Culture Of Acetobacter Xylinum Research Articles

Optimization of fermentation process to achieve bacterial cellulose on molasses medium and sugarcane juice medium

The objective of this thesis is studying the condition of fermentation using Acetobacter xylinum on molasses medium and sugarcane juice medium. Multi-objective optimization method was used to optimized the factors of fermentation process in order to achieve the highest yield of Bacterial Cellulose. The results showed that pepton: 1.0%; glucose 2.78% ; pH 4.9, tempurature 30oC in 107 hours were optimal fermentation conditions for molasses medium while pepton: 0.93% ; glucose: 3.65% ; pH 5.2; tempurature 30.5 oC in 102 hours were optimal fermentation conditions for sugarcane juice medium. These two media above can be used as new media for the culture of Acetobacter xylinum in comparision to coconut milk medium.

Formation and structure of the complexes of sub-elementary fibrils of bacterial cellulose with fluorescent brightener molecules

The formation and structure of the complexes of sub-elementary fibrils (SEFs) of bacterial cellulose with fluorescent brightener (FB) molecules have been investigated using WAXD, SEM, and computer calculations of WAXD profiles. It is confirmed for the first time that the SEF-FB complexes are formed in 10 min by washing the cultivation product, which is prepared by the culture of Acetobacter xylinum in the presence of FB, with the pH 7 citrate–phosphate buffer solution and their thin sheet-like structure is grown almost two-dimensionally in 24 h in the medium. The same SEF-FB complexes are also produced by washing the product with NaCl aqueous solutions having concentrations higher than 0.1 wt%, while the original SEF structure is unchanged at lower concentrations. This indicates that the concentration of salt ions in washing media is a main factor to dominate the formation of the SEF-FB complexes from the cultivation product. The calculations of WAXD profiles reveal that the chain-slid, parallel-set, and sheet-slid/contracted models well reproduce the WAXD profile observed for the SEF-FB complexes. In these models, the following modifications are conducted in the a,b-modified unit cell of cellulose Iβ; the slide of the center chain along the b″ axis, the rotation of each chain around its own molecular axis, and the slide and contraction of the individual sheets composed of the center or origin chains. A single FB molecule is successfully packed into an energetically-allowable space in between the (010) planes in the 2a″ × b″ × 4c″ cell for the chain-slid model or in between the corresponding planes for the parallel-set and sheet-slid/contracted models. However, the detailed structure of FB in the complex is not yet determined due to the low crystallinity of the complexes.

Self-supported silver nanoparticles containing bacterial cellulose membranes

Hydrated bacterial cellulose (BC) membranes obtained from cultures of Acetobacter xylinum were used in the preparation of silver nanoparticles containing cellulose membranes. In situ preparation of Ag nanoparticles was achieved from the hydrolytic decomposition of silver triethanolamine (TEA) complexes. Scanning electron microscopy (SEM) images and X-ray diffraction (XRD) patterns both lead to the observation of spherical metallic silver particles with mean diameter of 8 nm well adsorbed onto the BC fibriles.

Towards electronic paper displays made from microbial cellulose

Cellulose (in the form of printed paper) has always been the prime medium for displaying information in our society and is far better than the various existing display technologies. This is because of its high reflectivity, contrast, low cost and flexibility. There is a major initiative to push for a dynamic display technology that emulates paper (popularly known as "electronic paper"). We have successfully demonstrated the proof of the concept of developing a dynamic display on cellulose. To the best of our knowledge, this is the first significant effort to achieve an electronic display using bacterial cellulose. First, bacterial cellulose is synthesized in a culture of Acetobacter xylinum in standard glucose-rich medium. The bacterial cellulose membrane thus formed (not pulp) is dimensionally stable, has a paper-like appearance and has a unique microfibrillar nanostructure. The technique then involves first making the cellulose an electrically conducting (or semi-conducting) sheet by depositing ions around the microfibrils to provide conducting pathways and then immobilizing electrochromic dyes within the microstructure. The whole system is then cased between transparent electrodes, and upon application of switching potentials (2-5 V) a reversible color change can be demonstrated down to a standard pixel-sized area (ca. 100 microm2). Using a standard back-plane or in-plane drive circuit, a high-resolution dynamic display device using cellulose as substrate can be constructed. The major advantages of such a device are its high paper-like reflectivity, flexibility, contrast and biodegradability. The device has the potential to be extended to various applications, such as e-book tablets, e-newspapers, dynamic wall papers, rewritable maps and learning tools.

Additional properties of a soluble polymer of glucose from cultures of Acetobacter xylinum.

The results of differential, thermal analysis of a soluble, beta (1 leads to 2)-branched, beta (1 leads to 4)-D-glucan isolated from cultures of Acetobacter xylinum are consistent with previous conclusions about its structure. The O-acetyl content of the polymer is 8.3% which corresponds to a maximum substitution of one acetyl group per three glucose residues. Proton nuclear magnetic resonance spectra confirm that all the glycosidic bonds are beta linkages. Some preparations of the polymer are contaminated by another polymer containing mannose and rhamnose. No evidence was obtained to support a previous suggestion that the branched D-glucan is a precursor of bacterial cellulose and this suggestion is now withdrawn.

Electron Microscopy of a Non-pellicle-forming Strain of Acetobacter xylinum

A non-pellicle-forming culture of Acetobacter xylinum, isolated from a pellicle-forming culture by repeated transfer of the latter through agitated medium, has been examined. The cells of the non-pellicle-producing culture are often greatly elongated and possess a profusion of intra-cytoplasmic membranes. Freeze-fractured cells reveal extensive face views of both the outer and cytoplasmic membranes and show a cell coat composed of a large number of short fibrils arising from the outer membrane. X-ray diffraction of the cells in some cases shows the cellulose-I pattern but shadow-contrasted preparations do not show long microfibrils. It is suggested that the non-pellicle formers produce cellulose as only very short microfibrils which are synthesised all over the cell surface and that there are changes in the outer membrane compared to pellicle-producing cells. The possible significance of these differences between pellicle-forming and non-pellicle-forming A. xylinum strains is discussed.

The structure of novel C35 pentacyclic terpenes from Acetobacter xylinum.

A novel C(35) terpene and its monounsaturated analogue were isolated from cultures of Acetobacter xylinum, together with traces of their C(36) homologues. These substances were found to be hopane derivatives substituted by a five-carbon chain bearing four vicinal hydroxyl groups. For the parent hydrocarbon the term bacteriohopane is proposed. The elucidation of the structures utilized high-resolution mass spectrometry of the terpenes, degradation to C(32) hydrocarbons and detailed mass-spectrometric comparison of these with C(32) hydrocarbons synthesized from known pentacyclic triterpenes. High-resolution mass-spectral data of the terpenes are presented. N.m.r. data are in agreement with the proposed structures, which are further supported by the isolation from the same organism of 22-hydroxyhopane and derivative hopene(s).

Purification of the precursor of bacterial cellulose

AbstractThe precursor(s) of bacterial cellulose can be separated from cultures of Acetobacter xylinum by elution chromatography of lyophilized cells using chloroform, acetone, and 20% methanol in acetone. The last fraction, which contains the compound, may be purified by precipitation of glucose by diethyl ether and phase partition into petroleum ether, both at low temperature. Ability of the purified fraction to form cellulose microfibrils was demonstrated by electron microscopy. The active compound in the fraction was tentatively identified by thin layer chromatography, is very labile and has the properties of a lipid or lipid‐like substance.