Can Fungi Replace Plastics? Maybe, Say Researchers

Fungi, with the exception of shitake and certain other mushrooms, tend to be something we associate with moldy bread or dank-smelling mildew. But they really deserve more respect. Fungi have fantastic capabilities and can be grown, under certain circumstances, in almost any shape and be totally biodegradable. And, if this weren’t enough, they might have the potential to replace plastics one day. The secret is in the mycelia.
Union College Biology Professor Steve Horton likens this mostly underground portion of fungi (the mushrooms that pop up are the reproductive structures) to a tiny biological chain of tubular cells.
“It’s this linked chain of cells that’s able to communicate with the outside world, to sense what’s there in terms of food and light and moisture,” he said. “Mycelia can take in nutrients from available organic materials like wood and use them as food, and the fungus is able to grow as a result.”
“When you think of fungi and their mycelia, their function – ecologically – is really vital in degrading and breaking things down,” Horton added. “Without fungi, and bacteria, we’d be I don’t know how many meters deep in waste, both plant matter and animal tissue.”
Looking something like extremely delicate, white dental floss, mycelia grow in, through and around just about any organic substrate. Whether it’s leaves or mulch, mycelia digest these natural materials and can also bind everything together in a cohesive mat. And these mats can be grown in molds, such as those that might make a packing carton.
Ecovative Design, in Green Island, N.Y., is harnessing this particular mycological power and is being helped by Horton, and another Union researcher, Ronald Bucinell, associate professor of mechanical engineering.
Ecovative uses several species of fungi to manufacture environmentally-friendly products. The process starts with farming byproducts, like cotton gin waste; seed hulls from rice, buckwheat and oats; hemp or other plant materials. These are sterilized, mixed with nutrients and chilled. Then the mycelia spawn are added and are so good at proliferating that every cubic inch of material soon contains millions of tiny fungal fibers.
This compact matrix is then grown in a mold the shape of whatever item Ecovative is making. Once the desired texture, rigidity and other characteristics of the product are achieved, it’s popped from its mold and heated and dried to kill the mycelia and stop its growth.
The all-natural products, the creation of which can take less than 5 days, have no allergy concerns and are completely non-toxic. More impressive is the fact that they’re also impervious to fire (to a point), and just as water resistant as Styrofoam, but they won’t sit around taking up space in a landfill. They are also more UV-stable than foam since they are not petrochemical-based, and won’t emit volatile organic compounds. When exposed to the right microbes, they will break down in 180 days in any landfill or backyard.
Mycelium is comparatively inexpensive too as it can grow on farm waste that can’t be fed to animals or burned for fuel. Better yet, the fungi can be propagated without sunlight or much human oversight in simple trays at room temperature – no immense greenhouses with costly temperature-control systems needed. It also means a smaller carbon footprint and Ecovative is hoping to the point where they can displace all plastics and foams in the market.
source :http://www.newswise.com/articles/can-fungi-replace-plastics-maybe-say-union-college-researchers

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Biological Wires Carry Electricity Thanks to Special Amino Acids

In nature, the bacterium Geobacter sulfurreducens uses  nanowires, called pili, to transport electrons to remote iron particles or other microbes, but the benefits of these wires can also be harnessed by humans for use in fuel cells or bioelectronics. The study in mBio® reveals that a core of aromatic amino acids are required to turn these hair-like appendages into functioning electron-carrying biological wires.

"It's the aromatic amino acids that make it a wire," says lead author Derek Lovley of the University of Massachusetts, Amherst. Lovley and his colleagues removed the pivotal amino acids from the pili and replaced them with smaller, non-aromatic amino acids. Without these key components, Lovley says, the pili are nothing more than protein strings. "We showed it's not good enough to just make the string - you've got to make a wire," says Lovley.

G. sulfurreducens "breathes" by removing electrons from organic materials and funneling them to iron oxides or to other microorganisms, much the way humans pull electrons out of organic molecules in food and dump them on oxygen. The bacteria use their pili to reach out to iron oxides or other microbes, transferring the "waste" electrons along the structure to the destination. Geobacter's pili are only 3-5 nanometers wide, but they can be 20 micrometers long, many times longer than the cell itself.
Trafficking in electrons is how all living things breathe, but it is normally carried out by discrete proteins or other molecules that act like containers for shuttling electrons from one place to another. Lovley says earlier results showed the pili in G. sulfurreducens possess metallic-like conductivity, the ability to carry electrons along a continuous structure, a controversial finding in biology.

To investigate how pili accomplish this singular feat, Lovley says they looked to non-biological organic materials that can conduct electricity. "In those synthetic materials, it's aromatic compounds that are responsible for the conductivity. We hypothesized that maybe it's similar in the Geobacter pili. In this case, it would be aromatic amino acids." Aromatic compounds have a highly stable ring-shaped structure made of carbon atoms.

Turning to the pili, Lovley says his group looked for aromatic amino acids in the parts of the pili proteins that would most likely contribute to the conductivity. Using genetic techniques, they developed a strain of Geobacter that makes pili that lack aromatic amino acids in these key regions, then they tested whether these pili could still conduct electricity. They could not. Removing the aromatic amino acids was a bit like taking the copper out of a plastic-covered electrical wire: no copper means no current, and all you're left with is a string.

Removing aromatic amino acids from the pili prevents the bacteria from reducing iron, too, says Lovley, an important point because it adds further proof that Geobacter uses its pili as nanowires for carrying electrons to support respiration.

Metal reducers like Geobacter show a lot of promise for use in fuel cells, says Lovley, and by feeding electrons to the microbes that produce the methane, they're an important component of anaerobic digesters that produce methane gas from waste products. Understanding how they shuttle their electrons around and how to optimize the way the pili function could lead to better technologies.

Moving forward, Lovley says his own lab plans to explore the possibilities of biological nanowires, exploring how to make them more or less conductive.

source:http://www.asm.org/index.php/news-room-2/92-news-room/press-releases/91563-biological-wires-carry-electricity-thanks-to-special-amino-acids

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