Biogas Institute of Ministry of Agriculture

Selective activation of CH4 under mild conditions to produce liquid oxygenates is central to low-carbon chemical manufacturing. While O2 or H2O2 are commonly used oxidants, the direct oxidizing role of H2O itself remains poorly defined. Here, we use Au–TiO2 as a prototypical nanointerface to disentangle the effects of H2O versus O2 on photocatalytic CH4 oxidation. In-situ EPR spin-trapping, high-pressure DRIFTS, and DFT reveal two distinct pathways. With H2O as the sole oxidant, photogenerated holes oxidize H2O to •OH, which abstracts H from CH4 to form •CH3; subsequent surface reactions yield CH3OH and HCHO. Computations indicate that roughly one-third of the generated •OH participates effectively in the productive sequence. In contrast, when O2 is present, interfacial electrons preferentially reduce O2 to •OOH; coupling of •OOH with •CH3 forms CH3OOH intermediates that evolve to CH3OH/HCHO, but the elevated •OOH flux also accelerates deep oxidation to CO2 and suppresses H2 evolution. These mechanistic differences in radical identity, intermediate pools, and apparent barriers translate into divergent selectivity. Under optimized, O2-free conditions (1 wt % Au–TiO2, 80 °C, 20 bar CH4, UV–vis; H2O as oxidant/medium), liquid C1 oxygenates are obtained at 7.7 mmol g–1 h–1 with 100% selectivity. The study reveals that tuning the oxidant and the interfacial radical landscape at a nanoscale metal–oxide interface governs the precision activation of CH4 and provides mechanistic insight into H2O-driven, selective methane oxidation on Au–TiO2.

Strong hydration of cryoprotective agents reduces the glass transition temperature of water and suppresses ice formation. However, lethal cooling and warming remain a critical obstacle to cross-scale cryopreservation of clinical biospecimens. Herein, a snowman-like Janus nanohybrid composed of magnetic iron tetraoxide and photothermal polypyrrole is reported. Its cranial-corporal asymmetry enables heterogeneous hydration for a record high efficiency of ice confinement, reducing mean ice crystal area by 98.4%. Molecular dynamics simulations reveal that Janus architecture simultaneously enhances interactions with ice and strengthens the local hydration anisotropy, accounting for the effective inhibition of ice growth. Superflash warming over 920°C min‒1 by magnetically rotating its anisotropic structure for uniform heat dissipation narrows the hostile temperature window in micro-/macroscopic scenarios, as further confirmed by Monte Carlo modeling. This design enables cost-effective post-thaw magnetic retrieval, eliminating the need for heavy centrifuges, well-suited for scalable and on-site applications. As a result, cryopreserved samples from single cells, bacteria, to porcine trachea retain near-complete viability and functionality. Therefore, this study offers a promising technique to bridge the gap between microscale cell storage and whole-organ preservation.

Methanogenic archaea play a crucial role in the global carbon cycle and in climate change. Recent metagenomic sequencing has revealed a considerable number of (putative) H2-dependent methylotrophic methanogens (HMMs) across the archaeal tree and in diverse environments. Traditional isolation methods, such as dilution-to-extinction and roll-tube techniques, fail to cultivate fastidious HMMs. Here, we describe a four-stage isolation strategy designed to selectively isolate HMMs by using a flexible combination of methods to systematically reduce microbial complexity to a pure culture. In the initial stage, the growth conditions for the target HMM were optimized through closed-batch cultivation encompassing >50 conditions. Second, HMM-containing cultures were serially diluted in 96-well plates combined with substrate limitation to eliminate non-target archaea. In stage 3, the bacterial diversity in the culture was further decreased to a single bacterium by treatment with antibiotics and lysozyme. Finally, a last bacterial contaminant was removed by repeated addition of antibiotic mixtures and successive dilution transfers, leading to the successful isolation of the first pure culture of Methanosuratincola petrocarbonis LWZ-6, an HMM of the phylum Thermoproteota. This protocol also describes molecular methods, including 16S rRNA gene amplicon sequencing, metagenome sequencing and quantitative PCR, to track microbial community shifts and assess the growth advantage of the target HMM, enabling monitoring of the stepwise elimination of non-target microorganisms and ultimately confirming the purification of the target HMM. The duration of the protocol will vary for different HMMs depending on their substrate utilization, growth rate and method selection.