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)

October 16th 2017
Nordex Adds To Successes In Argentina, Winning 100 MW Pomona Wind Farm Order

The Nordex Group has added a further chapter to its success story in Argentina with an order for 26 N131/3900 turbines for the “Pomona” wind farm. The contract will be executed on a full EPC basis, including civil and electrical engineering, procurement, construction and manufacturing, delivery and installation of the wind turbines. Preparations for construction will be commencing in 2017, after which the wind power systems will be installed at the beginning of 2019. In addition, a ten-year full operation and maintenance contract has also been signed. 

October 9th 2017
ASEAN Eyes Clean Energy To Fuel Economic Growth And Build Climate Resilience

Governments of ASEAN and the International Renewable Energy Agency (IRENA), have established a strategy to accelerate the region’s transition to low-carbon, sustainable energy and build its climate resilience. “Increasing investment in renewable energy across Southeast Asia’s growing populations has significant social and economic benefits across the region, liberating them from expensive fossil fuel imports while boosting economic growth, supporting energy security, job creation and national resilience,” said Adnan Z. Amin, co-chair of the Dialogue.

October 17th 2017
Grids Integration, Energy Networks Boosted By Distributed Generation Growth

Renewable energy has continued to develop at ever increasing rates, with remarkable growth seen since the start of this decade. The pace of the energy transition is driving innovation and growth in related sectors. For energy networks and grids integrating small gas turbines, micro-turbines, fuel cells, biomass, small hydropower, wind and solar energy; distributed generation installation provides significant solutions in the restructured electricity regime. This is particularly so, where there is a larger uncertainty in demand and supply.

October 11th 2017
Engie Wins 832 MW Hydropower Plant Orders In Brazil, Strengthens Market Lead

During the auction held recently by the Brazilian Federal Government, ENGIE won concession contracts for two hydropower plants (HPP) for a total amount of around €950m (BRL3.531bn). The Jaguara HPP, located in Rio Grande (between the states of Minas Gerais and São Paulo), with a 424 MW installed capacity and the Miranda HPP, located in Rio Aragui, in Indianápolis (Minas Gerais State), with a 408 MW installed capacity. The concession contracts are signed for a 30-year period. They raise the installed capacity of ENGIE from 10,290 MW to 11,122 MW and reinforce ENGIE’s position as the largest private energy producer in Brazil.

October 16th 2017
Uganda Inaugurates Breakthrough Tororo PV Plant. A Future Model For Africa?

Production has commenced at the Tororo PV power plant; which, with 16 GWh of renewable energy generated annually, will cater for the energy requirements of 35,838 people and help reduce CO2 emissions by 7,200 tons. Overall, $19.6 million was invested to build the 10 MWp plant, with the engagement of several major organisations including KfW and FMO Development Banks, the World Bank and the EU. Attilio Pacifici, EU Ambassador said, “One of the key objectives of this plan is to encourage private sector participation in higher risk investments and we’re happy to demonstrate that Uganda is well positioned to be successful and a good model for replication.”



PS_Wind Energy_Masters_171