Bacterial factories are designed to produce bioplastics from conventional plastics

Scientists have managed to generate, through genetic engineering, strains of the Pseudomonas putida bacteria capable of using plastic waste as nutrients to transform them into degradable or compostable bioplastics.

Specifically, these researchers, from the Higher Council for Scientific Research (CSIC) in Spain, have managed to design, through computational methods and synthetic biology, a set of bacteria with the capacity to produce bacterial bioplastics (polyhydroxyalkanoates or PHAs) through the use of recalcitrant materials. , such as hydrolysates of polyethylene terephthalate (PET), which is one of the most used plastics in containers and bottles, and derivatives of lignin, one of the most abundant polymers in nature and which until now is difficult to use properly.

These new strains and the bioprocess implemented as proof of concept are the first fruits of the new and promising line of research and development. With what has been achieved so far, it is evident that these strains and other future ones have the potential to become a sustainable tool for the management and revaluation of plastic waste, transforming them into biodegradable or compostable bioplastics.

The study, the result of a collaboration between the Polymer Biotechnology group of the Margarita Salas Biological Research Center (CIB, of the CSIC), led by Auxiliadora Prieto, and the Systems Biotechnology group of the National Center for Biotechnology (CNB, of the CSIC ) directed by Juan Nogales, has implemented a multidisciplinary approach to overcome the numerous scientific-technical challenges that hindered the production of PHAs from raw materials, whose chemical structure is not related to that of bioplastic.

In the context of the current climate crisis and the emerging circular economy, a fundamental objective is to replace current plastics based on fossil sources with more sustainable and biodegradable alternatives such as PHAs. These compounds, produced by many bacteria, have wide applications in medicine and the packaging sector, and are considered a viable alternative to fossil fuel-derived plastics. PHAs are stored as intracellular reserve granules; However, its production presents a significant challenge due to the need to induce nutrient limitation, typically nitrogen, phosphorus or oxygen, in the culture medium for its production. This represents a major bottleneck in the production of PHAs, since it requires the implementation of complex bioprocesses.

In this work led by the CSIC, these obstacles are largely overcome. In the first instance, it has been possible to optimize the production of PHAs by reconfiguring the bacterial metabolism according to computational predictions. Finally, using synthetic biology, it has been possible to implement production independent of nutritional limitations, which allows simpler and more efficient bioprocesses to be implemented. In the words of María Manoli, first signatory of the work and belonging to the CIB, “the bacterial factories developed have shown on a laboratory scale the highest production of PHA in relation to the cellular biomass from PET hydrolysates reported so far.” Furthermore, she adds, “the strains developed were able to produce significant amounts of PHA from other residues, such as derivatives of lignin, a highly recalcitrant plant polymer.”

Genetically modified strain bacteria producing bioplastic. (Photo: CIB)

Taken together, “these results represent a very significant advance in addressing the current global crisis caused by the accumulation of plastic in the environment and show how a multidisciplinary approach, which includes computational predictions, genetic engineering and synthetic biology, allows us to put into practice value waste that is difficult to process into sustainable and biodegradable bioplastics,” highlights Nogales. “This change in production could not only reduce the carbon footprint in plastic production, but also contribute to mitigating the plastic crisis, which costs up to $600 billion each year,” she notes.

This work has given rise to a patent and has been developed in the context of two European projects, one of them with the collaboration of institutions in China.

The study is titled “A model-driven approach to upcycling recalcitrant feedstocks in Pseudomonas putida by decoupling PHA production from nutrient limitation.” And it has been published in the academic journal Cell Reports. (Source: CSIC)