When investigating bacteria that are already known and produce a plastic of high aggregate value from methane, scientists from USP discovered a micro-organism that generates another type of biopolymer.

A few months ago, biologist Elen Aquino Perpétuo and a team of researchers began a Project for the purpose of transforming the methane contained in natural gas, via bacteria, into high aggregate value plastic (PHB). The purpose of the study, which was developed at the Research Center for Gas Innovation (RCGI), with the support of FAPESP and of BG Brasil – a subsidiary of the Shell Group, was to establish a different chemical route for transforming methane. But, after only a short time into the investigation, the group discovered a bacteria that transforms methane into another type of polymer.

The biologist Elen Aquino Perpétuo

“We have not yet characterized this polymer; we do not know “who” it is. But we know that its accumulation, according to the bacteria under study, is something never before reported in the literature: something totally new,” Elen revealed. The bacteria is called Methylobacterium rhodesianum and was collected in the Santos Canal System.

Actually, Elen and her team were attempting to prove and compare the efficiency of some methanotrophic bacteria in the transformation of methane and methanol into PHB. To that end, during a phase of the investigation, they had already done tests with strains bought from the Methylobacter sp. and Methylocystis sp genuses.

“At this second moment, we collected samples at three different points of the Santos Canal System, to see if we could find, in nature, the bacteria that are able to make this transformation. And then we came upon the Methylobacterium extorquens, which is really a producer of PHB, ad with the Methylobacterium rhodesianum.”

According to the biologist, the news is not only the production of a different polymer by a different bacteria. “We discovered that, even to generate PHB, the bacteria isolated from the natural systems are more productive than the strains we bought. That could make the difference, because we know that, for the biological route to be economically viable, the bacteria have to be able to accumulate 60% of their dry weight in polymers,” she explains.

She points out that this percentage is calculated by taking into account the production of PHB from sugar. “The production of biopolymers is now done from sugar, which is a substrata that costs 30% more than that of methanol. Methane and methanol are cheaper substrata. Therefore, I am certain that this percentage will drop considerably.”

Biopolymer: a plastic of biodegradable origin


Elen says that, Without the team having optimized the production of PHB (manipulating variables like temperature, pH, and stirring), the Methylobacterium extorquens taken from the ocean environment already accumulates 30% of its weight in polymers. “We haven’t done the numbers, yet, but, taking into account the difference in price between methanol and sugar, I think it is already economically viable.”

The biologist also explains that the ocean environment, with its adverse conditions, such as salinity, widely varying temperatures and aeration, for example, challenges the capacity to adapt of the bacteria, which need to be more resistant, in order to survive. “The more adaptable the micro-organisms are, the more we will be able to modulate them, manipulating the variables we have already mentioned, so that they produce what we want.”

Future – The question now is, according to the scientist: where do we put our money from this point forward? “We will repeat the testing with the Methylobacterium rhodesianum, because we do not know if this new thing is economically viable. What we know is that, from an academic standpoint, the discovery of this bacteria that produces another polymer is important and will generate impactful publications.”

Elen remembers that the first objective, when she created the project, was to improve the production of PHB. “Summarizing, we are interested in both things: in making the production of PHB commercially viable according to the biological route and in publishing our discoveries regarding this other polymer. Now, what we will prefer to do from here forward, I believe will be decided during our meetings with Shell and with the RCGI team.”

The team also collected samples from the reservoir of the Balbina Hydroelectric Plant, in the State of Amazonas (AM). “We collect where there is methane, and the Balbina reservoir has a lot of methane. We haven’t had time to process these samples, yet, but we should begin in the coming weeks.”