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A major by-product of biodiesel production is waste glycerol, which has numerous potential applications. In this study, we isolated a novel bacterium capable of producing cellulose from waste glycerol, and identified it as a novel strain (named NEDO-01) of Gluconacetobacter intermedius. Scanning electron microscopy revealed that the morphology of the pellicle produced by NEDO-01 was similar to that of cellulose produced by Gluconacetobacter hansenii ATCC23769. Furthermore, X-ray diffraction and solid-state nuclear magnetic resonance spectroscopic analyses suggested that cellulose produced by NEDO-01 had molecular and crystalline structures similar to those of cellulose produced by ATCC23769. After the optimization of cultivation conditions, NEDO-01 mediated the one-step production of nanofibrillated bacterial cellulose (NFBC) from waste glycerol in a medium supplemented with carboxymethyl cellulose. Transmission electron microscopic analysis revealed that the NFBC was composed of relatively uniform fibers with diameters of approximately 20 nm. NFBC was produced as uniform water suspensions, the yield of which was 3.4 g/L from cultivation in 7.5 L medium in a 10-L jar fermenter. The bioconversion of waste glycerol to NFBC, which has superior fluidity, moldability, and miscibility, has a wide variety of applications, including potential uses in the medical and materials engineering fields. [ABSTRACT FROM AUTHOR]

La celulosa bacteriana es un polímero obtenido por fermentación con microrganismos de los géneros Acetobacter, Rhizobium, Agrobacterium y Sarcina, de las cuales la especie más eficiente es la Acetobacter Xylinum. Este polímero presenta la misma estructura química de la celulosa de origen vegetal, pero difiere en su conformación y propiedades fisicoquímicas, lo que lo hace atractivo para diversas aplicaciones, especialmente en las áreas de alimentos, procesos de separación, catálisis y en medicina, gracias a su biocompatibilidad. Sin embargo, el principal problema es la producción a gran escala limitada por los bajos rendimientos, lo que genera la necesidad de desarrollar alternativas que permitan disminuir o eliminar las causas de esta limitación. En este artículo se hace una revisión acerca de la síntesis, producción, propiedades y principales aplicaciones de la celulosa bacteriana, así como de algunas alternativas estudiadas para disminuir los inconvenientes en el escalamiento del proceso. MSC: 92-03

The acs operon of Gluconacetobacter is thought to encode AcsA, AcsB, AcsC, and AcsD proteins that constitute the cellulose syn-thase complex, required for the synthesis and secretion of crystalline cellulose microfibrils. A few other genes have been shown to be involved in this process, but their precise role is unclear. We report here the use of Tn5 transposon insertion mutagenesis to identify and characterize six non-cellulose-producing (Cel-) mutants of Gluconacetobacter hansenii ATCC 23769. The genes disrupted were acsA, acsC, ccpAx (encoding cellulose-complementing protein [the subscript "Ax" indicates genes from organisms formerly classified as Acetobacter xylinum]), dgcl (encoding guanylate dicydase), and crp-fnr (encoding a cyclic AMP receptor protein/fumarate nitrate reductase transcriptional regulator). Protein blot analysis revealed that (i) AcsB and AcsC were absent in the acsA mutant, (ii) the levels of AcsB and AcsC were significantly reduced in the ccpAx mutant, and (iii) the level of AcsD was not affected in any of the Cel- mutants. Promoter analysis showed that the acs operon does not include acsD, unlike the organization of the acs operon of several strains of closely related Gluconacetobacter xylinus. Complementation experiments confirmed that the gene disrupted in each Cel- mutant was responsible for the phenotype. Quantitative real-time PCR and protein blotting results suggest that the transcription of bglAx (encoding β-glucosidase and located immediately downstream from acsD) was strongly dependent on Crp/Fnr. A bglAx knockout mutant, generated via homologous recombination, produced only ~16% of the wild-type cellulose level. Since the crp-fnr mutant did not produce any cellulose, Crp/Fnr may regulate the expression of other gene(s) involved in cellulose biosynthesis. [ABSTRACT FROM AUTHOR]

It has been observed that certainstrains of the bacterium Gluconacetobacter xylinuscan produce sphere-likecellulose particles (SCP) under orbital shaking cultivation. Theseunique particles may have broad applications in materials science,especially in the biomedical field. The mechanism behind SCP formationand SCP biocompatibility, however, remain unknown. In this study,several factors potentially involved in the formation of SCP havebeen examined including the composition of initial inoculums, inoculumvolume, initial media glucose concentration, and temperature. Theresults revealed that cellulose fibers supposedly existing in theinitial inoculums did not relate to the initiation of cellulose sphericalstructure. Increased inoculum volume reduced the number of SCP, anddifferent initial glucose concentrations impacted the mean of approximatediameters of SCP, while the number of SCP remained unchanged underdifferent initial glucose concentrations. Additionally, the formationprocess of SCP has been clearly identified in this study by loweringthe culture temperature. Furthermore, rapid attachment and extensionof human osteoblast cells grown on SCP demonstrated their good biocompatibilityand the potential use of this kind of materials for biomedical applications. [ABSTRACT FROM AUTHOR]

The cellulose complementing factor (Ccp) is known to be involved in cellulose production in the Acetobacter species. However, its precise functions remain unclear. In the current study, we identified the coding region of the ccpAx gene (ccp gene from Acetobacter xylinum) and the localization of the CcpAx in cells by generating fusion proteins tagged to an enhanced green fluorescent protein (EGFP). From the results of N-terminal sequencing of CcpAx-EGFP-fusion protein, which recovered 65% of cellulose-producing abilities of the wild-type to the ccpAx gene-knockout mutant, the ccpAx gene was determined to encode a protein with the molecular weight of 8 kDa. The amino acid sequence deduced had high similarities with the C-terminal regions of Ccp proteins from other Acetobacter species. Fluorescence microscopy analysis showed that CcpAx was longitudinally localized along with one side of the cell membrane. Additionally, the localization of AxCeSD, which is thought to be a member of the cellulose synthase complex [terminal complex (TC)] in A. xylinum, was determined in the same manner as CcpAx. Fluorescence microscopy analysis showed that AxCeSD had a localization pattern similar to that of CcpAx. Pulldown assays and isothermal titration calorimetry analysis clearly showed a significant interaction between CcpAx and AxCeSD. Taken together, these data strongly suggest that CcpAx functions as a member of the TC in A. xylinum. [Copyright &y& Elsevier]

The structure of microbial cellulose (MC) produced by Acetobacter xylinum was studied in presence of Fluorescent Brightener, Direct Blue 1, 14, 15, 53, Direct Red 28, 75 and 79, as probe. X-ray diffraction pattern of the product showed that it was a crystalline complex of dye and cellulose. The product has the structure in which the monomolecular layer of the dye molecule is included between the cellulose sheets corresponding to the ( $$ 1\bar{1}0 $$) planes of microbial cellulose. As a result of dye inclusion, d-spacing of lower angle plane (100) of products becomes 8.0-8.8 Å instead of 6.1 Å of MC. The d-spacing for the higher angle plane must be (010) plane due to stronger van der Waals forces between the pyranose rings which reduced 5.3 Å space of (110) plane of MC to 3.9-4.5 Å in the product. However, cellulose regenerated from FB, DR28 products was cellulose I and IV, respectively, and that from each DB1, 14, 15, 53, DR75 and 79 products was cellulose II. Solid state C NMR and deuteration-IR showed the product was non-crystalline which was contrasted to X-ray results. The regenerated celluloses were cellulose I, IV and II, respectively. Thus the structure of the product depends on the characteristics of dye which affects the conformation of cellulose at the nascent stage by the direct interaction with cellulose chains. The different regenerated celluloses as well as different fine structure in the same cellulose allomorph were produced depending mainly on number and position of the sulfonate groups in the dye. [ABSTRACT FROM AUTHOR]

New composite hydrogels based on cellulose and poly(acrylamide) have been synthesized via radical polymerization of acrylamide in cellulose swollen in a reaction solution. In this study, both a plant form of cellulose and a bacterial form-that cultivated by Acetobacter xylinum bacteria-were used. The behavior of synthesized hydrogels during swelling in water, as well as the behavior of the samples swollen at equilibrium during deformation under uniaxial compression under various test conditions, have been studied. A comparative analysis of the main mechanical characteristics of hydrogels and the appropriate data for various types of articular cartilage, one of which-rabbit knee meniscus-has been tested in this study, has been performed. An average-strength hydrogel is very close to articular cartilage in all mechanical characteristics. The degrees of loading at the highest compression deformations observed during the function of joint cartilage (30-50%) is in the range 4-12 MPa for this hydrogel, and the average values of the compression modulus in the deformation ranges of 10-15 and 25-30% are 8.8 and 23.7 MPa, respectively. The behavior of hydrogels and rabbit meniscus under cyclic compression with the amplitude of 50% has been studied. Hydrogels and meniscus under this test conditions demonstrate clear viscoelastic behavior, evidenced by noticeable hysteresis for the first cycle and a decrease in the value of the maximum load with an increase in the number of cycles. Structural features of hydrogels, which can affect the behavior of the hydrogels under study, have been considered. On the whole, the results demonstrate the possibility of modeling the mechanical behavior of cartilage with the use of hydrogels of this type. [ABSTRACT FROM AUTHOR]

Abstract: Bacterial cellulose (BC) and bacterial cellulose–chitosan (BC–Ch) membranes were successfully produced in large scale. BC was synthesized by Acetobacter xylinum. BC–Ch was prepared by immersing BC in chitosan followed by freeze-drying. The surface morphology of BC and BC–Ch membranes were examined by a scanning electron microscope (SEM). SEM images showed that BC–Ch possessed a denser fibril network with smaller pores than BC. Infrared spectroscopy was used to confirm the incorporation of chitosan in BC–Ch. The swelling behavior, water retention capacity, and mechanical properties of BC and BC–Ch were further evaluated. Results indicated that both membranes maintained proper moisture contents for an extensive period without dehydration. The tensile strength and elongation at break for BC–Ch were slightly lower while the Young''s modulus was higher. Cell culture studies demonstrated that BC and BC–Ch had no cytotoxicity. In the antibacterial test, the addition of chitosan in BC showed significant growth inhibition against Escherichia coli and Staphylococcus aureus. The effects of BC and BC–Ch on skin wound healing were assessed by rat models. Histological examinations revealed that wounds treated with BC–Ch epithelialized and regenerated faster than those treated with BC or Tegaderm. Therefore, BC–Ch was considered as a potential candidate for wound dressing materials. [Copyright &y& Elsevier]

Background: Bacterial cellulose (BC) is a highly crystalline and mechanically stable nanopolymer, which has excellent potential as a material in many novel applications, especially if it can be produced in large amounts from an inexpensive feedstock. Waste fiber sludge, a residue with little or no value, originates from pulp mills and lignocellulosic biorefineries. A high cellulose and low lignin content contributes to making the fiber sludge suitable for bioconversion, even without a thermochemical pretreatment step. In this study, the possibility to combine production of BC and hydrolytic enzymes from fiber sludge was investigated. The BC was characterized using field-emission scanning electron microscopy and X-ray diffraction analysis, and its mechanical properties were investigated. Results: Bacterial cellulose and enzymes were produced through sequential fermentations with the bacterium Gluconacetobacter xylinus and the filamentous fungus Trichoderma reesei. Fiber sludges from sulfate (SAFS) and sulfite (SIFS) processes were hydrolyzed enzymatically without prior thermochemical pretreatment and the resulting hydrolysates were used for BC production. The highest volumetric yields of BC from SAFS and SIFS were 11 and 10 g/L (DW), respectively. The BC yield on initial sugar in hydrolysate-based medium reached 0.3 g/g after seven days of cultivation. The tensile strength of wet BC from hydrolysate medium was about 0.04 MPa compared to about 0.03 MPa for BC from a glucose-based reference medium, while the crystallinity was slightly lower for BC from hydrolysate cultures. The spent hydrolysates were used for production of cellulase with T. reesei. The cellulase activity (CMCase activity) in spent SAFS and SIFS hydrolysates reached 5.2 U/mL (87 nkat/mL), which was similar to the activity level obtained in a reference medium containing equal amounts of reducing sugar. Conclusions: It was shown that waste fiber sludge is a suitable raw material for production of bacterial cellulose and enzymes through sequential fermentation. The concept studied offers efficient utilization of the various components in fiber sludge hydrolysates and affords a possibility to combine production of two high value-added products using residual streams from pulp mills and biorefineries. Cellulase produced in this manner could tentatively be used to hydrolyze fresh fiber sludge to obtain medium suitable for production of BC in the same biorefinery. [ABSTRACT FROM AUTHOR]

A nanocellulose-gelatin (bacterial cellulose gelatin (BCG)) film was developed by a supplement of gelatin, at a concentration of 1%-10% w/v, in a coconut-water medium under the static cultivation of Acetobacter xylinum. The two polymers exhibited a certain degree of miscibility. The BCG film displayed dense and uniform homogeneous structures. The Fourier transform infrared spectroscopy (FTIR) results demonstrated interactions between the cellulose and gelatin. Incorporation of gelatin into a cellulose nanofiber network resulted in significantly improved optical transparency and water absorption capacity of the films. A significant drop in the mechanical strengths and a decrease in the porosity of the film were observed when the supplement of gelatin was more than 3% (w/v). The BCG films showed no cytotoxicity against Vero cells. [ABSTRACT FROM AUTHOR]

Nanofibers and bio-nonwoven fabrics of pure cellulose can be made from some bacteria such asAcetobacter xylinum. Bacterial cellulose fibers are very pure, 10 nm in diameter and about 0.5 micron long. The molecular formula of bacterial cellulose is similar to that of plant cellulose. Its fibers are very stiff and it has high tensile strength, high porosity, and nanofibrillar structure. They can potentially be produced in industrial quantities at greatly lowered cost and water content, and with triple the yield by a new process. This article presents a critical review of the available information on bacterial cellulose as a biological nonwoven fabric with special emphasis on its fermentative production and applications. Characteristics of bacterial cellulose biofabric with respect to its structure and physicochemical properties are discussed. Current and potential applications of bacterial cellulose in textile, nonwoven cloth, paper, films, synthetic fiber coating, food, pharmaceutical, and other industries are also presented. [ABSTRACT FROM PUBLISHER]

Biocellulose (BC), produced by Acetobacter xylinum (0416), was carried out using three types of medium composition under static surface culture. The media used in this experiment included CWHSM (Coconut water in Hestrin-Schramm medium), CM (Complex medium) and HSM (Hestrin-Schramm medium). CWHSM and CM used coconut water from agro-waste as the main source of sugar. The fermentation was conducted for 12 days and the results of BC dry weight, cell entrapped, pH medium and productivity were evaluated and compared. The results show that CWHSM is the most suitable medium for BC production with a productivity of up to 0.044 g 1-1 day-1. [ABSTRACT FROM AUTHOR]

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 I; 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 2 a″ × b″ × 4 c″ 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. [ABSTRACT FROM AUTHOR]

Bacterial cellulose is a polymer obtained by fermentation with microorganisms from Acetobacter, Rhizobium, Agrobacterium and Sarcina genera. Among them, Acetobacter xylinum is the most efficient specie. This polymer has the same chemical composition of plant cellulose, but its conformation and physicochemical properties are different, making it attractive for several applications, especially in the areas of food, separation processes, catalysis and health, due to its biocompatibility. However, the main problem is the production in mass that is constrained by low yield. It is therefore necessary to develop some alternatives. This paper presents a review about synthesis, production, properties and principal applications of bacterial cellulose, as well as some alternatives to reduce the difficulties for process scaling. [ABSTRACT FROM AUTHOR]

The structure and crystallization of carefully isolated sub-elementary fibrils (SEFs) of bacterial cellulose have been investigated using TEM, WAXD, and high-resolution solid-state C NMR. The addition of a suitable amount of fluorescent brightener (FB) to the incubation medium of Acetobacter xylinum effectively suppressed the aggregation of the SEFs into the microfibrils, as previously reported. However, this study confirmed for the first time that serious structural change in the SEFs occurs during the removal of excess FB by washing with buffer solutions having pH values higher than 6 or with the alkaline aqueous solution that was frequently used in previous studies. In contrast, the isolation of unmodified SEFs was successfully performed by utilizing a washing protocol employing pH 7 citrate-phosphate buffer solution containing 1% sodium dodecyl sulfate. High-resolution solid-state C NMR and WAXD measurements revealed that the SEFs thus isolated are in the noncrystalline state in which the pyranose rings of the almost parallel cellulose chains appear to be stacked on each other. The respective CHOH groups of the SEFs adopt the gt conformation instead of the tg conformation found in cellulose I and I crystals, and undergo significantly enhanced molecular motion in the absence of intermolecular hydrogen bonding associated with these groups. The main chains are also subject to rapid motional fluctuations while maintaining the parallel orientation of the respective chains, indicating that the SEFs have a liquid crystal-like structure with high molecular mobility. Moreover, the SEFs crystallize into cellulose I when the FB molecules that may adhere to the surface of the SEFs are removed by extraction with boiling 70 v/v% ethanol and 0.1N NaOH aqueous solution. On the basis of these results, the crystallization of the SEFs into the I and I forms is discussed, including the possible formation of the crystalline-noncrystalline periodic structure in native cellulose. [ABSTRACT FROM AUTHOR]

A single sugar α-linked glucuronic acid based oligosaccharide (SSGO) is water soluble oligosaccharides (WSOS) obtained by Gluconacetobacter hansenii PJK (KCTC 10505BP) as a byproduct during bacterial cellulose (BC) production. In this study, SSGO was used for the improvement of BC production by the vinegar bacterium, Acetobacter xylinum, which produces heteropolysaccharides as a byproduct. The addition of 1.0% SSGO to the chemically defined medium (CDM) resulted in an 89.3% increase in BC production by A. xylinum after 15 days of cultivation under static condition, and a 52.3% increase in BC production by G. hansenii. Both the dry cell weight and live cell density of A. xylinum increased 50% with the addition of 1.0% SSGO. SSGO successfully improved BC production by A. xylinum. [ABSTRACT FROM AUTHOR]

Abstract: The physical parameters of cellulose such as surface area and porosity are important in the development of cellulose composites which may contain valuable additives which bind to cellulose. In this area, the use of acid hydrolyzed nano-dimensional cellulose nanowhiskers (CNWs) has attracted significant interest, yet the surface area and porosity of these materials have not been explored experimentally. The objective of this work was to characterize the surface area and porosity of CNWs from different origins (plant cotton/bacterium Gluconacetobacter xylinus) and different acid treatments (H2SO4/HCl) by N2 adsorption; as well as to compare surface area and porosity of bacterial cellulose synthesized by static and agitated cultures. Our results showed that CNWs produced from H2SO4/HCl exhibited significantly increased surface area and porosity relative to starting material cotton fiber CF11. Micropores were generated in HCl hydrolyzed CNWs but not in H2SO4 hydrolyzed CNWs. Bacterial CNWs exhibited larger surface area and porosity compared to plant CNWs. Cellulose synthesized by G. xylinus ATCC 700178 from agitated cultures also exhibited less surface area and porosity than those from static cultures. [Copyright &y& Elsevier]

Microbial cellulose is a chemically pure form of plant cellulose with an ultrafine reticulated structure. In this study, microbial cellulose was biosynthesized in a static condition by acetobacter xylinium (Gluconacetobacter xylinus) of three different mono- and disaccharides, and its crystallinity structure was investigated and compared with each other and also with the crystalline structure of cellulose existing in cotton and ordinary viscose rayon fibers. According to the results, the cellulose production efficiency of monosaccharide (glucose) was higher than that of disaccharides (lactose and sucrose). The crystalline structures of all biosynthesized cellulose were cell I and their dominant allomorphs were I(alpha), contrary to native cellulose, which was I(beta). The crystallinity amount of microbial cellulose was less than 10-15% of cotton and greater than 9% of viscose. [ABSTRACT FROM PUBLISHER]

In this study, microcrystalline cellulose (MCC) was prepared from the acid hydrolysis of bacterial cellulose (BC) produced in culture medium of static Acetobacter xylinum. The MCC-BC produced an average particle size between 70 and 90 μm and a degree of polymerization ( DP) of 250. The characterization of samples was performed by thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy (SEM). The MCC shows a lower thermal stability than the pristine cellulose, which was expected due to the decrease in the DP during the hydrolysis process. In addition, from X-ray diffractograms, we observed a change in the crystalline structure. The images of SEM for the BC and MCC show clear differences with modifications of BC fiber structure and production of particles with characteristics similar to commercial MCC. [ABSTRACT FROM AUTHOR]

By analyzing with X-ray diffraction and FT-IR spectroscopy, the main effective factors among common culture conditions on crystallinity index and I fraction of cellulose produced by Gluconacetobacter xylinus were examined with Plackett-Burman design experiment. Varying pH value in the medium by adjusting the composition of citrate buffer or by adding HCl/NaOH solution indicates it is the content of citrate buffer rather than its function of pH buffering that gives the influence on crystallinity. Further experiment reveals that Na concentration of 0.174 mol/l in medium with citrate buffer added would decrease the crystallinity index significantly. Comparison of carbon sources shows that fructose leads to a higher crystallinity index than glucose, which suggests a relationship between crystallinity and production speed of bacterial cellulose affected by carbon sources. An interesting phenomenon was that a longer period of cultivation would decrease the crystallinity of bacterial cellulose. The reason is assumed to be the dense network of cellulose formed by bacterial cells that restrict the motion of themselves as the incubation period extends. Though the effect of inoculum age is still unclear, the influence on crystallinity of bacterial cellulose caused by variation of some ordinary culture conditions can be drawn out from data of this work. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, spherical Fe3O4/bacterial cellulose (BC) nanocomposites as adsorbents for heavy metal ions were biosynthesized from Gluconacetobacter xylinum by agitation fermentation. A pH controlling embedding method as a new approach was applied to biosynthesize spherical Fe3O4/BC nanocomposites. Scanning electron microscopy (SEM) images indicated that the Fe3O4 nanoparticles were enwrapped homogeneously in the spherical BC. The spherical Fe3O4/BC nanocomposites with 33wt% ferrous loading had 41emu/g of the saturated magnetization (σ s) and 27Oe of the related coercivity. The adsorption and elution capacities of the spheres for Pb2+, Mn2+, and Cr3+ were evaluated. The results indicated that the spherical Fe3O4/BC nanocomposites had high adsorption capacities and were recyclable after the elution of heavy metal ions. Compared with conventional preparation procedure for cellulose spheres, spherical Fe3O4/BC nanocomposites can be readily prepared without sophisticated steps and have high adsorption and elution capacities. [Copyright &y& Elsevier]

Abstract: Bacterial cellulose (BC) is a natural hydrogel, which is produced by Acetobacter xylinum (recently renamed Gluconacetobacter xylinum) in culture and constitutes of a three-dimensional network of ribbon-shaped bundles of cellulose microfibrils. Here, a two-step purification process is presented that significantly improves the structural, mechanical, thermal and morphological behaviour of BC sheet processed from these hydrogels produced in static culture. Alkalisation of BC using a single-step treatment of 2.5wt.% NaOH solution produced a twofold increase in Young’s modulus of processed BC sheet over untreated BC sheet. Further enhancements are achieved after a second treatment with 2.5wt.% NaOCl (bleaching). These treatments were carefully designed in order to prevent any polymorphic crystal transformation from cellulose I to cellulose II, which can be detrimental for the mechanical properties. Scanning electron microscopy and thermogravimetric analysis reveals that with increasing chemical treatment, morphological and thermal stability of the processed films are also improved. [Copyright &y& Elsevier]

To improve the yield of cellulose production in bacteria, we investigated the stimulatory effects of six different alcohols during fermentation of Acetobacter xylinum 186. Our study showed that after static fermentation at 30°C for 6 days, bacterial culture with 1.0% (v/v) of methanol added in the medium produced the highest bacterial cellulose (BC) yield at 103.5 mg/100 ml, which was 21.8% higher than the control group. Addition of 0.5% of ethylene glycol in the culture yielded 105.5 mg/100 ml BC, 24.1% higher than the control group. Adding 0.5% of n-propanol yielded 96.4 mg/100 ml BC, 13.4% higher; 3.0% of glycerol yielded 108.3 mg/100 ml BC, 27.4% higher; 0.5% of n-butanol yielded 132.6 mg/100 ml BC, 56.0% higher; and 4.0% of mannitol in the culture yielded 125.2 mg/100 ml BC, 47.3% higher, respectively. The rate of bacterial cellulose production increased with the growth rate of the bacteria. The stimulatory effects of these alcohols that we observed were significant in the later stage of fermentation, which was considered to be important for the biosynthesis of bacterial cellulose. [ABSTRACT FROM AUTHOR]

Background: Bacterial cellulose synthesized by acetobacter xylinum is a harmless microbial product with unique characteristics as an ideal dress that many studies have been done on. The aim of this study was to consider the capability of this product in absorption and release of tetracycline hydrochloride. Indication of this capability can pave the way for supplying a new dressing containing antibiotic from bacterial cellulose. Materials and Methods: In this experimental study, cellulose sheet was initially impregnated on aqueous solution of tetracycline hydrochloride. Then the release process was considered in diluted water and normal saline. Ultra violet spectrophotometry method was applied to the detection of the antibiotic during absorption and release processes. Results: The results of data analysis demonstrated that bacterial cellulose has a great potential in absorption of tetracycline hydrochloride and can release it in a wet environment. Conclusion: Considering the advantages of bacterial cellulose over traditional dressings, the results of this study can provide the ground for further research on supplying an ideal dressing containing antibiotic from this microbial product. [ABSTRACT FROM AUTHOR]

Bacterial cellulose (BC) is a unique and promising material for use as implants and scaffolds in tissue engineering. It is composed of a pure cellulose nanofiber mesh spun by bacteria. It is remarkable for its strength and its ability to be engineered structurally and chemically at nano-, micro-, and macroscales. Its high water content and purity make the material biocompatible for multiple medical applications. Its biocompatibility, mechanical strength, chemical and morphologic controllability make it a natural choice for use in the body in biomedical devices with broader application than has yet been utilized. This paper reviews the current state of understanding of bacterial cellulose, known methods for controlling its physical and chemical structure (e.g., porosity, fiber alignment, etc.), biomedical applications for which it is currently being used, or investigated for use, challenges yet to be overcome, and future possibilities for BC. [ABSTRACT FROM AUTHOR]

Cellulose and sugar from microalgae can be utilized for the production of biofuel ethanol. Increasing cellulose and sugar synthesis capacity is key for high yield production of this biofuel. To enhance cellulose production, we transferred acsAB, responsible for cellulose synthesis in bacterium Acetobacter xylinum, into the cyanobacterium, Anabaena sp. strain PCC7120, by conjugation. PCR confirmed the presence of acsAB in Anabaena sp. strain PCC7120 exconjugates. RT-PCR demonstrated the up-regulation of acsAB expression. Production of extracellular cellulose secreted from Anabaena sp. strain PCC7120 carrying acsAB was revealed using Calcofluor white staining and cellobiohydrolase I (CBHI)-FITC labeling. Further evidence obtained from the digestion of cellulose to glucose demonstrated that the amount of glucose released from cellulose was significantly increased in Anabaena sp. PCC7120 cells carrying acsAB as compared to the wild type. The photosynthetic efficiency and growth rate were increased in the transgenic strains. Cellulose synthesis is thus enhanced in Anabaena sp. strain PCC7120 expressing acsAB and does not negatively impact photosynthesis and growth. [ABSTRACT FROM AUTHOR]

Nata is white gelatinous bacterial cellulose produced by Acetobacter aceti ssp . xylinum through fermentation of coconut water. Drying behaviour of nata de coco was conducted with a hot air dryer for a temperature range of 50-90 °C. The experimental data obtained were fitted into seven empirical and/or semi-theoretical thin-layer drying models using nonlinear regression analysis. Results showed that Logarithmic model, Wang and Singh model fitted better than Verma et al. model although all these three models were suitable for predicting the drying process of nata de coco. The rehydration capacity was lost severely when the moisture content of the samples was nearly zero, but it can almost rehydrate to its initial state when the moisture content was above 8%. The drying kinetic properties and rehydration capacity of nata de coco indicated that most of the moisture in nata de coco was free water. [ABSTRACT FROM AUTHOR]

The novel bacterial cellulose (BC)/collagen composites were prepared by immersing wet BC pellicle excreted by Acetobacter xylinum in collagen solution followed by freeze-drying process. The product looks like a foam structure. The morphology of BC/collagen composite was examined by scanning electron microscope (SEM) and compared with pristine BC. SEM images showed that collagen molecules was not only coated on the BC fibrils surface but also could penetrate inside BC and hydrogen bond interactions were formed between BC and collagen. The prepared BC/collagen composite was also characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and mechanical test. With the incorporation of collagen in the BC, no changes happened in the crystal structure but the thermal stability was improved. Tensile test results indicate that the Young's Modulus and tensile strength have a big increase while the elongation at break has a slight decrease. The cytocompatibility of composite was preliminarily evaluated by cell adhesion studies. The tests were carried out using 3T3 fibroblast cells. The cells incubated with BC/collagen scaffolds for 48 h were capable of forming cell adhesion and proliferation. It showed much better cytocompatibility than pure BC. So, the prepared BC/collagen scaffolds are bioactive and may be suitable for cell adhesion/attachment suggesting that these scaffolds can be used for wound dressing or tissue-engineering scaffolds. Therefore, these results suggest that these novel BC/collagen scaffolds may have the potential to be sued for some biomedical applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

biological method is demonstrated to fabricate the polymer-inorganic nanocomposites (PINCs) utilizing bacterium as an efficient and versatile biofactory. Gluconacetobacter xylinum that can produce bacterial cellulose is incubated in the culture medium containing titanium or silica precursor. The PINCs can be acquired under the elaborate control of the culturing condition of G. xylinum, in which the formation of inorganic nanoparticles about several tens of nanometers in size synchronizes the fabrication of reticulated bacterial cellulose membrane composed of dense and finely branched nanofibers about 60-120 nm in diameter. The composition and chemical states, morphology, thermal stability of the inorganic nanoparticles, and nanocomposites were extensively characterized. A tentative mechanism for the formation of PINCs is proposed. It is hoped that this study may establish a generic platform toward facile and green synthesis of nanocomposite materials. [ABSTRACT FROM AUTHOR]

Abstract: Bacterial cellulose production by Acetobacter xylinum BPR 2001 was optimized using maple syrup as a carbon source. Twelve culture parameters were screened by the Plackett–Burman design and significant parameters were optimized by the response surface methodology using a three-level, four-factor Box–Behnken design. For fermentation in a rotary shaker, the optimal conditions for bacterial cellulose production were: maple syrup 30gcarbohydrate/l, (NH4)2SO4 3.3g/l, KH2PO4 1g/l, yeast extract 20g/l, citric acid 1.6g/l, trisodium citrate dehydrate 2.4g/l, ethanol 0.5% (v/v), acetic acid 0.5g/l, MgSO4·7H2O 0.8g/l, inoculum age 3 days, inoculum volume 6% (v/v), shaking speed 135rpm, and incubation temperature 25°C. Comparison of bacterial cellulose production with maple syrup or pure sugars showed maple syrup was a suitable carbon source. This was the first demonstration of conversion of maple syrup, a plentiful renewable resource, into bacterial cellulose, a nanobiomaterial ideal for many applications. [Copyright &y& Elsevier]

Metabolic pathways for amino sugars (N-acetylglucosamine; GlcNAc and glucosamine; Gln) are essential and remain largely conserved in all three kingdoms of life, i.e., microbes, plants and animals. Upon uptake, in the cytoplasm these amino sugars undergo phosphorylation by phosphokinases and subsequently deacetylation by the enzyme N-acetylglucosamine 6- phosphate deacetylase (nagA) to yield glucosamine-6-phosphate and acetate, the first committed step for both GlcNAc assimilation and amino-sugar-nucleotides biosynthesis. Here we report the cloning of a DNA fragment encoding a partial nagA gene and its implications with regard to amino sugar metabolism in the cellulose producing bacterium Glucoacetobacter xylinus (formally known as Acetobacter xylinum). For this purpose, nagA was disrupted by inserting tetracycline resistant gene (nagA::tetr; named as ΔnagA) via homologous recombination. When compared to glucose fed conditions, the UDP-GlcNAc synthesis and bacterial growth (due to lack of GlcNAc utilization) was completely inhibited in nagA mutants. Interestingly, that inhibition occurred without compromising cellulose production efficiency and its molecular composition under GlcNAc fed conditions. We conclude that nagA plays an essential role for GlcNAc assimilation by G. xylinus thus is required for the growth and survival for the bacterium in presence of GlcNAc as carbon source. Additionally, G. xylinus appears to possess the same molecular machinery for UDP-GlcNAc biosynthesis from GlcNAc precursors as other related bacterial species. [ABSTRACT FROM AUTHOR]

Abstract: A new preparation method of microcrystalline cellulose from Gluconacetobacter xylinus (BC) and kenaf (KF) is reported. The developed cellulose (DBC and DKF) materials showed different crystalline structures. DBC exhibited cellulose I lattice with high crystallinity (85%) whereas DKF showed cellulose II lattice with high crystalinity (70%). The particle size of DKF was 5–20μm while that of DBC was 1–5μm. The physical properties of the DBC and DKF materials were compared with those of the commercially available microcrystalline cellulose Avicel®PH 101. DBC exhibited lower value of the loose density than those of DKF and Avicel PH 101. Both microcrystalline DBC and Avicel PH 101 demonstrated similar behavior during flow and binding processes. The thermal properties of DBC and DKF materials were investigated by thermogravimetric analysis. The TGA results reveal increased thermal stability for DBC compared to DKF. Moreover, the weight loss of DBC occurred in one step degradation process from about 320°C to 380°C, which is mainly due to the decomposition of cellulose. [Copyright &y& Elsevier]

Bacterial cellulose (BC) synthesized from Acetobacter xylinum has drawn lots of attention and interest from biomedical device field due to its unique structure and properties. Characterized by its remarkable physical strength and extremely hydrophilic surface, BC has become a favorable material for wound healing, neuron protection, and vascular grafts. Moreover, due to its homologous structure with native extracellular matrix, BC nanofibrous matrix could also be a potent candidate for tissue-engineered scaffolding materials. In this review, the characters and properties of BC, as a promising material for regenerative medicine, are summarized. The progresses made on application of BC to wound dressing, vascular grafts, meniscus and cartilage repair, bone healing, and other biomedical fields are expatiated in details. In the end, the future expectation of BC is briefly discussed. Overall, this low cost, biocompatible, and versatile nanomaterial could eventually be developed as an excellent platform for a new generation of medical device and regenerative medicine. [ABSTRACT FROM AUTHOR]

Bacterial cellulose (BC) can be grown into any desired shape such as pellicles, pellets, and spherelike balls, depending on the cultivation method, additives, and cell population. In this study, Acetobacter xylinum(ATCC 700178) was grown in the production medium with different concentrations of carboxylmethylcellulose (CMC) and were evaluated for BC production by using a PCS biofilm reactor. The results demonstrated that BC production was enhanced to its maximum (∼13 g/L) when 1.5% of CMC was applied, which was 1.7-fold higher than the result obtained from control culture. The major type of the produced BC was also switched from BC pellicle to small pellets. The ratio of BC pellets in suspension increased from 0 to 93%. Fourier transform infrared (FTIR) spectroscopy demonstrated that CMC was incorporated into BC during fermentation and resulted in the decreased crystallinity and crystal size. The X-ray diffraction (XRD) patterns indicated that CMC-BC exhibited both lower crystallinity (80%) and crystal size (4.2 nm) when compared with control samples (86% and 5.3 nm). The harvested BC was subjected to paper formation and its mechanical strength was determined. Dynamic mechanical analysis (DMA) results demonstrated that BC paper sheets exhibited higher tensile strength and Young’s modulus when compared with regular paper. [ABSTRACT FROM AUTHOR]

Introduction: The present work aimed to assess the effect of bacterial cellulose (BC) from Acetobacter xylinum on some functions of peritoneal macrophages. Materials and methods: Mice peritoneal macrophages were lavaged and co-cultured with various concentrations of BC in microtiter plate. Viability of macrophages was determined by MTT assay. Nitric oxide (NO) amount was detected in culture supernatants of macrophages by Griess reagent and cytotoxicity effect of culture supernatants on WEHI-164 cells as tumor necrosis factor αα (TNF-αα) bioassay were done. Results: MTT assay for stimulated macrophages was not different ( p == 0.486) and amount of NO production in all doses was the same as unstimulated control macrophages ( p == 0.057). Supernatant of macrophages stimulated with 0.01 mg/mL of BC had cytotoxic effect on WEHI-164 fibrosarcoma cells ( p == 0.040). Conclusion: In this study, we showed that BC had no effect on macrophages viability and amount of NO production. BC suppressed the release of TNF-αα from macrophages innate immune cells as indication of beneficial effect on wound healing. This data and further studies would imply use of this biomaterial for more applications. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the feasibility of using a microbial biopolymer produced by Acetobacter xylinum as a carbon source for heterotrophic biological denitrification. The denitrification rate, COD availability and nitrite concentration were response parameters. Under the experimental conditions, a denitrification rate of about 0.74 kg NON/md at 6 h retention time was achieved with microbial cellulose (MC). The reactor effluent contained significantly COD concentrations (20-86 mg/L) so it was not carbon limited, and was receiving enough carbon to facilitate the denitrification process. The maximum nitrite concentration in the effluent was found to be 0.4 mg/L. However, decreasing the retention time to 3 h significantly reduced the efficiency. It can be concluded that the MC is a suitable carbon source for nitrate removal in a heterotrophic biological denitrification process. [ABSTRACT FROM AUTHOR]

Abstract: Bacterial cellulose microfibrils from non-conventional sources were produced by Gluconacetobacter swingsii sp. Agroindustrial residues such as pineapple peel juice and sugar cane juice were used as culture media. Hestrin and Schramm''s medium was used as a reference. The production of bacterial cellulose from pineapple peel juice (2.8g/L) was higher than that produced from Hestrin and Schramm''s medium (2.1g/L). The carbon and nitrogen resources in pineapple peel and sugar cane juice were sufficient for the microorganism development. Ribbon-like microfibrils with a width of 20–70nm were observed in all media. Changes in crystallinity and mass fraction of the Iα allomorph were observed. The aggregation of cellulose chains into microfibrils was slightly hindered by other polysaccharides in the agroindustrial waste that adhered to the surface of the subfibrils. In conclusion, agroindustrial residues can be used as a culture medium to produce bacterial cellulose with low cost for large-scale industrial production. [Copyright &y& Elsevier]

Heterotrophic nitrification-aerobic denitrifier bacteria were used to treat domestic sewage in this study, and the removal rate of NH4+-N was 68.85% within 5 days. Different bacterial cellulose membrane adsorption methods were used to immobilize strains to treat domestic sewage, which indicated that dynamic adsorption method of bacterial cellulose membrane was relatively stable in the course of sewage treatment. After 6 days, the removal rate of total nitrogen was up to 86.66%. In the sequencing batch bioreactor, the removal rates of total nitrogen, NH4+-N and CODcr can reach 80%. In the continuous bioreactor, the removal rates of total nitrogen and NH4+-N were up to 50%, and that of CODcr could reach about 70%. Bacterial cellulose membrane used to immobilize heterotrophic nitrification- aerobic denitrifier bacteria was hardly degraded, and has a great application prospect in the treatment of domestic sewage. [ABSTRACT FROM AUTHOR]

A bacterium capable of producing a deep blue pigment was isolated from the environment and identified as Pantoea agglomerans. The pigment production characteristics of the bacterium under various conditions were studied. The optimal agar plate ingredients for pigment production by the bacterium were first studied: the optimal ingredients were 5 g/liter glucose, 10 g/liter tryptic soy broth, and 40 g/liter glycerol at pH 6.4. Bacterial cells grew on the agar plate during the incubation, while the pigment spread into the agar plate, meaning that it is water soluble. Pigment production was affected by the initial cell density. Namely, at higher initial cell densities ranging from 106.3 to 108.2 CFU/cm² on the agar plate, faster pigment production was observed, but no blue pigment was produced at a very high initial density of 109.1 CFU/cm². Thus, the cell population of 108.2 CFU/cm² was used for subsequent study. Although the bacterium was capable of growing at temperatures above and below 10°C, it could produce the pigment only at temperatures of =10°C. Moreover, the pigment production was faster at higher temperatures in the range of 10 to 20°C. Pigment production at various temperature patterns was well described by a new logistic model. These results suggested that the bacterium could be used in the development of a microbial temperature indicator for the low-temperature-storage management of foods and clinical materials. To our knowledge, there is no other P. agglomerans strain capable of producing a blue pigment and the pigment is a new one of microbial origin. [ABSTRACT FROM AUTHOR]

Abstract: Nanocellulose (bacterial cellulose, BC), such as that produced by Acetobacter xylinum, has shown promising results as a replacement material for small diameter vascular grafts. The surface morphology of the lumen and mechanical properties of such tubes are crucial for their performance. The growth of a BC tube in a vertical fermentation bioreactor using silicone tubing for support and as an oxygen delivery membrane has not been studied in detail previously. Oxygen concentration and the number of bacteria added influence the production of the BC tubes. A dense and smooth luminal surface was formed after 4days on a 3mm silicone support. The bacteria were found to be in high concentration close to the silicon support and decreased in number further away. In the region with a high bacteria concentration, dense thin layers of BC were formed since the bacteria moved close together in this region. The presented observations were summarized in a theoretical model of BC tube growth. [ABSTRACT FROM AUTHOR]

Background: Due to problems caused by traditional dressings, scientists have long been in search for producing alternative cellulose. Unique characteristics of bacterial cellulose synthesized by acetobacter xylinum, due to its nanostructure cellulose, resulted in attempts to devise an ideal dressing with this cellulose. The main aim of this study is to evaluate the effect of impregnated bacterial cellulose on staphylococcus aureus culture. Materials and Methods: In this descriptive-analytical study, cellulose disks synthesized by bacterial cellulose and cellulose blank disks (without antibiotic) were placed in 3.3% ciprofloxacin hydrochloride. These disks were, then, together with ciprofloxacin standard, control cellulose, and cellulose blank disks, placed on the cultured media of staphylococcus aureus. After 24 hours, the results were obtained through the measurement of growth inhibition zone. Determining the amount of antibiotic absorbed into bacterial cellulose can be done through the comparison of the effects of cellulose disks containing different concentrations of ciprofloxacin hydrochloride and ciprofloxacin standard disks. Results: Both cellulose and blank disks created a growth inhibition zone in staphylococcus aureus media, whereas the growth inhibition zone of cellulose and cellulose blank disks (negative control) were insignificant. Conclusion: Noticing the unique characteristics of bacterial cellulose as a dressing and its proven ability in absorption and release of ciprofloxacin hydrochloride, the prospects are seen for production of antibiotics containing dressings of this microbial product in future. [ABSTRACT FROM AUTHOR]