Greener Glass

Researchers at the University of Duisberg-Essen in Germany have discovered a bacterial enzyme that creates a key raw material for making acrylic glass and acryclic paints. This enzyme could provide a new pathway to producing acrylics without using fossil fuels or generating much toxic waste.

While bacteria have been used to create various plastics before, this is the first time scientists have discovered a biosynthetic pathway to making acrylic glass–the clear, durable plastic often used as a shatter-resistant alternative to glass. The researchers believe that acrylic glass made with the newly discovered bacterial enzyme could hit the market in roughly a decade. “We have the enzyme,” says Thore Rohwerder, a microbiologist at the University of Duisberg-Essen. “Now we need a process that’s going to produce really high amounts. I’m optimistic about it.”

Acrylic glass is made by polymerizing methyl methacrylate, or MMA, in baths of methyacrylic acid, a highly corrosive chemical solvent. The MMA is derived from petrochemicals. As a result, large amounts of fossil fuels are used, and toxic byproducts are left over.

Rohwerder and his colleague Roland Müller, from the Hemholtz Centre for Environmental Research in Germany, were originally studying a method for biodegrading methyl tertiary butyl ether (MTBE), a gasoline additive. In a paper published in the Journal of Applied and Environmental Microbiology in June 2006, they described an enzyme in bacteria that degraded MTBE. The researchers also mentioned an added benefit of the enzyme–it created 2-HIBA, a precursor to acrylic glass.

However, it wasn’t until this year that the research team decided to develop the enzyme for creating acrylic glass. This discovery, according to Jalal Hawari, a chemist with the National Research Council Canada, has been much sought after. “[Acrylic glass] is very widely used–everyone’s trying to develop a biological way to get it,” he says. “If they manage to do it, that will be a very big achievement.”

The enzyme in question produces 2-HIBA, which is turned into acrylic glass after a series of simple organic-chemistry reactions. “This [process] is very difficult for chemists, but very easy for the enzyme,” says Rohwerder. Sugar, alcohols, or fatty acids feed the bacteria, which then use the enzyme to make the plastic precursor.

Another benefit is that the enzyme may help avoid the use of chemical solvents. “To do chemical polymerization, … they have to carry out the reactions in organic solvents,” says Hawari. “But when you work with biology, you can do it in water.”

While the researchers can vouch for the product’s quality, getting the microbes to produce sufficient quantity may prove difficult. “It’s the biology that causes the problems,” says Rohwerder. “You have to manipulate the [bacteria’s] metabolism; you have to make sure the enzyme is working well in the organism.”

Christophe Schilling, the founder and president of Genomatica, a chemical company based in San Diego (and one of Technology Review’s “TR100 in 2003” ) notes that the success of the plastic hangs on economics. “Ultimately we have to engineer an organism that can produce enough of the chemical in certain yields and rates that make the process economical,” Schilling says.

The German company Evonik Industries has purchased the rights to the patent application for the enzyme, and it will reconfigure the process to industrial proportions. With the company’s help, the researchers estimate that a functioning pilot plant could be up and running in four years, and a self-sustaining industry in about ten. Rohwerder cautions that this timeline could change. “We never know. If the process runs [well] in two years, super,” he says. “But it also [depends on] how many millions you want to spend. If we get some millions of euros, we will do it in two years.”