Influence of surface characteristics of cellulose carriers on ethanol production by immobilized yeast cells

Ethanol production was carried out by growing yeast cells immobilized on porous cellulose carriers. The effects of the chemical modification of cellulose carriers on cell immobilization and ethanol production were examined with respect to ion-exchange capacity and chemical structure. The ion-exchange capacity of 0·1 meq/g-carriers had no effect on immobilization but affected ethanol production by repeated batch cultures using immobilized yeast cells. Diethylaminoethyl was a suitable function group for immobilization and ethanol production. Ethanol productivity of the 10th batch cycle with diethylaminoethyl cellulose carriers was 23% greater than that of the first batch cycle.     

竹材剩余物竹粉的选择性酚化产物研究

以苯酚为液化试剂,在低温和低酸催化剂浓度等温和条件下对竹粉进行选择性酚化,分离得到液化液和竹纤维素微粉。采用红外光谱、X射线衍射、SEM和热重分析了竹粉液化前后组成形貌和结构性能变化。结果表明竹粉在热化学酚化条件下发生了降解反应,并产生了具有新的取代基苯环结构等其它酚化产物;竹粉中的纤维素无定型组分和木质素组分完全被酚化,而未被酚化的残渣为具有高度结晶结构的纤维素粉;竹粉通过热化学酚化,得到了具有很好流动性的高活性酚化液,而分离得到的竹纤维粉具有比竹粉更高的疏水性和更好的热稳定性。在此基础上阐明了竹粉热化学选择性酚化的机理。     

Image analysis of modified cellulose fibers from sugarcane bagasse by zirconium oxychloride

Surface modification of natural fibers has been made using different methods. In this paper, cellulose fibers from sugarcane bagasse were bleached and modified by zirconium oxychloride in situ. The chemically modified cellulose fibers were compared to those of bleached ones. Cellulose fibers were modified with ZrO₂·nH₂O nanoparticles through the use of zirconium oxychloride in acidic medium in the presence of cellulose fibers using urea as the precipitating agent. The spatial distribution characterization of hydrous zirconium oxide on cellulose fibers was carried out by combining both processing and image analyses obtained by SEM and statistical methodologies. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TG) were also used to characterize the nanocomposite. Results indicated that ZrO₂·nH₂O nanoparticles of about 30-80 nm diameter deposited on cellulose fibers were heterogeneously dispersed.     

Heavy metal adsorbents prepared from the modification of cellulose: a review

A number of industries currently produce varying concentrations of heavy metal laden waste streams with significant consequences for any receiving environmental compartment. In recent years, increasing emphasis has been placed on environmental impact minimisation and resulting from this the range and capability of natural and prepared materials capable of heavy metal removal has seen steady development. In particular considerable work has been carried out on the use of both natural materials and their modifications. These natural materials, in many instances are relatively cheap, abundant in supply and have significant potential for modification and ultimately enhancement of their adsorption capabilities. This review paper reviews the current state of research on the use of the naturally occurring material cellulose, its modified forms and their efficacy as adsorbents for the removal of heavy metals from waste streams. Adsorbents based on direct modification of cellulose are evaluated initially and subsequently modifications resulting from the grafting of selected monomers to the cellulose backbone with subsequent functionalisation are assessed. The heavy metal adsorption capacities for these modified cellulose materials were found to be significant and levels of uptake were comparable, in many instances, to both other naturally occurring adsorbent materials and commercial ion exchange type resins. Many of the modified cellulose adsorbents proved regenerable and re-usable over a number of adsorption/desorption cycles allowing recovery of the adsorbed heavy metal in a more concentrated form.     

The C27-steroid hydroxylating system from bovine liver mitochondria. Isolation of ferredoxin (hepatoredoxin) by affinity chromatography on cytochrome-c-sepharose

A technique for the isolation of highly purified hepatoredoxin involving the DE-32 cellulose chromatography of post-mitochondrial supernatant, ammonium-sulfate fractionation, Sephadex G-75 gel chromatography, 1-amino-2-hydroxypropyl-Sepharose ion-exchange chromatography and cytochrome-c-Sepharose affinity chromatography is described. The protein was purified 160-fold with a yield of 19%. The synthesis of cytochrome-c-Sepharose was carried out in a way preventing modification of the lysine-containing binding domain of the cytochrome c molecule. To achieve this, free carboxyl groups were modified with histamine to introduce imidazole residues in cytochrome c and the modified protein was immobilized on bromoacetyl-Sepharose.     

Effect of addition of sodium alginate on bacterial cellulose production by <Emphasis Type="Italic">Acetobacter xylinum</Emphasis>

Bacterial cellulose (BC) production by Acetobacter xylinum NUST4.1 was carried out in the shake flask and in a stirred-tank reactor by means of adding sodium alginate (NaAlg) into the medium. When 0.04% (w/v) NaAlg was added in the shake flask, BC production reached 6.0 g/l and the terminal yield of the cellulose was 27% of the total sugar initially added, compared with 3.7 g/l and 24% in the control, respectively. The variation between replicates in all determinations was less than 5%. During the cultivation in the stirred-tank reactor, the addition of NaAlg changed the morphology of cellulose from the irregular clumps and fibrous masses entangled in the internals to discrete masses dispersing into the broth, which indicates that NaAlg hinders formation of large clumps of BC, and enhances cellulose yield. Because the structure of cellulose is changed depending on the culture condition such as additives, structural characteristics of BC produced in the NaAlg-free and NaAlg medium are compared using scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD). SEM photographs show some differences in reticulated structures and ribbon width and FT-IR spectra indicate that there is the hydrogen bonding interaction between BC and NaAlg, then X-ray diffraction (XRD) analysis reveals that BC produced with NaAlg-added has a lower crystallinity and a smaller crystalline size. The results show that enhanced yields and modification of cellulose structure occur in the presence of NaAlg.     

Surface modification of cellulose with triazine derivative to improve printability with reactive dyes

Chemical modification of cellulose with triazine derivative, 2,4,6-tri-[(2-hydroxy-3-trimethyl-ammonium)propyl]-1,3,5-triazine chloride (Tri-HTAC), was investigated. Micro-FT-IR and nitrogen element analysis were applied to characterize molecular structure of the modified cellulose. The printing properties of the modified cellulose fabric with Tri-HTAC were discussed. Tri-HTAC was able to form covalent bonds with cellulose fibers. The apparent color strength of printed samples with three reactive dyes on the modified cellulose was higher than the corresponding color yields on the unmodified cellulose fabric. Compared with unmodified cellulose, the increases of the color yield were about 6–13%. The fixation rate was accelerated by the modification with Tri-HTAC. The wet rubbing and washing fastnesses of the printed cellulose fabrics modified with Tri-HTAC were better than those of the printed unmodified cellulose fabric. The modified cellulose with Tri-HTAC imparted good printing properties.     

Water-soluble 3-O-(2-methoxyethyl)cellulose: synthesis and characterization

The synthesis of novel 3-O-(2-methoxyethyl)cellulose via 2,6-di-O-thexyldimethylsilyl ethers was successfully carried out. Treatments of 3-O-(2-methoxyethyl)-2,6-di-O-thexyldimethylsilylcellulose with tetrabutylammonium fluoride trihydrate led to a complete removal of the protecting groups. Structure characterization carried out by means of 1D and 2D NMR spectroscopy proves a high regioselectivity. The novel cellulose ether is soluble in dimethyl sulfoxide, N,N-dimethylacetamide, N-methylpyrrolidone, and water. Size-exclusion chromatography revealed a distinct aggregation behavior in water.     

Homogeneous modification of sugarcane bagasse cellulose with succinic anhydride using a ionic liquid as reaction medium

The homogeneous chemical modification of sugarcane bagasse cellulose with succinic anhydride using 1-allyl-3-methylimidazolium chloride (AmimCl) ionic liquid as a reaction medium was studied. Parameters investigated included the molar ratio of succinic anhydride/anhydroglucose units in cellulose in a range from 2:1 to 14:1, reaction time (from 30 to 160min), and reaction temperature (between 60 and 110 degrees C). The succinylated cellulosic derivatives were prepared with a low degree of substitution (DS) ranging from 0.071 to 0.22. The results showed that the increase of reaction temperature, molar ratio of SA/AGU in cellulose, and reaction time led to an increase in DS of cellulose samples. The products were characterized by FT-IR and solid-state CP/MAS (13)C NMR spectroscopy, and thermal analysis. It was found that the crystallinity of the cellulose was completely disrupted in the ionic liquid system under the conditions given. The data also demonstrated that homogeneous modification of cellulose with succinic anhydride in AmimCl resulted in the production of cellulosic monoester. The thermal stability of the succinylated cellulose decreased upon chemical modification.     

碱性木聚糖酶研究进展*

木聚糖是一种在自然界中含量仅次于纤维素的丰富的可再生资源,木聚糖酶是一类可以将木聚糖水解成单糖和寡糖的酶,利用木聚糖酶将木聚糖分解后的产物被广泛应用于食品、造纸以及纺织等行业。木聚糖酶按其对酸碱环境的耐受能力分为碱性木聚糖酶、中性木聚糖酶和酸性木聚糖酶,其中碱性木聚糖酶适合应用于造纸工业中,尤其在造纸的制浆、促进漂白及废纸脱墨等多种工艺中,可以显著提高纸张质量,有效降低氯气排放量,从而减少对环境的污染。随着生物技术的进步,利用基因工程技术可以对碱性木聚糖酶进行分子改造,以提高其耐碱、耐热能力,扩大其在工业应用中的条件范围。介绍碱性木聚糖酶在分子改造方面的研究进展以及其在造纸漂白和制浆、废纸脱墨中的应用。     

Esterification of cellulose-enriched agricultural by-products and characterization of mechanical properties of cellulosic films

Two agricultural by-products, wheat bran and maize bran have been examined for their suitability to be transformed into biomaterials by esterification by lauroyl chloride. Influence of biochemical characteristic of cellulose (cellulose content, viscosity-average degree of polymerization, crystallinity) was studied on eight samples enriched in cellulose after chemical removal of heteroxylans and lignin. After an acidic pre-treatment, esterification was carried out with lauroyl chloride and an optimized reaction time of 8 h was used.

Chemical compositions were similar for all cellulose esters obtained, but cellulose content of initial material had a marked influence on the amount of esterified product. A film was easily obtained by casting and the mechanical (tensile strength and elongation), thermomechanical and calorimetric properties were determined. The possible role of grafted fatty acid as internal plasticizer was finally discussed.     

Modification of nanocellulose with a xyloglucan-RGD conjugate enhances adhesion and proliferation of endothelial cells: implications for tissue engineering

This paper describes a novel method for introducing the RGD cell adhesion peptide to enhance cell adhesion onto bacterial cellulose (BC). BC and cotton linters as reference were modified with xyloglucan (XG) and xyloglugan bearing a GRGDS pentapeptide. The adsorptions followed Langmuir adsorption behavior, where both XGs probably decorate the cellulose surfaces as a monolayer. The adsorption maximum of the XGs reached around 180 mg/g on BC and only about three times as much on cotton linters. The adsorption was verified with colorimetric methods. The specific surface area of BC measured with XG and XG-GRGDS was about 200 m (2)/g and was almost three times less for cotton linters, 60 m (2)/g. The difference in the amounts of XGs adsorbed might be explained by the swollen network of bacterial cellulose and a more exposed and accessible bulk as compared to cotton linters. The nanocellulose material was modified homogeneously throughout the material, as seen by the z-scan in confocal microscopy. Moreover, the modification in the water phase, in comparison with organic solvents, was clearly advantageous for preserving the morphology, as observed with SEM. The modification slightly increased the wettability, which might explain the decrease in or undetectable adsorption of adhesive protein shown by QCM-D. Initial cell studies showed that adhesion of human endothelial cells is enhanced when the BC hydrogel is modified with XG-GRGDS. QCM-D studies further revealed that the cell enhancement is due to the presence of the RGD epitope on XG and not to a nonspecific adsorption of fibronectin from cell culture medium. Optimization and proliferation studies of human endothelial cells onto bacterial cellulose modified with XG-GRGDS are currently being carried out at the Vascular Engineering Center, Sahlgrenska University Hospital, Gothenburg.     

Utilization of hydroxypropyl cellulose and poly(acrylic acid)-hydroxypropyl cellulose composite as thickeners for textile printing

Trials were carried out to partially replace kerosene oil with hydroxypropyl cellulose (HPC), poly(acrylic acid)-hydroxypropyl cellulose composite (poly (AA)-HPC) and their mixture in pigment printing paste. Partial replacement was carried out under a variety of conditions. Variables studied include type and concentration of the aqueous thickening agent and type of pigment dyes. In addition to that, poly (AA)-HPC composite was tried to replace sodium alginate in reactive printing. The fastness properties, color strength and stiffness were measured for the reactive and pigment printed samples.     

Relations between soil microflora and CO2 evolution upon decomposition of cellulose

Summary The investigation was carried out to study the relation between CO₂ evolution and the changes in microflora in the case of cellulose-decomposition in soil with special attention to the heterogeneity of soil crumbs.The rates of CO₂ evolution correlated with the number of Gram-negative bacteria, while the number of cellulose-decomposing microorganisms did not. The Gram-negative bacteria probably contribute directly to CO₂ evolution by decomposing simple sugars produced from cellulose by cellulose-decomposing microorganisms. Both the Gram-negative bacteria and cellulose-decomposing microorganisms seemed to grow luxuriantly on the surface area of soil crumbs with added cellulose powder. Therefore, it is speculated that there is a cooperation between the Gram-negative bacteria and the cellulose-decomposing microorganisms with respect to cellulose decomposition in soil. The main locus where this reaction takes place may be the surface area of soil crumbs.This work was carried out at the Laboratory of Microbiology, Agricultural University, Wageningen, The Netherlands during author's stay as guest researcher.     

A study of producing ethanol from cellulose using Clostridium thermocellum

The feasibility of producing ethanol in a continuous system from cellulose using Clostridirrrn thermocellum was investigated. This anaerobic and therniophilic bacterium was able to degrade cellulose directly into ethanol with acetic acid, hydrogen. and carbon dioxide as by-products of this fermentation. The fermentation was first carried out in a batch mode to study the effects of buffers, temperature, and agitation on microbial growth and ethanol production. From the compounds used to control pH. sodium bicarbonate had the most preferred effects on generation time and ethanol production. As expected, there was a positive relationship between temperature and growth rate. On the other hand, agitation did not benefit from ethanol production or microbial growth. The possibility of noncompetitive inhibition within such a system was deduced from the calculation of the kinetic constants K(m) and V(max). Continuous fermentations were carried out at 60 degrees C and pH 7.0 using 1.5 and 3% pure cellulose as a limiting substrate. The maximum ethanol concentration reached during the 1.5% cellulose fermentation was 0.3%. and 0.9% during the 3% cellulose fermentation. The yield of ethanol was about 0.3 grams per gram of consumed cellulose. The overall yield in both schemes was around 0.45 and 0.75 grams per gram of cellulose degraded. It was concluded that cellulose could be degraded continuously in a system with C. thermocellum for production of ethanol. While the continuous system like the batch method is feasible, it may not be promising as yet because of the slow generation time of this microorganism.     

Crystal Morphology Engineering of Pharmaceutical Solids: Tabletting Performance Enhancement

Crystal morphology engineering of a macrolide antibiotic, erythromycin A dihydrate, was investigated as a tool for tailoring tabletting performance of pharmaceutical solids. Crystal habit modification was induced by using a common pharmaceutical excipient, hydroxypropyl cellulose, as an additive during crystallization from solution. Observed morphology of the crystals was compared with the predicted Bravais–Friedel–Donnay–Harker morphology. An analysis of the molecular arrangements along the three dominant crystal faces [(002), (011), and (101)] was carried out using molecular simulation and thus the nature of the host–additive interactions was deduced. The crystals with modified habit showed improved compaction properties as compared with those of unmodified crystals. Overall, the results of this study proved that crystal morphology engineering is a valuable tool for enhancing tabletting properties of active pharmaceutical ingredients and thus of utmost practical value.     

不同预处理及发酵方式对提高蔗渣发酵产物蛋白含量的研究

采用不同的预处理方法对蔗渣进行预处理,并测定了其各个组分的含量。利用霉菌对蔗渣进行微生物降解,并讨论了不同发酵方式对产物中蛋白含量的影响。结果表明,木霉与热带假丝酵母共发酵时蛋白含量最高,为17．74％。     

Preparation and properties of aqueous dispersions of cellulose nanospheres

A process for the formation of cellulose nanospheres appropriate as biodegraded bulking agent for composite materials has been considered. The properties of the starting material and resulting dispersions of cellulose nanospheres were studied. It was found that the characteristic structural modification of the cellulose nanospheres was cellulose II, and their size largely depended on the initial cellulose-containing precursor.     

Cellulose acetate as solid phase in ELISA for plague

Antigen from Yersinia pestis was adsorbed on cellulose acetate discs (0.5 cm of diameter) which were obtained from dialysis membrane by using a paper punch. ELISA for human plague diagnosis was carried out employing this matrix and was capable to detect amount of 1.3 microg of antigen, 3,200 times diluted positive serum using human anti-IgG conjugate diluted 1:4,000. No relevant antigen lixiviation from the cellulose acetate was observed even after washing the discs 15 times. The discs were impregnated by the coloured products from the ELISA development allowing its use in dot-ELISA. Furthermore, cellulose acetate showed a better performance than the conventional PVC plates.     

Chemical Modification of the Carboxyl Terminal of Nisin A with Biotin does not Abolish Antimicrobial Activity Against the Indicator Organism, Kocuria rhizophila

Nisin is an antimicrobial peptide that is widely used for food preservation. Although it has potent activity against a number of food pathogens, suggesting potential therapeutic applications, its potential for clinical use is limited by proteolytic susceptibility and poor oral bioavailability. Derivatization of nisin could overcome these issues; however, many nisin analogues, prepared by modification at the N-terminal and C-terminal have previously been shown to be inactive. A method for the C-terminal modification was developed using biotinylation as a model derivative. Purification of the modified nisin was carried out using reverse phase chromatography. Confirmation of nisin modification was confirmed by Mass Spectroscopy. The C-terminal modification of nisin resulted in only a twofold reduction in antimicrobial activity of the conjugate against the indicator organism, Kocuria rhizophila. The C-terminal modification could be used to increase the therapeutic potential of nisin by creating more favourable physicochemical characteristics. This is the first study that showed that nisin modification can be carried out successfully without destroying its antimicrobial activity.