New Method Uses Predatory Bacterium to Extract Bioplastic Materials

PHA purified bioplastic obtained from the bacterium P. putida KT2440. Image: CIB

A method using a predatory bacterium to extract bioplastic materials from the inside of other bacteria without degrading it, has been developed by a team of Spanish researchers. The system, that has been already patented, will enable these products to be obtained at low cost and also at industrial scale in bacterial cell factories.

A group of scientists from the Centre for Biological Research (CIB-CSIC) in Madrid, have come up with a system for producing PHA bioplastics, which are an alternative to plastics obtained from petroleum. The system functions “using predatory bacteria to extract the bioproduct from inside other bacteria, which are killed in the predatory process”, explains Virginia Martínez, lead author of the study. The findings of the study were featured in Scientific Reports (Nature Group).

Currently, Martínez is a researcher at the biotech firm Evolva in Copenhagen. She earlier worked at the CIB’s Polymer Biotechnology Laboratory, and as a specialist in developing bacterial cell factories.

The aim is to sustainably obtain the products we’re interested in, such as bioplastics, a very interesting alternative where very large amounts of money are at stake. [The issue] is that bacteria can produce and accumulate up to 90% of their own weight as bioplastic. But the polymer is contained inside the cell and it is difficult to extract. Until now, different detergents and cell disruption systems have been developed and applied to lyse the producers and release the product. However, these processes are not environmentally friendly and also quite inefficient, which increases production costs.

Virginia Martínez, CIB-CSIC

The team aimed to reduce costs and improve the downstream process by choosing a bacterium that preys upon other bacteria, called Bdellovibrio bacteriovorus. The researchers genetically redesigned the predator, transforming it into a biological tool that enables the disruption of bioplastic-producing bacteria, helping the extraction and further purification of the bioproduct.

A Pioneering Method

This ground-breaking extraction method, that has already been patented, is both novel and unique.

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. We also engineered the predator so that it doesn’t degrade the bioplastic accumulated by the prey.

Virginia Martínez, CIB-CSIC

This lytic system allows the bioplastic to be recovered in just one step “with no need for complex equipment or toxic compounds,” Martínez stresses.

This new method can also be used to acquire other added-value compounds, such as proteins or enzymes that were earlier accumulated in other bacteria.

This is because of the ability of B. bacteriovorus to attack different bacterial strains, including those that are widely used at high cell density and in industry. In addition, “it is safe for use by humans, as it does not attack mammalian cells,” the researcher points out.

A few companies have started to point out their interest in this system as is it now patented.

We hope it will be used commercially to produce bioplastics or any other intracellular compound. This is an innovative process because it is the first time a predatory bacterium strategy has been used as an alternative method for the recovery of intracellular products of industrial interest.

Virginia Martínez, CIB-CSIC

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