In a new publication in the journal Biotechnology for Biofuels and Bioproducts, the results of a study are presented that significantly contribute to the development of sustainable alternatives to fossil fuels, such as plastic. This discovery opens up the prospect of economically viable circular use of the bioeconomy without carbon emissions, as reported by Enna Bartlett from the University of Manchester.
Doctor Matthew Faulkner and his team conducted a study to improve the production of citramalate - a compound that plays a key role in creating renewable plastics, such as acrylic glass or plexiglass.
Using an innovative approach called "design of experiments," researchers were able to increase citramalate production by 23 times by studying and optimizing key process parameters.
Cyanobacteria are microscopic organisms capable of photosynthesis, which can convert sunlight and CO2 into organic compounds. Their promising use in industry is due to their ability to convert CO2, a major greenhouse gas, into valuable products. However, the slow growth and limited efficiency of these organisms have posed challenges for large-scale industrial application until now.
"Our research aims to address one of the main challenges when using cyanobacteria in sustainable production," explains Faulkner. "We have made this technology commercially attractive by optimizing how these organisms convert carbon into useful products."
Researchers focused on studying the strain of cyanobacteria Synechocystis sp. PCC 6803, which is well-known for its properties. Citramalate, the object of their study, is produced in a single fermentation step based on pyruvate and acetyl-CoA (an important compound for many biochemical reactions). By fine-tuning process parameters such as light intensity, CO2 concentration, and nutrient availability, researchers were able to significantly increase citramalate production.
Since the initial experiments yielded only small amounts of citramalate, the team decided to use a design of experiments approach to systematically explore the relationship between several factors. As a result, they were able to increase citramalate production to 6.35 grams per liter (g/l) in 2-liter photobioreactors, with a productivity of 1.59 g/l/day.
Although productivity slightly decreased when scaling up the reactor volume to 5 liters due to light delivery issues, the study shows that such problems can be manageable when scaling up biotechnological processes.
However, the results of this study are not limited to just plastics. Pyruvate and acetyl-CoA, key metabolites necessary for citramalate production, are also precursors to many other important biotechnological compounds. Therefore, the optimization methods demonstrated in this study can be applied to the production of various materials, ranging from bioenergy to pharmaceuticals.
This research also contributes to global efforts to mitigate the consequences of climate change and reduce the use of non-renewable resources, increasing the efficiency of carbon capture and utilization.
"Our research highlights the importance of the circular bioeconomy," notes Faulkner. "We are not only reducing carbon emissions by turning them into valuable products but also creating a sustainable cycle where carbon serves as the foundation for everyday products."
The team plans to further refine their methods and explore ways to scale up production while maintaining efficiency. They are also exploring the possibility of adapting their approach to optimize other metabolic pathways in cyanobacteria to expand the range of sustainable bioproducts that can be produced.