S-scheme towards interfacial charge transfer between POMs and MOFs for efficient visible-light photocatalytic Cr (VI) reduction.

The establishment of heterojunctions was considered as an exceptional strategy to obtain high-efficiency charge separation and enhanced photocatalytic performance. Herein, a series of FePMo/MIL-53(Fe) (FeM-53) heterojunctions were successfully constructed through in-situ growth of FePMo onto MIL-53(Fe) surface and their photocatalytic capacity were examined by visible-light-induced Cr(VI) reduction. Interestingly, the as-fabricated composites offered various photocatalytic activities controllably relying on the mass ratio of FePMo to MIL-53(Fe). Particularly, the one with the 10% ratio displayed the highest Cr(VI) reduction rate (100%) within 75 min, which was respectively over 4 and 2 folds higher than pure FePMo and MIL-53(Fe). The boosted photoactivity might be ascribed to the establishment of S-scheme heterojunction with suitable band alignment between FePMo and MIL-53(Fe), which broadened the light absorption range and improved charge separation. Further mechanism investigations implied both •O2- and e- were the key reactive species for Cr(VI) removal. Besides, the composite preserved excellent stability after 4 consecutive tests, and performed well in the presence of organic dyes. Such a S-scheme heterojunction may promise for highly efficient environmental mitigation.

S-scheme MOF-on-MOF heterojunctions for enhanced photo-Fenton Cr(VI) reduction and antibacterial effects.

The photocatalytic efficiency is commonly restrained by inferior charge separation rate. Herein, the S-scheme MIL-100(Fe)/NH2-MIL-125(Ti) (MN) photo-Fenton catalyst with the built-in electric field (BEF) was successfully constructed by a simple ball-milling technique. As a result, the MN-3 (the mass ratio of MIL-100(Fe) to NH2-MIL-125(Ti) was 3) composite presented the best visible-light-induced photocatalytic ability, in contrast to pure MIL-100(Fe) and NH2-MIL-125(Ti). The reduction efficiency of Cr(VI) almost reached 100% within 35 min of illumination. Moreover, the MN-3 heterojunction also exhibited the highest antibacterial activity, and about 100% E. coli and more than 90% S. aureus were killed within 60 min of illumination. In photo-Fenton system, In the photo-Fenton system, e-, O2•- and Fe2+ played vital roles for Cr(VI) reduction, and •OH, h+ and O2•- and 1O2 were responsible for sterilization. Additionally, 5 cyclic tests and relevant characterizations confirmed the excellent repeatability and stability of the composite. Also, the S-scheme charge transfer process was put forward. This work offers a novel idea for establishing the MOF-on-MOF photo-Fenton catalyst for high-efficiency environmental mitigation.

Chitooligosaccharides Attenuated Hepatic Encephalopathy in Mice through Stabilizing Gut-Liver-Brain Disturbance.

SCOPE: Hepatic encephalopathy (HE) refers to neurological dysfunction associated with hepatic inadequacy and gut dysbiosis. Chitooligosaccharides (COS) possesses prominent biological activities including incalculable hepatoprotective, neuroprotective and prebiotic effects. This study evaluates the protective effects of COS on HE from the influence of gut-liver-brain axis in mice. METHODS AND RESULTS: Hepatic injured mice show minimal symptoms of HE, reflecting in cognitive impairment, and learning and memory retardation, while they are reversed by COS following orally administrated. Furthermore, COS ameliorates brain function through inhibiting microglial and astrocyte activation in cerebral cortex and hippocampus, promoting neuronal regeneration characterized by the increase of neuron-specific marker (neuronal nuclear antigen, NeuN). Concurrently, neuroinflammation and hepatitis are restrained by COS through descending toll-like receptors 4/Nuclear factor kappa B (TLR4/NF-κB) pathway. Additionally, the dysbiosis of the composition and structure of gut microbiota is displayed in mice with HE, while it is modified by COS through decreasing the relative abundances of Muribaculaceae, Lactobacillus, and Enterorhabdus. The enhancement of blood ammonia is crucially slipped to basal levels by COS. CONCLUSION: The present study shows that COS could prevent the pathological process of HE through regulating the gut-liver-brain cross-talk, which provids new insight into fundamental roles of COS.

Preparation and applications of keratin biomaterials from natural keratin wastes.

Keratin is a kind of natural polymer that is abundant in feathers, wool, and hair. Being one of the natural biomolecules, keratin has excellent biological activity, biocompatibility, biodegradability, favorable material mechanical properties, and natural abundance, which exhibit significant biological and biomedical application potentials. At present, the strategies commonly used for preparing keratin from hair, feathers, wool, etc. include physical, chemical, and enzymatic methods. The present article mainly reviews the structure, classification, preparation methods, and the main biological applications of keratin, and these applications cover wound healing, hemostasis, targeted release of tissue engineering drugs, and so on. It is expected to lay the foundations for its future in-depth investigations and wide applications of keratin biomaterials. KEY POINTS: • There are several pathways to prepare biologically active keratin from wool, feathers, and human hair, etc • Promoting blood coagulation by keratin is related to the adhesion and activation of platelets and the aggregation of fibrin • The biological applications of keratin, including wound healing and tissue engineering, are summarized.

A combination of bioinformatics analysis and rational design strategies to enhance keratinase thermostability for efficient biodegradation of feathers.

Keratinase has shown great significance and application potentials in the biodegradation and recycle of keratin waste due to its unique and efficient hydrolysis ability. However, the inherent instability of the enzyme limits its practical utilization. Herein, we obtained a thermostability-enhanced keratinase based on a combination of bioinformatics analysis and rational design strategies for the efficient biodegradation of feathers. A systematical in silico analysis combined with filtering of virtual libraries derived a smart library for experimental validation. Synergistic mutations around the highly flexible loop, the calcium binding site and the non-consensus amino acids generated a dominant mutant which increased the optimal temperature of keratinase from 40 °C to 60 °C, and the half-life at 60 °C was increased from 17.3 min to 66.1 min. The mutant could achieve more than 66% biodegradation of 50 g/L feathers to high-valued keratin product with a major molecular weight of 36 kDa. Collectively, this work provided a promising keratinase variant with enhanced thermostability for efficient conversion of keratin wastes to valuable products. It also generated a general strategy to facilitate enzyme thermostability design which is more targeted and predictable.

Versatile strategies for bioproduction of hyaluronic acid driven by synthetic biology.

Owing to its outstanding water-retention ability, viscoelasticity, biocompatibility and non-immunogenicity, Hyaluronic acid (HA), a natural linear polymer alternating linked by d-glucuronic acid and N-acetylglucosamine, has been widely employed in cosmetic, medical and clinical applications. With the development of synthetic biology and bioprocessing optimization, HA production via microbial fermentation is an economical and sustainable alternative over traditional animal extraction methods. Indeed, recently Streptococci and other recombinant systems for HA synthesis has received increasing interests due to its technical advantages. This review summarizes the production of HA by microorganisms and demonstrates its synthesis mechanism, focusing on the current status in various production systems, as well as common synthetic biology strategies include driving more carbon flux into HA biosynthesis and regulating the molecular weight (MW), and finally discusses the major challenges and prospects.

Significant improvement in conversion efficiency of isonicotinic acid by immobilization of cells via a novel microsphere preparation instrument.

An instrument for the automatic preparation of microspheres was designed and manufactured, and by which cells were immobilized as efficient biocatalyst with small particle diameter, high crosslinking uniformity, and high porosity. The concentration of polymer solution, crosslinking agent and other conditions for preparing the cells microspheres were determined, and the conversion conditions of isonicotinic acid from 4-cyanopyridine were optimized to minimize mass-transfer limitations, and improve thermal and storage stability. The immobilized cells microspheres, which were continuously used for 23 batches, showed a total transformation capacity of 4.6 mol/L 4-cyanopyridine and a cumulative mass of 566.31 g/L of isonicotinic acid, which demonstrated the potential of the durable biocatalyst with efficient conversion capacity.

Determining the degree of acetylation of chitin/chitosan using a SSNMR 13C method on the basis of cross polarization reciprocity relation.

The degree of acetylation (DA) is an essential parameter for chitin and its derivatives, which determines the chemical and physical properties of the polymers. As a consequene, fast and accurate technique to determine DA is widely required when developing the relating materials. Herein, an improved quantitative SSNMR method of rQCPZRC, based on the cross polarization reciprocity relation, was discussed and employed for DA testing. Three chitin/chitosan samples were chosen to evaluate the performance of rQCPZRC. In comparison with quantitative DP and optimized contact time CP methods, rQCPZRC is revealed as an accurate and reliable DA testing method with relative percentage errors of less than 5%. Moreover, the experimental time of rQCPZRC for each sample is 5.5 h, notably shorter than DP of 36-85 h. Thus, our work suggests rQCPZRC as a tool for DA testing, which is capable to accomplish with high accuracy and efficiency.

A Novel Complex of Chitosan⁻Sodium Carbonate and Its Properties.

Chitosan has excellent properties, as it is nontoxic, mucoadhesive, biocompatible, and biodegradable. However, the poor water solubility of chitosan is a major disadvantage. Here, a novel chitosan-sodium carbonate complex was formed by adding a large amount of sodium carbonate to a chitosan/acetic acid solution, which is water-soluble. Fourier transform infrared spectroscopy, energy dispersive spectrometry, scanning electron microscopy, and solid-state nuclear magnetic resonance techniques were used to detect and characterize the aforementioned complex, which appeared to be a neat flake crystal. Solid-state nuclear magnetic resonance (SSNMR) was used to verify the connections between carbonate, sodium ions, and the protonated amino group in chitosan on the basis of 13C signals at the chemical shift of 167.745 ppm and 164.743 ppm. Further confirmation was provided by the strong cross-polarization signals identified by the SSNMR 2D 13C⁻¹H frequency-switched Lee⁻Goldberg heteronuclear correlation spectrum. The cytotoxicity of a film prepared using this complex was tested using rat fibroblasts. The results show that the film promoted cell proliferation, which provides evidence to support its nontoxicity. The ease of film-forming and the results of cytocompatibility testing suggest that the chitosan-sodium carbonate complex has the potential for use in tissue engineering.

Structural and Immunological Activity Characterization of a Polysaccharide Isolated from Meretrix meretrix Linnaeus.

Polysaccharides from marine clams perform various biological activities, whereas information on structure is scarce. Here, a water-soluble polysaccharide MMPX-B2 was isolated from Meretrix meretrix Linnaeus. The proposed structure was deduced through characterization and its immunological activity was investigated. MMPX-B2 consisted of d-glucose and d-galctose residues at a molar ratio of 3.51:1.00. The average molecular weight of MMPX-B2 was 510 kDa. This polysaccharide possessed a main chain of (1→4)-linked-α-d-glucopyranosyl residues, partially substituted at the C-6 position by a few terminal ß-d-galactose residues or branched chains consisting of (1→3)-linked ß-d-galactose residues. Preliminary immunological tests in vitro showed that MMPX-B2 could stimulate the murine macrophages to release various cytokines, and the structure-activity relationship was then established. The present study demonstrated the potential immunological activity of MMPX-B2, and provided references for studying the active ingredients in M. meretrix.