Home About us Contact
|
Home About us Contact | ||
|
|
||
Bacterial Cellulose (bacterial + cellulose)
Selected AbstractsCreating Hierarchical Structures in Renewable Composites by Attaching Bacterial Cellulose onto Sisal Fibers,ADVANCED MATERIALS, Issue 16 2008Julasak Juntaro The growth of bacterial-cellulose nanofibrils on the surfaces of micrometer-scale natural fibers provides a route to a new class of hierarchical, renewable, degradable composites. The nanofibrils improve the interaction between the primary fibers and the matrix, leading to improved mechanical properties and water resistance. [source] Efficient Homogeneous Chemical Modification of Bacterial Cellulose in the Ionic Liquid 1- N -Butyl-3-methylimidazolium ChlorideMACROMOLECULAR RAPID COMMUNICATIONS, Issue 19 2006Kerstin Schlufter Abstract Summary: Bacterial cellulose (BC), a unique type of cellulose, with high degree of polymerization of 6,500 could be dissolved easily in the ionic liquid 1- N -butyl-3-methylimidazolium chloride. For the first time, well-soluble BC acetates and carbanilates of high degree of substitution (up to a complete modification of all hydroxyl groups) were accessible under homogeneous and mild reaction conditions. Characterization of the new BC derivatives by NMR and FTIR spectroscopy shows an unexpected distribution of the acetyl moieties in the order O-6,>,O-3,>,O-2. 13C NMR spectrum (DMSO- d6) of a cellulose acetate with a DS of 2.25 synthesized in 1- N -butyl-3-methylimidazolium chloride. [source] Novel nanoporous membranes from regenerated bacterial celluloseJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Muenduen Phisalaphong Abstract Bacterial cellulose (BC) in an NaOH/urea aqueous solution was used as a substrate material for thefabrication of a novel regenerated cellulose membrane. The dissolution of BC involved swelling BC in a 4 wt % NaOH/3 wt % urea solution followed by a freeze,thaw process. The BC solution was cast onto a Teflon plate, coagulated in a 5 wt % CaCl2 aqueous solution, and then treated with a 1 wt % HCl solution. Supercritical carbon dioxide drying was then applied to the formation of a nanoporous structure. The physical properties and morphology of the regenerated bacterial cellulose (RBC) films were characterized. The tensile strength, elongation at break, and water absorption of the RBC membranes were 4.32 MPa, 35.20%, and 49.67%, respectively. The average pore size of the RBC membrane was 1.26 nm with a 17.57 m2/g surface area. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Improvements in the production of bacterial synthesized biocellulose nanofibres using different culture methodsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2010Amir Sani Abstract This review summarizes previous work that was done to improve the production of bacterial cellulose nanofibres. Production of biocellulose nanofibres is a subject of interest owing to the wide range of unique properties that makes this product an attractive material for many applications. Bacterial cellulose is a natural nanomaterial that has a native dimension of less than 50 nm in diameter. It is produced in the form of nanofibres, yielding a very pure cellulose product with unique physical properties that distinguish it from plant-derived cellulose. Its high surface-to-volume ratio combined with its unique properties such as poly-functionality, hydrophilicity and biocompatibility makes it a potential material for applications in the biomedical field. The purpose of this review is to summarize the methods that might help in delivering microbial cellulose to the market at a competitive cost. Different feedstocks in addition to different bioreactor systems that have been previously used are reviewed. The main challenge that exists is the low yield of the cellulosic nanofibres, which can be produced in static and agitated cultures. The static culture method has been used for many years. However, the production cost of this nanomaterial in bioreactor systems is less expensive than the static culture method. Biosynthesis in bioreactors will also be less labour intensive when scaled up. This would improve developing intermediate fermentation scale-up so that the conversion to an efficient large-scale fermentation technology will be an easy task. Copyright © 2009 Society of Chemical Industry [source] Efficient Homogeneous Chemical Modification of Bacterial Cellulose in the Ionic Liquid 1- N -Butyl-3-methylimidazolium ChlorideMACROMOLECULAR RAPID COMMUNICATIONS, Issue 19 2006Kerstin Schlufter Abstract Summary: Bacterial cellulose (BC), a unique type of cellulose, with high degree of polymerization of 6,500 could be dissolved easily in the ionic liquid 1- N -butyl-3-methylimidazolium chloride. For the first time, well-soluble BC acetates and carbanilates of high degree of substitution (up to a complete modification of all hydroxyl groups) were accessible under homogeneous and mild reaction conditions. Characterization of the new BC derivatives by NMR and FTIR spectroscopy shows an unexpected distribution of the acetyl moieties in the order O-6,>,O-3,>,O-2. 13C NMR spectrum (DMSO- d6) of a cellulose acetate with a DS of 2.25 synthesized in 1- N -butyl-3-methylimidazolium chloride. [source] Influence of cultivation conditions on mechanical and morphological properties of bacterial cellulose tubesBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2007Aase Bodin Abstract Bacterial cellulose (BC) was deposited in tubular form by fermenting Acetobacter xylinum on top of silicone tubes as an oxygenated support and by blowing different concentrations of oxygen, that is, 21% (air), 35%, 50%, and 100%. Mechanical properties such as burst pressure and tensile properties were evaluated for all tubes. The burst pressure of the tubes increased with an increase in oxygen ratio and reached a top value of 880 mmHg at 100% oxygen. The Young's modulus was approximately 5 MPa for all tubes, irrespective of the oxygen ratio. The elongation to break decreased from 30% to 10,20% when the oxygen ratio was increased. The morphology of the tubes was characterized by Scanning Electron Microscopy (SEM). All tubes had an even inner side and a more porous outer side. The cross section indicated that the tubes are composed of layers and that the amount of layers and the yield of cellulose increased with an increase in oxygen ratio. We propose that an internal vessel wall with high density is required for the tube to sustain a certain pressure. An increase in wall thickness by an increase in oxygen ratio might explain the increasing burst pressure with increasing oxygen ratio. The fermentation method used renders it possible to produce branched tubes, tubes with unlimited length and inner diameters. Endothelial cells (ECs) were grown onto the lumen of the tubes. The cells formed a confluent layer after 7 days. The tubes potential as a vascular graft is currently under investigation in a large animal model at the Centre of Vascular Engineering, Sahlgrenska University Hospital, Gothenburg. Biotechnol. Bioeng. 2007;97: 425,434. © 2006 Wiley Periodicals, Inc. [source] Dynamic modelling of bacterial cellulose formationENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2009Michael Hornung Abstract The interest in cellulose produced by bacteria from surface cultures has increased steadily in recent years because of its potential for use in medicine and cosmetics. Unfortunately, the low yield of this production process has limited the commercial usefulness of bacterial cellulose. The aim of this paper is to show the effect of substrate mass transfer on the growth of the bacteria and on their physiological potential for product formation by means of a dynamic mathematical model. [source] Mechanism of substrate inhibition in cellulose synergistic degradationFEBS JOURNAL, Issue 16 2001Priit Väljamäe ,A comprehensive experimental study of substrate inhibition in cellulose hydrolysis based on a well defined system is presented. The hydrolysis of bacterial cellulose by synergistically operating binary mixtures of cellobiohydrolase I from Trichoderma reesei and five different endoglucanases as well as their catalytic domains displays a characteristic substrate inhibition. This inhibition phenomenon is shown to require the two-domain structure of an intact cellobiohydrolase. The experimental data were in accordance with a mechanism where cellobiohydrolases previously bound to the cellulose by means of their cellulose binding domains are able to find chain ends by lateral diffusion. An increased substrate concentration at a fixed enzyme load will also increase the average diffusion distance/time needed for cellobiohydrolases to reach new chain ends created by endoglucanases, resulting in an apparent substrate inhibition of the synergistic action. The connection between the binding properties and the substrate inhibition is encouraging with respect to molecular engineering of the binding domain for optimal performance in biotechnological processes. [source] Novel nanoporous membranes from regenerated bacterial celluloseJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Muenduen Phisalaphong Abstract Bacterial cellulose (BC) in an NaOH/urea aqueous solution was used as a substrate material for thefabrication of a novel regenerated cellulose membrane. The dissolution of BC involved swelling BC in a 4 wt % NaOH/3 wt % urea solution followed by a freeze,thaw process. The BC solution was cast onto a Teflon plate, coagulated in a 5 wt % CaCl2 aqueous solution, and then treated with a 1 wt % HCl solution. Supercritical carbon dioxide drying was then applied to the formation of a nanoporous structure. The physical properties and morphology of the regenerated bacterial cellulose (RBC) films were characterized. The tensile strength, elongation at break, and water absorption of the RBC membranes were 4.32 MPa, 35.20%, and 49.67%, respectively. The average pore size of the RBC membrane was 1.26 nm with a 17.57 m2/g surface area. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Loading of Bacterial Cellulose Aerogels with Bioactive Compounds by Antisolvent Precipitation with Supercritical Carbon DioxideMACROMOLECULAR SYMPOSIA, Issue 2 2010Emmerich Haimer Abstract Bacterial cellulose aerogels overcome the drawback of shrinking during preparation by drying with supercritical CO2. Thus, the pore network of these gels is fully accessible. These materials can be fully rewetted to 100% of its initial water content, without collapsing of the structure due to surface tension of the rewetting solvent. This rehydration property and the high pore volume of these material rendered bacterial cellulose aerogels very interesting as controlled release matrices. Supercritical CO2 drying, the method of choice for aerogel preparation, can simultaneously be used to precipitate solutes within the cellulose matrix and thus to load bacterial cellulose aerogels with active substances. This process, frequently termed supercritical antisolvent precipitation, is able to perform production of the actual aerogel and its loading in one single preparation step. In this work, the loading of a bacterial cellulose aerogel matrix with two model substances, namely dexpanthenol and L-ascorbic acid, and the release behavior from the matrix were studied. A mathematical release model was applied to model the interactions between the solutes and the cellulose matrix. The bacterial cellulose aerogels were easily equipped with the reagents by supercritical antisolvent precipitation. Loading isotherms as well as release kinetics indicated no specific interaction between matrix and loaded substances. Hence, loading and release can be controlled and predicted just by varying the thickness of the gel and the solute concentration in the loading bath. [source] Synergistic cellulose hydrolysis can be described in terms of fractal-like kineticsBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2003Priit Väljamäe Abstract A fractal-like kinetics model was used to describe the synergistic hydrolysis of bacterial cellulose by Trichoderma reesei cellulases. The synergistic action of intact cellobiohydrolase Cel7A and endoglucanase Cel5A at low enzyme-to-substrate ratios showed an apparent substrate inhibition consistent with a case where two-dimensional (2-D) surface diffusion of the cellobiohydrolase is rate-limiting. The action of Cel7A core and Cel5A was instead consistent with a three-dimensional (3-D) diffusion-based mode of action. The synergistic action of intact Cel7A was far superior to that of the core at a high enzyme-to-substrate ratio, but this effect was gradually reduced at lower enzyme-to-substrate ratios. The apparent fractal kinetics exponent h obtained by nonlinear fit of hydrolysis data to the fractal-like kinetics analogue of a first-order reaction was a useful empirical parameter for assessing the rate retardation and its dependence on the reaction conditions. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 254,257, 2003. [source] | ||||||||||||||||