Expect higher grass pollen, allergen exposure in coming century

A study provides the first evidence that pollen production is significantly stimulated by elevated carbon dioxide in a grass species as a result of climate change, which may have significant impact on human health. Credit: UMass Amherst

Results of a new study by scientists at the University of Massachusetts Amherst strongly suggest that there will be notable increases in grass pollen production and allergen exposure up to 202 percent in the next 100 years, leading to a significant, worldwide impact on human health due to predicted rises in carbon dioxide (CO2) and ozone (O3) due to climate change.

While CO2 stimulates reproduction and growth in plants, ozone has a negative impact on plant growth, the authors point out. In this study in Timothy grass, researchers led by environmental health scientist Christine Rogers of the UMass Amherst School of Public Health and Health Sciences (SPHHS) determined the interactive effects of CO2 and ozone at projected higher levels on pollen production and concentrations of a Timothy grass pollen protein that is a major human allergen. Findings are reported in the current issue of PLOS ONE.

Rogers and plant science colleagues at UMass Amherst, with postdoctoral researcher and first author Jennifer Albertine, write, "The implications of increasing CO2 for human health are clear. Stimulation of grass pollen production by elevated CO2 will increase airborne concentrations and increase exposure and suffering in grass pollen-allergic individuals."

Rogers notes that, "This is the first evidence that pollen production is significantly stimulated by elevated carbon dioxide in a grass species and has worldwide implications due to the ubiquitous presence of grasses in all biomes and high prevalence of grass pollen allergy. These results are similar to our other studies performed in other highly allergenic taxa such as ragweed but with more extreme outcomes and wider impacts."

For these experiments, the researchers exposed grass plants in specially designed continuously stirred tank reactor chambers that allow researchers to expose plants to different atmospheric gas concentrations. They established four experimental atmospheric treatments:

• control, current atmosphere (30 ppb O3 and 400 ppm CO2)
• elevated O3, current CO2 (80 ppb O3, 400 ppm CO2)
• current O3, elevated CO2 (30 ppb O3, 800 ppm CO2)
• elevated O3, elevated CO2 (80 ppb O3, 800ppm CO2)

At the appropriate plant development stage, Albertine and colleagues bagged flowers, captured and measured pollen amounts and extracted the allergen protein Phl p 5 from pollen samples for measurement by enzyme-linked immunosorbent assay (ELISA).

They found that elevated CO2 of 800 ppm, increased pollen production per flower by 53 percent while the different ozone levels had no effect on the amount of pollen produced. There was also a trend of increased number of plants flowering in response to elevated CO2 further increasing pollen production up to 200 percent. While elevated ozone did decrease the Phl p 5 allergen content in pollen, "the strong CO2-stimulation of pollen production suggests increased exposure to Timothy grass allergen overall," even if O3 projections are realized, the authors note.

They add that the health implications of increased ozone are "more complex" because higher levels of this greenhouse gas irritate mucous membranes and worsen the allergic airway response. Projected ozone increases "would likely elicit negative respiratory health effects independent of any health effects as a result of increased pollen by elevated CO2."

Source:  University of Massachusetts at Amherst

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New conversion process turns biomass 'waste' into lucrative chemical products

Purdue's R.B. Wetherill Professor of Chemistry, holds a small vial containing results of a new catalytic process that can convert the lignin in wood into high-value chemical products for use in fragrances and flavoring.
Credit: Purdue University photo/Mark Simons

A new catalytic process is able to convert what was once considered biomass waste into lucrative chemical products that can be used in fragrances, flavorings or to create high-octane fuel for racecars and jets.

A team of researchers from Purdue University's Center for Direct Catalytic Conversion of Biomass to Biofuels, or C3Bio, has developed a process that uses a chemical catalyst and heat to spur reactions that convert lignin into valuable chemical commodities. Lignin is a tough and highly complex molecule that gives the plant cell wall its rigid structure.

Mahdi Abu-Omar, the R.B. Wetherill Professor of Chemistry and Professor of Chemical Engineering and associate director of C3Bio, led the team.

"We are able to take lignin -- which most biorefineries consider waste to be burned for its heat -- and turn it into high-value molecules that have applications in fragrance, flavoring and high-octane jet fuels," Abu-Omar said. "We can do this while simultaneously producing from the biomass lignin-free cellulose, which is the basis of ethanol and other liquid fuels. We do all of this in a one-step process."

Plant biomass is made up primarily of lignin and cellulose, a long chain of sugar molecules that is the bulk material of plant cell walls. In standard production of ethanol, enzymes are used to break down the biomass and release sugars. Yeast then feast on the sugars and create ethanol.

Lignin acts as a physical barrier that makes it difficult to extract sugars from biomass and acts as a chemical barrier that poisons the enzymes. Many refining processes include harsh pretreatment steps to break down and remove lignin, he said.

"Lignin is far more than just a tough barrier preventing us from getting the good stuff out of biomass, and we need to look at the problem differently," Abu-Omar said. "While lignin accounts for approximately 25 percent of the biomass by weight, it accounts for approximately 37 percent of the carbon in biomass. As a carbon source lignin can be very valuable, we just need a way to tap into it without jeopardizing the sugars we need for biofuels."

The Purdue team developed a process that starts with untreated chipped and milled wood from sustainable poplar, eucalyptus or birch trees. A catalyst is added to initiate and speed the desired chemical reactions, but is not consumed by them and can be recycled and used again. A solvent is added to the mix to help dissolve and loosen up the materials. The mixture is contained in a pressurized reactor and heated for several hours. The process breaks up the lignin molecules and results in lignin-free cellulose and a liquid stream that contains two additional chemical products, Abu-Omar said.

The liquid stream contains the solvent, which is easily evaporated and recycled, and two phenols, a class of aromatic hydrocarbon compounds used in perfumes and flavorings. A commonly used artificial vanilla flavoring is currently produced using a phenol that comes from petroleum, he said.

The team also developed an additional process that uses another catalyst to convert the two phenol products into high-octane hydrocarbon fuel suitable for use as drop-in gasoline. The fuel produced has a research octane rating greater than100, whereas the average gas we put into our cars has an octane rating in the eighties, he said.

The processes and resulting products are detailed in a paper published online in the Royal Society of Chemistry journal Green Chemistry. The U.S. Department of Energy funded the research.

In addition to Abu-Omar, co-authors include Trenton Parsell, a visiting scholar in the Department of Chemistry; chemical engineering graduate students Sara Yohe, John Degenstein, Emre Gencer, and Harshavardhan Choudhari; chemistry graduate students Ian Klein, Tiffany Jarrell, and Matt Hurt; agricultural and biological engineering graduate student Barron Hewetson; Jeong Im Kim, associate research scientist in biochemistry; Basudeb Saha, associate research scientist in chemistry; Richard Meilan, professor of forestry and natural reserouces; Nathan Mosier, associate professor of agricultural and biological engineering; Fabio Ribeiro, the R. Norris and Eleanor Shreve Professor of Chemical Engineering; W. Nicholas Delgass, the Maxine S. Nichols Emeritus Professor of Chemical Engineering; Clint Chapple, the head and distinguished professor of biochemistry; Hilkka I. Kenttamaa, professor of chemistry; and Rakesh Agrawal, the Winthrop E. Stone Distinguished Professor of Chemical Engineering.

The catalyst is expensive, and the team plans to further study efficient ways to recycle it, along with ways to scale up the entire process, Abu-Omar said.

"A biorefinery that focuses not only on ethanol, but on other products that can be made from the biomass is more efficient and profitable overall," he said. "It is possible that lignin could turn out to be more valuable than cellulose and could subsidize the production of ethanol from sustainable biomass."

The U.S. Department of Energy-funded C3Bio center is an Energy Frontier Research Center. It is part of Discovery Park's Energy Center and the Bindley Bioscience Center at Purdue.

Purdue Research Foundation has filed patent applications and launched a startup company, Spero Energy, which was founded by Abu-Omar.

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Source:  Purdue University

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