Bioplastic is rapidly moving into the mainstream and giving petroleum-based plastics a run for their money. But there are still ways its development can be improved to make it less expensive and as easy to manufacture as traditional plastic materials.
Now researchers in Spain have found a way to do this by using bacteria in a unique way. A team of scientists from the Centre for Biological Research (CIB-CSIC) in Madrid have created a system for producing PHA plastics that use predatory bacteria to extract the bioproduct from inside other bacteria, which are killed in the process, said Virginia Martinez, one of the researchers on the project.
PHAs are typically linear polyesters produced in nature by bacterial fermentation of sugar or lipids. The key advantage of this type of bioplastic is that it is biodegradable and thus less harmful to the environment than petroleum-based plastics.
|PHA-purified bioplastic obtained from the bacterium P. putida KT2440 that was extracted using a predator bacterium. (Source: Centre for Biological Research, Madrid)|
Martinez is currently a researcher at the biotechnology company Evolva in Copenhagen and specialist in developing bacterial cell factories. She previously worked at the CIB’s Polymer Biotechnology Laboratory with a particular focus on eco-friendly engineering technologies and techniques. “The aim is to sustainably obtain the products we’re interested in, such as bioplastics,” she said.
The method Martinez and her team developed, which has already been patented, make it possible to create PHA bioplastic at low cost and at industrial scale in bacterial cell factories, she said. Researchers published a study of their work in the journal Scientific Reports.
Bacteria can produce bioplastic that’s the equivalent of 90 percent of their own weight. But until now, the polymer contained inside the cell has been difficult to extract and done so only using different detergents and cell-disruption systems, researchers said.
The drawbacks of these processes are that they “are not environmentally friendly and also quite inefficient, which increases production costs,” Martinez said. The method invented by her and the CIB team alleviates these issues by using a bacterium that preys upon other bacteria—the Bdellovibrio bacteriovorus—to do the extraction of the bioplastic without degrading it, she said.
“What we did was to use the predatory bacterium B. bacteriovorus as a lytic agent to kill other bacteria—in this particular case P. putida KT2440, a natural PHA producer—and recover the intracellular bioproduct,” Martinez said. “We also engineered the predator so that it doesn’t degrade the bioplastic accumulated by the prey.”
The system eliminates the need for complex equipment or toxic substances to extract the bioplastic. It also could be used to gather other valuable compounds from the bacteria, such as enzymes or proteins, because the predator bacteria can attack a wide variety of strains, Martinez said.
She said that their patented system already has piqued early commercial interest for the production of bioplastic, and researchers hope it will soon be used as an alternative method for recovering bioplastic and other “intracellular products of industrial interest,” Martinez added.