•Deposition of chitosan improved mechanical property of BNC tubes and increased grafting amount of heparin.•EDC/NHS catalyzed both amide bonds and ester bonds formation in BNC/CH-Hep composites.•Performance of BNC tubes was improved after introducing chitosan and heparin for application as vascular grafts.•Physicochemical and mechanical properties, hemocompatibility and cytocompatibility were compared.•3D surface structure and roughness of BNC-based tubes were firstly obtained and discussed.In order to improve property of bacterial nano-cellulose (BNC) to achieve the requirements of clinical application as small caliber vascular grafts, chitosan (CH) was deposited into the fibril network of the BNC tubes fabricated in unique Double-Silicone-Tube bioreactors. Heparin (Hep) was then chemically grafted into the BNC-based tubes using EDC/NHS crosslinking to improve performance of anticoagulation and endothelialization. Physicochemical and mechanical property, blood compatibility, and cytocompatibility were compared before and after compositing. The results indicated that strength at break was increased but burst pressure decreased slightly after compositing. Performance of the BNC tubes was improved remarkably after introducing chitosan and heparin. The EDC/NHS crosslinking catalyzed both amide bonds and ester bonds formation in the BNC/CH-Hep composites. Three-dimensional surface structure and roughness were firstly obtained and discussed in relation to the hemocompatibility of BNC-based tubes. This work demonstrates the heparinized BNC-based tubes have great potential in application as small-diameter vascular prosthesis.Download high-res image (171KB)Download full-size image

Bacterial nano-cellulose (BNC) hydrogel has been suggested as a promising biomaterial for artificial blood vessels. However, some properties of BNC do not achieve all of the requirements of a native blood vessel – compliance, for instance. In order to improve the properties of BNC tubes, poly(vinyl alcohol) (PVA) was introduced in the BNC tubes to make composites. Two types of pristine BNC tubes with different inner structures were produced in two bioreactors. A PVA tube and PVA–BNC tubular composites were made for comparison by using a thermally-induced phase separation method. The morphology, water permeability, cytotoxicity, and mechanical properties, including the axial stretch strength, suture retention, burst pressure, and compliance of all the tubes, were evaluated and compared. The results indicated that PVA impregnated into BNC tubes and then significantly improved the properties of BNC, especially the mechanical properties and water permeability. The BNC tube itself played a great role in the performances of the composites as the skeleton base material. The PVA–BNC composite tubes could constitute new biomaterial candidates for vascular grafts.

•BC/PAM composite was utilized as the template to in situ synthesize AgNPs.•A green route was proposed to synthesize AgNPs by UV irradiation.•Influences of the templates, i.e., BC/PAM and BC were investigated on AgNPs synthesis.•A lower silver content and higher particle size of AgNPs were got by BC/PAM-AgNPs.•High antibacterial effects were got by BC/PAM-AgNPs and BC-AgNPs nanocomposites.In this work, a bacterial cellulose/polyacrylamide (BC/PAM) double network composite was prepared to act as the template for in situ synthesis of silver nanoparticles (AgNPs). Effects of reaction conditions of the BC/PAM composite were investigated on its microstructure, mechanical properties and thermal stabilities. Both the BC/PAM composite and pure BC were utilized to prepare the corresponding silver impregnated nanocomposites, i.e., BC/PAM-AgNPs and BC-AgNPs, by an environmental friendly method, UV irradiation. The influences of the templates were investigated on the AgNPs formation and the antibacterial activities of the nanocomposites by both the zone of inhibition and dynamic shake flask methods. It was shown that the BC/PAM composite displayed a denser microstructure and higher thermal stabilities than pure BC. The BC/PAM-AgNPs nanocomposite exhibited a bigger particle size and lower mass content of AgNPs than the BC-AgNPs one. For the antibacterial test, two nanocomposites exhibited a close antibacterial effect, with a high log reduction above 3 and killing ratio above 99.9%, respectively.

This paper reviews recent progress made in identifying electrocatalysts for carbon dioxide (CO2) reduction to produce low-carbon fuels, including CO, HCOOH/HCOO−, CH2O, CH4, H2C2O4/HC2O4−, C2H4, CH3OH, CH3CH2OH and others. The electrocatalysts are classified into several categories, including metals, metal alloys, metal oxides, metal complexes, polymers/clusters, enzymes and organic molecules. The catalyts' activity, product selectivity, Faradaic efficiency, catalytic stability and reduction mechanisms during CO2 electroreduction have received detailed treatment. In particular, we review the effects of electrode potential, solution–electrolyte type and composition, temperature, pressure, and other conditions on these catalyst properties. The challenges in achieving highly active and stable CO2 reduction electrocatalysts are analyzed, and several research directions for practical applications are proposed, with the aim of mitigating performance degradation, overcoming additional challenges, and facilitating research and development in this area.

Lignocellulosic biomass serves as a potential alternative feedstock for production of bacterial nanocellulose (BNC), a high-value-added product of bacteria such as Gluconacetobacter xylinus. The tolerance of G. xylinus to lignocellulose-derived inhibitors (formic acid, acetic acid, levulinic acid, furfural, and 5-hydroxymethylfurfural) was investigated. Whereas 100 mM formic acid completely suppressed the metabolism of G. xylinus, 250 mM of either acetic acid or levulinic acid still allowed glucose metabolism and BNC production to occur. Complete suppression of glucose utilization and BNC production was observed after inclusion of 20 and 30 mM furfural and 5-hydroxymethylfurfural, respectively. The bacterium oxidized furfural and 5-hydroxymethylfurfural to furoic acid and 5-hydroxymethyl-2-furoic acid, respectively. The highest yields observed were 88% for furoic acid/furfural and 76% for 5-hydroxymethyl-2-furoic acid/5-hydroxymethylfurfural. These results are the first demonstration of the capability of G. xylinus to tolerate lignocellulose-derived inhibitors and to convert furan aldehydes.

Novel proton-conducting polymer electrolyte membranes have been prepared from bacterial cellulose by incorporation of phosphoric acid (H3PO4/BC) and phytic acid (PA/BC). H3PO4 and PA were doped by immersing the BC membranes directly in the aqueous solution of H3PO4 and PA, respectively. Characterizations by FTIR, TG, TS and AC conductivity measurements were carried out on the membrane electrolytes consisting of different H3PO4 or PA doping level. The ionic conductivity showed a sensitive variation with the concentration of the acid in the doping solution through the changes in the contents of acid and water in the membranes. Maximum conductivities up to 0.08 S cm−1 at 20 °C and 0.11 S cm−1 at 80 °C were obtained for BC membranes doped from H3PO4 concentration of 6.0 mol L−1 and, 0.05 S cm−1 at 20 °C and 0.09 S cm −1 at 60 °C were obtained for BC membranes doped from PA concentration of 1.6 mol L−1. These types of proton-conducting membranes share not only the good mechanical properties but also the thermal stability. The temperature dependences of the conductivity follows the Arrhenius relationship at a temperature range from 20 to 80 °C and, the apparent activation energies (Ea) for proton conduction were found to be 4.02 kJ mol−1 for H3PO4/BC membrane and 11.29 kJ mol−1 for PA/BC membrane, respectively. In particular, the membrane electrode assembly fabricated with H3PO4/BC and PA/BC membranes reached the initial power densities of 17.9 mW cm−2 and 23.0 mW cm−2, which are much higher than those reported in literature in a real H2/O2 fuel cell at 25 °C.Highlights► Two proton-conducting membranes were prepared by immersing bacterial cellulose (BC) into H3PO4 and PA. ► H3PO4/BC membrane showed a high proton conductivity of 0.15 S cm−1. ► PA/BC membrane showed a high proton conductivity of 0.08 S cm−1. ► The MEA fabricated with H3PO4/BC showed an initial power density of 17.9 mW cm−2. ► The MEA fabricated with PA/BC showed an initial power density 23.0 mW cm−2.

A kind of antibacterial bacterial cellulose (BC) dry film was developed and characterized as a potential functional wound dressing for acute traumas treatment. To achieve this, a freeze-dried BC film was immersed in a benzalkonium chloride solution, which belongs to cationic surfactant type antimicrobial agent, followed by another freeze-drying step. Some physical and antimicrobial properties of the prepared BC films were investigated and the results showed that the drug-loading capacity of the BC dry film was about 0.116 mg/cm2 when soaked in 0.102% benzalkonium chloride solution. High water absorbing capacity, an important quality for wound dressings was also achieved with a swelling ratio of 26.2 in deionized water and of 37.3 in saline solution. With respect to the antimicrobial effect, a stable and prolonged antimicrobial activity for at least 24 h was obtained especially against Staphylococcus aureus and Bacillus subtilis, which were general Gram-positive bacteria that found on the contaminated wound.

A new carbon source for bacterial cellulose production was successfully developed from konjac powder by using dilute acid hydrolysis and was detoxified by different alkaline treatment methods to remove microbial growth inhibitors. The various treatments included the addition of calcium hydroxide or sodium hydroxide to pH 10, and subsequent adjustment of the pH to 5 with acid as well as treatment with activated charcoal or laccase, respectively. The results showed that the detoxification effect using Ca(OH)2 was much better than that using NaOH. If activated charcoal or laccase was added in the process, the detoxification effects would go further and bacterial cellulose production could be improved more. Based on the same concentration of total sugars, bacterial cellulose production using the hydrolyzates was three times higher than that using glucose, six times higher than that using mannose, and five times higher than that using glucose–mannose mixture as carbon source in static cultures. The addition of extra calcium in glucose media in the form of CaCl2 at pH 5 did result in an improvement of less than 50% in BC production, which was not comparable to the Ca(OH)2 treatments at pH 10. The possible mechanisms behind the findings were discussed and potential stimulatory factors for the fermenting bacterium formed during the alkaline processing deserve further attention. The results indicate that konjac powder could serve as a feedstock for bacterial cellulose production and cultivation of Amorphophallus rivieri Durieu would bring more economic benefits to farmers in future.

Bacterial nano-cellulose (BNC) hydrogel has been suggested as a promising biomaterial for artificial blood vessels. However, some properties of BNC do not achieve all of the requirements of a native blood vessel – compliance, for instance. In order to improve the properties of BNC tubes, poly(vinyl alcohol) (PVA) was introduced in the BNC tubes to make composites. Two types of pristine BNC tubes with different inner structures were produced in two bioreactors. A PVA tube and PVA–BNC tubular composites were made for comparison by using a thermally-induced phase separation method. The morphology, water permeability, cytotoxicity, and mechanical properties, including the axial stretch strength, suture retention, burst pressure, and compliance of all the tubes, were evaluated and compared. The results indicated that PVA impregnated into BNC tubes and then significantly improved the properties of BNC, especially the mechanical properties and water permeability. The BNC tube itself played a great role in the performances of the composites as the skeleton base material. The PVA–BNC composite tubes could constitute new biomaterial candidates for vascular grafts.

This paper reviews recent progress made in identifying electrocatalysts for carbon dioxide (CO2) reduction to produce low-carbon fuels, including CO, HCOOH/HCOO−, CH2O, CH4, H2C2O4/HC2O4−, C2H4, CH3OH, CH3CH2OH and others. The electrocatalysts are classified into several categories, including metals, metal alloys, metal oxides, metal complexes, polymers/clusters, enzymes and organic molecules. The catalyts' activity, product selectivity, Faradaic efficiency, catalytic stability and reduction mechanisms during CO2 electroreduction have received detailed treatment. In particular, we review the effects of electrode potential, solution–electrolyte type and composition, temperature, pressure, and other conditions on these catalyst properties. The challenges in achieving highly active and stable CO2 reduction electrocatalysts are analyzed, and several research directions for practical applications are proposed, with the aim of mitigating performance degradation, overcoming additional challenges, and facilitating research and development in this area.