Beetle-inspired biocatalyst generates hydrogen peroxide for power systems

A laboratory study has identified a radical-mediated biochemical route that may explain how the bombardier beetle Pheropsophus occipitalis produces hydrogen peroxide in its defensive glands, then used the mechanism to build a biomimetic energy system that makes and consumes the peroxide on demand. The researchers report that laccase-driven oxidation of hydroquinone generated hydrogen peroxide through reactive intermediates, while immobilized enzymes on a cerium oxide–titanium dioxide support produced 191.79% of the peroxide concentration measured against the substrate benchmark, a 9.2-fold improvement over free laccase. The work connects an insect defense mechanism with a possible alternative to power systems based on pre-stored concentrated hydrogen peroxide.

P. occipitalis stores hydroquinone and hydrogen peroxide in separate glandular reservoirs and brings them together during an attack, allowing enzymes to produce defensive quinones and propellant gases. The origin of the beetle’s peroxide had remained uncertain, even though earlier research had identified laccase in its defensive chemistry. The new experiments support the proposal that laccase converts hydroquinone through radical intermediates in a pathway that also regenerates oxygen.

Evidence came from electron paramagnetic resonance spectroscopy and molecular docking, rather than from a direct measurement of peroxide production inside a living beetle. When hydroquinone was oxidized by free laccase, freeze-trapped EPR spectra detected a hydroquinone radical after five minutes and a p-hydroxycatechol radical after 15 minutes. Separate spin-trapping experiments identified DMPO adducts associated with hydroxyl, carbon-centered, and hydroperoxyl radicals.

The authors interpret these observations as evidence for several connected radical routes, including a secondary pathway in which hydroxyl radicals recombine to form hydrogen peroxide. The proposed mechanism differs from the conventional four-electron reduction of molecular oxygen to water by laccase. In the side pathway described by the researchers, molecular oxygen accepts one electron to form a hydroperoxyl radical, and two hydroperoxyl radicals can then generate one molecule of hydrogen peroxide while returning one molecule of oxygen.

A second oxygen-independent route involves homolytic cleavage of water, producing hydroxyl radicals and hydrogen atoms; collision of hydroxyl radicals can yield additional peroxide. At the same time, hydrogen atoms can recombine with hydroquinone semiquinone radicals, helping regenerate hydroquinone and extend the lifetime of reactive intermediates. These reactions form a proposed triple synergy among oxygen regeneration, hydrogen turnover, and catalysis by cerium.

For every mole of oxygen consumed through the single-electron route, the authors calculate that 1.5 moles can be regenerated within the local reaction environment: one through hydroperoxyl-radical disproportionation and another half through peroxide decomposition. This could lessen dependence on dissolved oxygen, whose concentration in water is limited. Molecular docking also indicated that hydroquinone and its chlorinated derivative can occupy the enzyme’s hydrophobic pocket, with calculated binding free energies of −4.6 and −5.1 kilocalories per mole, respectively.

These computational results support substrate compatibility but do not independently establish reaction rates in the animal. Because free enzymes are comparatively unstable and inefficient for sustained peroxide production, the team modified laccase and catalase with methoxy polyethylene glycol and co-immobilized them on cerium oxide–titanium dioxide composite supports. Transmission electron microscopy showed globular structures on cerium oxide after enzyme attachment, while X-ray photoelectron spectroscopy detected carbon and nitrogen associated with the enzymes and an increased proportion of Ce4+ relative to Ce3+.

The adsorption efficiencies were 38.89% for laccase and 72.78% for catalase, and the immobilized enzymes retained catalytic activity. Their reported activity half-lives were six to eight hours, although the study does not establish long-term durability beyond those observations. Cerium oxide contributes more than a physical support.

Its reversible Ce4+/Ce3+ redox couple acts as an electron shuttle, accepting electrons during hydroquinone oxidation and participating in subsequent reactions, while oxygen vacancies support gas exchange. Titanium dioxide contributes photosensitizing and radical-generating properties. The composite therefore combines structural protection, improved electron transfer, and catalytic assistance, whereas the oxygen-containing support may also help shield enzymes from damage associated with radical reactions and heat released during peroxide decomposition.

These are laboratory-scale chemical and materials results; the research did not quantify the power, efficiency, noise, service life, or environmental performance of a complete field-ready energy device. Inspired by the beetle’s compartmentalized anatomy, the researchers also fabricated a three-dimensional fractal microchannel catalyst bed by additive manufacturing. Its branching network was intended to distribute fluids more uniformly, reduce flow resistance, and improve mass transfer.

A pulsed cascade booster coordinates the bed with valves, a peroxide reservoir, a concentration sensor, a condenser’s heat-management function, and a catalase bed. When sensed peroxide falls below a preset threshold, hydroquinone is routed through the laccase bed to generate peroxide in a closed circulation loop. The operating sequence separates peroxide formation from its immediate use rather than requiring a reservoir of concentrated peroxide under high pressure.

Water and benzoquinone are recycled to the hydroquinone reservoir, where reduction of benzoquinone can restore the precursor for another cycle. The authors describe this arrangement as a way to reduce the safety risks of transporting and storing concentrated peroxide. It also resembles the biological division of labor in the beetle, where precursor storage, catalytic reaction, and jet output occur in separate compartments.

That similarity is a design principle, however, rather than evidence that the artificial system reproduces the speed, control, or endurance of the insect’s defense apparatus. Several qualifications remain important. Most experiments used hydroquinone, commercially sourced enzymes, and controlled laboratory mixtures, so the method does not yet demonstrate that all peroxide in P. occipitalis arises through the proposed pathway.

The claimed 191.79% peroxide concentration is a relative value referenced to a 1% hydroquinone benchmark, not a 191.79% pure hydrogen peroxide solution. The researchers also propose that radicals may recombine into peroxide, but the EPR spectra were interpreted through spin-trapping signals whose overlaps and cancellations can complicate assignment. The results therefore establish a laboratory-scale route for mild, on-demand peroxide production and utilization, while the complete energy device remains a proposed system whose practical performance was not quantified in the study.

Subject of Research: Beetle-inspired laccase catalysis for on-demand hydrogen peroxide generation and utilization

Article Title: Establishment of new energy supply construction inspired by the defensive mechanism of Pheropsophus occipitalis

Article References: Wang, L., Zhang, Y., Che, F., Yao, X., Yu, J., Li, W., Wang, R., & Yin, R. (2026). Establishment of new energy supply construction inspired by the defensive mechanism of Pheropsophus occipitalis. Frontiers in Chemistry, 14, Article 1831087. https://doi.org/10.3389/fchem.2026.1831087

Image Credits: AI Generated

DOI: 10.3389/fchem.2026.1831087

Keywords: hydrogen peroxide, biomimicry, laccase, hydroquinone, enzymatic catalysis, bombardier beetle, cerium oxide, titanium dioxide, radical chemistry, portable energy, biomimetic engineering, Establishment