In a study published in the Bioresource Technology magazine, members of the Research Center for Gas Innovation (RCGI) describe a method that allows the production of bioplastic from a cheap, abundant raw material that does not compete with the food industry: carbon dioxide ( CO2).

In the research, cyanobacteria, also known as blue algae, were used, which are prokaryotic microorganisms capable of performing photosynthesis. When subjected to stress conditions in a culture medium with excess light, cyanobacteria capture CO2 and produce granules of polyhydroxybutyrate (PHB), a type of bioplastic. These cyanobacteria, of the genus Synechocystis sp., Were collected in mangrove areas near Cubatão, in São Paulo.

“As it is a contaminated area, heavily impacted by chemical components, the microorganisms found there are extremely resistant, which is interesting for the research”, explains Elen Aquino, project coordinator and professor at the Federal University of São Paulo (Unifesp).

The method described in the article, in addition to being cheaper and not competing with other markets, contributes to the capture and fixation of one of the gases responsible for the greenhouse effect, transforming it into a product with high added value. According to the researcher, 31% of the biomass produced by cyanobacteria in the presence of light was PHB. The group still intends to do optimization tests. The hypothesis is that it would be possible to increase productivity by subjecting cyanobacteria to a second stress, such as the removal of a nutrient from the environment, for example.

In Brazil, the production of bioplastics on a large scale is still a distant reality. According to Aquino, there is only one company in the interior of São Paulo that produces PHB with bacteria that use sugar as a carbon source. Bioplastics can also be obtained from vegetable oils and cassava starch, among other renewable sources.

"The production of PHB is still very expensive. It is considered a noble plastic, used mainly for the manufacture of orthopedic prostheses."

The next step in the study is to make the so-called "microbial consortium" to try to enhance the production of bioplastic: placing bacteria and cyanobacteria to grow together in a culture medium, in the presence of CO2 and CH4. Unlike cyanobacteria, the bacteria used in another project capture methane gas (CH4) and also transform it into PHB. "That way, we would be able to work with the two main greenhouse gases", he highlights.

RCGI is an Engineering Research Center (CPE) formed by FAPESP and Shell at the Polytechnic School of the University of São Paulo (Poli-USP).

The article Light excess stimulates Poly-beta-hydroxybutyrate yield in a mangrove-isolated strain of Synechocystis sp. can be read at https://www.sciencedirect.com/science/article/abs/pii/S0960852420316539.

* With information from the RCGI Communication Advisory.