Google+

Scientists Seek Enzymes That Don’t Mind Working At High Temperatures

In the middle of a cattle ranch near Gerlach, Nev., enclosed by a corrugated metal fence, are small pools of steaming water. Close to the surface of these pools, water temperatures reach about 90° Celsius; deeper down, it’s even hotter. Landowners have sectioned off the area around the pools and installed an overflow pipe to keep the water from seeping out and harming livestock or people.

Despite the dangers involved, one September day Joel Graham leaned over the barrier and plunged in his gloved hand to scoop up sediment and water samples.

At this locale, the biologist from the University of Maryland, Baltimore was fishing for microorganisms that can thrive at very high temperatures. Such extremophiles contain reaction-driving proteins called enzymes unlike any found in less harrowing environs.

Enzymes show up in all living things — from the simplest microbes to humans — and are essential for survival. They do jobs such as digesting food and helping to make sure genetic material gets properly copied. While a lot of known enzymes live and work best around the temperature of the human body, Graham and colleagues are among a cadre of scientists looking for new enzymes that can function when conditions get superheated.

The collective hope? That such enzymes could be co-opted to perform industrial processes. In many of the world’s factories, setting the thermostat on high keeps reactions moving quickly and prevents bacteria and other microbes from contaminating or eating up desired products. Papermaking, textile manufacturing and some food processing might all benefit from the help of heat-loving enzymes.

Graham’s team is particularly interested in a class of enzymes that help break down the grassy parts of plants, an area where researchers have made recent progress. Finding such enzymes, and employing them in large quantities, could lead to biofuel production on an industrial scale, helping society reduce its dependence on fossil fuels.

Some scientists are hoping a newly discovered enzyme pulled from the field may be an ideal high-temperature grass muncher. Other researchers, instead of getting their hands dirty in hot pools, are designing never-before-seen heat-loving enzymes in the lab. Many lab enzymes are in some way inspired by versions already found in nature.

“The environment contains a lot of solutions to a lot of human problems,” Graham says. “If you find a directed way to go after what you’re looking for, it’s actually not that hard to find something new and useful.”

Enzyme-palooza

access

FUELED BY HEATFrom a hot pool in Nevada (top image), researchers pulled a cellulose-busting enzyme called EBI-244. The enzyme shows its maximum breakdown activity above 100° Celsius (shown on graph), making it a good candidate for use in biofuel production.Source (graph): J. Graham et al/Nature Communications 2011; (photo): J. Graham et al/Nature Communications 2011

People have been using enzymes to perform chemical reactions outside the body for millennia. Food processing with enzymes, for example, dates back at least 4,000 years, when people stored milk in the excised stomachs of animals. Digestive enzymes in an animal’s gut caused milk to curdle, forming other dairy products like curds and whey.

Today, a cocktail of various proteins help coagulate milk to make solid curds for cheese. Other enzymes soften cotton during textile manufacturing or treat paper in the pulp industry. Enzymes even lend a hand in the synthesis of drugs and supplements such as vitamin E.

But enzyme-driven processes these days can get much more involved than just throwing starting materials into an animal gut. Often materials need to undergo additional reactions, treatment with a solvent or dyeing with a chemical, before or after an enzyme can do its job. For many of these reactions, heat is required as a catalyst.

The problem: Most known enzymes work only at conditions matching those of the organism from which they came. So temperatures have to be repeatedly ramped up and lowered at various stages of a multistep process. “You have to cool it down for the biological part and heat it back up for the next step,” says Vicki Thompson of Idaho National Laboratory in Idaho Falls. “That makes the process more expensive, and it’s wasteful of energy.”

During low-temperature stages, materials can also be vulnerable to attack from a plethora of microbes.

The breakdown of long chains of glucose molecules from plants, or cellulose, faces such troubles. Cellulose stored in corn stover — the grassy part of corn that people don’t eat and a potential biofuel source — is tied up in complex chemical arrangements, making it hard for enzymes working alone to get access.

So the biomass has to be mashed up a bit first. It’s heated and treated with corrosive chemicals like acids or salty solutions, which expose the cellulose. But the plant products have to be neutralized and cooled before a collection of room-temperature enzymes can digest the material into usable sugars.

Cellulose-breaking enzymes, called cellulases, made by organisms that normally thrive under extreme conditions, in places like hot springs or hydrothermal vents, could offer a solution.

“You can take those enzymes and use them under the industrial conditions that you are interested in,” explains Thompson, who has been studying organisms that live in extreme environments and the proteins they make for more than a decade.

access

LAB-GROWNTo design an ideal plant-munching enzyme, or cellulase, researchers combined features from three parents (HI, HJ and CT, shown above with sugar in orange). The resulting enzyme, HJPlus, outperformed the parents in cleaving cellulose chains to produce cellobiose, but further changes (yellow) made for an even better enzyme, 3C61P.Indira Wu

Pulled from a pool

Biologist Thomas Brock unearthed one of the first known extremophiles from hot pools in Yellowstone National Park in Wyoming in the 1960s. Later named Thermus aquaticus, the bacterium thrived best at temperatures around 70° C. This finding suggested life could exist in all kinds of places that were previously thought of as dead zones.

Explorations in volcanic soil, hot vents, deep seas and salt deserts have turned up thousands of extremophiles since, says Thompson. A sizable portion love the heat. Notably, a heat-loving, DNA-building enzyme from T. aquaticus has been a major boon for genetic engineering and forensics. To analyze DNA from collected samples, scientists need large amounts of uncontaminated copies. By simply adding the enzyme, Taq polymerase, to a starting strand of DNA and other genetic ingredients, scientists can make lots of DNA copies with no contamination to worry about.

Over the last two decades, Frank Robb of the University of Maryland, Baltimore has scoured some of the hottest corners of the Earth — from the hot springs at Yellowstone to the deep-sea vents of the Okinawa Trough — in search of interesting heat-loving enzymes. An ability to break down cellulose is one sought-after skill in the “help wanted” ads.

Robb and Graham want cellulases that can do their thing at temperatures of 100° C or even higher. The more types the better, since some enzymes specialize in cutting the cellulose into chunks and some break it down even further into glucose.

Recently, after examining genetic material from samples collected at the hot springs in Nevada, Robb and Graham turned up an enzyme called EBI-244 that can perform one of the early cellulose breakdown steps at temperatures as high as 109° C. Though other heat-loving cellulases have previously been found, none do the job as well as EBI-244 at such high temperatures.

“Nobody ever thought or had seen an enzyme that worked at those temperatures, and it’s so stable at those temperatures,” says Isaac Cann of the University of Illinois at Urbana-Champaign, who also studies cellulases and their role in biofuels production.

And the enzyme, described in Nature Communications last year, can also survive in acidic conditions and put up with harsh solvents.

Researchers can’t collect nearly enough heat-loving cellulases in the field to run a cellulose-degrading factory (kilogram amounts are needed). Instead, scientists typically hook up the genetic material that codes for a specific enzyme to a bacterium’s or yeast’s molecular machinery, tricking the organism into producing the protein. But for many enzymes, EBI-244 included, it has been a challenge.

“It’s just a painstaking and tedious process to get suitable quantities,” says Douglas Clark, a biochemical engineer at the University of California, Berkeley who collaborated with Robb and Graham in identifying EBI-244.

Despite the barriers, the discovery of EBI-244 is exciting because of what scientists can learn from it. The DNA that codes for the enzyme is unlike the DNA for any known cellulase; it was traced back to a never-before-seen extremophile. “It’s very strange to find one that doesn’t fit into a well-defined category,” Graham says. “That was the most exciting part.”

The next challenge will be to study the enzyme’s physical structure, to unlock its heat-loving secrets.

“We would love to know more about it,” says Clark. “Could we begin to use the information gained from studying this enzyme to engineer not only other cellulases, but other proteins?”

Into the lab

Rather than hunt for enzymes that can function under extreme conditions in the field, chemical engineer Frances Arnold of Caltech makes her own. She brings the principles of breeding to the lab: guiding the development of new and better proteins using known proteins as parents.

Arnold’s lab starts off by using a computer program to put together stretches of amino acids, the building blocks of proteins, from different enzymes. By mixing and matching chunks from each parent, the team’s computer software figures out what types of children would emerge if these enzymes could “breed.” The idea is to pick parents with different features — like ones that thrive in high heat, or can grow up in large quantities — to produce a child with the best of all the qualities.

Arnold and colleagues mine the results, looking for prospective children with the most promising futures — that is, with proteins likely to perform interesting functions and assemble into a desired shape in the lab. The children can then undergo small-scale changes that make them even better.

“You’re better off making it in the laboratory, because no natural enzyme will fulfill all the requirements of your desired applications,” says Arnold.

Arnold produces her computer-based cellulases with the help of simple organisms in the lab. She doesn’t try to grow huge loads of her heat-loving cellulases, but she does start with proteins from filamentous fungi, which are known to grow up easily.

After a recent cellulase “breeding,” Arnold’s team reported making new enzymes that could work at about 70° C. Some of the parent enzymes could break down cellulose only at temperatures around 57° C. Since that report, Arnold has been able to coax more proteins to work at similar temperatures.

She has since sold licenses for making these cellulose-breaking prodigies to private companies, though she doesn’t yet know whether the enzymes are being used for large-scale plant munching.

Despite the recent breakthroughs, there’s a lot of work to be done before heat-loving enzymes can usher in an era of cheap biofuels.

Individual proteins, whether unearthed from hot zones or made in the lab, will have to come together as members of a cellulose-converting team. Once many different heat-loving enzymes are found, scientists need to get them to work well as a group.

“Cellulases are a particularly hard problem because it’s not just one enzyme. It’s a whole family of enzymes. If you improve one component, it does not mean you have a better product,” Arnold says. “You have to improve many components and then find the right mixture of those components. It’s a challenging thing.”

Once the right team is found, scientists still have to overcome the hurdle of inexpensively making a lot of proteins in the right ratios. The same hurdle will probably hold for enzymes in other heat-dependent processes.

“We haven’t yet figured out all the rules for making highly stable enzymes that also do what they need to do and can be produced in an economical fashion,” Arnold says. “We’re trying.”

Source: Science News /  Rebecca Cheung   /  Photo Credit: Indira Wu

Entertainment

Ghetto Kid Mugged for Sneakers Seeks Revenge in Coming-of-Age Drama

  Kicks Blu-ray Review by Kam Williams Ghetto Kid Mugged for Sneakers Seeks Revenge in Coming-of-Age Drama Brandon (Jahking Guillory) saved up for a pricey pair of Air Jordan, only to suffer the utter humiliation of having them stolen right off his feet at gunpoint by a gang of ghetto predators. Thus arrives a moment of truth for the nerdy 15 year-old who finds himself stuck at an unpleasant station in life where he's not only routinely … [Read More its Good for You.....]

Books

Volume 2 of Yes Sir, Yes Sir, 3 Bags Full! – You Do NOT Want to Miss This

  Volume 2 of Yes Sir, Yes Sir, 3 Bags Full! – You Do NOT Want to Miss This Book Review by Amy Lignor What began in an unforgettable Volume 1—living Jerry Hall’s story and dealing with the heart-wrenching issues of the Viet Nam* War—continues here. The action of battle, fraught with the unending horrors that the “unwanted veterans” dealt with, grows even more painful. And as war comes closer to an end, what should have been peaceful … [Read More its Good for You...]

Art

The Day After the Day Of

  The Day After the Day Of by Paul Ilechko   The sky sheds its tears. This morning is the morning of the day after. The day of mourning, the day after the day of.  I beseech the sky to shed tears in order to wash away the tears on my face.   This is the first day of the time after. This is the beginning of a new time, the days of pain, the days of sorrow. We are in mourning. The sky looks down and sheds its tears for … [Read More its Good For You...]

Real Estate

New Home Sales Jump in April

  New Home Sales Jump in April By Burt Carey Sales of new homes hit their highest rate since 2008 in April, according to the Commerce Department’s U.S. Census Bureau. April sales increased 16.6 percent over March figures, which correlates to a seasonally adjusted rate of 619,000 home sales projected for the year. The median price of those new homes was $321,000, the highest median price ever recorded. That’s up 9.7 percent … [Read More its Good for You.....]

Lifestyle

Paging Norman Rockwell

  Paging Norman Rockwell by Amy Lignor   For those who may not have had the pleasure before – and all you true Christmas “classic” lovers who have always wanted to see it – Stockbridge, Massachusetts, is the most brilliant and beautiful place during the holiday season. Made famous by the original Norman Rockwell, whose museum is part of the line of historic buildings making up that classic Main Street, Stockbridge is dressed up … [Read More its Good for You...]

Outdoors

Winterize Now to Avoid Costly Repairs Next Spring

    By Craig Lamb At the first sign of warm weather next spring you’ll be itching to get the boat out on the water. You want to get in and go, taking in the sunshine and fresh air after the long winter. What you don’t want is for the first trip out to be cut short, taking an unplanned detour to the dealership instead of the water. Now is the time to winterize your boat. Doing so can avoid costly repairs due to neglecting … [Read More its Good for You...]

Sports

The Best & Worst (So Far) of the 2016 NFL Season

  The Best & Worst (So Far) of the 2016 NFL Season by Amy Lignor     Okay…we’re almost dead center, folks, so it’s time to sum up the best and silliest actions and reactions that the 2016 NFL season has provided fans thus far.   Analysts are always yapping, and most likely nothing they say will actually come true. However, right now almost everyone is agreeing to the fact that Tom Brady has a score to settle. Yes, … [Read More its Good for You...]

Business

We Are Still…All in This Together!

  We Are Still…All in This Together! by Amy Lignor   December 7, 1941. Sunday morning was lovely on the Hawaiian island of Oahu. A typical Sunday, in fact, where people were moving calmly and in a relaxed “weekend-mode” stance at the U.S. Navy’s Pacific Fleet Headquarters. Just before the clocks struck 8:00 a.m., however, the country of Japan launched planes from six aircraft carriers in what would be considered the “first wave” of … [Read More its Good for You...]

Travel

Exploring the Holidays Around the Globe

  Exploring the Holidays Around the Globe by Amy Lignor   Thanksgiving has been had. Games have been watched and the golden turkey has caused a great many belts to be loosened. So…here it comes!   From hanging the stockings on the chimney with care to the red-nosed reindeer who had to be there; from Santa heading down that chimney just right to lovely sleigh bells ringing softly in the night, the holiday season is a truly … [Read More its Good for You...]

Green Living

Forecasting Climate Change

  Forecasting Climate Change by Amy Lignor As with anything in this world, it depends on whose opinion or observations you trust as to just how bad climate change is becoming. As 2016 begins to wrap up, climate scientists, atmospheric physicists, chemists, oceanographers – you name it – no one can come up with any other explanation for climate change and the warming of our planet other than human activity. How fast is it happening? … [Read More its Good for You...]