Biological Reactors Make Hydrogen Fuel from Sewage

Biological Reactors Make Hydrogen Fuel from Sewage

All kinds of biodegradable garbage—from sewage to leftover food—could yield valuable hydrogen fuel, an alternative to fossil fuels, with the aid of microbes cultivated in special reactors.

When hydrogen is burned, it yields just energy and water. That being an attractive sort of fuel, researchers globally are investigating ways to generate hydrogen en masse in hopes of replacing fossil fuels, the burning of which releases the global warming gas carbon dioxide. Unfortunately, most of the hydrogen available today for use is actually generated from fossil fuels.

Now environmental engineers at Pennsylvania State University are perfecting a way of generating hydrogen from biodegradable garbage—that is, organic matter from plants, animals and other organisms. The idea, first announced in 2005 but improved upon in newer work, is to take liquid waste, such as effluent from sewers, breweries or food processing plants, and feed it to soil- or wastewater-derived bacteria raised in reactors designed to foster their growth. These microbes then break down the organic matter, releasing hydrogen gas.

"We could use all sorts of wastewaters, turning them into hydrogen instead of using energy to treat the wastewater," Penn State researcher Bruce Logan told LiveScience.

These microbes do need a low voltage supplied by researchers to generate the hydrogen, which Logan and colleagues discovered in 2005. Still, burning some of the hydrogen the bacteria produce can help generate the electricity the germs require to make the gas. Back in 2005, the researchers envisioned the process largely as a way to cut down on the cost of dealing with sewage. Now, they say the reactors can prove significantly efficient as hydrogen producers.

For example, when given acetic acid—a common leftover of fermentation—the bacteria in the reactors generated hydrogen at up to nearly 99 percent of the theoretical maximum yield. The reactors also worked when stuffed with cellulose, found in plants.

"This could really make a hydrogen economy work from renewable energy sources," Logan said.

Future research will focus on improving the rates of hydrogen production and lowering the cost of reactor materials.

"We hope to see pilot tests of this soon," Logan said. "We have been contacted by several companies, but so far no plans—yet—for a demonstration project." 

Through Genetics, Tapping a Tree’s Potential as a Source of Energy

Through Genetics, Tapping a Tree’s Potential as a Source of Energy

 

It might be true that “only God can make a tree,” as the poet Joyce Kilmer wrote. But genetic engineers can fundamentally redesign them. 

Ying-Hsuan Sun, a postdoctoral research assistant, with black cottonwood trees in a greenhouse at North Carolina State University.

Aiming to turn trees into new energy sources, scientists are using a controversial genetic engineering process to change the composition of the wood. A major goal is to reduce the amount of lignin, a chemical compound that interferes with efforts to turn the tree’s cellulose into biofuels like ethanol.

Vincent L. Chiang, co-director of the forest biotechnology group at North Carolina State University, has developed transgenic trees with as little as half the lignin of their natural counterparts. “I think the transgenic tree with low lignin will contribute significantly to energy needs,” he said.

Environmentalists say such work can be risky, because lignin provides trees with structural stiffness and resistance to pests. Even some scientists working on altering wood composition acknowledge that reducing lignin too much could lead to wobbly, vulnerable trees.

“Nature would have selected for lower-lignin trees if they could survive,” said Shawn Mansfield, associate professor of wood science at the University of British Columbia.

People working in the field also acknowledge that they will face resistance from others who see trees as majestic symbols of pristine nature that should not be genetically altered like corn and soybeans.

“The general public is not going to look at trees at this point as a row crop,” said Susan McCord, executive director of the Institute of Forest Biotechnology in Raleigh, N.C. “The same is true of foresters. The people who go into that work, they love trees. They view them very differently than a row of corn.”

Ethanol is mainly made from the starch in corn kernels. To increase the supply to make a dent in the nation’s energy picture, scientists are looking at using cellulose, a component of the cell wall in plants.

Proponents of using trees for this say they are good sources of cellulose and are also good at absorbing carbon dioxide, helping to fight global warming. Also, trees can be cut as needed rather than having to be harvested at a given time each year like a crop.

But the cellulose is covered by lignin, another component of the cell wall, making it difficult for enzymes to reach the cellulose and break it down into simple sugars that can be converted to ethanol. Pulp and paper companies break down lignin using acids and steam. Ethanol producers would have to do the same.

Trees that have less lignin might reduce or eliminate these steps. That could save at least 10 cents a gallon in ethanol costs, said Michael Ladisch, director of the Laboratory of Renewable Resources Engineering at Purdue.

Scientists understand the steps in creating lignin and can make lower-lignin trees by blocking one of them. One way is to put in a reverse copy of a gene that codes for an enzyme in lignin formation. The reverse copy silences that gene and reduces production of that enzyme.

Dr. Chiang said a 50 percent reduction in lignin appeared to be the maximum achievable, adding, “The tree doesn’t allow you to go further.”

The new focus on biofuels has brought a renewed interest in tree biotechnology, and new money for it, from the Energy Department. The field has been languishing because of technical challenges, costs, environmental concerns and financial problems in the forest products industry.

The revival has dismayed critics like Anne Petermann, a leader of the Stop Genetically Engineered Trees Campaign. She said energy concerns were being used “as a really great opportunity to sell this controversial technology to the public.”

Just one company in the United States is known to be pursuing genetic engineering of forest trees vigorously. The company, ArborGen, is small but has some big backers, being jointly owned by three forest products companies: International Paper, MeadWestvaco and Rubicon, based in New Zealand

ArborGen, based in Summerville, S.C., is developing a low-lignin eucalyptus that it hopes to sell in South America, where the fast-growing trees are already used for pulp and paper. For the United States, the company is developing a eucalyptus genetically engineered to survive cold snaps, allowing the trees to be grown more widely.

“In the next 5 to 10 years, you’ll be seeing transgenic trees on the market,” said Maud Hinchee, the chief technology officer at ArborGen.

Two genetically engineered trees are approved by the Agriculture Department, both for crops: papaya trees resistant to the ringspot virus, and plum trees resistant to plum pox virus.

The only known approval of a genetically engineered forest tree has come in China, where insect-resistant poplars have been widely planted.

Genetically modifying forest trees raises questions beyond those of crops. Trees can establish themselves in the wild, while corn would have trouble surviving without a farmer’s tender care.

A biologist, Claire Williams, said the wind could carry pollen from some trees like pines hundreds of miles, making it difficult to prevent a trait like reduced lignin from spreading to wild trees. 

Dr. Williams, who works for the State Department but was interviewed while she was working at Duke, said the long life spans of trees made it “almost impossible to evaluate the long-term consequences of transgenic trees.”

Loblolly pines, the main tree the forest industry grows in the Southeast, at the greenhouse.

Loblolly pine, the main tree the forest industry grows in the Southeast, takes 25 years to go from seed to harvest.

Critics also say transgenic trees would usually be grown on plantations, which, they say, lack the beauty and wildlife of natural forests.

Supporters of transgenic tree research say that because of the long time it takes to grow trees, conventional breeding is difficult.

“The only way to domesticate trees is through genetic engineering,” said Richard Meilan, associate professor of molecular tree physiology at Purdue. He said plantations of fast-growing trees for energy production would reduce the need to cut trees in natural forests. “Let’s domesticate those trees and grow them as commodities and not sacrifice our wild forests,” Dr. Meilan said.

The low-lignin trees, some experts say, have not been tested enough under real field conditions. “To mess with physiology like this, you really need to get out of the laboratory,” said Steven H. Strauss, a professor of forest science at Oregon State University who has conducted field tests of transgenic trees.

The one big field trial of low-lignin trees, conducted over four years in Britain and France, found that they appeared to grow normally and were not more vulnerable to insects, according to a paper published by the investigators in Nature Biotechnology in 2002.

And Jeffrey F. Pedersen, a research geneticist for the Agriculture Department in Lincoln, Neb., found that sorghum with reduced lignin was actually more resistant to a particular fungus than similar varieties with normal levels. He said arresting lignin production could lead to a buildup in the plant of chemical lignin precursors that also have pathogen-fighting properties.

Dr. Chiang of North Carolina State said his trees appeared normal, at least in the greenhouse. He has found that trees that produce less lignin might produce more cellulose, making them even more useful in producing ethanol, pulp or paper without reducing tree strength.

Some field tests are under way outside the United States, Dr. Chiang said, by corporate sponsors of his research who do not want to be identified.

Dr. Hinchee said ArborGen was aiming to reduce lignin 10 percent to 20 percent, to be on the safe side. “It’s not to our advantage to have a tree that’s weak in some other way,” she said.

Rather than reduce lignin, Purdue researchers, working under a $1.4 million three-year grant from the Energy Department, are trying to alter it.

Lignin can be made of two types of alcohols, said Clint Chapple, a biochemist who is working on the project with Professors Meilan and Ladisch. Pulp and paper companies know that one type is easier to remove. By boosting or inactivating various genes, the scientists plan to create trees with different mixes of the two alcohols and test how easy it is to make ethanol.

Dr. Meilan said that after determining an optimal composition, the team hoped to find such trees in the wild that could be reproduced, eliminating the need for genetic engineering.

But it is not certain that can be done. “I believe in the end,” he said, “we will have to rely on genetically engineered trees for our energy plantations.” 

Robotic Roaches Mess with Real Bugs' Minds

Robotic Roaches Mess with Real Bugs' Minds

A handful of artificially intelligent cockroaches alter the instincts of their natural brethren, shedding light on pack mentality

 

BEST FRIENDS?: Not exactly, but if you disguise a robot well enough, you can make a cockroach believe that it is one of the gang.
Courtesy of Université Libre de Bruxelles

Safety in numbers has pretty much ruled in the animal kingdom. But now researchers are discovering that artificially intelligent robots can change animals' natural instinct to live as a group, prompting them to form new patterns of behavior.

Take the typical three-centimeter- (1.2-inch-) long American cockroach, Periplaneta americana. It tends to live in groups with fellow cockroaches in the darkest shelters available. But could new robotic interlopers alter their age-old way of life? In a word—yes.

Researchers at the Free University of Brussels (U.L.B.) in Belgium, École Polytechnique Fédérale de Lausanne (E.P.F.L.) in Switzerland and the University of Rennes in France, along with other European educational institutions report in Science that when they introduced a few socially integrated autonomous robots (boxy in design but made to smell like the real deal) into cockroach communities, they altered the collective decision-making process and triggered new behavior patters in the bugs. The findings show that it may be possible to use robots to study and control how groups of animals from insects to vertebrates interact.

Cockroaches may not get much respect outside of laboratory settings, but they were better subjects for this test than ants or bees, because they have less elaborate social structures yet still "produce a collective intelligence," says José Halloy, the senior research scientist at U.L.B who coordinated the project.

Cockroaches do not comparison shop or communicate their preferences to one another when selecting shelter. They will, however, instinctively choose darker over more illuminated areas. They will also use their antennae to feel whether other cockroaches are present. Cockroaches will settle in if a place is dimly lit and well populated. "If three or four cockroaches are together under a shelter," Halloy says, "the probability of one of them leaving drops significantly."

During the five-year study, Halloy and his team introduced a number of robot cockroaches into this natural dynamic to see if they could influence the group dynamic. "In that way, the robots were used as tools to improve our knowledge of biology," he says.

The key was constructing robo-bugs tiny enough to successfully infiltrate cockroach clans. To do this, engineers at E.P.F.L. decided to build robots modeled after American cockroaches, which are generally twice the size of cockroaches indigenous to Asia or Europe. The robots were programmable and ran on a battery that lasted at least four hours. The robots were designed to operate autonomously (without any sort of remote control), to detect the difference between light and dark, and to sense the presence of cockroaches and other robots that came within about four centimeters (1.6 inches) of them.

The hardest part of the experiment, Halloy says, was getting the real cockroaches to accept the imposters. To do this, the team tapped biologists at Rennes to develop a pheromone that would fool the insects (which recognize each other via scents picked up by their antennae) into believing that the robo-invaders were fellow cockroaches. The pheromone was sprayed on a piece of paper wrapped around each bot. "Without that smell,'' Halloy says, "the cockroaches avoided the robots."

Researchers confined the real and faux cockroaches to a circular arena with two shelters, each large enough to house the entire group. The robots were programmed to behave in ways that contrasted with the behavior of normal roaches so that researchers could see if the vermin would follow the robots' lead. When the ersatz insects chose shelters with more light, more than half of the cockroaches abandoned their instincts and joined the robots there.

Halloy says researchers now plan to study the effect of artificial intelligence on a vertebrate animal, in this case chicks. To do this, he says, E.P.F.L. engineers will develop larger chicklike robots that can hear, interpret and respond to real chicks' verbal cues. The robot chicks (the first prototype is due in March) must also be accepted by their peers. One way to do this, Halloy says, is to remove newborn chicks from their mothers within 12 hours of hatching and place them with a robotic surrogate mother and artificially intelligent siblings. No word yet on how closely these robo-chick might resemble the real thing.

Homing in on the Silenced Gene Behind Mental Retardation

Homing in on the Silenced Gene Behind Mental Retardation

A new stem cell line with the mutation for fragile X syndrome may help uncover the mechanism behind the debilitating disorder

BIRTHING A NEW LINE: This blastomere (a cluster of eight cells that will develop into an embryo) was the source of the fragile X stem cell line that Israeli researchers used to model the development of the disorder.

For years, research on fragile X syndrome, the most common genetic mental illness, has suffered from an inadequate mouse model. But Israeli researchers unveiled an improved model that uses human embryonic stem cells to track the mechanism at the root of the disorder, which affects one in 4,000 boys and one in 6,000 girls.

In humans, the disorder stems from a mutation on the X chromosome as a three-base sequence begins to repeat over and over in a section of the fragile X mental retardation 1 gene (FMR1). The portion of the gene where this error multiplies does not code for a protein, which means that several repetitions of the sequence can occur without damaging the fragile X mental retardation protein (FMRP). People who have a gene with a sequence that is repeated 50 or fewer times are considered normal; those with fewer than 200 repetitions are carriers of the disorder. Individuals with more than 200 triplets, however, have disruptions to the promoter region of FMR1 that block the gene from being transcribed into RNA and forming a protein, thereby prompting onset of the syndrome.

Scientists had a tough time studying this process in mice, because the repeated sequence does not accumulate the same way in rodents. Hence, they could not determine the action that halted FMRP production, causing disorders from anxiety to attention deficit disorder as well as cognitive difficulties ranging from learning disabilities to mental retardation. The Israeli team reports in Cell Stem Cell how its model helped determine the process in which FMR1 is silenced.

"Human embryonic stem cells should not be considered only as sources in transplantation medicine; they can be used also…to create models for human genetic disorders," says study co-author Nissim Benvenisty, a geneticist at The Hebrew University of Jerusalem. "This is the first example where we in this field learn something new about a human genetic disorder that we couldn't learn from the existing models."

Using embryos from a female carrier (who had 170 triplets on her FMR1 gene), the researchers created a stem cell line that developed a mutation severe enough to be consistent with fragile X. They implanted this cell line into a mouse with a severely suppressed immune system, which allowed it to proliferate into a teratoma—a tumor composed of cells that can form varying tissue types. The researchers then placed the cells in a lab culture, where they could be monitored as they began to differentiate.

The researchers observed that the FMR1 gene remained active and FMRP was produced before the cells differentiated. After that point, however, they saw some epigenetic effects (influences on the activity of a gene that are not due directly to DNA mutations). As differentiation progressed, the scientists noted that the chromatins (DNA chemical complexes) in the cells' nuclei were structurally modified, effectively silencing the FMR1 gene. "It's going from an open conformation where it is transcribed [into RNA and then translated into protein] to a closed conformation where it is not transcribed," Benvenisty says.

He adds: the gene becomes methylated—a process in which a bulky methyl molecule is added to a gene's DNA backbone, blocking it from being transcribed into a protein. This process offers a sort of maintenance of the inactive state.

FMR1 inactivation "is a unique example in which epigenetic modification is in response to genomic modification," Stephen Warren, a human geneticist at Emory University in Atlanta wrote in an editorial that accompanied the study.

Karen Usdin, a senior investigator who works on fragile X syndrome at the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Md., says this is the model she would have wanted to develop for the illness. (She explains that restrictions on embryonic stem cell research, in place since 2001, prevent federal funding being used to generate new embryonic stem cell lines including those with specific disease mutations.) "It does create a wonderful model system," she says. "It allows you to begin to dissect out the process of gene silencing and test drugs that can reverse that process." 

"What we are trying to do now is…prevent the silencing," says Benvenisty. The Israeli team plans to study different drugs that hold the promise of preventing the conformational change that shuts off FMR1. Once they home in on potential candidates, Benvenisty says, researchers will have to determine if they are effective enough "to reverse the silencing when [the gene is] methylated." 

Mystery Probed in Record-Setting Cosmic Explosion

Mystery Probed in Record-Setting Cosmic Explosion

Last September, a supernova burst into a cosmic flame 100 times more intense than any event on record—and left scientists scratching their heads. 

Now, two new studies attempt to explain the remarkable explosion. One sets up the explosion with a cannibalistic star, while the other describes how colliding layers of jettisoned gas could outshine all other supernovae. 

Researchers from the Netherlands and California detail their theories in today's issue of the journal Nature. 

Stellar glutton 

Simon Portegies Zwart, an astrophysicist at the University of Amsterdam, said supernova 2006gy's brightness was strange enough. Chemical analysis revealed something weirder. 

"It possessed silicon and other heavy materials, which indicates a white dwarf," Portegies Zwart said. But the analysis also turned up hydrogen—a lightweight fuel all but converted into helium in older white dwarf stars. "The combination makes this supernova incredibly strange," he told SPACE.com. 

Portegies Zwart thinks a "runaway collision" could form such an oddity; if stuck in a crowded neighborhood, such as the center of a galaxy, an old star could drag in young stellar neighbors and bring hydrogen to the party. 

"It would be like a chain collision on the highway. As a large star absorbs smaller ones, it grows more massive and pulls in more stars," he said. A few thousand years after cannibalizing its neighbors, the gluttonous giant would meet its demise as a supernova. 

"This would be a rare event. About one in every 6,000 supernova would have similar characteristics," he said. 

If the explosion fades in the next year or two, as predicted, Portegies Zwart expects to detect a dense star cluster in its place—and lend support to his team's theory. 

Shell shock 

Stan Woosley, an astrophysicist at the University of California Santa Cruz, also expects to see a packed stellar neighborhood when the explosion fades. 

"These big massive stars are always born in dense clusters," said Woosley, whose team attempts to explain how, exactly, 2006gy burned so brightly. 

Stars about 90 to 130 times more massive than the Sun could create the unprecedented supernova as they end up fusing heavy carbon and oxygen atoms for fuel, he said. The process creates sets of annihilating particles, sucking away energy used to push gas outward—and keeping the star from exploding. 

But the struggle against gravity eventually fails. When the star explodes, it rockets a shell of 20 suns worth of gas into space at more than 220,000 mph (360,000 kph). 

"The star would be massive enough to explode, but not too powerful to unbind itself entirely," Woosley said, noting the event would equal roughly the Sun's entire 10 billion- year energy output in an instant. 

Because the star is still intact, however, Woosley said, a second explosion would ensue about seven years later, jettisoning another gas shell at more than 2.2 million mph (3.6 million kph). "When the second, inner envelope catches up, all of that collision energy is turned into light," he said. 

What's more, Woosley said, is that another bright outburst could happen again. 

"Ordinarily, supernovae happen only once," Woosley said. "Our model indicates it can happen again. If it did, we'd have some pretty definitive proof."