Synthesis techniques, mechanism, and prospects of high-loading single-atom catalysts for oxygen reduction reactions

The importance of the oxygen reduction reaction (ORR) in fuel cells and zinc-air batteries is self-evident, and effective catalysts could significantly improve the catalytic efficiency of ORR. Single-atom catalysts are gaining increasing interest due to their high atom efficiency and effective catalytic performance compared to other catalyst types. While the optimal loading of catalytic sites in single-atom catalysts significantly influences their catalytic efficiency. However, creating stable single-atom catalysts with high-loading remains a difficult task. Therefore, we showcase and describe the latest developments in techniques for producing single-atom catalysts with high-loadings. In addition, the performance of noble metal, non-precious metal, and diatomic catalysts in ORR processes is summarized. What’s more, the key difficulties and opportunities in the sector are demonstrated by examining the synthesis techniques and evaluating the performance and structure. This review will help researchers to advance the research process of high-loading single-atom catalysts and accelerate their practical application in the field of ORR research.

Bioconversion of lignocellulosic biomass into bacterial nanocellulose:challenges and perspectives

Nanocellulose has various outstanding properties and great potential for replacing petrochemical products.The utilization of lignocellulose to produce nanocellulose is of great significance to the sustainable development of the economy and society.However,the direct extraction of nanocellulose from lignocellulose by chemical method is challenged by toxic chemicals utilization,energy and time consumption,and waste water generation.Therefore,this paper addressed the conversion of lignocellulosic biomass into bacterial nanocellulose(BNC)by the biological method.Moreover,this article highlights the recent advances in potentials and challenges of lignocellulosic biomass for BNC production through the bioconversion process,including biomass pretreatment,enzymatic hydrolysis,glucose and xylose fermentation,GA accumulation,and inhibitor tolerant.The development in metabolic and evolutionary engineering to enhance the production capacity of BNC-producing strain is also discussed.It is expected to provide guidance on the effective bioproduction of nanocellulose from lignocellulosic biomass.

Pterostilbene supresses inflammation-induced melanoma metastasis by impeding neutrophil elastase-mediated thrombospondin-1 degradation

Objective: Chronic inflammation plays a fatal role in tumor metastasis. Pterostilbene(PTE) is a natural dimethylated analogue of resveratrol with anticancer and anti-inflammatory activities. This study aimed to investigate the inhibitory effect of PTE on inflammation-associated metastasis and explore the underlying mechanisms.Methods: Lipopolysaccharide(LPS)-induced lung inflammation and melanoma metastasis models were established in mice. After PTE treatment for four weeks, the organ index, histological changes, proinflammatory cytokines, and the expression and activity of neutrophil elastase(NE), a biomarker of neutrophil influx in the lungs, were analysed. Additionally, direct effects of PTE on NE-induced B16 cell migration were explored in wound healing and Transwell assays, and the expression of thrombospondin-1(TSP-1) and epithelial-mesenchymal transition(EMT) markers were also detected.Results: PTE obviously attenuated the LPS-induced metastasis of circulatory B16 cells to lungs by reducing the number of metastatic nodules on the lung surfaces and the lung weight/body weight ratio. PTE treatment also significantly reduced LPS-activated increase levels of tumor necrosis factor(TNF)-a and interleukin(IL)-6 in the lungs of tumor-bearing mice. In addition, increased expression and enzyme activity of NE and decreased expression of TSP-1 were observed, and these were blocked by PTE. In vitro, PTE at concentrations without cytotoxicity also markedly suppressed NE-triggered B16 cell migration, prevented NE-induced TSP-1 proteolysis and reversed the expression of vimentin, N-cadherin and Ecadherin.Conclusion: PTE could block inflammation-enhanced tumor metastasis, and the underlying mechanism might be associated with the inhibition of NE-mediated TSP-1 degradation.

Next-generation probiotic candidates targeting intestinal health in weaned piglets:Both live and heat-killed Akkermansia muciniphila prevent pathological changes induced by enterotoxigenic Escherichia coli in the gut

The use of next-generation probiotics(NGP)in pigs for combating diseases has been subject to limited research.Here we explored the potential of a well-known NGP candidate Akkermansia muciniphila tar-geting pig gut health.In the first screening experiment,we found that the abundance of A.muciniphila peaked at 14 d old but decreased at weaning(21 d old;P<0.05),suggesting the weaning period may be an effective window for A.muciniphila intervention.Following that,48 crossbred weaned pigs at 28 d old were randomly assigned to five groups:control(CON),high/low live A.muciniphila(HA/LA),and high/low heat-killed A.muciniphila(HIA/LIA).From 1 to 28 d old,the CON group received gastric infusion of anaerobic sterile saline every other day;the HA and LA groups were gavaged every other day with 1 × 1010 CFU/5 mL and 5 × 108 CFU/5 mL live A.muciniphila,respectively;and the HIA and LIA groups were gavaged every other day with 1 × 1010 CFU/5 mL and 5 × 108 CFU/5 mL heat-killed A.muciniphila,respectively.At d 29,pigs in the CON group were randomly and equally divided into two groups,one of which was named the enterotoxigenic Escherichia coli(ETEC)group,and all groups except CON received a 5-d ETEC challenge.The supplementation of A.muciniphila numerically reduced the diarrhea rate of weaned pigs compared to the pigs that only received the ETEC challenge(P=0.57),but the LIA group had a higher diarrhea rate than the CON group(P<0.05).Consistent with this,the supplementation of A.muciniphila improved the small intestinal morphology and structure,proportion of CD4+T lymphocytes in the blood,as well as the expression of genes related to intestinal barrier and antioxidant indices of pigs with ETEC challenge,especially for the LA group(P<0.05).Meanwhile,A.muciniphila supplementation reduced the expression of ETEC virulence factor genes in the ileum and colon of pigs challenged by ETEC(P<0.05).Therefore,A.muciniphila may protect the intestinal health of weaned piglets from damage caused by ETEC infection,but the effect may vary depending on the concentration and activity of A.muciniphila.