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91.
Properties of bacterial cellulose transparent film regenerated from dimethylacetamide–LiCl solution
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Excellent transparent films were prepared from bacterial cellulose (BC) sheets by solubilization of its defibrillated freeze‐dried specimens in a solvent of dimethylacetamide (DMAc) containing 8.0% (w/w) lithium chloride (LiCl), and their properties were compared with those of the native BC. Fibrillar structure of the native BC disappeared after dissolution, and the film formed after dissolution also loose this structure. Occurence of structural transformation from crystalline to amorphous state was also evidenced by X‐ray diffraction, solid state cross polarization/magic angle spinning 13C‐NMR and attenuated total reflectance–Fourier transform infrared spectroscopic analyses. In addition, excellent 3D uniform structure of the transparent BC film was further evidenced by X‐ray micro computed tomography. Plastic‐like characteristic was enhanced by film formation after dissolving the BC specimens in the DMAc–LiCl solution as shown by changing mechanical properties, a slight decrease in tensile strength (67.2 to 59.6 MPa) and breaking stress (67.2 to 58.4 MPa) but significant increase in elongation at break from 3.4 to 10.5%, and improvement of work of fracture from 5.8 to 21.2 kJ/m2. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
92.
以细菌纤维素为原料,在非均相体系中与环氧氯丙烷反应,合成了环氧化细菌纤维素.研究了反应条件:如环氧氯丙烷用量、NaOH用量、反应温度及反应时间对环氧基含量的影响.结果表明:合成EBC的最佳条件为反应温度35℃,反应时间3h,细菌纤维素以干重计算约0.5g,环氧氯丙烷的用量为30 mL,w=30% NaOH的用量为40 ... 相似文献
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从某焦化厂处理废水的活性污泥中筛选到一株苯酚高效降解菌(Wust-C),该菌属革兰氏阴性菌.对Wust-C降解苯酚的特性进行试验研究.结果表明,在初始苯酚浓度为1 000 mg/L的试样中,培养24 h后,Wust-C对苯酚的降解率可达98%;初始苯酚浓度为300 mg/L试样中的苯酚可在8h内完全降解.采用海藻酸钠对菌体进行固定化后,Wust-C的降酚效率进一步得到提高.培养24 h后,固定化Wust-C对初始苯酚浓度为1 200 mg/L试样中的苯酚降解率达到100%,初始苯酚浓度为300 mg/L试样中的苯酚可在4h内完全降解.Wust-C的加入对混合菌群降解苯酚起到了促进作用. 相似文献
96.
The pretreatment of rice straw is often used to enhance the hydrolysis. 1-allyl-3-methylimidazolium chloride([AMIM]Cl) is a kind of low viscous,nontoxic and recyclable ionic liquid. It was used to treat rice straw and improve the enzymatic hydrolysis of rice straw in this study. The factors influencing the pretreatment were as follows:the dosage of rice straw in [AMIM]Cl,crush mesh of rice straw,pretreatment temperature and time. After the pretreatment with a 3 %(the weight ratio of rice straw to ionic liquid) rice straw dosage in [AMIM]Cl at 110 ℃ for 1 h,the yield of reducing sugar of regenerated rice straw by 33 U/mL cellulase hydrolysis was 53.3 %,which was two times higher than that of un-treated rice straw(23.7 %) . More researches regarding straw biorefinery to bacterial cellulose are being performed in the lab and prospective results will be published in near future. 相似文献
97.
Anicuta Stoica-Guzun Marta Stroescu Iuliana Jipa Loredana Dobre Sorin Jinga Traian Zaharescu 《Macromolecular Symposia》2012,315(1):198-204
The development of biodegradable packaging materials, especially from renewable resources is a constant preoccupation of nowadays, because of the environmental problems caused by synthetic polymers. The combination of cellulose with other polymeric materials could be an ecologic alternative and a way to use renewable resources for food packaging. Bacterial cellulose which is produced by microbial fermentation is also a promising material which can be used not only in biomedical application, but also as food packaging material. In this research different composite films between poly(vinyl alcohol)-bacterial cellulose (PVA-BC) were obtained by casting method. The obtained films were UV irradiated for different periods of times from 1 to 10 hours, using a mercury lamp, Philips TUV-30, emitting light mainly at 254 nm. Changes in FT-IR spectra before and after UV irradiation and the modification of transparency and of the swelling characteristics of the films were observed. As it was expected the composites materials are sensitive at UV exposure. 相似文献
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Friederike Kramer Dieter Klemm Dieter Schumann Nadine Heßler Falko Wesarg Wolfgang Fried Dietmar Stadermann 《Macromolecular Symposia》2006,244(1):136-148
Summary: Using a “never-dried” procedure (according to Figure 4) shaped bacterial nanocellulose (BC, 1% cellulose, 99% water) has been modified by the formation of BC-polymer composites. For this purpose, acrylate and methacrylate monomers and methacrylate crosslinkers were photopolymerized inside an ethanol-swollen nanofiber network. Using the ethanol as solvent and as confirmed by model reactions the synthetic polymer (SP) part of the composites is constructed of crosslinked polymers (number of repeating units in the range of 500). As part of ongoing work on the development of (bio)materials from the innovative pool of BC composites these investigations are recently directed towards the creation of collagen-like materials. Thus, for these purposes, mainly water absorption capacity, strength, and elasticity have to be controlled, whilst still retaining essential features of BC like shape, nanofiber network, pore system, and proved biocompatibility. Using acrylic acid, 2-ethylhexyl acrylate, 2-hydroxyethyl methacrylate, N-vinyl pyrrolidone as acrylate monomers and triethylene glycol dimethacrylate and 1,4-butandiol dimethacrylate as crosslinkers of different concentrations either a filling of the pores or a coating of the fibers in the BC nanocomposites could be achieved. The small cellulose content of the composites significantly increases the water absorption value and the strength of the material as well as the ability of re-swelling in the case of fiber coated composites. Sample 12 is an optimized BC-SP composite regarding important properties of hyaline cartilage like Young's modulus in the range of 5–20 MPa using the well-known Simplex-method. 相似文献
100.
Thorbjrn Vincent Snderby Zahra Najarzadeh Daniel Erik Otzen 《Molecules (Basel, Switzerland)》2022,27(13)
Functional amyloid is produced by many organisms but is particularly well understood in bacteria, where proteins such as CsgA (E. coli) and FapC (Pseudomonas) are assembled as functional bacterial amyloid (FuBA) on the cell surface in a carefully optimized process. Besides a host of helper proteins, FuBA formation is aided by multiple imperfect repeats which stabilize amyloid and streamline the aggregation mechanism to a fast-track assembly dominated by primary nucleation. These repeats, which are found in variable numbers in Pseudomonas, are most likely the structural core of the fibrils, though we still lack experimental data to determine whether the repeats give rise to β-helix structures via stacked β-hairpins (highly likely for CsgA) or more complicated arrangements (possibly the case for FapC). The response of FuBA fibrillation to denaturants suggests that nucleation and elongation involve equal amounts of folding, but protein chaperones preferentially target nucleation for effective inhibition. Smart peptides can be designed based on these imperfect repeats and modified with various flanking sequences to divert aggregation to less stable structures, leading to a reduction in biofilm formation. Small molecules such as EGCG can also divert FuBA to less organized structures, such as partially-folded oligomeric species, with the same detrimental effect on biofilm. Finally, the strong tendency of FuBA to self-assemble can lead to the formation of very regular two-dimensional amyloid films on structured surfaces such as graphite, which strongly implies future use in biosensors or other nanobiomaterials. In summary, the properties of functional amyloid are a much-needed corrective to the unfortunate association of amyloid with neurodegenerative disease and a testimony to nature’s ability to get the best out of a protein fold. 相似文献