Nanozymes are nanomaterial-based enzyme mimics that have dominated recent research because of their remarkable catalytic activity, stability, and low cost. Among them, CeO2 nanomaterials (CeO2 NMs) possess distinct physicochemical properties and inherent catalytic properties mimicking oxidase (OXD), peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), phosphatase, nuclease, and photolyases. The surface valence state, Ce4+/Ce3+ conversion, and oxygen vacancies (OVs) on the surface of CeO2 NMs are closely associated with enzyme-like activities. Surface modification (ions, small molecules, and macromolecular capping) can strongly promote or inhibit their catalytic activities. CeO2 NMs have emerged as attractive materials for biochemical applications including biocatalytic conversion, pollutant destruction, antimicrobial therapies, biosensors, and disease therapies. We summarize here the development history, catalytic mechanisms, and surface modification methods of CeO2 mimetic enzymes and the exploration of their applications as alternatives to natural enzymes in biochemical fields. Further, we outline potential challenges and prospects and hope to provide better guidance for the design and application of these promising artificial enzymes.

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Biohydrogen is a clean and renewable energy, but the low yield caused by the lack of reducing power in cells greatly restricts the industrialization of biohydrogen production. Photobiohybrid systems (PBSs) can integrate the high light energy utilization efficiency of photocatalysts with the excellent catalytic performance of microorganisms. Here, gold nanoparticles were targeted into Clostridium butyricum as intracellular photosensitizers to construct a PBS that could efficiently produce biohydrogen under visible light, with the apparent quantum yield as high as 19.31%. Compared with the dark-fermented C. butyricum, the biohydrogen production of PBS increased by 88.74%. The mechanism of photoelectrons from Au NPs to C. butyricum was elucidated by the transcriptome. Compared with the darkfermented biohybrids, the expressions of biohydrogen generation-related enzymes, such as hydrogenase and pyruvate formate lyase genes, in the PBS were all upregulated more than 2 times. Furthermore, the genes of riboflavin synthase, electron transfer flavoprotein (ETF), and FAD-dependent oxidoreductase, which are closely related to electron transformation, were all significantly upregulated. The photoelectrons were transferred to the hydrogenase via ETF and FAD 2+ to enhance biohydrogen production, independent of pyruvate decomposition. This PBS provides theoretical guidance for constructing an efficient light-driven microbial manufacturing system.