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Fuel pumps save microbes
RESEARCH NEWS
Fuel pumps save microbes BIOMATERIALS
A novel approach to engineering microbes could boost yields of biofuel production in next-generation fuels. The approach exploits the microbes’ in-built efflux pumps, a class of membrane transporter that exports toxins from the cell to manage toxic compounds. Current biofuels containing ethanol and linear, unbranched fatty acids are of limited use as gasoline, diesel, and aviation fuel substitutes. However, it might be possible to engineer microorganisms to produce butanol, isopentanol, and geraniol as superior alternatives to ethanol for gasoline replacements. Similarly, compounds such as geranyl acetate and farnesylhexanoate, with between 9 and 23 carbon atoms in branching chains, are better biodiesel alternatives because they have lower freezing points. For aviation, cyclic alkenes, such as limonene and pinene can be used as precursors to jet fuel. Unfortunately, while these compounds are more useful as fuels, they tend to be toxic to
microbes and some are well known antimicrobial agents. The problem of toxicity means that the fermentation process used to produce the fuels becomes quickly self-limiting as the microbes do not thrive in the presence of the target compound. Now, US researchers at the Joint BioEnergy Institute, Emeryville, California, have devised a solution. To help the biofuel-producing microbes cope with their toxic product, the team has generated a library of cellular “pumps” that might expel the fuel-like products from an engineered microbe and preclude toxicity. They have tested 43 such protein efflux pumps from various microbes engineered into Escherichia coli against seven representative biofuel compounds. By using a competitive growth test, they could quickly determine which efflux pumps worked best and improved survival [Dunlop et al., Mol Sys Biol (2011) doi: 10.1038/msb.2011.21].
They found that for the lower molecular weight fuels, n-butanol and isopentanol, none of the pumps improved microbial tolerance. However, they identified pumps that restored microbial growth in the presence of the otherwise toxic biofuels for the other five fuels tested; in some cases toxicity was merely reduced rather than eliminated. In a production strain they were also able to improve overall biofuel yields. Product toxicity is a common problem in strain engineering for many biotechnology applications, the team explains. Their approach to engineering tolerance into biofuel compounds being produced by microbial fermentation might allow the next-generation of biofuels to become viable. As metabolic pathways for the efficient production of carbon-rich compounds are developed, the technique will work in parallel to counteract the inevitable toxicity of such compounds in the fermentation brew. David Bradley
Materials in 3D TOOLS AND TECHNIQUES A new tomography technique for imaging 3D
information is required when modeling properties
the number of slices required to section a predetermined volume of material. The ablation event and incoming laser are orthogonal to the plane of the sample surface. Images are captured optically during the sectioning experiment using a high resolution CCD detector. Statistical analysis of the datasets was then carried out.
in materials or for predicting synthetic routes.
With this set up the scientists were successfully
A group of scientists in the United States has
able to distinguish TiN particles in steel, with
developed a tomography technique harnessing
a diameter larger than 1 micron. Imaging
the characteristics of femtosecond laser ablation
enhancements, including in situ SEM and
to build 3D datasets. This automated technique
the integration of laser induced breakdown
nanometer scale materials in cubic millimeter volumes has been developed. Three-dimensional information on the distribution of elements or phases within materials is critical when dealing with compounds that are anisotropic or heterogeneous in nature. This
provides a new way of imaging complex materials in a fraction of the time when compared to existing technologies, such as mechanical or focused ion beam techniques. It is well known how tomographic imaging can elucidate problems in medicine, geology, oceanography, and materials science. 2D slices of samples that can be successfully reconstructed into 3D rich datasets may be acquired with a wide variety of techniques that use electrons, neutrons, x-rays, ions, visible light, or acoustic waves. However, this technique is accompanied by many restrictions,
306
Schematic of the instrumentation. Image courtesy of McLean Echlin. in terms of the resolution, quality of data, sample preparation and of course acquisition time. It is also a very skilled and labor intensive procedure. In this study the scientists, from UC Santa Barbara and the University of Michigan, have succeeded in overcoming many of these obstacles. The newly developed femtosecond laser based technique involves laser ablation followed by optical imaging of the ablated surface, with no subsequent surface preparation required. These steps are repeated for
JULY-AUGUST 2011 | VOLUME 14 | NUMBER 7-8
spectroscopy, are currently on-going in order to improve the resolution by an order of magnitude. This new tomography method is ideal for imaging multiphase systems containing phases with similar densities that are inherently difficult to image using other techniques, such as x-ray based measurements. Many experiments and observations still need to be carried out; for instance, making use of the non-contact mode of laser machining, which will allow materials to be sampled in vacuum, and to take advantage of other analysis techniques such as EBSD and EDS.
Jonathan Agbenyega
Fuel pumps save microbes BIOMATERIALS
A novel approach to engineering microbes could boost yields of biofuel production in next-generation fuels. The approach exploits the microbes’ in-built efflux pumps, a class of membrane transporter that exports toxins from the cell to manage toxic compounds. Current biofuels containing ethanol and linear, unbranched fatty acids are of limited use as gasoline, diesel, and aviation fuel substitutes. However, it might be possible to engineer microorganisms to produce butanol, isopentanol, and geraniol as superior alternatives to ethanol for gasoline replacements. Similarly, compounds such as geranyl acetate and farnesylhexanoate, with between 9 and 23 carbon atoms in branching chains, are better biodiesel alternatives because they have lower freezing points. For aviation, cyclic alkenes, such as limonene and pinene can be used as precursors to jet fuel. Unfortunately, while these compounds are more useful as fuels, they tend to be toxic to
microbes and some are well known antimicrobial agents. The problem of toxicity means that the fermentation process used to produce the fuels becomes quickly self-limiting as the microbes do not thrive in the presence of the target compound. Now, US researchers at the Joint BioEnergy Institute, Emeryville, California, have devised a solution. To help the biofuel-producing microbes cope with their toxic product, the team has generated a library of cellular “pumps” that might expel the fuel-like products from an engineered microbe and preclude toxicity. They have tested 43 such protein efflux pumps from various microbes engineered into Escherichia coli against seven representative biofuel compounds. By using a competitive growth test, they could quickly determine which efflux pumps worked best and improved survival [Dunlop et al., Mol Sys Biol (2011) doi: 10.1038/msb.2011.21].
They found that for the lower molecular weight fuels, n-butanol and isopentanol, none of the pumps improved microbial tolerance. However, they identified pumps that restored microbial growth in the presence of the otherwise toxic biofuels for the other five fuels tested; in some cases toxicity was merely reduced rather than eliminated. In a production strain they were also able to improve overall biofuel yields. Product toxicity is a common problem in strain engineering for many biotechnology applications, the team explains. Their approach to engineering tolerance into biofuel compounds being produced by microbial fermentation might allow the next-generation of biofuels to become viable. As metabolic pathways for the efficient production of carbon-rich compounds are developed, the technique will work in parallel to counteract the inevitable toxicity of such compounds in the fermentation brew. David Bradley
Materials in 3D TOOLS AND TECHNIQUES A new tomography technique for imaging 3D
information is required when modeling properties
the number of slices required to section a predetermined volume of material. The ablation event and incoming laser are orthogonal to the plane of the sample surface. Images are captured optically during the sectioning experiment using a high resolution CCD detector. Statistical analysis of the datasets was then carried out.
in materials or for predicting synthetic routes.
With this set up the scientists were successfully
A group of scientists in the United States has
able to distinguish TiN particles in steel, with
developed a tomography technique harnessing
a diameter larger than 1 micron. Imaging
the characteristics of femtosecond laser ablation
enhancements, including in situ SEM and
to build 3D datasets. This automated technique
the integration of laser induced breakdown
nanometer scale materials in cubic millimeter volumes has been developed. Three-dimensional information on the distribution of elements or phases within materials is critical when dealing with compounds that are anisotropic or heterogeneous in nature. This
provides a new way of imaging complex materials in a fraction of the time when compared to existing technologies, such as mechanical or focused ion beam techniques. It is well known how tomographic imaging can elucidate problems in medicine, geology, oceanography, and materials science. 2D slices of samples that can be successfully reconstructed into 3D rich datasets may be acquired with a wide variety of techniques that use electrons, neutrons, x-rays, ions, visible light, or acoustic waves. However, this technique is accompanied by many restrictions,
306
Schematic of the instrumentation. Image courtesy of McLean Echlin. in terms of the resolution, quality of data, sample preparation and of course acquisition time. It is also a very skilled and labor intensive procedure. In this study the scientists, from UC Santa Barbara and the University of Michigan, have succeeded in overcoming many of these obstacles. The newly developed femtosecond laser based technique involves laser ablation followed by optical imaging of the ablated surface, with no subsequent surface preparation required. These steps are repeated for
JULY-AUGUST 2011 | VOLUME 14 | NUMBER 7-8
spectroscopy, are currently on-going in order to improve the resolution by an order of magnitude. This new tomography method is ideal for imaging multiphase systems containing phases with similar densities that are inherently difficult to image using other techniques, such as x-ray based measurements. Many experiments and observations still need to be carried out; for instance, making use of the non-contact mode of laser machining, which will allow materials to be sampled in vacuum, and to take advantage of other analysis techniques such as EBSD and EDS.
Jonathan Agbenyega