Hualin Wang

Kinetics and functional effectiveness of nisin loaded antimicrobial packaging film based on chitosan/poly(vinyl alcohol).

The aim of this study was to evaluate the kinetics and functional effectiveness of Nisin loaded chitosan/poly(vinyl alcohol) (Nisin-CS/PVA) as an antibacterial packaging film. The films were prepared by coating method and Staphylococcus aureus (S. aureus, ATCC6538) was used as test bacterium. The intermolecular hydrogen bonds between CS and PVA molecules were confirmed. The elasticity of films was significantly improved by the incorporation of PVA, and the film could also bear a relative high tensile strength at 26.7 MPa for CS/PVA=1/1. As CS/PVA ratio decreased, the water vapor permeability (WVP) decreased and reached its minimum value 0.983 × 10(-10)gm(-1)s(-1) at CS/PVA=1/1, meanwhile, oxygen permeability (OP) increased but still lower than 0.91 cm(3) μm m(-2)d(-1)kPa(-1) for CS/PVA=1/1 as the CS/PVA ratio was above 1:1. The initial diffusion of nisin (Mt/M ∞ < 2/3) from CS/PVA film could be well described by the Fickian diffusion equation. Owing to the positively charged nisin at pH below isoelectric point (pI, 8.8) and its increasing dissolubility in water as the pH reduced, the diffusion of nisin from the films strongly depended on pH and ionic strength besides CS/PVA ratio and temperature. Moreover, the thermodynamic parameters suggested the spontaneous and endothermic diffusion of nisin from the films. The resulting data can provide some valuable information for the design of film in structure and ingredient.

Preparation, characterization of electrospun meso-hydroxylapatite nanofibers and their sorptions on Co(II)

In this work, mesoporous hydroxylapatite (meso-HA) nanofibers were prepared via calcination process with polyvinyl alcohol/HA (PVA/HA) hybrid nanofibers fabricated by electrospinning technique as precursors, and the removal efficiency of meso-HA nanofibers toward Co(II) was evaluated via sorption kinetics and sorption isotherms. Furthermore, the sorption behaviors of Co(II) on meso-HA nanofibers were explored as a function of pH, ionic strength, and thermodynamic parameters. There existed hydrogen bonds between HA and PVA matrix in precursor nanofibers which could change into meso-HA nanofibers with main pore diameter at 27nm and specific surface area at 114.26m(2)/g by calcination process. The sorption of Co(II) on meso-HA was strongly dependent on pH and ionic strength. Outer-sphere surface complexation or ion exchange was the main mechanisms of Co(II) adsorption on meso-HA at low pH, whereas inner-sphere surface complexation was the main adsorption mechanism at high pH. The sorption kinetic data were well fitted by the pseudo-second-order rate equation. The sorption isotherms could be well described by the Langmuir model. The thermodynamic parameters (ΔH°, ΔS° and ΔG°) calculated from the temperature-dependent sorption isotherms suggested that the sorption process of Co(II) on meso-HA nanofibers was spontaneous and endothermic.

Release behavior of tetracycline hydrochloride loaded chitosan/poly(lactic acid) antimicrobial nanofibrous membranes

The present work aimed to evaluate the release behavior of tetracycline hydrochloride loaded chitosan/poly(lactic acid) (Tet-CS/PLA) antimicrobial nanofibrous membranes fabricated via electrospinning technique. The electrospinning solution was a blend of Tet, CS formic acid solution and PLA chloroform/ethanol solution. The interaction between CS and PLA in CS/PLA nanofibers was confirmed to be hydrogen bond. The incorporation of Tet caused a slight decrease in the diameter of nanofibers with Tet content below 30%. Tet-CS/PLA nanofibrous membrane showed a slight initial burst within the first 4h before a gradual increase in cumulative release, and the release percentage increased with increasing Tet contents. Tet release (Mt/M∞<0.6) from the medicated nanofibers could be described by Fickian diffusion model and the release profiles showed two sequential stages. Tet-CS/PLA nanofibrous membranes exhibited an effective and sustainable inhabitance on the growth of Staphylococcus aureus, and the antimicrobial activity increased rapidly with increasing Tet contents below 20%. Furthermore, the incorporation of Tet promoted the degradation of nanofibrous membranes.

Synthesis and bioactivity of gelatin/multiwalled carbon nanotubes/hydroxyapatite nanofibrous scaffolds towards bone tissue engineering

The objective of this study was to develop a novel three-dimensional biomimetic gelatin/multiwalled carbon nanotubes/hydroxyapatite (gelatin/MWNTs/HA) nanofibrous scaffold via electrospinning technique for bone tissue engineering. The mechanical properties, structure, morphology and the bioactivity of nanofibrous scaffolds in vitro were investigated. Attentions were focused on the adhesion, mineralization, viability and proliferation of human fetal osteoblastic cells (hFOBs) on scaffold. Resulting scaffolds provided relative good mechanical support (7.9 ± 0.32 MPa) and high porosity (91.2%) to mimic a favorable environment for hFOBs. The hydrogen bonds between gelatin molecules and MWNTs/HA units were confirmed, and the incorporation of HA or MWNTs/HA nanoparticles caused an increase in porosity and strength of scaffolds, meanwhile the surface of nanofibers tended to be rough. HA nanoparticles showed a chelating effect to promote osteogenesis and mineralization of bone, and MWNTs had a synergetic effect with HA to induce the apatite formation. As compared to gelatin and gelatin/HA scaffolds, gelatin/MWNTs/HA scaffold exhibited the best viability hFOB cells cultured in vitro, most excellent morphology of hFOB cells seeded into scaffold and a significantly increasing in proliferation. The nanofibrous scaffold will have great potential as an excellent scaffold for in bone tissue engineering.

High Levels of Malic Acid Production by the Bioconversion of Corn Straw Hydrolyte Using an Isolated Rhizopus Delemar Strain

The microbial fermentation of malic acid, which is one of the most important organic acid platforms used widely in food and chemical engineering, has attracted considerable interest. A malate production strain was isolated, a mutation was induced, and regulation of the metabolic network was then conducted. The identification results showed that the malic acid production strain, HF- 119, belonged to Rhizopus delemar. An analysis of the metabolic pathway showed that the malic acid flux of this strain occurred through three main pathways, and many byproducts, such as succinic acid, fumaric acid and ethanol, were produced. Although corn straw hydrolyte was used, the metabolism of xylose was not as rapid as that of glucose. Subsequently, breeding of the strains and regulation of the metabolic network resulted in an increase in malate yield, and the strain HF-121 produced more than 120 g/L malic acid within 60 h. The ability to produce malic acid from biomass hydrolyte highlights the industrial development potential of this strain.

Diffusion and Antibacterial Properties of Nisin-Loaded Chitosan/Poly (L-Lactic Acid) Towards Development of Active Food Packaging Film

Nisin-loaded chitosan/poly (L-lactic acid) (nisin-CS/PLLA) antimicrobial films were prepared by coating method. The structure and mechanical properties of nisin carrier CS/PLLA films were investigated, and the antibacterial behavior of nisin-CS/PLLA against Staphylococcus aureus ATCC6538 was assessed. Furthermore, the diffusion behaviors of nisin from films were evaluated by diffusion kinetics and thermodynamics, and the diffusion efficiency was investigated as a function of CS/PLLA ratio, pH, and ionic strength. When CS/PLLA ratio was at 1:1 (w/w) and above, a notable enhancement was observed in the tensile strength with the increase of PLLA content, while the elongation at break was decreased slightly at the same time. However, a significant decrease in tensile strength and elongation at break were present when the CS/PLLA ratio was below 1:1. There existed intermolecular hydrogen bonds between CS and PLLA molecules. The diffusion of nisin from film was strongly dependent on pH and ionic strength. The thermodynamic parameters (ΔHo, ΔSo, and ΔGo) indicated that the diffusion process of nisin from film was spontaneous and endothermic. From diffusion and antimicrobial activity results, nisin-CS/PLLA films revealed well-controlled release and better antimicrobial activity against S. aureus, which may have potential as a novel active food packaging film.

Preparation, antimicrobial and release behaviors of nisin-poly (vinyl alcohol)/wheat gluten/ZrO2 nanofibrous membranes

Abstract A novel nisin-loaded poly (vinyl alcohol)/wheat gluten/zirconia (Nisin-PVA/WG/ZrO2) nanofibrous membranes was prepared via electrospinning technique. The drug carrier PVA/WG/ZrO2 nanofibers showed a increase in average diameter with the increase of ZrO2 content, and the fibers tended to conglutinate when ZrO2 content reached 12 wt% and above. Hydrogen and Zr–O–C bonds existed among PVA, WG, and ZrO2 units improved the thermal stability of polymeric matrix. The loading dosage of nisin caused no significant changes in the size and morphology of nanofibers at nisin content below 6 wt%. The antimicrobial activity and release experimental results showed that the nisin-PVA/WG/ZrO2 nanofibrous membranes displayed well-controlled release and better antimicrobial activity against Staphylococcus aureus, and the nisin release from the nanofibers could be described by Fickian diffusion model. In our opinions, these nisin-PVA/WG/ZrO2 nanofibrous membranes may have potential as a new nanofibrous membrane in drug delivery, wound dressing, and active food packaging.

Synthesis of antimicrobial Nisin-phosphorylated soybean protein isolate/poly(l-lactic acid)/ZrO2 membranes

Electrospinning technique was used to fabricate the model drug Nisin loaded phosphorylated soybean protein isolate/poly(l-lactic acid)/zirconium dioxide (Nisin-PSPI/PLLA/ZrO2) nanofibrous membranes. The average diameter of drug carrier PSPI/PLLA/ZrO2 nanofibers increased with the increase of content PSPI and some spindle-shape beads appeared when PSPI content reached 25 wt%. The loading dosage of Nisin caused no significant changes in the size and morphology of nanofibers when Nisin content was below 9 wt%. There existed hydrogen and Zr-O-C bonds among PSPI, PLLA and ZrO2 units, and the crystalline of PLLA matrix decreased owning to the introducing of PSPI and ZrO2 units. Moreover, the water absorption capability and degradation rate of PSPI/PLLA/ZrO2 nanofibrous membranes increased with increasing PSPI content. The antimicrobial activity and release experimental results showed that Nisin-PSPI/PLLA/ZrO2 nanofibrous membranes displayed well controlled release and better antimicrobial activity against Staphylococcus aureus (S. aureus), and the Nisin release from the medicated nanofibers could be described by Fickian diffusion model. The Nisin-PSPI/PLLA/ZrO2 nanofibrous membranes may have potential as a new nanofibrous membrane in drug delivery, food active packaging and wound dressing.

Kinetics and Antioxidant Capacity of Proanthocyanidins Encapsulated in Zein Electrospun Fibers by Cyclic Voltammetry

The proanthocyanidins encapsulated in zein (zein-PA) fibers was via electrospinning technique. The kinetics and antioxidant capacity of PA from zein fibers was investigated by cyclic voltammetry. Circular dichroism was used to investigate the secondary structure change of zein and its influence on the shape of fibers. The addition of PA caused a significant increase in viscosity and made fibers wider. These hydrogen bonds between zein and PA molecules would favor the α-helix change and decrease the β-folds of zein in electrospinning solutions, leading to a round-shaped tendency of fibers and enhancing the thermal properties slightly. Zein-PA fibers showed high encapsulation efficiency close to 100%, and the encapsulated PA retained its antioxidant capacity in fibers. Zein-PA fibers showed a good controlled release toward PA, and the predominant release of PA from fibers was Fickian diffusion, which could be well described by first-order model and Hixson-Crowell model.

Synthesis, antimicrobial and release of chloroamphenicol loaded poly(l-lactic acid)/ZrO2 nanofibrous membranes

Electrospinning technique was used to fabricate chloroamphenicol loaded poly (L-lactic acid)/ZrO2 (CP-PLLA/ZrO2) nanofibrous membranes. The average diameter of drug carrier PLLA/ZrO2 nanofibers increased with ZrO2 concentration increasing and ribbon-shape fibers were present when ZrO2 content reached 3% and above. The existence of hydrogen and ZrOC bonds between PLLA and ZrO2 units improved the thermal stability of PLLA. The model drug CP loading showed no significant changes on the size and shape of nanofibers when CP content was below 8%, but the fibers were uneven and interspersed with ball-shape beads when CP content rose up to 10%. From the antimicrobial activity and release experimental result, the CP-PLLA/ZrO2 nanofibrous membranes revealed well controlled release and better antimicrobial activity against Staphylococcus aureus, which may have potential as a new nanofibrous membrane in drug delivery and wound dressing.