New research may improve the efficiency of the biofuel production cycle

May 14, 2012 by Anne M Stark
Different bacterial responses to ionic liquid. In (A), a fermentative bacterium is exposed to sugars for biofuel synthesis along with an ionic liquid (IL) used during the production process. The ionic liquid exerts a toxic effect soon after it enters the cell (B). In contrast, the rainforest isolate E. lignolyticus in (C) can tolerate relatively high levels of the ionic liquid, even as it secretes enzymes (D) that degrade plant cellulosic material to glucose and other sugars. A mechanistic model for bacterial resistance to ionic liquid includes: reducing membrane permeability to ionic liquid by remodeling the phopholipid bilayer (introduction of kinked fatty acids in lower left inset); removing intracellular ionic liquid through membrane transport proteins (efflux pumps shown as purple cones in lower middle inset); and, slowing the influx of ionic liquid by decreasing the number of porins (transmembrane cylinders in lower right inset). Green objects: glucose (rings) and cellulosic materials (sheets); red objects: ionic liquid; purple objects: enzymes.

(Phys.org) -- Using new experimental methods and computational analysis, a team of scientists from the Joint BioEnergy Institute (JBEI), led by Lawrence Livermore's Michael Thelen, discovered how certain bacteria can tolerate manmade toxic chemicals used in making biofuels.

By deciphering the makeup of a bacterium found in the soil of a , scientists may have a better understanding of how to more efficiently produce biofuels.

The production of derived from plant biomass offers a promising technology for reducing and dependence on fossil fuels.

While sugars stored within the plant cell wall, known as lignocellulose, are plentiful enough to supply most energy needs on the planet, their extraction is difficult and requires chemical pretreatment followed by enzymatic digestion using micro-organisms. However, while – salty solvents – improve the digestibility of lignocellulose, they also are toxic to bacteria used in subsequent conversion steps.

Using new experimental methods and , a team of scientists from the Joint BioEnergy Institute (JBEI), led by Lawrence Livermore's Michael Thelen, discovered how certain bacteria can tolerate manmade used in making biofuels.

"Discovering microbes naturally tolerant to salty liquids and understanding their mechanisms of tolerance should significantly enhance biofuel production," Thelen said.

The team describes an in-depth characterization of native bacterial resistance to the toxic effects of an ionic solvent used in biofuel production in the May 14 online edition of the journal, the Proceedings of the Natural Academy of Sciences (PNAS).

Microbes found in natural environments, such as decomposing forest soils, produce highly efficient enzymes to degrade lignocellulose and are often able to adapt to stressful changes in the environment. An alternative approach involves harnessing the positive traits of these native bacteria to engineer existing laboratory strains for more effective biofuel processing in the presence of toxic solvents.

Thelen and his colleagues isolated Enterobacter lignolyticus strain SCF1, a bacterium that can degrade lignocellulose from . They found that SCF1 grows well in the presence of relatively high concentrations of an ionic liquid that is used for pretreatment. This chemical is highly toxic to other bacterial species.

The El Yunque National Forest in Puerto Rico is a tropical rainforest where a strain of the microbe Enterobacter lignolyticus was found that can tolerate an ionic liquid used to dissolve cellulosic biomass for microbial-based biofuel production. Credit: (Photo by Kristen DeAngelis)

"We looked into how SCF1 tolerates this ionic liquid by using high-throughput growth assays, composition analysis of the bacterial cell membrane, and by determining all of the genes that are differentially expressed when SCF1 cells are exposed to an ionic liquid," Thelen said.

By mapping these analyses onto all of the known metabolic reactions identified in the genome sequence of SCF1, the team found that the bacteria can resist the toxic effects of an ionic liquid by adjusting the composition of membranes to reduce cell permeability, and by increasing a type of transport protein that can pump the toxic chemical out of the cell before damage occurs.

"Vigorous efforts to discover and analyze micro-organisms with properties similar to those of SCF1 have the potential to greatly benefit industrial processes," Thelen said. "These results will be used as a foundation for genetic engineering of ionic liquid-tolerant microorganisms for a more efficient production process."

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Burnerjack
1 / 5 (1) May 14, 2012
Even if Biofuel could be scaled up appropriately, it's STILL diesel or a byproduct of diesel, right? And at what cost? Wouldn't it be cleaner and MUCH more practical to move towards Natural Gas as a primary fuel? Too simple? No need for lucrative research funding perhaps? I suspect many people are under the assuption this fuel would be vastly cleaner and more environmentally sound. Kids, it's STILL diesel. it just come from a hole in the ground. It is cleaner, kind of like "clean coal".
shavera
5 / 5 (2) May 14, 2012
No it absolutely is not a byproduct of diesel. It's a product of plant life. For instance it takes carbon dioxide out of the air and fixes it into the fuel. It doesn't come out of the ground.
Burnerjack
not rated yet May 14, 2012
So, shavera, it doesn't pollute the atmosphere when burned?
Sean_W
1 / 5 (1) May 14, 2012
Even if Biofuel could be scaled up appropriately, it's STILL diesel or a byproduct of diesel, right? And at what cost? Wouldn't it be cleaner and MUCH more practical to move towards Natural Gas as a primary fuel? Too simple? No need for lucrative research funding perhaps? I suspect many people are under the assuption this fuel would be vastly cleaner and more environmentally sound. Kids, it's STILL diesel. it just come from a hole in the ground. It is cleaner, kind of like "clean coal".


It can also be ethanol, butanol and a number of other chemicals which are currently supplied by refining them from oil. Many new chemistry techniques have been discovered recently to build chemicals up from smaller ones rather than breaking large molecules of oil down. Many of these chemicals are more valuable than fuel yet synthesizing them saves oil. The carbon comes from the air as the plant grows and is released when the fuel or chemical is burned. Natural gas would complement biofuels.
Sean_W
3 / 5 (2) May 14, 2012
Natural gas would probably need to be chemically altered into something liquid (butanol or even gasoline if the economics work out) if used as a transportation fuel. It may be better to use natural gas for heat & power while using electric vehicles or biosynthesized gasoline. One of the interesting things being developed is using a separate source of energy in the form of electricity or EM radiation to drive reactions in favorable directions in addition to more conventional catalysts. And new methods of physically manipulating the products--like using microbubbles to separate chemicals--are being explored. Even our ability to concentrate CO2 out of the air for industries not located near a high CO2 producing industry is improving. You might end up seeing power sources like nuclear, solar & geothermal being used to build up most any chemical from simple constituents from biomass, natural gas & the air & water. Such electrosynthesis could make use of less reliable power alternatives.
Sean_W
3 / 5 (2) May 14, 2012
So, shavera, it doesn't pollute the atmosphere when burned?


Trace pollutants are created which would soon break down.. Other than that it is just the CO2, nitrogen gas, oxygen and water consumed by the plant being returned to the atmosphere.

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