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1.
Acetobacter xylinum produces highly crystalline cellulose extracellulary using glucose as a carbon source. The polymer formed is free of other biogenic compounds, separable in a simple way and characterized by its high water-absorption capacity. Stepwise solvent exchange from water to unpolar solvents leads to a drastic decrease of the water content of the bacterial cellulose without decrease of the highly swollen and activated state. Heterogeneous as well as homogeneous derivatizations, e.g. carboxymethylation, silylation and acetylation, were performed on the wet or dried biopolymer. Furthermore, different methods for formation of hollow fibres during biosynthesis were investigated. Such tubes may have applications as biocompatible material in medicine.  相似文献   

2.
不同培养方式对细菌纤维素产量和结构性质的影响   总被引:9,自引:0,他引:9  
考察了自行筛选的Acetobacter xylinum NUST4.2在静置培养和发酵罐培养获得的细菌纤维素(BC)的产量、基本结构和性能的差异。结果表明:静置培养时产纤维素7.5g/L,产率为0.052g/L/h,在机械搅拌发酵罐中培养3d产量达3.13g/L,产率达0.043g/L/h;SEM分析显示静置培养和发酵罐培养得到的纤维素均具有网状结构,但静置获得的纤维素丝带相互缠绕且层状重叠,更加致密,丝带更细;FT-IR分析知搅拌不改变纤维素的化学结构,但能减弱分子间氢键,和XRD结合分析可知静置培养的纤维素具有更高结晶指数,更高Iα含量和更大晶粒尺寸,但不改变晶型,仍为纤维素I型,说明搅拌会干扰纤维素初始纤丝的结晶,有利于形成更小的晶粒和较Iα稳定的Iβ。与棉纤维素相比,静置培养获得的纤维素的热稳定性更好,而发酵罐培养获得的纤维素则阻燃性更好。  相似文献   

3.
Culture conditions in a jar fermentor for bacterial cellulose (BC) production from A. xylinum BPR2001 were optimized by statistical analysis using Box-Behnken design. Response surface methodology was used to predict the levels of the factors, fructose (X1), corn steep liquor (CSL) (X2), dissolved oxygen (DO) (X3), and agar concentration (X4). Total 27 experimental runs by combination of each factor were carried out in a 10-L jar fermentor, and a three-dimensional response surface was generated to determine the effect of the factors and to find out the optimum concentration of each factor for maximum BC production and BC yield. The fructose and agar concentration highly influenced the BC production and BC yield. However, the optimum conditions according to changes in CSL and DO concentrations were predicted at almost central values of tested ranges. The predicted results showed that BC production was 14.3 g/L under the condition of 4.99% fructose, 2.85% CSL, 28.33% DO, and 0.38% agar concentration. On the other hand, BC yield was predicted in 0.34 g/g under the condition of 3.63% fructose, 2.90% CSL, 31.14% DO, and 0.42% agar concentration. Under optimized culture conditions, improvement of BC production and BC yield were experimentally confirmed, which increased 76% and 57%, respectively, compared to BC production and BC yield before optimizing the culture conditions.  相似文献   

4.
Aims: Bacterial cellulose is an extracellular polysaccharide secreted by Acetobacter xylinum, which has become a novel material increasingly used in food and medical industries. However, its broad application is limited by its low yield and high cost. 1‐Methylcyclopropene (1‐MCP) is a potent inhibitor to either exogenous or endogenous ethylene during the biological senescence of plants, which has been broadly applied in commercial preservation of fruits and vegetables. The purpose of this study was to investigate the effects of 1‐MCP on both the growth of Acet.  xylinum and its cellulose production to demonstrate the potential enhancement of bacterial cellulose yield. Methods and Results: Three groups of samples were fermented under agitated culture with 125 rev min?1 rotational speed. To the culture media, 0·14 mg of 1‐MCP contained in 100 mg dextrose powder was added on assigned days or on the first culture day only. Results from the measurement of bacterial cell concentration and bacterial cellulose yield at the end of a 12‐day culture demonstrated that cultures excluding 1‐MCP displayed a higher cell concentration and a lower cellulose production, while cultures containing 1‐MCP produced 15·6% more cellulose (1‐MCP added on day 1) and 25·4% (1‐MCP added on each assigned day) with less biomass. Conclusions: 1‐MCP was able to affect the growth of Acet. xylinum cells and resulted in increasing bacterial cellulose yield up to 25·4% over controls, which did not contain 1‐MCP. Significance and Impact of the Study: This was the first study to use the growth inhibitor of plants to investigate its effects on bacterial growth and production. It also demonstrated a significant enhancement of bacterial cellulose yield by the addition of 1‐MCP during the common agitated culture of Acet. xylinum.  相似文献   

5.
About 14.5 kb of DNA fragments from Acetobacter xylinum ATCC23769 and ATCC53582 were cloned, and their nucleotide sequences were determined. The sequenced DNA regions contained endo-beta-1,4-glucanase, cellulose complementing protein, cellulose synthase subunit AB, C, D and beta-glucosidase genes. The results from a homology search of deduced amino acid sequences between A. xylinum ATCC23769 and ATCC53582 showed that they were highly similar. However, the amount of cellulose production by ATCC53582 was 5 times larger than that of ATCC23769 during a 7-day incubation. In A. xylinum ATCC53582, synthesis of cellulose continued after glucose was consumed, suggesting that a metabolite of glucose, or a component of the medium other than glucose, may be a substrate of cellulose. On the other hand, cell growth of ATCC23769 was twice that of ATCC53582. Glucose is the energy source in A. xylinum as well as the substrate of cellulose synthesis, and the metabolic pathway of glucose in both strains may be different. These results suggest that the synthesis of cellulose and the growth of bacterial cells are contradictory.  相似文献   

6.
During the bacterial production of cellulosic films on non-agitated liquid media, the mass of the system does not change. An equation is therefore proposed to evaluate the volume of inoculated medium to be placed in a given tray so that, when no more free aqueous medium may be detected under the wet pellicle produced, a dried film of a desired average thickness is produced.  相似文献   

7.
醋酸杆菌发酵生产细菌纤维素的研究进展   总被引:10,自引:0,他引:10  
简要介绍醋酸杆菌发酵生产纤维素研究进展,内容包括:产纤维素的微生物、醋酸菌纤维素的结构特点、生物合成途径、一般提取处理及分析测定方法、商业用途、工业化发酵生产醋酸菌纤维素过程中存在的主要问题及发展前景。  相似文献   

8.
9.
Factors affecting the yield and properties of bacterial cellulose   总被引:12,自引:0,他引:12  
Acetobacter xylinum E25 has been applied in our studies in order to find optimal culture conditions for effective bacterial cellulose (BC) production. The strain displays significantly higher stability in BC production under stationary culture conditions. In contrast, intensive agitation and aeration appear to drastically reduce cellulose synthesis since such conditions induced formation of spontaneous cellulose nonproducing mutants (Cel−), which dominated in the culture. Mutation frequency strictly depends on the medium composition in agitated cultures. Enrichment of the standard SH and Yamanaka media with 1% ethanol significantly enhanced BC production in stationary cultures. Horizontal fermentors equipped with rotating discs or rollers were successfully applied in order to improve culture conditions. Relatively slow rotation velocity (4 rpm) and large surface area enabling effective cell attachment are optimal parameters for cellulose production. Physical properties of BC samples synthesized either in stationary cultures or in a horizontal fermentor revealed that cellulose from stationary cultures demonstrated a much higher value of Young's modulus, but a much lower value of water-holding capacity. Journal of Industrial Microbiology & Biotechnology (2002) 29, 189–195 doi:10.1038/sj.jim.7000303 Received 01 March 2002/ Accepted in revised form 18 July 2002  相似文献   

10.
Silicone rubber membrane bioreactors for bacterial cellulose production   总被引:1,自引:0,他引:1  
Cellulose production byAcetobacter pasteurianus was investigated in static culture using four bioreactors with silicone rubber membrane submerged in the medium. The shape of the membrane was flat sheet, flat sack, tube and cylindrical balloon. Production rate of cellulose as well as its yield on consumed glucose by the bacteria grown on the flat type membranes was approximately ten-fold greater than those on the non-flat ones in spite of the same membrane thickness. The membrane reactor using flat sacks of silicone rubber membrane as support of bacterial pellicle can supply greater ratio of surface to volume than a conventional liquid surface culture and is promising for industrial production of bacterial cellulose in large scale.  相似文献   

11.
Aim: The purpose of this work was to study the feasibility of producing economic flame retardant bacterial cellulose (BC) and evaluating its behaviour in paper production. Methods and Results: This type of BC was prepared by Gluconacetobacter subsp. xylinus and substituting the glucose in the cultivation medium by glucose phosphate as a carbon source; as well as using corn steep liquor as a nitrogen source. The investigated processing technique did not dispose any toxic chemicals that pollute the surroundings or cause unacceptable effluents, making the process environmentally safe. The fire retardant behaviour of the investigated BC has been studied by non‐isothermal thermogravimetric analysis (TGA & DTGA). The activation energy of each degradation stage and the order of degradation were estimated using the Coats–Redfern equation and the least square method. Strength, optical properties, and thermogravimetric analysis of BC‐phosphate added paper sheets were also tested. Conclusions: The study confirmed that the use of glucose phosphate along with glucose was significant in the high yield production of phosphate containing bacterial cellulose (PCBC1); more so than the use of glucose phosphate alone (PCBC2). Incorporating 5% of the PCBC with wood pulp during paper sheet formation was found to significantly improve kaolin retention, strength, and fire resistance properties as compared to paper sheets produced from incorporating bacterial cellulose (BC). Significance and Impact of the Study: This modified BC is a valuable product for the preparation of specialized paper, in addition to its function as a fillers aid.  相似文献   

12.
AIMS: Gluconacetobacter xylinum is well known for its ability to produce large amounts of cellulose, however, little is known about its cell physiology. Our goal was to study the respiratory metabolism and components of the respiratory system of this bacterium in static cultures. To reach our goal, a medium formulation had to be designed to improve cell growth and cellulose production together with a novel method for the recovery of cells from cellulose pellicles. METHODS AND RESULTS: Successive modifications of a nutrient medium improved G. xylinum cell growth 4.5-fold under static culture conditions. A blender homogenization procedure for the releasing of cells from the cellulose matrix gave a high yield of cells recovered. Respiratory activities of purified cells were greatly stimulated by exogenous substrates and showed to be resistant to KCN. Unexpectedly, exogenous NADH was oxidized at high rates. Cytochromes a, b, c and d were identified after spectral analyses. CONCLUSIONS: Partial bioenergetic characterization of G. xylinum cells allowed us to propose a scheme for its respiratory system. In addition, the growth medium for biomass production and the procedure for the efficient recovery of cells from cellulose pellicles were significantly improved. SIGNIFICANCE AND IMPACT OF THE STUDY: This work provides the first-ever bioenergetic characterization of G. xylinum grown in static cultures. In addition, a novel methodology to obtain purified cells in suitable quantities for biochemical research is described.  相似文献   

13.
Bacterial cellulose (BC), which is produced by some bacteria, has unique structural, functional, physical and chemical properties. Thus, the mass production of BC for industrial application has recently attracted considerable attention. To enhance BC production, two aspects have been considered, namely, the engineering and genetic viewpoints. The former includes the reactor design, nutrient selection, process control and optimization; and the latter the cloning of the BC synthesis gene, and the genetic modification of the speculated genes for higher BC production. In this review, recent advances in BC production from the two viewpoints mentioned above are described, mainly using the bacteriumGluconacetobacter xylinus.  相似文献   

14.
Three sets of cellulose synthase genes were cloned from a cellulose-producing bacterium Acetobacter xylinum JCM 7664. One set of genes (bcsAI/bcsBI/bcsCI/bcsDI) were highly conserved with the well-established type I genes in other strains of A. xylinum, while the other two (bcsABII-A, bcsABII-B) were homologous to the known type II (acsAII). Unexpectedly, they were immediately followed by a gene cluster of bcsX/bcsY/bcsCII/ORF569, likely forming an operon. Western blotting demonstrated that the BcsY protein accumulated in cells. Since BcsY showed striking similarities to a number of membrane-bound transacylases, it was hypothesized that the type II cellulose synthase produces acylated cellulose, which might be anchored on the cytoplasmic membrane. An insertion sequence of IS1380-type was found just upstream of the one type II gene (bcsABII-B), suggestive of nonfunctioning.  相似文献   

15.
Yasutake Y  Kawano S  Tajima K  Yao M  Satoh Y  Munekata M  Tanaka I 《Proteins》2006,64(4):1069-1077
Previous studies have demonstrated that endoglucanase is required for cellulose biosynthesis both in bacteria and plants. However, it has yet to be elucidated how the endoglucanases function in the mechanism of cellulose biosynthesis. Here we describe the crystal structure of the cellulose biosynthesis-related endo-beta-1,47-glucanase (CMCax; EC 3.2.1.4) from the cellulose-producing Gramnegative bacterium, Acetobacter xylinum (= Gluconacetobacter xylinus), determined at 1.65-A resolution. CMCax falls into the glycoside hydrolase family 8 (GH-8), and the structure showed that the overall fold of the CMCax is similar to those of other glycoside hydrolases belonging to GH-8. Structure comparison with Clostridium thermocellum CelA, the best characterized GH-8 endoglucanase, revealed that sugar recognition subsite +3 is completely missing in CMCax. The absence of the subsite +3 leads to significant broadness of the cleft at the cellooligosaccharide reducing-end side. CMCax is known to be a secreted enzyme and is present in the culture medium. However, electron microscopic analysis using immunostaining clearly demonstrated that a portion of CMCax is localized to the cell surface, suggesting a link with other known membrane-anchored endoglucanases that are required for cellulose biosynthesis.  相似文献   

16.
An Acetobacter xylinum adapted to a medium containing N-acetylglucosamine (GlcNAc) has been used to prepare a novel polysaccharide containing residual GlcNAc in cellulose. The maximum amount of incorporation was found to be 4 mol% in cellulose, when a mixed medium containing 1.4% glucose (Glc) and 0.6% GlcNAc was used for the culture of A. xylinum. The resulting polysaccharide was lysozyme-susceptible. The aminosugar residue incorporated into bacterial cellulose was found to be only GlcNAc, even if galactosamine (GalN) and glucosamine (GlcN) were applied, whereas there was little effect by mannosamine (ManN). As the major component of the resulting polysaccharide was Glc residues, even if the only carbon source in the culture medium was GlcNAc, it was suggested that there must be several enzyme systems to convert GlcNAc into Glc in the bacteria. Several ammonium salts were also found to be effective for the incorporation of GlcNAc residues when the incubation system was converted to rotatory and aerobic incubation from static incubation. The amount of residual GlcNAc was remarkably increased by the addition of lysozyme-susceptible phosphoryl-chitin (P-chitin) and increased slightly with addition of P-chitin that was less lysozyme-susceptible. However, little effect was found on addition of highly substituted P-chitin.  相似文献   

17.
Acetobacter xylinum NQ-5 (ATCC 53582) and AY-201 (ATCC 23769) cultivated in the Hestrin–Schramm medium containing d-glucose with a natural 13C-abundance of 1.1% were investigated regarding their cell division rates and the bacterial movements. Comparative studies were carried out in the presence of d-glucose-U-13C6 with a uniform 13C-labeling of 99% as the sole carbon source. The bacterial growth rates in numbers were found to increase in the 13C-enriched media by about 13% for NQ-5 and 26% for AY-201, respectively. The movements of single cells caused by the inverse force of the secretion and deposition of cellulose nanofibers on nematic ordered cellulose (NOC) templates were investigated by real-time video analyzes using light microscopy. As a result, d-glucose-U-13C6 reduced the speed of motion for both strains, which was an opposite trend to the above growth rates in the cell division. The deposited cellulose fibers were proved to be in a cellulose crystalline form by CP/MAS 13C NMR and NIR FT Raman spectroscopic measurements, although the biosynthesized and thereafter-deposited cellulose has a strong interaction with the surface of NOC.  相似文献   

18.
Utilization of -xylose as carbon source for production of bacterial cellulose was studied. Seventeen strains of acetic acid bacteria were screened for their cellulose productivity in -glucose, -xylose, and -xylose/ -xylulose mixed media, respectively. -Xylose was not well metabolized by any bacterial strains that exhibited high cellulose production in -glucose medium. Consequently, bacterial cellulose production in -xylose medium was unsuccessful. -Xylose, however, became utilizable substrate for bacterial strains if xylose-isomerase was added to the medium. Acetobacter xylinus IFO 15606 was the best cellulose producer in -xylose/ -xylulose mixed medium, so cultural conditions were studied for enhanced cellulose production. With pH controlled, the strain could produce cellulose at a yield exceeding 0.3 g per 100 ml of -xylose/ -xylulose mixed medium, which was comparable to the yields in -glucose medium by excellent producers in the literature.  相似文献   

19.
细菌纤维素的研究进展   总被引:2,自引:0,他引:2  
细菌纤维素是一种新型微生物合成材料,在食品、医药、纺织、化工等方面有着巨大的应用潜力。简要介绍了细菌纤维素的性质和结构特点,系统阐述了细菌纤维素的生物合成途径及影响细菌纤维素产量的因素。  相似文献   

20.
细菌纤维素的合成与调控进展   总被引:1,自引:0,他引:1  
细菌纤维素是1种天然的高纯度生物多聚物,与木质纤维素相比,其生产和加工过程更为方便和环保,因此已成为1种极有潜力的生物材料。葡糖酸醋杆菌是目前已知的产纤维素能力最高的菌株。综述了葡糖酸醋杆菌的细菌纤维素合成和调控机制以及为提高产量所进行的基因工程手段和培养方法。  相似文献   

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