the enterococcal lipidome is highly resilient in response to both genetic and environmental perturbation, likely contributing to stress survival.

Filed Under: Analytical Chemistry, Campagna

Honors Day 2021

May 17, 2021 by Kayla Benson

Department of Chemistry recognized the achievements among students, faculty and staff members of the department. Below, you will find a complete list of recipients for the Honors Day 2021.

UNDERGRADUATE AWARDS

ACS-Hach Land Grant Scholarship Allyssa C. Evans, Natalie J. Parsons
CRC Press General Chemistry Award Amy N. Okafor
C.W. Keenan Outstanding General Chemistry Student Award Matthew P. McCoig
Department of Chemistry Scholarships Rowan K. Borsari, Macy M. Hudson
Dr. Lucy E. Scroggie Scholarship Rachel L. Sparks
Halbert and Anne Carmichael Scholarship Isabelle M. Dancer, Ghaeath S. Abbas
C.A. Buehler Chemistry Scholarship Nicholas M. Legaux
Melaven-Rhenium Scholarships Rowan K. Borsari, Macy M. Hudson, Clayton T. West

GRADUATE AWARDS

Keenan Teaching Award Aleksandra Antevska
Outstanding Teaching Award Kevin M. Blatchford, Avery L. Wood
Gleb Mamantov Graduate Chemistry Scholar Jinchao Lou
Jerome Eastham Fellowship in Organic Chemistry Shelby L. Strausser
Eugene John Barber Fellowship in Physical Chemistry Gavin A. McCarver
Judson Hall Robertson Fellowship in Analytical Chemistry Amber L. H. Gray

STUDENT RECOGNITIONS

Goldwater Scholarship Elijah G. Hix
Winners of the Board of Visitor’s Poster Competition Alan D. Fried, Luther J. Langston II
Shull Wollan Center Graduate Research Fellowship Pagnareach Tin
Selected to Attend NX School Alexandria N.  Bone

FACULTY AWARDS

Ziegler Professorship S. Michael Kilbey
2021 Emerging Leader in Molecular Spectroscopy Bhavya Sharma
OpenEye Outstanding Junior Faculty Award Kostas Vogiatzis
Excellence in Research Award Bin Zhao

FACULTY RECOGNITION

New Faculty Viktor Nemykin, Joshua A. Baccile
In Memoriam Fred M. Schell, Albert A. Tuinman

Filed Under: Artsci, News

Jenkins Group Published in Langmuir and Chemical Science

May 12, 2021 by Kayla Benson

The Jenkins Group published their work “Imidazolinium N-Heterocyclic Carbene Ligands for Enhanced Stability on Gold Surfaces” in Langmuir. This work explores the preparation and stability of NHC-coated gold surfaces using imidazolium and imidazolinium NHC ligands. X-ray photoelectron spectroscopy and surface-enhanced Raman spectroscopy demonstrate the attachment of NHC ligands to the gold surface and show enhanced stability of imidazolinium compared to the traditional imidazolium under harsh acidic conditions.

The Jenkins Group also published their work “Actinide tetra-N-heterocyclic carbene ‘sandwiches’” in Chemical Science. “We synthesized new “sandwich” complexes by placing two NHC macrocycles around a single actinide ion,” Jenkins said. “I am particularly excited about this paper since it is work that I began on my sabbatical at the University of Edinburgh almost four years ago.  It is the beginning of a new research area in my group, which is f-block NHC chemistry.” 

Graphical abstract: Actinide tetra-N-heterocyclic carbene ‘sandwiches’The complexes were characterized by a range of experimental methods and DFT calculations. X-ray crystallography confirms the geometry at the metal centre can be set by the size of the macrocyclic ring, leading to either square prismatic or square anti-prismatic shapes; the geometry of the latter is retained in solution, which also undergoes reversible, electrochemical one-electron oxidation or reduction for the uranium variant. DFT calculations reveal a frontier orbital picture that is similar to thorocene and uranocene, in which the NHC ligands show almost exclusively σ-donation to the metal without π-backbonding.

Filed Under: Artsci, Jenkins, News

Heberle Published in BBA – Biomembranes

May 2, 2021 by Kayla Benson

The Heberle Lab published their research “Investigation of the domain line tension in asymmetric vesicles prepared via hemifusion” Biochimica et Biophysica Acta Biomembranes.

The plasma membrane (PM) is asymmetric in lipid composition. The distinct and characteristic lipid compositions of the exoplasmic and cytoplasmic leaflets lead to different lipid-lipid interactions and physical-chemical properties in each leaflet. The exoplasmic leaflet possesses an intrinsic ability to form coexisting ordered and disordered fluid domains, whereas the cytoplasmic leaflet seems to form a single fluid phase.

To better understand the interleaflet interactions that influence domains, the lab compared asymmetric model membranes that capture salient properties of the PM with simpler symmetric membranes. Using asymmetric giant unilamellar vesicles (aGUVs) prepared by hemifusion with a supported lipid bilayer, they investigate the domain line tension that characterizes the behavior of coexisting ordered + disordered domains. The line tension can be related to the contact perimeter of the different phases. Compared to macroscopic phase separation, the appearance of modulated phases was found to be a robust indicator of a decrease in domain line tension. Symmetric GUVs of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC)/1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC)/cholesterol (chol) were formed into aGUVs by replacing the GUV outer leaflet with DOPC/chol = 0.8/0.2 in order to create a cytoplasmic leaflet model. These aGUVs revealed lower line tension for the ordered + disordered domains of the exoplasmic model leaflet.

Filed Under: Heberle

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