Group of researchers also optimizing the production of biodegradable plastic from methanol, via bacteria

A cross-disciplinary team from the FAPESP Shell Research Centre for Gas Innovation (RCGI) is studying microalgae that have the potential of production bioproducts from carbon dioxide and methane coming from natural gas. The scientists collected samples in the Santos coastal region (cities of Cubatão and Guarujá) and isolated 24 different microalgae. Four of these produced both lipids and biopolymers. Under the guidance of Professor Elen Aquino Perpetuo, a biologist and the coordinator of the RCGI’s Projects 17 and 18, the group also is selecting bacteria for specifically producing PHB (a high added-value biopolymer) from methanol.

“The bacteria research is a step ahead, because we already know which are the most promising for producing PHB. In the case of the microalgae, we are still identifying those that have the greatest production potential, in order to take the next step, which is to optimize that production,” summarized Bruno Karolski, biologist and post-Doctoral student in chemical engineering at the Polytechnic School of the University of São Paulo (Poli/USP).

According to him, the initial idea was to use natural gas directly in the culture of microalgae, so that the carbon dioxide present in the natural gas would be captured by them, but the group is now studying whether or not it is worth separating the natural gas into CO2 and CH4 and administering only the CO2 to the microalgae.

“Four of the 24 microalgae that we isolated showed rapid growth, high cell concentration, production of lipids, and also signs of the production of PHB. We identified three of these four: two strains of Chlamydomonas sp., with different production characteristics, plus Didymogenes sp. Our preliminary data indicate that for two of them, it is possible to obtain these bioproducts simultaneously, but we still do not know under what conditions they produce more lipids or more PHB. What we do know is that, when placing the four selected microalgae under the same conditions, two of them stand out because one produces more PHB and the other, more lipids,” Karolski states. He also says that the lipids produced by the microalgae, which are long chain fatty acids and have a high energy potential, are useful, for example, for manufacturing biodiesel.

According to Letícia Oliveira Bispo Cardoso, who is a chemist and a Doctoral student in USP’s biotechnology program, there are reports of the effective production of PHB by microalgae, but only when genetically modified. “In our case, we are exploring the diversity of microalgae of an environment on the Santos coast, for the purpose of finding those that are capable of producing PHB and also large concentrations of lipids,” she explained.

Bacteria and plastic – The scientists were able to extract PHB produced from methanol from five of the 180 strains of bacteria with which they worked: Methylobacterium extorquens, Methylobacterium rhodesianum, Methylopila oligotropha, Methylobacterium radiotolerans, and Methylobacterium populi.

Methylobacterium extorquens is the one that has given the best results, so far: using methanol as a substrate, the bacteria produced 40% of PHB in 72 hours. The percentage of PHB is equivalent to what is reported in the literature, and now we are exploring greater concentrations of oxygen, testing stirring and different concentrations of methanol, in order to see if we are able to optimize this production,” Letícia says.

Researchers also report quite positive results with Methylopila oligotropha. “There are few reports in the literature of producing PHB with this bacteria, however, we achieved a production of 25% of PHB. This is very promising,” Karolski stressed.

Ms. Cardoso points out that not much PHB is produced, worldwide, from methanol, because the most common source of carbon for PHB is sugar. She says that the opportunity provided by the research, in this case, is to lower the cost of the source of carbon for producing PHB. “Sugar is an expensive raw material for making plastic and that ends up affecting the final value of the biopolymer. This is one of the economically relevant factors, among others, that could help expand PHB’s share of the plastics market,” she explained.

Karolski reminds that the RCGI has projects that focus on the production of methanol from methane and carbon dioxide. “That is: we are attempting to use greenhouse gases to form methanol and, then, from methanol to produce a biodegradable plastic. Thus, we will be mitigating GHGs and, at the same time, obtaining bioproducts of high added-value.”

The group also has a biologist and post-Doctoral student in chemical engineering at Poli/USP, Louise Hase Gracioso, and Bruna Bacaro Borrego, who is graduating with and environmental engineering degree from UNIFESP. Professor Cláudio Augusto Oller do Nascimento is also a member of the teams for the RCGI’s Projects 17 and 18.