Turning tough plant materials into usable fuel has long been one of the biggest challenges in renewable energy. At the center of this effort is cellulose, Earth’s most abundant renewable polymer. Despite being made entirely of glucose, its tightly packed crystalline structure—combined with lignin and hemicellulose—makes it extremely difficult to break down. Nature accomplishes this only slowly, and with the help of complex enzyme systems.
Now, scientists at the Brazilian Center for Research in Energy and Materials (CNPEM), along with collaborators in Brazil and abroad, have discovered a powerful new enzyme that can unlock cellulose more efficiently than ever before. Known as CelOCE (cellulose oxidative cleaving enzyme), this metalloenzyme could dramatically enhance the production of second-generation ethanol, a clean fuel made from agricultural waste such as sugarcane bagasse and corn straw. The research was recently published in Nature.
CelOCE cleaves cellulose through a previously unknown mechanism. Instead of producing the final product itself, it enables other enzymes in the cocktail to work more effectively by breaking open the crystalline structure. Its role is to make the cellulose accessible, essentially unlocking the structure so that other enzymes can convert it into sugar.
This discovery represents a major shift in how scientists understand the biochemical breakdown of cellulose. Until now, the dominant approach relied on monooxygenases, which oxidize glycosidic bonds to help other enzymes perform their tasks. That was considered the cutting edge for two decades. CelOCE changes that perspective. It is not a monooxygenase, and its performance is significantly better—roughly twice as effective in enhancing cellulose breakdown when added to enzyme mixtures.
CelOCE works by attaching to the end of a cellulose fiber and cleaving it oxidatively. This disrupts the fiber’s structural stability and allows classical enzymes, like glycoside hydrolases, to do their job more effectively. One of the enzyme’s most innovative features is its dimeric structure, made up of two identical subunits. While one subunit binds to the cellulose, the other generates hydrogen peroxide needed for the oxidative reaction. This means CelOCE is self-sufficientand eliminates the need for external peroxide sources, a common complication in industrial applications.
As a metalloenzyme, CelOCE contains a copper atom at its catalytic core. It was not engineered but rather discovered in a microbial community found in soil covered with sugarcane waste near a biorefinery in São Paulo, Brazil. To identify it, researchers applied a broad scientific toolkit that included metagenomics, proteomics, mass spectrometry, synchrotron-based X-ray techniques, CRISPR-based gene editing, and large-scale bioreactor testing.
The team not only discovered the enzyme but also demonstrated its real-world potential by testing it in 65- and 300-liter pilot plant bioreactors. This means CelOCE is ready for immediate integration into commercial biofuel production, a particularly significant advancement for Brazil, a global leader in biofuels and agricultural biomass.
Currently, cellulose-to-ethanol conversion efficiency ranges from 60% to 80%, leaving a substantial amount of biomass untapped. CelOCE is expected to push those numbers higher, potentially transforming agricultural waste into a more productive fuel source. Any increase in efficiency—given the massive scale of global biomass waste—translates into substantial gains in renewable energy output.
Beyond ethanol, CelOCE’s minimalist and efficient catalytic design could also be applied in other areas such as environmental remediation and industrial biotechnology.
This enzyme discovery represents a significant leap forward in sustainable fuel technology. With its unique self-sustaining mechanism, high efficiency, and readiness for deployment, CelOCE may help reshape how the world turns waste into energy, driving progress in both energy security and the global climate transition.
By Impact Lab
