Theanine synthesized by immobilizing Pseudomonas nitroreducens LY in nanofibrous membranes

Pseudomonas nitroreducens LY was immobilized in nanofibers by an electrospinning process. We studied the impact of polymer concentration on the electrospinning process, and we also studied the viability of the immobilized cells and their impact factors. Furthermore, theanine was synthesized by the immobilized P. nitroreducens LY. Fibers with an average diameter of 220 nm were obtained with 8% (w/v) polyvinyl alcohol (PVA) and a potential of 17 kV. The highest survival rate (30%) of the immobilized P. nitroreducens LY was achieved at this condition. The P. nitroreducens LY in the fibers was stored at −20 °C for 3 months with no detectable decrease in cell viability. Using the nanofibers to immobilize P. nitroreducens LY, the theanine yield was 10.74 g/l with the conversion rate of sodium glutamate at 20.55%. Together, these results demonstrate the potential for application of advanced nanomaterials in microbial cell immobilizing technology by electrospinning.     

Superhydrophobicity of cellulose triacetate fibrous mats produced by electrospinning and plasma treatment

Nano/micro-fibrous cellulose triacetate (CTA) mats were prepared by electrospinning a fixed concentration of CTA with different methylene chloride (MC)/ethanol (EtOH) ratios and with various concentrations of CTA at a fixed MC/EtOH 80/20 (v/v) ratio. All of the electrospun CTA mats had a high water contact angle (WCA) compared to the CTA cast film. At a solvent composition of 80/20 (v/v) and 5 wt.% CTA concentration, the CTA mat without plasma treatment had good surface roughness and electrospinning processability, and its WCA was 142°. To further improve its hydrophobicity, the CTA fibrous mat electrospun from the 5 wt.% solution of CTA was treated with a CF₄ plasma for various times. Superhydrophobicity could be obtained after the CF₄ plasma treatment. The WCA of the CTA mat reached as high as 153° after plasma treatment for 60 s.     

Improved reproducibility in the determination of the molecular weight of chitosan by analytical size exclusion chromatography

The reproducibility of the determination of the molecular weight of chitosans in the 90–210 kDa range (M_n) by analytical size exclusion chromatography with multi-angle laser light scattering (SEC-MALLS) was improved by reducing the salt concentration in the mobile phase from (0.3 M acetic acid, 0.2 M sodium acetate, and 0.8 mM sodium azide) to (0.15 M acetic acid, 0.1 M sodium acetate, and 0.4 mM sodium azide) using Tosoh TSKgel G6000PW_XL and G5000PW_XL columns in series. The variability of measured molecular weight was significantly reduced by lowering the acetate concentration in the mobile phase, while the average molecular weight did not change significantly. The coefficient of variation of the number-average molecular weight, CV(M_n), decreased from 7–12% to 3–6% upon mobile phase dilution. This reduced variability in molecular weight of chitosans obtained from SEC is a significant improvement when precise values of chitosan molecular weight are required, for example in stability studies where viscosity changes in concentrated chitosan solutions are assessed, and in gene delivery applications.     

Production of (R)-mandelic acid by immobilized cells of Saccharomyces cerevisiae on chitosan carrier

The asymmetric microbial reduction of phenylglyoxylic acid (PGA) to (R)-mandelic acid ((R)-MA) with immobilized Saccharomyces cerevisiae cells on globular chitosan was studied. The immobilization conditions and characterization of the immobilized cells were carried out. Chitosan–acetic acid solution was injected into a mixture of 20% NaOH and 30% CH₃OH aqueous solution to obtain globular chitosan, and then the globular chitosan was treated with 1% solution of glutaraldehyde to immobilize yeast cells, which were used to synthesize (R)-MA. The optimum conditions were identified as the substrate concentration of 10 mmol L⁻¹, pH of 6.5 and reaction temperature of 30 °C with the yield of 62% for (R)-MA and the enantiomeric excess (e.e.) of 98% for (R)-MA. The immobilized cells showed good operation and storage stability.     

Removal of acetic acid and sulfuric acid from biomass hydrolyzate using a lime addition–capacitive deionization (CDI) hybrid process

In this study, we developed a lime addition–capacitive deionization (CDI) hybrid process that can efficiently remove acetic acid and sulfuric acid from the model mixture of glucose, xylose, acetic acid, and sulfuric acid, which are the major components from the biomass hydrolyzate by acid hydrolysis. The key parameters of lime addition process (type of lime, amount of lime, stirrer speed, and reaction time) and CDI process (voltage, flow rate, and feed concentration) were also optimized. In the lime addition process, the optimal lime type, (sulfuric acid + acetic acid)/lime molar ratio, stirrer speed, and reaction time for the removal of sulfuric acid were CaCO₃, 1:1, 200 rpm, and 6 min, respectively. For the CDI process, the optimal voltage and flow rate were 1.2 V and 20 mL/min, respectively. The efficiency of acid removal increased as the initial acetic acid concentration decreased. This hybrid process was able to remove 98.08% of sulfuric acid and 76.97% of acetic acid from the mixture of glucose, xylose, acetic acid, and sulfuric acid. The process was able to recover almost all sugar (>99%) at high purity (97.53%).     

Mixed culture of Saccharomyces cerevisiae and Acetobacter pasteurianus for acetic acid production

Mixed culture of Saccharomyces cerevisiae and Acetobacter pasteurianus was carried out for high yield of acetic acid. Acetic acid production process was divided into three stages. The first stage was the growth of S. cerevisiae and ethanol production, fermentation temperature and aeration rate were controlled at 32 °C and 0.2 vvm, respectively. The second stage was the co-culture of S. cerevisiae and A. pasteurianus, fermentation temperature and aeration rate were maintained at 34 °C and 0.4 vvm, respectively. The third stage was the growth of A. pasteurianus and production of acetic acid, fermentation temperature and aeration rate were controlled at 32 °C and 0.2 vvm, respectively. Inoculation volume of A. pasteurianus and S. cerevisiae was 16% and 0.06%, respectively. The average acetic acid concentration was 52.51 g/L under these optimum conditions. To enhance acetic acid production, a glucose feeding strategy was subsequently employed. When initial glucose concentration was 90 g/L and 120 g/L glucose was fed twice during fermentation, acetic acid concentration reached 66.0 g/L.     

Improved 2,3-butanediol production from corncob acid hydrolysate by fed-batch fermentation using Klebsiella oxytoca

Corncob acid hydrolysate, detoxed by sequently boiling, overliming and activated charcoal adsorption, was used for 2,3-butanediol production by Klebsiella oxytoca ACCC 10370. The effects of acetate in hydrolysate and pH on 2,3-butanediol production were investigated. It was found that acetic acid in hydrolysate inhibited the growth of K. oxytoca while benefited the 2,3-butanediol yield. With the increase in acetic acid concentration in medium from 0 to 4 g/l, the lag phase was prolonged and the specific growth rate decreased. The acetic acid inhibition on cell growth can be alleviated by adjusting pH to 6.3 prior to fermentation and a substrate fed-batch strategy with a low initial acetic acid concentration. Under the optimum condition, a maximal 2,3-butanediol concentration of 35.7 g/l was obtained after 60 h of fed-batch fermentation, giving a yield of 0.5 g/g reducing sugar and a productivity of 0.59 g/h l.     

Cross-linking chitosan into UV-irradiated cellulose fibers for the preparation of antimicrobial-finished textiles

Chitosan cross-linked cellulose fibers were prepared using non-toxic procedures in order to confer antimicrobial properties to cellulose fibers. Citric acid was used as the cross-linker and NaH₂PO₄ as catalyst in previously UV-irradiated cellulose fibers. Further heat dried-cure process and washing with detergent, water and acetic acid (0.1 M) gave a maximum incorporation of chitosan of 27 mg per gram of functionalized textile. The thermogravimetric analysis of the material with the highest chitosan content showed an increased thermal stability compared to cellulose and chitosan. The UV-irradiation induced morphological changes, such as less entangled cellulose fibers, as observed by scanning electron microscopy, which was prompted to enhance the chitosan incorporation. The biomass and spore germination percentage of Penicillium chrysogenum and colony forming units per millilitre for Escherichia coli decreased significantly on the composed materials as compared to raw cellulose fiber and it was similar to that obtained with a commercial antimicrobial cellulose fiber.     

A novel three-dimensional tubular scaffold prepared from silk fibroin by electrospinning

Effects of electrospinning parameters (including voltage, collection distance, solution concentration and flow rate) on the morphology and diameter distribution of regenerated SF (silk fibroin) fiber were investigated. Afterward, SF tubular scaffold composed of homogenous fibers was fabricated at voltage of 18 kV, collection distance of 18 cm, concentration of 37%, and flow rate of 0.15 mL/min. After methanol treatment, SF tubular scaffold showed tensile strength of 3.57 MPa and porosity of 80.85%. It is satisfied that our work offers a simple method to fabricate seamless and porous tubular scaffold from SF without any additives and organic solvents. Furthermore, the results suggest that this tubular scaffold shows promising applications in small-diameter vascular graft.     

Rapid harvesting of freshwater microalgae using chitosan

In this study, chitosan was used as a flocculant to harvest freshwater microalgae Chlorella vulgaris. The recovery efficiency of C. vulgaris was tested at various chitosan concentrations. 120 mg/L of chitosan showed the highest efficiency (92 ± 0.4%) within 3 min. The maximum concentration factor of 10 was also achieved at this dose of chitosan. The harvesting efficiency was pH dependent. pH 6.0 showed the highest harvesting efficiency (99 ± 0.5%). Measurement of zeta-potential confirmed that the flocculation was induced by charge neutralization. This study showed that a biopolymer, chitosan, can be a promising flocculant due to its high efficacy, low dose requirements, and short settling time.     

Control of wild oat (Avena fatua) using some phenolic compounds I – Germination and some growth parameters

The percentage of germination of wild oat was significantly inhibited by increasing the concentrations of phenolic compounds. Ferulic acid was the most effective compound which completely inhibited germination at a concentration of 3.0 mM. At the same time, wheat and barley were slightly affected with different concentrations of the four phenolic compounds. The percentage of germination of wheat significantly decreased with increasing of ferulic acid reaching a maximum inhibition at 3.0 mM concentration. On the other hand, the germination of wheat was not affected with the other three phenolic compounds. The percentage of germination of barley was not affected with all phenolic compounds except for hydroxy phenolic acetic acid which has significant effect at a concentration of 3.0 mM. Salicylic acid significantly inhibited the growth parameters gradually in wild oat, wheat and barley. The shoot/root ratio was decreased in wild oat and barley, while the ratio increased in wheat. The growth parameters were completely inhibited at 3.0 mM of ferulic acid for both wild oat and wheat but slightly inhibited for barley. The shoot/root ratio was increased in all concentrations of ferulic acid except at 3.0 mM which was completely inhibited for both wild oat and wheat, while the ratio was increased in all treatments of ferulic acid in the case of barley. The growth parameters were highly significant and decreased in wild oat, wheat and barley with increasing the concentrations of hydroxybenzoic acid and hydroxyphenyl acetic acid. The shoot/root ratio was not changed in all concentrations except at 3.0 mM in the case of wild oat, the ratio was decreased at 2.0 and 3.0 mM in the case of wheat, while the ratio increased in most of hydroxybenzoic acid concentrations in the case of barley. The shoot/root ratio was increased with increasing of the hydroxyphenyl acetic acid concentrations.     

Clarification of passion fruit juice with chitosan: Effects of coagulation process variables and comparison with centrifugation and enzymatic treatments

Clarification is an important step in the fruit juice processing industry. In this study, chitosan from shrimp shells is proposed as an alternative aid for passion fruit juice clarification being a natural and environmental friendly adsorbent. Experiments were carried out in Jar tests varying chitosan concentration, pH, and slow velocity speed and time. The obtained results were evaluated in terms of turbidity, color, total soluble solids (TSSs), and viscosity reductions. The best condition found in these tests for chitosan treatment was compared with centrifugation and enzymatic treatments. Two different rotation speeds (4000 and 12,000 rpm) were applied for the centrifugation process. Enzymatic treatment was carried out with 1 mL L^?1 of Pectinex 3X L (Novo Nordisk, Switzerland) for 90 min, at 50 °C. The enzymatic treatment was reliable only for viscosity reduction, while the chitosan treatment after a mild centrifugation showed the best result for passion fruit clarification.     

Chitosan topical gel formulation in the management of burn wounds

Wound healing properties of chitosan with different molecular weight and degree of deacetylation ranges have been examined. The macroscopic image and histopathology were examined using chitosan, Fucidin^® ointment and to blank. The rate of contraction was evaluated by determination of the unclosed area as a function of time. The treated wounds were found to contract at the highest rate with high molecular weight–high degree of deacetylation chitosan-treated rats as compared to untreated, treated, and Fucidin^® ointment-treated rats. Wounds treated with high molecular weight chitosan had significantly more epithelial tissue (p < 0.05) than wounds with any other treatment and the best re-epithelization and fastest wounds closure were found with the high molecular weight chitosan treatment group. Histological examination and collagenase activity studies revealed advanced granulation tissue formation and epithelialization in wounds treated with high molecular weight chitosan (p < 0.05). High molecular weight with high degree of deacetylation chitosan samples therefore demonstrates potential for use as a treatment system for dermal burns.     

Characterization and evaluation of hydrophobically modified chitosan scaffolds: Towards design of enzyme immobilized flow-through electrodes

Chitosan scaffolds were fabricated by application of thermally induced phase separation from aqueous solutions of unmodified chitosan and hydrophobically modified chitosan polymer. The final pore structure, in terms of diameter and geometry, were correlated to freezing temperature and freezing time for both the unmodified and hydrophobically modified chitosan polymer. Results showed that the resulting pore structure is strongly dependent upon the freezing temperature and less dependant upon the freezing time. For scaffolds produced from unmodified chitosan, the pore size decreased as expected with decreasing freezing temperature from ?5 °C to ?10 °C. However, an inconsistency in this trend was observed as the freezing temperature was decreased to ?20 °C. Combined analysis of pore size distribution and average pore diameter suggested that the freezing process was mainly mass transfer dominated at ?5 °C and ?10 °C, but principally heat transfer dominated at ?20 °C. In comparison, the scaffolds produced from hydrophobically modified chitosan (butyl-chitosan) followed the expected trend of decreasing mean pore diameter with decreased freezing temperatures throughout the entire temperature range. The scaffolds produced from the unmodified chitosan were more stable and rigid, and possessed average pore diameters that were generally smaller than those fabricated from the hydrophobically modified chitosan. The generally larger pores in the butyl-modified chitosan scaffolds might be explained by increased phase separation rates due to the introduced hydrophobicity of the chitosan polymer. Among the scaffolds fabricated from the butyl-modified chitosan, those produced at ?20 °C yielded the most uniform pore structure, the smallest average pore diameters, and the least temporal broadening of pore size distribution.     

Challenges in enzymatic hydrolysis and fermentation of pretreated Arundo donax revealed by a comparison between SHF and SSF

The perennial herbaceous crop Arundo donax is a potential feedstock for second-generation bioethanol production. In the present work, two different process options were investigated for the conversion of two differently steam-pretreated batches of A. donax. The pretreated raw material was converted to ethanol with a xylose-consuming Saccharomyces cerevisiae strain, VTT C-10880, by applying either separate hydrolysis and fermentation (SHF) or simultaneous saccharification and fermentation (SSF). The highest overall ethanol yield and final ethanol concentration were achieved using SHF (0.27 g g^?1 and 20.6 g L^?1 compared to 0.24 g g^?1 and 19.0 g L^?1 when SSF was used). The performance of both SHF and SSF was improved by complementing the cellulolytic enzymes with hemicellulases. The higher amount of acetic acid in one of the batches was shown to strongly affect xylose consumption in the fermentation. Only half of the xylose was consumed when batch 1 (high acetic acid) was fermented, compared to that 94% of the xylose was consumed in fermentation of batch 2 (lower acetic acid). Furthermore, the high amount of xylooligomers present in the pretreated materials considerably inhibited the enzymatic hydrolysis. Both the formation of xylooligomers and acetic acid thus need to be considered in the pretreatment process in order to achieve efficient conversion of A. donax to ethanol.     

Hydroxyapatite based biocomposite scaffold: A highly biocompatible material for bone regeneration

The conventional approaches for treating bone defects such as autografts donor tissue shortages and allografts transmission of diseases pose many shortcomings. The objective of this study was to design a nano strontium/magnesium doped hydroxyapatite (Sr/Mg-HA) with chitosan (CTS) and multi-walled carbon nanotubes (MWCNT) (Sr/Mg-HA/MWCNT/CTS) biocomposite was created to support the growth of osteoblasts using a solvent evaporation method. To help the growth of osteoblasts, a solvent evaporation technique was used to design a nano strontium/magnesium doped hydroxyapatite with chitosan and multi-walled carbon nanotubes biocomposite. We studied the biocompatibility and efficiency in vitro of biocomposite following physicochemical analyzes. Tests of biocompatibility, cell proliferation, mineralization, and osteogenic differentiation have shown that in-vitro safety and effectiveness of biocomposite are good. The performance of biocomposite was more efficient in in-vitro as well as in vivo experiments than in Sr/Mg-HA nanoparticles. Briefly, the Sr/Mg-HA/MWCNT/CTS biocomposite is an ideal candidate for effective bone repair in clinics with excellent mechanical properties with durable multi-biofunctional antibacterial properties and osteoinductivity.     

Preparation of gold nanopowders and nanoparticles using chitosan suspensions

Simple methods for preparation of gold nanopowders and nanoparticles are reported. Gold/chitosan nanoparticles were prepared by using basic chitosan suspension as a dispersant and as a reductant. The resulting nanoparticles were processed by pyrolysis and thus obtain black gold nanopowder. The FESEM images indicate that most diameters of the nanopowder prepared were in the range of 50 and 200 nm. Hydrolysis is another quick decomposition method for chitosan. Acetic acid was adopted to implement the hydrolysis. The AEM images of the auberginic suspension show that the average gold nanoparticle diameter was less than 40 nm with good dispersion. Use of chitosan suspensions can produce gold nanopowder as well as gold nanoparticle without using toxic organic chemicals.     

Immunotherapeutic effects of chitin in comparison with chitosan against Leishmania major infection

Chitin and chitosan microparticles (MPs) are important immune system stimulators. The aim of this study was to evaluate the protective effects of these compounds in comparison with each other against Leishmania infection in BALB/c mice infected with Leishmania major (L. major).Female BALB/c mice were injected subcutaneously with 2 × 10⁵ promastigotes. Chitin and/or chitosan MPs (< 40 μm) were subcutaneously injected in the BALB/c mice with two-day intervals until two weeks. Mice in all groups were sacrificed at 12 weeks post-infection. Enumeration of viable parasites was performed using limiting dilution assay. Furthermore, the animals (5 mice/group) were sacrificed two weeks post-infection. The lymph node cells were isolated and the effects of the chitinous MPs on the proliferation and production of cytokines such as tumor necrosis factor alpha (TNF-α) and interleukin-10 (IL-10) were determined. The mean sizes of lesions were significantly smaller in chitin (0.6 ± 0.12 mm) and chitosan treated groups (1.2 ± 0.8 mm) than in the control group (6.2 ± 1.7 mm) (P < 0.05). The parasite load in the lymph nodes of the treated mice was significantly lower than that in the lymph nodes of controls (1.31 × 10⁶ vs 8.24 × 10⁷ parasite/lymph node [P = 0.032] and 7.49 × 10⁶ vs 8.24 × 10⁷ parasite/lymph node [P = 0.05] for chitin and chitosan MPs treatment, respectively). We found that chitinous MPs induced cell proliferation and that chitin but not chitosan increased TNF-α and IL-10 production. Chitin appears that it has more effect than chitosan against leishmaniasis. The current study revealed that chitinous MPs had significant activity against L. major and could be considered as new therapeutic modality in leishmaniasis.     

Bacterial cellulose nanofibers for albumin depletion from human serum

Cibacron Blue F3GA (CB) was covalently attached onto the bacterial cellulose (BC) nanofibers for human serum albumin (HSA) depletion from human serum. The BC nanofibers were produced by Acetobacter xylinum in the Hestrin–Schramm medium in a static condition for 14 days. The CB content of the BC nanofibers was 178 μmol/g. The specific surface area of the BC nanofibers was determined to be 914 m²/g. HSA adsorption experiments were performed by stirred-batch adsorption. The non-specific adsorption of HSA on the BC nanofibers was very low (1.4 mg/g polymer). CB attachment onto the BC nanofibers significantly increased the HSA adsorption (1800 mg/g). The maximum HSA adsorption was observed at pH 5.0. The HSA adsorption capacity decreased drastically with an increase of the aqueous phase concentration of sodium chloride. The elution studies were performed by adding 1 M NaCl to the HSA solutions in which adsorption equilibria had been reached. The elution results demonstrated that the binding of HSA to the adsorbent was reversible. The depletion efficiencies for HSA were above 96.5% for all studied concentrations. Proteins in the serum and eluted portion were analyzed by SDS-PAGE for testing the efficiency of HSA depletion from human serum. Eluted proteins include mainly HSA.     

Encapsulated boron as an osteoinductive agent for bone scaffolds

The aim of this study was to develop boron (B)-releasing polymeric scaffold to promote regeneration of bone tissue. Boric acid-doped chitosan nanoparticles with a diameter of approx. 175 nm were produced by tripolyphosphate (TPP)-initiated ionic gelation process. The nanoparticles strongly attached via electrostatic interactions into chitosan scaffolds produced by freeze-drying with approx. 100 μm pore diameter. According to the ICP-OES results, following first 5 h initial burst release, fast release of B from scaffolds was observed for 24 h incubation period in conditioned medium. Then, slow release of B was performed over 120 h. The results of the cell culture studies proved that the encapsulated boron within the scaffolds can be used as an osteoinductive agent by showing its positive effects on the proliferation and differentiation of MC3T3-E1 preosteoblastic cells.