17 November 2016 2016 01:04 PM GMT

NREL Scientists Discover How Bacterium Uses CO2 And Cellulose To Make Biofuels

Scientists at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) made the surprise discovery that a metabolic pathway to take up CO2 exists and functions in a microorganism capable of breaking down and fermenting cellulosic biomass to produce biofuels including hydrogen and hydrocarbons.

Clostridium thermocellum is among the most efficient bacteria indirectly converting cellulosic materials into hydrogen and hydrocarbons biofuels. Most bacteria feeding upon organic carbon compounds, such as glucose or xylose, release CO2 as a waste byproduct, decreasing the maximum amount of products the microorganism can produce per carbon atom measured as carbon efficiency.

Other scientists have found the addition of a form of CO2, known as bicarbonate, into the medium containing the bacterium actually promotes the growth of C. thermocellum, yet its mechanistic details remained a puzzle. This enhanced growth implied the bacterium had the ability to use CO2 and prompted NREL researchers to investigate the phenomena enhancing the bacterium’s growth.

“It took us by surprise that this microbe can recapture some of the CO2 released during growth while they consume sugars derived from cellulosic biomass,” said Katherine J. Chou, a staff scientist with NREL’s Photobiology group and co-author of the new paper “CO2-fixing one-carbon metabolism in a cellulose-degrading bacterium Clostridium thermocellum.” The research is in the new issue of the journal Proceedings of the National Academy of Sciences of the United States of America.

Using carbon isotopes coupled with mass spectrometry analysis, the researchers were able to track how CO2enters the cell, identify the enzymes critical to CO2 uptake, and how CO2 incorporates into products thereby discovering a new metabolic route unknown to the scientific community. Many species of bacteria have the pathway in place for CO2 uptake, but before the new research, the pathway was not associated with the role of carbon dioxide assimilation (otherwise known as CO2 fixation).

The pathway enables the bacterium to use both CO2 and organic carbons during its growth, which is counter-intuitive because it’s much more common for this type of organism to use one and not the other, especially in heterotrophic microbes.

NREL researchers and their collaborators determined adding bicarbonate increased the apparent carbon efficiency of C. thermocellum from 65.7 percent to 75.5 percent. The finding underscores the metabolic plasticity of the microbe and raises various possibilities on how the bacterium is able to use both organic carbons and CO2 without breaking the rules of thermodynamics in energy conservation. The discovery also provides a paradigm shift in the fundamental understandings of carbon metabolism in a cellulose degrading bacterium.

“Our findings pave the way for future engineering of the bacterium as a way to improve carbon efficiency and to reduce the amount of CO2 released into the environment,” Chou said. With the observed improved carbon efficiency, this work inspires future research to redirect more cellular electrons in support of increased hydrogen production, a key goal for the funded research. In addition to Chou, the co-authors from NREL are Wei Xiong, Lauren Magnusson, Lisa Warner, and Pin-Ching Maness. Two BioEnergy Science Center (BESC) co-authors are Paul Lin and James Liao from the University of California, Los Angeles, where Chou earned her Ph.D. in chemical and biomolecular engineering.

The latest research into the bacterium was financed by the NREL Director’s Fellowship Program, Energy Department’s Fuel Cell Technologies Office, as well as Office of Biological and Environmental Research in the DOE Office of Science. NREL is the U.S. Department of Energy’s primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for the Energy Department by The Alliance for Sustainable Energy, LLC.

Photo: Courtesy of National Renewable Energy Laboratory (NREL)

December 13th 2017
EDF Commissions 179 MW At Two Solar Power Plants In Nevada

Policy makers led by US Senator Harry Reid were present at a celebration formally recognising Switch Stations 1 and 2 solar power plants, with a combined generation capacity of 179 MWac, as fully commissioned and in commercial operation. Senator Reid stated “Less than a decade ago, Nevada’s solar energy landscape was nonexistent, but this commissioning helps fulfil the vision I had to make our state the leader in renewable energy development. A technology giant like Switch committing to using 100% renewable energy is truly visionary and grows our clean energy economy by creating hundreds of good-paying construction jobs here.”

December 12th 2017
Global Trade In Biofuels Featured At International Renewable Mobility Conference

A significant proportion of global energy use, is in transportation. Action is crucially needed to bring about an energy turnaround in this sector and it’s a topic that has moved higher up the political agenda again since Dieselgate, and with growing calls for a rapid introduction of electromobility. In Germany, the Working Group on Energy Balances (AG Energiebilanzen) has calculated the final energy consumption of 728 TWh by the transport sector in 2016. Data from the German Environment Agency (UBA) reveals that over 90 percent of fuel deployed is derived from mineral oil. World-leading experts meeting in a parallel forum at the 15th International Conference on Renewable Mobility will analyse biofuel trading worldwide, examining various perspectives on requirements, the current state of play and forecasts.

December 12th 2017
Renewable Future Challenges UK And Germany To Build Flexibility In Power Systems

A new economic study highlights that future energy systems in the UK and Germany, with very high levels of variable renewable generation, must be complemented by flexible resources, including energy storage. The study was released by Bloomberg New Energy Finance (BNEF). “This study highlights a seismic shift in how power systems will operate in the future. As wind and solar become the cheapest options for power generation, the race is on to develop and deploy the flexible resources that will complement them,” said Albert Cheung, head of global analysis at Bloomberg New Energy Finance.

December 8th 2017
Tata Power Solar Commissions India’s First Rooftop Solar Carport In Delhi

Tata Power Solar set another landmark by commissioning an unprecedented rooftop solar project in India – a solar carport on the rooftop of the sprawling 70,000 sq.m Unity One mall, in Rohini, Delhi. The unique rooftop carport is estimated to set off 438 tonnes of carbon emissions annually. The company won the bid in an open tender process fielded by Delhi Metro Rail Corporation for multi-level car parking. The project enables the mall to earn on the unused and excess solar electricity produced. It also cuts down the need to install a second meter or an expensive battery storage system as it is directly connected to the local power grid.

December 10th 2017
EU Parliament Aims Higher For Renewables In Its 2030 Climate And Energy Goals

The European Parliament’s Industry & Energy (ITRE) and Environment (ENVI) committees have voted their position on the Energy Union Governance Regulation, just a week after the ITRE committee called for raising the EU’s 2030 renewable energy target to 35% instead of 27%. The Governance Regulation sets out how EU Member States will deliver the EU’s 2030 Climate and Energy goals including the binding EU renewables target and how they will give visibility to renewable energy investors on post-2020 deployment volumes. The IEA now says that wind will be Europe’s leading electricity source soon after 2030.



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