2024-07-03 07:43:12
Scientists have managed to generate, through genetic engineering, strains of the Pseudomonas putida bacteria capable of using plastic waste as nutrients to transform it into degradable or compostable bioplastics.
Specifically, these researchers, from the Spanish National Research Council (CSIC), have managed to design, using 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 polyethylene terephthalate (PET) hydrolysates, which is one of the most commonly used plastics in containers and bottles, and lignin derivatives, one of the most abundant polymers in nature and which until now has been difficult to properly exploit.
These new strains and the bioprocess implemented as a 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 clear that these strains and others in the future have the potential to become a sustainable tool for the management and revaluation of plastic waste, transforming it into biodegradable or compostable bioplastics.
The study, the result of a collaboration between the Polymer Biotechnology group of the Margarita Salas Biological Research Centre (CIB, CSIC), led by Auxiliadora Prieto, and the Systems Biotechnology group of the National Biotechnology Centre (CNB, CSIC) led by Juan Nogales, has implemented a multidisciplinary approach to overcome the numerous scientific and technical challenges that hinder 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 key objective is to replace current fossil-based plastics with more sustainable and biodegradable alternatives such as PHAs. These compounds, produced by many bacteria, have wide applications in medicine and in the packaging sector, and are considered a viable alternative to fossil-fuel-derived plastics. PHAs are stored as intracellular reserve granules; however, their production presents a significant challenge due to the need to induce nutrient limitation, typically nitrogen, phosphorus or oxygen, in the culture medium for their production. This represents a major bottleneck in the production of PHAs, as it requires the implementation of complex bioprocesses.
In this work led by the CSIC, these obstacles have been largely overcome. In the first instance, the production of PHAs has been optimized by reconfiguring bacterial metabolism according to computational predictions. Finally, using synthetic biology, it has been possible to implement production independent of nutritional limitations, which allows for the implementation of simpler and more efficient bioprocesses. In the words of María Manoli, first author of the work and member of the CIB, “the bacterial factories developed have shown, on a laboratory scale, the highest production of PHA in relation to cellular biomass from PET hydrolysates reported to date.” In addition, she adds, “the strains developed were capable of producing significant quantities of PHA from other waste, such as derivatives of lignin, a highly recalcitrant plant polymer.”
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, makes it possible to convert difficult-to-process waste into sustainable and biodegradable bioplastics,” Nogales highlights. “This change in production could not only reduce the carbon footprint of plastic production, but also contribute to mitigating the plastic crisis, which costs up to $600 billion each year,” he notes.
This work has given rise to a patent and has been developed in the context of two European projects, one of them in collaboration with institutions from China.
The study is titled “A model-driven approach to upcycling recalcitrant feedstocks in Pseudomonas putida by decoupling PHA production from nutrient limitation.” It has been published in the academic journal Cell Reports.