Biocatalytic Conversion Of Cyclohexanol To Adipic Acid

Together with project partners from the Helmholtz Centre for Environmental Research (UFZ) and Istanbul Technical University (ITÜ), the b-ACT matter research team has taken a further step forward in the development and optimisation of sustainably produced adipic acid. In a paper recently published in the journal Cell Reports Physical Science, the research team presents a new method for the biocatalytic conversion of cyclohexanol to adipic acid. Adipic acid is a key building block for plastics such as nylon 66and has, until now, been derived almost exclusively from fossil raw materials such as petroleum.

Global chemical production of adipic acid relies primarily on fossil-based raw materials, which leads to environmental problems such as increased greenhouse gas emissions. Microbial biofilms play a crucial role in developing technologies for alternative, sustainable production of the acid.

The research team led by Dr. Rohan Karande and Prof. Tilo Pompe is using a technology that combines microorganisms with porous material to create hybrid living systems that operate continuously and efficiently. At the heart of the new technology is a state-of-the-art biofilm bioreactor system in which the recombinant bacterial strain Pseudomonas taiwanensis VLB120 forms biofilms on a porous material made of poplar and polyethylene terephthalate (PET). These biofilms achieve a high cell concentration and are extremely robust – they tolerate process stressors and enable stable, continuous operation for weeks.

Through targeted optimization using a design of experiments (DoE), the researchers developed a biofilm with a biomass density of approximately 300 grams of dry biomass per square meter. In the subsequent bioconversion phase, cyclohexanol was efficiently and stably converted to adipic acid – a process that ran stably for several weeks using a dynamic glucose feed concept.

The results show that living hybrid materials not only represent a promising alternative to conventional petrochemical processes but can also serve as an efficient foundation for a more sustainable chemical industry. The method is resource-efficient and could be applied in the future to wastewater treatment, bioremediation, and green chemistry.

"This work represents an important step toward a circular economy in which microorganisms are used for the sustainable production of valuable chemicals," says Alexander Franz, lead author of the publication.