New bioprocesses for converting plant materials into valuable chemicals

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A team of scientists at the University of Illinois at Urbana-Champaign has developed a bioprocess using artificial yeast that completely and efficiently transforms plants consisting of acetate and xylose into high-value bioproducts.

Lignocellulosic, a wood-based material that gives plant cells structure, is the most abundant raw material on the planet and has long been seen as a source of renewable energy.It is mainly acetate and sugar glucose Xylose, All of these are released during decomposition.

In a treatise published in Nature CommunicationsThe team described its research to provide a viable way to overcome the toxicity of acetate to fermenting microorganisms such as yeast, which is one of the major obstacles to the commercialization of lignocellulosic biofuels. ..

“This is the first approach to demonstrate the efficient and full utilization of xylose and acetate for the production of biofuels,” said Yong Soo Jin, a professor of food science and human nutrition. Jin, an affiliate of the Carl R. Woese Institute for Genomic Biology, led the study with then-graduate student Liang Sun, the first author of this treatise.

Their methodology makes full use of xylose and acetate from the cell wall of switchgrass, converting acetate from unwanted by-products to valuable substrates and increasing the efficiency of yeast to convert sugars in hydrosolates. rice field.

“The ability to economically produce fine chemicals such as triacetic acid lactone (TAL) and vitamin A from the same precursor molecule using substances that are considered toxic and considered useless as an auxiliary carbon source for xylose. Okay, “said Acetyl Coenzyme A, Jin.

TAL is a versatile platform chemical currently available from petroleum refining and is used in the manufacture of plastics and food ingredients, says Sun, a PhD student at the University of Wisconsin-Madison. ..

In a previous study, co-author Soo Rin Kim, then Fellow of the Energy Biosciences Institute, designed a strain of the yeast Saccharomyces cerevisiae for rapid and efficient consumption of xylose. Kim is currently a faculty member at Kyungpook National University in South Korea.

In the current study, they created hemicellulose hydrolysates using switchgrass harvested at the U. of I. Energy Farm. Manipulated yeast cells were used to ferment glucose, xylose, and acetate in hydrosalate.

When glucose and acetate are provided together, S. Sacevisiae rapidly converted glucose to ethanol, lowering pH levels in cell cultures. However, acetate consumption was strongly inhibited and the culture was toxic to yeast cells under low pH conditions.

“These two carbon sources formed a synergistic effect that promoted the efficient metabolism of both compounds,” Sun said when the acetate was fed to xylose. “Xylose supported cell proliferation and provided sufficient energy for acetic acid assimilation, so yeast was able to metabolize acetic acid as a substrate very efficiently to produce large amounts of TAL.”

At the same time, the pH level of the medium increased as the acetate was metabolized, which promoted the consumption of xylose by yeast, Sun said.

When they analyzed S. cerevisiae gene expression by RNA sequencing, they found that important genes involved in acetic acid uptake and metabolism were dramatically upregulated by xylose compared to glucose. , Sun said.

Yeast cells fed both acetate and xylose accumulated more biomass with increased lipid and ergosterol levels of 48% and 45%, respectively. Ergosterol is a fungal hormone that plays an important role in stress adaptation during fermentation.

Co-utilization of acetate and xylose also increases the yeast supply of ergosterol and the precursor molecule of lipids, acetyl-CoA, provides a shortcut for metabolism, converts acetate to acetyl-CoA, and produces TAL. Was one step closer, Sun said.

“With xylose acetate As a carbon source, we were able to dramatically improve TAL production. This is 14 times the production previously reported using S. cerevisiae manipulated. High-value bioproducts derived from acetyl-CoA, such as steroids and flavonoids. “

The process used a carbon source of lignocellulosic biomass so thoroughly that Jin and Sun said they could seamlessly integrate into cellulosic biorefinery.

“It’s about the sustainability of our society,” Sun said. “We need to make full use of these undeveloped resources to build a sustainable future. Within 50 or 100 years, we will produce the energy and materials we need for our daily lives. We hope to rely primarily on these renewable and abundant ingredients to do. The goal, but for now, to make sure this is happening gradually, we do a little bit. I’m just doing it. ”

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For more information:
Liang Sun et al, Complete and efficient conversion of plant cell wall hemicellulose to high value bioproducts by artificial yeast, Nature Communications (2021). DOI: 10.1038 / s41467-021-25241-y

Quote: A new bioprocess for converting plant materials into valuable chemicals (August 17, 2021) from https: // Acquired on August 17, 2021.

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