No abstract

Hydrogen is regarded as an attractive alternative energy carrier due to its high gravimetric energy density and only water production upon combustion. However, due to its low volumetric energy density, there are still some challenges in practical hydrogen storage and transportation. In the past decade, using chemical bonds of liquid organic molecules as hydrogen carriers to generate hydrogen in situ provided a feasible method to potentially solve this problem. Research efforts on liquid organic hydrogen carriers (LOHCs) seek practical carrier systems and advanced catalytic materials that have the potential to reduce costs, increase reaction rate, and provide a more efficient catalytic hydrogen generation/storage process. In this work, we used methanol as a hydrogen carrier to release hydrogen in situ with the single-site Pt 1 /CeO 2 catalyst. Moreover, in this reaction, compared with traditional nanoparticle catalysts, the single site catalyst displays excellent hydrogen generation efficiency, 40 times higher than 2.5 nm Pt/CeO 2 sample, and 800 times higher compared to 7.0 nm Pt/CeO 2 sample. This in-depth study highlights the benefits of single-site catalysts and paves the way for further rational design of highly efficient catalysts for sustainable energy storage applications.

Microbial trimethylamine (TMA)-lyase activity promotes the development of atherosclerosis by generating of TMA, the precursor of TMA N-oxide (TMAO). TMAO is well documented, but same can not be said of TMA-producing bacteria. This work aimed to identify TMA-producing genera in human intestinal microbiota. We retrieved the genomes of human-associated microorganisms from the Human Microbiome Project database comprising 1751 genomes, Unified Human Gastrointestinal Genome collection consisting 4644 gut prokaryotes, recapitulated 4930 species-level genome bins and public gut metagenomic data of 2134 individuals from 11 populations. By sequence searching, 216 TMA-lyase-containing species from 102 genera were found to contain the homologous sequences of cntA/B, yeaW/X, and/or cutC/D. We identified 13 strains from 5 genera with cntA sequences, and 30 strains from 14 genera with cutC showing detectable relative abundance in healthy individuals. Lachnoclostridium (p = 2.9e−05) and Clostridium (p = 5.8e−04), the two most abundant cutC-containing genera, were found to be much higher in atherosclerotic patients compared with healthy persons. Upon incubation with choline (substrate), L. saccharolyticum effectively transformed it to TMA at a rate higher than 98.7% while that for C. sporogenes was 63.8–67.5% as detected by liquid chromatography-triple quadrupole mass spectrometry. In vivo studies further showed that treatment of L. saccharolyticum and choline promoted a significant increase in TMAO level in the serum of ApoE−/− mice with obvious accumulation of aortic plaque in same. This study discloses the significance and efficiency of the gut bacterium L. saccharolyticum in transforming choline to TMA and consequently promoting the development of atherosclerosis.