FRANKFURT. Whether laundry detergents, mascara, or Christmas chocolate – many everyday products contain fatty acids from palm oil or coconut oil. However, the extraction of these raw materials is associated with massive environmental issues: rainforests are cleared, habitats for endangered species are destroyed, and traditional farmers lose their livelihoods. The team led by Prof. Martin Grininger at Goethe University in Frankfurt, Germany, has now developed a biotechnological approach that could enable a more environmentally friendly production method.

A Molecular Assembly Line with Precise Control
At the heart of this research is an enzyme called fatty acid synthase (FAS) – a type of molecular assembly line that builds fatty acids in all living organisms. “FAS is one of the most important enzymes in a cell's metabolism and has been fine-tuned by evolution over millions of years,” explains Grininger.

The enzyme typically produces palmitic acid, a 16-carbon fatty acid that serves as a building block for cell membranes and energy storage. Industry, however, primarily requires shorter variants with 6 to 14 carbon atoms, which today are sourced from plant oils produced on large-scale oil palm plantations linked to deforestation and biodiversity loss. The decisive advantage of the new, FAS-based method: “Fundamentally, our advantage lies in the very precise control of chain length. We can theoretically make any chain length, and we're demonstrating this with the example of C12 fatty acid, which otherwise can only be obtained from palm kernels or coconut,” says Grininger.

Understanding Through Modification
Grininger and his team have significantly contributed to understanding the molecular foundations of FAS over the past 20 years. They discovered that chain length is regulated by the interplay between two subunits: ketosynthase repeatedly elongates the chain by two carbon atoms while thioesterase cleaves off the finished chain as a fatty acid. “We then asked ourselves whether we could go beyond analysis and build FAS with new chain length regulation,” says Grininger. “True understanding begins when you can change or customize a phenomenon.”

Two Targeted Interventions Lead to Success
Grininger’s doctoral student Damian Ludig took up this idea. “We asked what would happen if we specifically intervened in the interaction between these two subunits,” Ludig explains. “Could we then control the chain length of the fatty acids that are produced?”

Ludig employed protein engineering methods where individual amino acids can be exchanged or entire protein regions modified. “Two changes to FAS through protein engineering ultimately led us to our goal,” says Ludig. “In the ketosynthase subunit, I first exchanged one amino acid which resulted in chains being extended only with low efficiency beyond a certain length. Additionally, I replaced the thioesterase subunit with a similar protein from bacteria that shows activity in cleaving short chains.” Depending on further adjustments, Ludig was able to produce short- and medium-length fatty acids.

From Frankfurt to Dalian
Collaboration with Prof. Yongjin Zhou’s research group at Dalian Institute of Chemical Physics, Chinese Academy of Sciences, ultimately achieved breakthrough results. Supported by the German Research Foundation (DFG) and the National Natural Science Foundation of China (NSFC), Zhou and his lab succeeded in developing yeast strains that produce fatty acids containing only 12 carbon atoms instead of 16. Various designer FAS from Grininger's lab were integrated into these yeasts for optimization.
Both laboratories have already filed patents for their technologies. “On the Chinese side, Unilever was involved in this project. Our development has thus far taken place without industrial participation. However, we are striving for a collaboration with an industry partner in order to bring the technology into application,” says Grininger.

Thinking Ahead: From Fatty Acids to Pharmaceuticals
In a second project, Felix Lehmann from Grininger's lab took the research even further by investigating how universally applicable FAS are for tailored biosyntheses: “This question is also driven by necessity – to continually develop chemical processes towards more sustainable green chemistry,” explains Grininger.

The specific question was: Can FAS be redirected to make not only fatty acids, but also entirely different compounds, such as styrylpyrones? These molecules are precursors to substances derived from kava plants that attract medical interest due to their potential anxiolytic properties. Here, too, Lehmann achieved success with relatively few modifications: “First we cut away part of FAS that we didn't need for our target products; then we altered ketosynthase so that cinnamic acid could be used as starting material,” he explains. The team even integrated another protein into the FAS structure so it became part of multi-enzyme complex.

“In this project we systematically examined how entire biosynthetic pathways can be constructed with FAS from readily available building blocks,” Grininger explains. While the results do not yet have immediate practical applications, they provide important guidance for the future design of novel synthases.

At the Intersection of Chemistry and Biology
“Our lab has made significant strides towards biocatalysis and biotechnological applications over recent years, driven by the contributions of many projects and collaborations. We will continue down this path”, Grininger summarizes. “Within the Cluster of Excellence SCALE, we will also use this enzyme to generate tailored biomembranes, whose analysis will help deepen our understanding of key organelles such as the endoplasmic reticulum and mitochondria.”

Whether technology can indeed alleviate palm oil issues now depends on successful scaling up alongside industry partners. The scientific foundation has certainly been laid and the lab still has many ideas to explore.