Industry News
A Tale of Two Bottles
6 years, 2 months ago Posted in: Industry News 0

by Anna McEntire, Utah State University

Picture two water bottles. Same size, same color, same weight.

One of the bottles, like most bottles in the world, is petro-chemically derived—meaning it was made from oil.

The other bottle is bioplastic. Its source is renewable. It’s biodegradable. And it has the same tensile strength, UV resistance and melting point as the other bottle. The bioplastic bottle is equal or superior in every way except for one: it costs more.

USU researcher Charles Miller is trying to fix that and equalize the playing field for this emerging material.

Bioplastics have the potential to help wean the United States from foreign oil and reduce the impact of the 60 billion pounds of plastic that are disposed of each year. But, just as with any product, you can’t expect it to take off until the price comes down.

“Half the cost of producing bioplastic is from downstream processing—separating it from the bacteria that produce it,” said Miller, an assistant professor in the department of biological engineering. “That’s why you can produce traditional plastic for 75 cents a pound, while bioplastics cost anywhere from $1.25-2.25 per pound.”

Plastics are composed of polymers, or very large molecules. Those molecules are formed when smaller particles, called monomers, are formed together in a long chain. Traditional processes heat crude oil or other fossil fuels to break it into its small particles, which are then chemically bonded into plastic polymers.

Bioplastics, on the other hand, are naturally occurring byproducts from fermented bacteria or plant leaves. They have nearly all the same characteristics as traditional plastics, with the added benefit of not sticking around in a landfill for thousands of years. Miller works with a type of plastic called polyhydroxyalkanoates (PHAs), which are thermoplastics, meaning they can be melted and reformed over and over again.

Certain conditions can cause these organisms to store excess nutrients in the form of bioplastics, in the same way a human stores fat. Through biological engineering, a cell’s mass may grow to 90 percent bioplastic polymers.

“To prevent the bacteria from degrading it, or using it as a food source, we genetically engineer ones that don’t naturally eat it, to make the bioplastic,” said Miller.

The trick is getting the plastic out.

“Most processes today use organic solvents, like chloroform or bleach, to dissolve the other cell parts,” says Miller. “Those solvents can be costly and harmful for the environment.”

Miller has devised a system where the bioplastic doesn’t have to be extracted from the bacteria. Instead, it secretes the plastic outside the cell. In other words, the plastic comes to you.

Miller is investigating the use of phasin, a protein, as a type of transporter for the plastic to be secreted from, or exit, the cell.

“When introduced to the cell, phasin binds to the plastic and minimizes its granule size, so it can easily exit the cell,” said Miller. “So, instead of a large glob of plastic, you have lots of little pebbles.”

The phasin can be “tagged” with a signal peptide, which tells the cell to translocate, or expel the phasin. Because the phasin is attached to the plastic granule, it takes it out of the cell with it. Microscope pictures of the successful bioplastic secretion look a little bit like a messy tube of squeezed toothpaste.

Currently, Miller works to create bioplastics in E. coli, but future large-scale production could occur in other organisms. And the potential uses are even more varied than the sources: already, PHAs have been used for bottles, cosmetic containers, pens, and golf tees. They can also be used for paper coatings, food substitutes, and medical devices.

Miller has applied for a patent for his technology, and he believes bioplastic secretion could be just what’s needed to make the industry price competitive with traditional synthetic plastics.

“We’re also considering other methods that could bring the production price down,” said Miller. “If we can identify cheaper carbon sources, for example from municipal waste water systems, biofuel byproducts or other environmental waste, that could reduce the cost even more.”

If that’s the case, in the future, we should be seeing a whole lot more of the second bioplastic bottle.

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