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This work investigated the suitability of using date syrup for producing bacterial cellulose (BC) by Gluconacetobacter xylinus (PTCC 1734). In the preliminary study, BC was produced in Hesterin-Schramm (HS) medium. The highest production yield was achieved after 12 days of cultivation at the initial pH of 8. Considering this result, BC was produced in modified HS media containing date syrup. In the modified HS1 (MHS1) medium, glucose was omitted, and in the modified HS2 (MHS2) medium, neither glucose nor peptone was present. Interestingly, the production yield in the modified media was about 75% higher than the production using HS medium. The amounts of BC produced using MHS1 and MHS2 media were obtained as 5.03 gL-1 and 5.17 gL-1, respectively. Structure analysis of these specimens indicated long fibrils, with diameters less than 70 nm. However, the crystallinity index of BC obtained from MHS1 media, containing peptone, was higher than that of BS produced in MHS2. [ABSTRACT FROM AUTHOR]

Microbial-assisted synthesis can advance nanocellulose production, while addressing the economics and environmental friendliness of conventional techniques. Bacterial nanocellulose (BNC) is a linear exopolysaccharide with 3-D structures and nanofibril networks synthesized by various bacteria. The physical, chemical and mechanical properties of BNC have been characterized for various applications. However, limited knowledge of the thermal degradation and kinetic properties of BNC currently hampers its utilization as renewable biopolymers as heat, temperature, and heating rates influence life span and future applications. Therefore, this study examines the thermal, chemical, morphological, microstructure, and kinetic properties of Gluconacetobacter xylinus synthesized BNC through thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and isoconversional Ozawa–Flynn–Wall (OFW) kinetic modeling. The SEM results showed that BNC has a highly dense fibril structure with overlapping knots, which denotes a high surface area, porosity and crystallinity, whereas EDX revealed C, O, and Na. TGA revealed BNC undergoes three-stage thermal degradation with mass loss of 53.57% and residual mass of 46.43% on average. Kinetic modeling revealed the average activation energy (Ea = 59.39 kJ/mol) and pre-exponential factor (ko = 1.62 × 1010 min−1) for BNC indicating high thermal reactivity. Thus, G. xylinus- synthesized BNC has potential for many applications in the future. [ABSTRACT FROM AUTHOR]

Quorum sensing is a mechanism that facilitates cell-to-cell communication. Through signal molecular density for signal recognition, which leads to the regulation of some physiological and biochemical functions. Gluconacetobacter xylinus CGMCC 2955, which produces bacterial cellulose (BC), synthesizes the LuxR protein belonging to the LuxI/LuxR type QS system. Here, a luxR overexpression vector was transformed into G. xylinus CGMCC 2955. The overexpression of luxR increased the yield of BC by 15.6% after 16 days static culture and reduced the cell density by 15.5% after 120-h-agitated culture. The glucose was used up by G. xylinus-pMV24-luxR at 72-h-agitated fermentation, which 12 h earlier than the wild-type (WT). The total N-acylhomoserine lactones (AHL) content of the luxR-overexpressing strain and the WT strain attained 1367.9 ± 57.86 mg/L and 842.9 ± 54.22 mg/L, respectively. The C12-HSL and C14-HSL contents of G. xylinus-pMV24-luxR were 202 ± 21.66 mg/L and 409.6 ± 0.91 mg/L, which were significantly lower than that of WT. In contrast, C6-HSL showed opposite results. The difference of AHL content proved that overexpression of luxR improved the binding of AHL and showed preference for some specific AHL. The metabolic results demonstrated that upon glucose exhaustion, the consumption of gluconic acid was promoted by luxR overexpression, and the content of D- (+)-trehalose, an antiretrograde metabolite, increased significantly. Key points: • The overexpression of luxR increased the yield of bacterial cellulose • The content of signal molecules was significantly different • Differential metabolites were involved in multiple metabolic pathways [ABSTRACT FROM AUTHOR]

Although the unique nanostructure of bacterial cellulose (BC) imparts superior mechanochemical properties and thus allows for diverse applications, the high production cost of BC necessitates the development of more cost‐effective solutions, for example, those using lignocellulosic biomass as a substrate and relying on its pretreatment and saccharification to generate fermentable sugars. However, the various species (e.g., aliphatic acids, furans, and phenolics) produced during pretreatment may interfere with bacterial cell growth and BC production. Herein, we investigated the effects of aliphatic (acetic and formic) acids, furans (5‐hydroxymethylfurfural [5‐HMF] and furfural), and phenolics (syringaldehyde and p‐coumaric acid) on the production of BC. This production was enhanced at low aliphatic acid concentrations (1 g/L acetic acid and 0.5 g/L formic acid) but was suppressed by at least 90% in cases of 0.75 g/L formic acid, 0.4 g/L furfural, 4 g/L 5‐HMF, 2.5 g/L syringaldehyde, and 2.5 g/L p‐coumaric acid. BC production efficiencies of 97.86%, 76.66%, and 73.50% were observed for Miscanthus, barley straw, and pine tree hydrolysates, respectively, under optimal conditions. Therefore, these results provided the possibility to utilize the most abundant and sustainable lignocellulose on the planet for BC production. [ABSTRACT FROM AUTHOR]

• Polyurethane foam allows bacterial cellulose production in solid state culture. • The highest yield was 2.46 g L-1 with 0.125 cm3 foam and 15% inoculum for 96 h. • Polyurethane foam presents high water storage capacity and oxygen diffusion. • Bacteria synthesize the biopolymer as biofilm adhered to the solid matrix scaffold. The polyurethane foam (PUF) allowed the growth of Gluconacetobacter xylinus for prompt production of bacterial cellulose (BC) due to high water storage capacity that let high water activity, as well as diffusion of oxygen through the PUF pores. PUF was studied in two sizes cut (0.13 cm3) and minced (0.08 cm3). Additionally, the study assessed the level of inoculum on the growth and the formation of BC. The highest yield of BC was 2.46 g L-1 of cellulose achieved with cut foam and 15% inoculum at 96 h. Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD) and solid state 13C cross polarization and magic angle spinning nuclear magnetic resonance (CP/MAS NMR) analyses evidence crystalline structure type I for the produced microbial cellulose. According to scanning electron microscopy (SEM) analysis, the bacteria synthesized the biopolymer as a biofilm adhered to the solid support; thereby BC displays a honeycomb geometry. [ABSTRACT FROM AUTHOR]

Oxygen plays a key role during bacterial cellulose (BC) biosynthesis by Gluconacetobacter xylinus. In this study, the Vitreoscilla hemoglobin (VHb)-encoding gene vgb, which has been widely applied to improve cell survival during hypoxia, was heterologously expressed in G. xylinus via the pBla-VHb-122 plasmid. G. xylinus and G. xylinus-vgb were statically cultured under hypoxic (10 and 15% oxygen tension in the gaseous phase), atmospheric (21%), and oxygen-enriched conditions (40 and 80%) to investigate the effect of oxygen on cell growth and BC production. Irrespective of vgb expression, we found that cell density increased with oxygen tension (10-80%) during the exponential growth phase but plateaued to the same value in the stationary phase. In contrast, BC production was found to significantly increase at lower oxygen tensions. In addition, we found that BC production at oxygen tensions of 10 and 15% was 26.5 and 58.6% higher, respectively, in G. xylinus-vgb than that in G. xylinus. The maximum BC yield and glucose conversion rate, of 4.3 g/L and 184.7 mg/g, respectively, were observed in G. xylinus-vgb at an oxygen tension of 15%. Finally, BC characterization suggested that hypoxic conditions enhance BC's mass density, Young's modulus, and thermostability, with G. xylinus-vgb synthesizing softer BC than G. xylinus under hypoxia as a result of a decreased Young's modulus. These results will facilitate the use of static culture for the production of BC. [ABSTRACT FROM AUTHOR]

Durian is one important tropical fruit with high nutritional value, but its shell is usually useless and considered as waste. To explore the efficient and high-value utilization of this agricultural and food waste, in this study, durian shell was simply hydrolyzed by dilute sulfuric acid, and the durian shell hydrolysate after detoxification was used for bacterial cellulose (BC) production by Gluconacetobacter xylinus for the first time. BC was synthesized in static culture for 10 days and the highest BC yield (2.67 g/L) was obtained at the 8th day. The typical carbon sources in the substrate including glucose, xylose, formic acid, acetic acid, etc. can be utilized by G. xylinus. The highest chemical oxygen demand (COD) removal (16.40%) was obtained at the 8th day. The highest BC yield on COD consumption and the highest BC yield on sugar consumption were 93.51% and 22.98% (w/w), respectively, suggesting this is one efficient bioconversion for BC production. Durian shell hydrolysate showed small influence on the BC structure by comparison with the structure of BC generated in traditional Hestrin-Schramm medium detected by FE-SEM, FTIR, and XRD. Overall, this technology can both solve the issue of waste durian shell and produce valuable bio-polymer (BC). [ABSTRACT FROM AUTHOR]

The main goal of this work was to reinforce softwood pulp (SP) with bacterial cellulose (BC) to generate a sustainable biocomposite. BC is a nanocellulose, which was anticipated to increase interfacial adhesion between the cellulosic fibers and BC. The organism used was Gluconacetobacter xylinus , which was incubated in a static Hestrin-Schramm culture at 28 °C for 14 days. The specimens of BC, SP and the reinforced SP with BC were characterized using X-ray diffraction (XRD), FT-IR, FESEM, and physico-mechanical testing. The crystallinity index was found to be 83 and 54% for BC and SP, respectively. FT-IR spectra showed that the composition of BC was fully different from that of SP fibers. Based on FESEM images, one can conclude that BC and softwood fibers do form a good combination with a nonporous structure. BC fibers fill in among the softwood fibers in the sheet. The physical and mechanical properties showed that as the dosage of BC increased, the properties of tensile index, tear index, and burst index greatly improved, while the porosity and the elongation decreased. The reason for the improved mechanical properties can be attributed to the increase of interfibrillar bonding which reduced porosity. This would be due to the high aspect ratio of BC that is capable of connecting between the cellulosic fibers and BC nanofibers, enhancing a large contact surface and therefore producing excellent coherence. This study suggests that BC could be a promising material for reinforcing composites at low loading. [ABSTRACT FROM AUTHOR]

The aim of the present study was to evaluate the impact of a rotating magnetic field (RMF) on cellular and biochemical properties of Gluconacetobacter xylinus during the process of cellulose synthesis by these bacteria. The application of the RMF during bacterial cellulose (BC) production intensified the biochemical processes in G. xylinus as compared to the RMF-unexposed cultures. Moreover, the RMF had a positive impact on the growth of cellulose-producing bacteria. Furthermore, the application of RMF did not increase the number of mutants unable to produce cellulose. In terms of BC production efficacy, the most favorable properties were found in the setting where RMF generator was switched off for the first 72 h of cultivation and switched on for the further 72 h. The results obtained can be used in subsequent studies concerning the optimization of BC production using different types of magnetic fields including RMF, especially. [ABSTRACT FROM AUTHOR]

Cellulosic nanomaterials provide a novel and sustainable platform for the production of high performance materials enabled by nanotechnology. Bacterial cellulose (BC) is a highly crystalline material and contains pure cellulose without lignin and hemicellulose. BC offers an opportunity to provide control of the products’ propertiesin-situ, via specific BC production methods and culture conditions. The BC potential in advanced material applications are hindered by a limited knowledge of optimal BC production conditions, efficient process scale-up, separation methods, and purification methods. There is a growing body of work on the production of bacterial cellulose nanocrystals (BCNs) from BC fibers. However, there is limited information regarding the effect of BC fibers’ characteristics on the production of nanocrystals. This review describes developments in BC and BCNs production methods and factors affecting their yield and physical characteristics. [ABSTRACT FROM PUBLISHER]

Bacterial cellulose (BC), a natural polymer synthesized by bacteria, has received considerable attention owing to its impressive physicomechanical properties. However, the low productivity of BC-producing strains poses a challenge to industrializing this material and making it economically viable. In the present study, UV-induced random mutagenesis of Gluconacetobacter xylinus ATCC 53524 was performed to improve BC production. Sixty mutants were obtained from the following mutagenesis procedure: the correlation between UVC fluence and cell death was investigated, and a limited viability condition was determined as a UVC dose to kill 99.99 %. Compared to the control strain, BC production by the mutant strains LYP25 and LYP23 improved 46.4 % and 44.9 %, respectively. Fermentation profiling using the selected strains showed that LYP25 was superior in glucose consumption and BC production, 13.8 % and 41.0 %, respectively, compared to the control strain. Finally, the physicochemical properties of LYP25-derived BC were similar to those of the control strain; thus, the mutant strain is expected to be a promising producer of BC in the bio-industry based on improved productivity. [Display omitted] [ABSTRACT FROM AUTHOR]

The aim of the study was to analyze the changes in the parameters of bacterial cultures and bacterial cellulose (BC) synthesized by four reference strains of Gluconacetobacter xylinus during 31-day cultivation in stationary conditions. The study showed that the most visible changes in the analyzed parameters of BC, regardless of the bacterial strain used for their synthesis, were observed in the fi rst 10-14 days of the experiment. It was also revealed, that among parameters showing dependence associated with the particular bacterial strain were the rate and period of BC synthesis, the growth rate of bacteria anchored to the cellulose fi brils, the capacity to absorb water and the water release rate. The results presented in this work may be useful in the selection of optimum culturing conditions and period from the point of view of good effi ciency of the cellulose synthesis process. [ABSTRACT FROM AUTHOR]

Cellulose is one of the most abundant biological polymers on Earth, and is synthesized by the cellulose synthase complex in cell membranes. Although many cellulose synthase genes have been identified over the past 25 years, functional studies of cellulose synthase using recombinant proteins have rarely been conducted. In this study, we conducted a functional analysis of cellulose synthase with site-directed mutagenesis, by using recombinant cellulose synthase reconstituted in living Escherichia coli cells that we recently constructed (cellulose-synthesizing E. coli , CESEC). We demonstrated that inactivating mutations at an important amino acid residue reduced cellulose production. In this study, an interesting loss-of-function mutation occurred on Cys308, whose main chain carbonyl plays an important role for locating the cellulose terminus. Mutating this cysteine to serine, thus changing sulfur to oxygen in the side chain, abolished cellulose production in addition to other apparent detrimental mutations. This unexpected result highlights that the thiol side-chain of this cysteine plays an active role in catalysis, and additional mutation experiments indicated that the sulfur–arene interaction around Cys308 is a key in cellulose-synthesizing activity. Data obtained by CESEC shed light on the function of cellulose synthase in living cells, and will deepen our understanding of the mechanism of cellulose synthase. [ABSTRACT FROM AUTHOR]

Aims A high-quality inoculum of Gluconacetobacter xylinus is important to produce bacterial cellulose ( BC), a versatile biomaterial. This work aims to develop a method of preparing an inoculum of this bacterium with high cell density and without mutants. Methods and Results Inocula of G. xylinus ACCC 10220 without and with cellulase or carboxymethyl cellulose ( CMC) were prepared in shaken culture. BC pellets and BC-negative mutants were present in the inoculum without additives but absent in the inoculum with additives. Based on BC weights statically produced in fresh BC-producing media initiated by different seed culture, the 24-h-shaken inoculum with 1·50% (w/v) CMC was the best because of high biomass and absence of mutants. The BC weights in fresh media inoculated by the 96-h-static inoculum and 24-h-shaken CMC inoculum at 7% (v/v) were 0·70 and 1·05 g l−1, respectively, implying significant difference ( P < 0·01) in BC weights. However, structure properties of the two BC samples, including the crystallinity index, mass fraction of cellulose I α, degree of polymerization (DP) and micromorphology were slightly different. Conclusions The 24-h-shaken CMC inoculum was the most suitable for a starter culture of BC. Significance and Impact of the Study A novel method of preparing G. xylinus inoculum in shaken culture was developed, featuring high biomass, absence of mutants and no BC entanglements. Cellulase or CMC added into the medium completely suppressed mutation of G. xylinus, and CMC facilitated to form colloidal BC with the low DP in shaken culture, indicating less BC stress to cells. These findings suggested the mutation could be induced by BC stress, and not by shear stress commonly accepted. [ABSTRACT FROM AUTHOR]

Bacterial cellulose (BC) can be used in medical, biomedical, electronic, food, and paper industries because of its unique properties distinguishing it from plant cellulose. BC production was statistically optimized by Gluconacetobacter xylinus strain using carob and haricot bean (CHb) medium. Eight parameters were evaluated by Plackett–Burman Design and significant three parameters were optimized by Central Composite Design. Optimal conditions for production of BC in static culture were found as: 2.5 g/L carbon source, 2.75 g/L protein source, 9.3% inoculum ratio, 1.15 g/L citric acid, 2.7 g/L Na 2 HPO 4 , 30 °C incubation temperature, 5.5 initial pH, and 9 days of incubation. This study reveals that BC production can be carried out using carob and haricot bean extracts as carbon and nitrogen sources, and CHb medium has higher buffering capacity compared to Hestrin and Schramm media. Model obtained from this study is used to predict and optimize BC production yield using CHb medium. [ABSTRACT FROM AUTHOR]

In this work, a simple and green route to the synthesis of the bacterial nanocellulose-calcium carbonate (BNC/CaCO 3 ) hybrid bionanocomposites using one-step in situ biosynthesis was studied. The CaCO 3 was incorporated in the bacterial nanocellulose structure during the cellulose biosynthesis by Gluconacetobacter xylinus PTCC 1734 bacteria. Hestrin-Schramm (HS) and Zhou (Z) culture media were used to the hybrid bionanocomposites production and the effect of ethanol addition was investigated. Attenuated total reflection Fourier transform infrared spectroscopy, field emission scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, inverse gas chromatography and thermogravimetric analysis were used to characterize the samples. The experimental results demonstrated that the ethanol and culture medium play an important role in the BNC/CaCO 3 hybrid bionanocomposites production, structure and properties. The BNC/CaCO 3 biosynthesized in Z culture medium revealed higher O/C ratio and amphoteric surface character, which justify the highest CaCO 3 content incorporation. The CaCO 3 was incorporated into the cellulosic matrix decreasing the bacterial nanocellulose crystallinity. This work reveals the high potential of in situ biosynthesis of BNC/CaCO 3 hybrid bionanocomposites and opens a new way to the high value-added applications of bacterial nanocellulose. [ABSTRACT FROM AUTHOR]

Rotating magnetic field (RMF) is an interesting alternative to conventional bacterial cellulose (BC) production methods. The BC synthesis processes may be affected by RMF, which facilitates the transfer of oxygen and nutrients from the media to the microbial cells. RMF may also directly influence the various physical and chemical properties of BC. The main aim of the present study was to evaluate the impact of the RMF on the BC in regard to its yield and material properties. The correlation between the efficiency of polymer production and the different time of exposure to the RMF was also analyzed to determine the conditions of lower energy consumption during the cellulose formation process. It was found that the Gluconacetobacter xylinus cultures exposed to the RMF for a half of the time of the entire cellulose production process (72 h), considering the results obtained in controls, synthesized BC more effectively than bacteria continuously exposed to the RMF for 144 h. Furthermore, the application of the RMF, regardless of the exposure mode, did not negatively affect the polymer material properties. It was concluded that the use of the RMF may provide a novel technique for altering cellulose biogenesis and may be used in multiple biotechnological applications. [ABSTRACT FROM AUTHOR]

In this work, we discuss the possibilities of using bacterial cellulose (BC) produced by Gluconacetobacter xylinus as carrier support for the immobilization of probiotic strains of Lactobacillus spp. In our study, immobilization of the microorganisms was performed by the adsorption of bacterial cells on the surface of the synthetized BC and by a simultaneous cultivation of the probiotic bacteria with cellulose-synthetizing G. xylinus . Co-cultures were conducted in stationary cultures, in which BC was synthesized as pellicles on the medium surface and in shaken cultures in which BC was synthetized in the forms of beads. The experiments carried out also included the analysis of the survival of immobilized probiotic bacteria in the presence of gastric juices and bile salts solution. The results showed that immobilization of probiotic Lactobacillus in BC during co-culture with G. xylinus was the most effective immobilization method, providing high-level protection of the microorganisms against the influence of gastric juices and bile salts. [ABSTRACT FROM AUTHOR]

Production of bacterial nanocellulose (BNC) is becoming increasingly popular owing to its environmentally friendly properties. Based on this benefit of BNC production, researchers have also begun to examine the capacity for cellulose production through microbial hosts. Indeed, several research groups have developed processes for BNC production, and many studies have been published to date, with the goal of developing methods for large-scale production. During BNC bioproduction, the culture medium represents approximately 30 % of the total cost. Therefore, one important and challenging aspect of the fermentation process is identification of a new cost-effective culture medium that can facilitate the production of high yields within short periods of time, thereby improving BNC production and permitting application of BNC in the biotechnological, medical, pharmaceutical, and food industries. In this review, we addressed different aspects of BNC production, including types of fermentation processes and culture media, with the aim of demonstrating the importance of these parameters. [ABSTRACT FROM AUTHOR]

The bacterial cellulose (BC) pellicle produced from Gluconacetobacter xylinus has many attractive properties to be used in food and biomedical applications. However, the by-product, gluconic acid produced during BC production will decrease the pH of culture that usually leads to a significant decrease of BC production by G. xylinus. To well control the pH of a static cultivation for BC pellicle production is not an easy task. In this study, acetate buffer was employed to maintain a pH suitable for BC production during static cultivation. The effect of buffer pH, ionic strength and surface area/volume (S/V) ratio of cultured medium on BC production was investigated. BC produced from 200 mM, pH 4.75 acetate buffered medium was 3.56 g/L, much higher than that obtained from YPD medium (0.66 g/L) and HS medium (1.23 g/L), respectively. When G . xylinus was cultivated at high glucose concentration (60 g/L) at S/V ratio of 0.55 cm −1 , the BC produced and conversion were improved to 7.23 g/L and 0.2, respectively. As S/V ratio increased to 1.31 cm −1 , a larger amount of gluconic acid (41.55 g/L) was obtained but with a slightly decreased BC production to 5.24 g/L. The results demonstrated that acetate buffered medium can effectively improve BC pellicle production in a static cultivation. [ABSTRACT FROM AUTHOR]

In this study, lipid fermentation wastewater (fermentation broth after separation with yeast biomass) with high Chemical Oxygen Demand (COD) value of 25,591 mg/L was used as substrate for bacterial cellulose (BC) production by Gluconacetobacter xylinus for the first time. After 5 days of fermentation, the highest BC yield (0.659 g/L) was obtained. Both monosaccharide and polysaccharides present in lipid fermentation wastewater could be utilized by G. xylinus simultaneously during fermentation. By this bioconversion, 30.0% of COD could be removed after 10 days of fermentation and the remaining wastewater could be used for further BC fermentation. The crystallinity of BC samples in lipid fermentation wastewater increased gradually during fermentation but overall the environment of lipid fermentation wastewater showed small influence on BC structure by comparison with that in traditional HS medium by using FE-SEM, FTIR, and XRD. By this work, the possibility of using lipid fermentation wastewater containing low value carbohydrate polymer (extracellular polysaccharides) for high value carbohydrate polymer (BC) production was proven. [ABSTRACT FROM AUTHOR]

An aerobic, Gram-negative bacterium, Gluconacetobacter xylinus , was successfully employed to produce a stretchable cellulose nanofiber pellicle using dissolved oxygen in a conventional cultured medium. The obtained nanofibers were highly crystalline with the metastable cellulose I α phase being apparently the dominant phase by more than 90%. The obtained pellicle could be stretched by up to 1.5 times to provide oriented crystalline nanofibrous films. Low heating of the nanofibrous film induced the transformation of the dominant cellulose I α crystalline phase into the I β crystalline phase without a loss of crystallinity or the high Young's modulus. The film also exhibited unique and anisotropic viscoelastic and mechanical properties as well as superior thermal stability compared with conventional high-performance synthetic polymeric materials. In addition, when G. xylinus cells were transferred to the oriented surface after stretched, they started to synthesize cellulose ribbons that parallel the nanofiber orientation of the substrate. This function as a template was evidenced by direct video imaging of the motion of the bacteria. The application of a bacterial culture using dissolved oxygen in the medium offers the fabrication of novel anisotropic and nanofibrous scaffold of cellulose I α . [ABSTRACT FROM AUTHOR]

The aim of the study was to assess the influence of rotating magnetic field (RMF) on production rate and quality parameters of bacterial cellulose synthetized by Glucanacetobacter xylinus . Bacterial cultures were exposed to RMF (frequency f = 50 Hz, magnetic induction B = 34 mT) for 72 h at 28 °C. The study revealed that cellulose obtained under RMF influence displayed higher water absorption, lower density and less interassociated microfibrils comparing to unexposed control. The application of RMF significantly increased the amount of obtained wet cellulose pellicles but decreased the weight and thickness of dry cellulose. Summarizing, the exposure of cellulose-synthesizing G. xylinus to RMF alters cellulose biogenesis and may offer a new biotechnological tool to control this process. As RMF-modified cellulose displays better absorbing properties comparing to non-modified cellulose, our finding, if developed, may find application in the production of dressings for highly exudative wounds. [ABSTRACT FROM AUTHOR]

In this study, a novel bioreactor for producing bacterial cellulose (BC) is proposed. Traditional BC production uses static culture conditions and produces a gelatinous membrane. The potential for using various types of bioreactor, including a stirred tank, conventional airlift, and modified airlift with a rectangular wire-mesh draft tube, in large-scale production has been investigated. The BC obtained from these bioreactors is fibrous or in pellet form. Our proposed airlift bioreactor produces a membrane-type BC from Gluconacetobacter xylinus , the water-holding capacity of which is greater than that of cellulose types produced using static cultivation methods. The Young's modulus of the product can be manipulated by varying the number of net plates in the modified airlift bioreactor. The BC membrane produced using the proposed bioreactor exhibits potential for practical application. [ABSTRACT FROM AUTHOR]

Both static and agitated culture methods have their own disadvantages on producing bacterial cellulose (BC). To reveal the metabolic differences between these two culture methods, the intracellular metabolic profile characterization of Gluconacetobacter xylinus was investigated using gas chromatography coupled with mass spectrometry. A total of 79 intracellular metabolites in G. xylinus were detected and quantified. Trehalose was mainly responsible for the discrimination among different cultural groups. Coupled with metabolic network, BC production was divided into two stages in agitated culture. At the first stage, glucose was more converted to gluconic acid at high rotational speeds, resulting in a low conversion rate of glucose to BC. At the second stage, gluconic acid acted as carbon source pool for BC synthesis under glucose-limited conditions. However, the accumulation of self-protection metabolites (trehalose, amino acids and gluconic acid) on the 2nd day at 280 rpm branches much carbon source from BC synthesis, resulting in the inhibition of BC synthesis. The highest conversion rate of glucose to BC was observed in static culture, attributing to the inhibition of Glucose-6-phosphate dehydrogenase and the accumulation of by-products. These might be the possible reasons that G. xylinus in static and agitated cultures gave distinct BC yields. [ABSTRACT FROM AUTHOR]

Arabinans and galactans are major components of the side-chains of pectin in plant cell walls. In order to understand how pectin side-chains interact with cellulose, in this work we studied the interaction of de-branched arabinan (from sugar beet) and linear galactan (from potato) during the synthesis of cellulose by Gluconacetobacter xylinus (ATCC 53524) to mimic in muro assembly. The binding studies reveal that arabinan and galactan are able to bind extensively (>200 mg/g of cellulose) during cellulose deposition, and more than pectin (from apple) in the absence of calcium. 13 C NMR revealed that associated arabinan, galactan or apple pectin molecules were neither rigid nor affected cellulose crystallinity, and there was no apparent change in cellulose architecture as reflected in scanning electron micrographs. De-binding of arabinan, galactan or apple pectin occurred as a result of washing, indicating a reversible binding to cellulose, which was modelled in terms of a surface-controlled process. Implications for structural models of primary plant cell walls and possible roles for cellulose binding of arabinan- and galactan-rich pectins in biological processes are discussed. [ABSTRACT FROM AUTHOR]

To reduce the cost of bacterial cellulose ( BC) production, the possibility of using acetone-butanol-ethanol ( ABE) fermentation wastewater with high COD value (18 050 mg l−1) for BC production by Gluconacetobacter xylinus was evaluated. After 7 days of fermentation, the highest BC yield (1·34 g l−1) was obtained. The carbon sources including sugars (glucose and xylose), organic acids (acetic acid and butyric acid) and alcohol compounds (ethanol and butanol) were utilized by G. xylinus simultaneously during fermentation. Although the COD decrease ratio (about 14·7%) was low, the highest BC yield on COD consumption (56·2%, g g−1) was relatively high and the remaining wastewater could be used for further BC fermentation. Besides, the environment of ABE fermentation wastewater showed small influence on the BC structure by comparison with the BC products obtained in traditional HS medium using field emission scanning electron microscope ( FE- SEM), Fourier transform infrared spectroscopy ( FTIR) and X-ray diffraction ( XRD). Overall, ABE fermentation wastewater is one promising substrate for BC production. Significance and Impact of the Study The possibility of using acetone-butanol-ethanol ( ABE) fermentation wastewater for bacterial cellulose ( BC) production by Gluconacetobacter xylinus was evaluated in this study. This is the first time that ABE fermentation wastewater was used as substrate for BC fermentation. The results provide detail information of metabolism of G. xylinus in ABE fermentation wastewater and the influence of wastewater environment on the structure of BC samples. Overall, this bioconversion could reduce the cost of BC production greatly. [ABSTRACT FROM AUTHOR]

In this work, the effects of carbon sources and culture media on the production and structural properties of bacterial cellulose (BC) have been studied. BC nanofibers were synthesized using Gluconacetobacter xylinus strain PTCC 1734. Media used were Hestrin–Schramm (H), Yamanaka (Y), and Zhou (Z). Five different carbon sources, namely date syrup, glucose, mannitol, sucrose, and food-grade sucrose were used in these media. All the produced BC pellicles were characterized in terms of dry weight production, biomass yield, thermal stability, crystallinity and morphology by thermogravimetric analysis (TGA), x-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). The obtained results showed that mannitol lead to the highest yield, followed by sucrose. The highest production efficiency of mannitol might be due to the nitrogen source, which plays an important role. The maximum improvement on the thermal stability of the composites was achieved when mannitol was used in H medium. In addition, the crystallinity was higher in BC formed in H medium compared to other media. FE-SEM micrographs illustrated that the BC pellicles, synthesized in the culture media H and Z, were stable, unlike those in medium Y that were unstable. The micrographs of BC produced in media containing mannitol and sucrose provided evidence of the strong interfacial adhesion between the BC fibers without noticeable aggregates. [ABSTRACT FROM AUTHOR]

Glucose dehydrogenase (GDH) locates in the cytoplasmic membrane of Gluconacetobacter xylinus oxidizes glucose to gluconic acid that decreases the conversion of glucose to bacterial cellulose (BC). In this study, a mutant of G. xylinus was generated by knocking-out the membrane bound GDH gene via homologous recombination of a defect GDH gene. The production of BC by G. xylinus mutant (GDH-KO strain) using glucose as a carbon source was investigated. Without the membrane bound GDH activity, the mutant strain still produces BC and increases glucose utilization efficiency for cellulose biosynthesis. In contrast, the wild-type strain oxidized a large fraction of glucose to gluconic acid that decreased the conversion yield of glucose to BC. Our results showed that the BC production from GDH-KO strain was about 40 and 230% higher than that of wild-type strain in static and shaken culture, respectively. [ABSTRACT FROM AUTHOR]

Background Recently, naturally derived facial masks with beneficial biological properties have received increasing interest. In this study, silk sericin-releasing bacterial nanocellulose gel was developed to be applied as a bioactive mask for facial treatment. Results The silk sericin-releasing bacterial nanocellulose gel produced at a pH of 4.5 had an ultrafine and extremely pure fiber network structure. The mechanical properties and moisture absorption ability of the gel were improved, compared to those of the commercially available paper mask. Silk sericin could be control-released from the gel. A peel test with porcine skin showed that the gel was less adhesive than the commercially available paper mask, which would be removed from the face more easily without pain. The in vitro cytotoxicity test showed that the gel was not toxic to L929 mouse fibroblast and HaCaT human keratinocyte cells. Furthermore, when implanted subcutaneously and evaluated according to ISO10993-6 standard, the gel was not irritant to tissue. Conclusion The silk sericin-releasing bacterial nanocellulose gel had appropriate physical and biological properties and safety for the facial treatment application. [ABSTRACT FROM AUTHOR]

Bacterial cellulose (BC) has unique properties, such as high crystallinity, a high degree of polymerisation, high tensile strength and high purity, compared with native cellulose. In this study, a previously determined BC production medium was improved in static culture, and the production cost was evaluated and compared with molasses and with other defined media, such as Hestrin–Schramm, Zhou, Yamanaka and Park, using Gluconacetobacter xylinus . In addition to this analysis, because the surface area/volume ratio is an important parameter in static culture, different surface area/volume ratios were analysed in the range of 0.2–1.46. The defined medium (M1A05P5) and culture type contained glucose (10 g/L), yeast extract (10 g/L), peptone (7 g/L), acetic acid (1.5 ml/L), and ethanol (5 ml/L), and the pH was adjusted to 5.0 in static culture. The highest productivity was observed in the M1A05P5 medium that was 5-fold higher than either molasses or Park's medium. Although the molasses medium was proposed as a cost-effective medium, the production price of BC was the lowest in the M1A05P5 medium. Therefore, the newly developed medium and strategy were highly promising candidates for the industrial-scale production of BC. [ABSTRACT FROM AUTHOR]

We investigated the autonomous bottom-up fabrication of three-dimensional honeycomb cellulose structures, using Gluconacetobacter xylinus as a bacterial nanoengine, on cellulose honeycomb templates prepared by casting water-in-oil emulsions on glass substrates (Kasai and Kondo, Macromol. Biosci., 4, 17–21, 2004). The template film had a unique molecular orientation state along the honeycomb frames, but was non-crystalline. When G. xylinus , used as a nanofiber-producing bacterium, was incubated on the honeycomb scaffold in a culture medium, it secreted cellulose nanofibers only on the upper surface of the honeycomb frame. The movement was regulated by a selective interaction between the synthesized nanofiber and the surface of the honeycomb frames of the template. The relationship between directed deposition of synthesized nanofibers and ordered fabrication from the nano- to the micro-scale could provide a novel bottom-up methodology, using bacteria, for the design of three-dimensional honeycomb structures as functional materials with nano/micro hierarchical structures, with low energy consumption. [ABSTRACT FROM AUTHOR]

In this work, acetic acid was found as one promising substrate to improve xylose utilization by Gluconacetobacter xylinus CH001. Also, with the help of adding acetic acid into medium, the bacterial cellulose (BC) production by G. xylinus was increased significantly. In the medium containing 3 g l acetic acid, the optimal xylose concentration for BC production was 20 g l. In the medium containing 20 g l xylose, the xylose utilization and BC production by G. xylinus were stimulated by acetic acid within certain concentration. The highest BC yield (1.35 ± 0.06 g l) was obtained in the medium containing 20 g l xylose and 3 g l acetic acid after 14 days. This value was 6.17-fold higher than the yield (0.21 ± 0.01 g l) in the medium only containing 20 g l xylose. The results analyzed by FE-SEM, FTIR, and XRD showed that acetic acid affected little on the microscopic morphology and physicochemical characteristics of BC. Base on the phenomenon observed, lignocellulosic acid hydrolysates (xylose and acetic acid are main carbon sources present in it) could be considered as one potential substrate for BC production. [ABSTRACT FROM AUTHOR]

A strain of acidogenic bacterium was isolated from the fermentation liquid of Cantonese-style rice vinegar produced by traditional surface fermentation. 16S rDNA identification confirmed the bacterium as Gluconacetobacter xylinus, which synthesizes bacterial cellulose, and the acid productivity of the strain was investigated. In the study, the effects of the membrane integrity and the comparison of the air–liquid interface membrane with immerged membrane on total acidity, cellulose production, alcohol dehydrogenase (ADH) activity and number of bacteria were investigated. The cellulose membrane and the bacteria were observed under SEM for discussing their relationship. The correlations between oxygen consumption and total acid production rate were compared in surface and shake flask fermentation. The results showed the average acid productivity of the strain was 0.02 g/(100 mL/h), and the integrity of cellulose membrane in surface fermentation had an important effect on total acidity and cellulose production. With a higher membrane integrity, the total acidity after 144 h of fermentation was 3.75 g/100 mL, and the cellulose production was 1.71 g/100 mL after 360 h of fermentation. However, when the membrane was crushed by mechanical force, the total acidity and the cellulose production were as low as 0.36 g/100 mL and 0.14 g/100 mL, respectively. When the cellulose membrane was forced under the surface of fermentation liquid, the total acid production rate was extremely low, but the activity of ADH in the cellulose membrane was basically the same with the one above the liquid surface. The bacteria were mainly distributed in the cellulose membrane during the fermentation. The bacterial counts in surface fermentation were more than in the shake flask fermentation and G. xylinus consumed the substrate faster in surface fermentation than in shake flask fermentation. The oxygen consumption rate and total acid production rate of surface fermentation were respectively 26.13 times and 2.92 times that of shake flask fermentation. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Bacterial cellulose was increased by semi-continuous process in molasses medium. [•] Different processes were performed to compare the yield of cellulose. [•] Several incubation periods were studied to find the best yield of cellulose. [•] Morphological structure of cellulose showed in different media and processes. [ABSTRACT FROM AUTHOR]

Background Bacterial cellulose (BC) is a polymeric nanostructured fibrillar network produced by certain microorganisms, principally Gluconacetobacter xylinus. BC has a great potential of application in many fields. Lignocellulosic biomass has been investigated as a cost-effective feedstock for BC production through pretreatment and hydrolysis. It is well known that detoxification of lignocellulosic hydrolysates may be required to achieve efficient production of BC. Recent results suggest that phenolic compounds contribute to the inhibition of G. xylinus. However, very little is known about the effect on G. xylinus of specific lignocellulose-derived inhibitors. In this study, the inhibitory effects of four phenolic model compounds (coniferyl aldehyde, ferulic acid, vanillin and 4-hydroxybenzoic acid) on the growth of G. xylinus, the pH of the culture medium, and the production of BC were investigated in detail. The stability of the phenolics in the bacterial cultures was investigated and the main bioconversion products were identified and quantified. Results Coniferyl aldehyde was the most potent inhibitor, followed by vanillin, ferulic acid, and 4- hydroxybenzoic acid. There was no BC produced even with coniferyl aldehyde concentrations as low as 2 mM. Vanillin displayed a negative effect on the bacteria and when the vanillin concentration was raised to 2.5 mM the volumetric yield of BC decreased to ~40% of that obtained in control medium without inhibitors. The phenolic acids, ferulic acid and 4-hydroxybenzoic acid, showed almost no toxic effects when less than 2.5 mM. The bacterial cultures oxidized coniferyl aldehyde to ferulic acid with a yield of up to 81%. Vanillin was reduced to vanillyl alcohol with a yield of up to 80%. Conclusions This is the first investigation of the effect of specific phenolics on the production of BC by G. xylinus, and is also the first demonstration of the ability of G. xylinus to convert phenolic compounds. This study gives a better understanding of how phenolic compounds and G. xylinus cultures are affected by each other. Investigations in this area are useful for elucidating the mechanism behind inhibition of G. xylinus in lignocellulosic hydrolysates and for understanding how production of BC using lignocellulosic feedstocks can be performed in an efficient way. [ABSTRACT FROM AUTHOR]

Background Bacterial cellulose (BC) is a nanostructured material with unique properties and wide applicability. In order to decrease the production cost of bacterial cellulose, lignocellulosebased media have considerable potential as alternative cost-effective feedstocks. However, pretreatment and enzymatic hydrolysis of lignocellulose to sugars also generate fermentation inhibitors. Detoxification of lignocellulosic hydrolysates is needed to achieve efficient production of BC. In this investigation, different methods for detoxification of spruce hydrolysate prior to production of BC were compared with respect to effects on potential inhibitors and fermentable sugars, sugar consumption, BC yield, and cell viability. The objectives were to identify efficient detoxification methods and to achieve a better understanding of the role played by different inhibitors in lignocellulosic hydrolysates. Results In a first series of experiments, the detoxification methods investigated included treatments with activated charcoal, alkali [sodium hydroxide, calcium hydroxide (overliming), and ammonium hydroxide], anion and cation ion-exchange resins, and reducing agents (sodium sulfite and sodium dithionite). A second series of detoxification experiments included enzymatic treatments (laccase and peroxidase). The potential inhibitors studied included aliphatic acids, furan aldehydes, and phenolic compounds. The best effects in the first series of detoxification experiments were achieved with activated charcoal and anion exchanger. After detoxification with activated charcoal the BC yield was 8.2 g/L, while, it was 7.5 g/L in a reference medium without inhibitors. Treatments with anion exchanger at pH 10 and pH 5.5 gave a BC yield of 7.9 g/L and 6.3 g/L, respectively. The first series of experiments suggested that there was a relationship between the BC yield and phenolic inhibitors. Therefore, the second series of detoxification experiments focused on treatments with phenoloxidizing enzymes. The BC yield in the laccase-detoxified hydrolysate reached 5.0-5.5 g/L after 14 days cultivation, which demonstrated the important inhibitory role played by phenolic compounds. Conclusions The investigation shows that detoxification methods that efficiently remove phenolics benefit bacterial growth and BC production. Negative effects of salts could not be excluded and the osmotolerance of Gluconacetobacter xylinus needs to be further investigated in the future. Combinations of detoxification methods that efficiently decrease the concentration of inhibitors remain as an interesting option. [ABSTRACT FROM AUTHOR]

Aims To evaluate the possibility of elephant grass acid hydrolysate converting into bacterial cellulose ( BC) produced by Gluconacetobacter xylinus CH001 and to characterize the morphology and structure of the cellulose produced. Methods and Results Acid-hydrolysed and detoxified elephant grass acid hydrolysate was inoculated with G. xylinus CH001. After 14 days of static fermentation, about 6·4 g l−1 of BC could be generated. Meanwhile, 60·4% (w/w) of BC yield on sugar consumption was obtained. Scanning electron micrographs illustrated that the network of cellulose fibres became denser, and the diameter changed with the growth. FT- IR spectra showed almost same results for all the BC samples collected on different culture time. X-ray diffractograms demonstrated that the crystalline form of BC was cellulose I, the crystallinity increased to 53·58%, and the crystallinity index reached up to 99%. Conclusions Elephant grass acid hydrolysate could be utilized efficiently for BC production by G. xylinus CH001. Structure analysis on the cellulose produced showed its potential of being excellent material for further application. Significance and Impact of the Study Our studies for the first time examined the bioconversion of low-cost elephant grass into high-value BC and the changes in its morphology and structure following the culture time. [ABSTRACT FROM AUTHOR]

The development of bacterial cellulose (BC) fibrils biosynthesized by Gluconacetobacter xylinus was investigated using atomic force microscopy (AFM). After various incubation times at 30 °C, both the length of BC fibrils and their average diameters increased significantly. After the first 2-h incubation, not only single BC microfibrils with an average diameter of 5.8 ± 0.7 nm were biosynthesized but single microfibrils also began to bind with each other forming bundles. After longer incubation times of 6 h, 16 h, and 48 h, only BC bundles and ribbons or even only ribbons were detectable. The development of BC fibrils and the formation of BC bundles/ribbons along with the biosynthesis time were illustrated using AFM. Furthermore, single BC fibrils were twisted in a right-handed manner. The twisting of BC fibrils possibly promoted the formation of bigger ribbons. [ABSTRACT FROM AUTHOR]

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]

Thin stillage (TS), wastewater from rice wine distillery, was used as a cost-free feedstock to replace the costly traditional Hestrin and Schramm (HS) medium for BC production by Gluconacetobacter xylinus. Due to the rich organic acids and amino acids content in TS, BC production was significantly enhanced as 50 (v/v) % of HS medium was replaced with TS. In the 50/50 TS–HS medium, BC concentration of 6.26 g/l could be obtained after 7 days static cultivation which is approximately 50% higher than that could be produced in HS-only medium. The BC produced by TS containing medium had slightly denser reticulated structures and higher crystallinity index values but with lower water holding capacities than that obtained from HS medium. Based on the 50% cost-free TS, the 50/50 TS–HS medium had a BC production feedstock cost about 67% lower than that of traditional HS medium. The employment of cost-free TS to replace a portion of HS medium to achieve a higher BC production not only can reduce the BC production cost but also solve the wastewater disposal problem of winery industry. [Copyright &y& Elsevier]

Gluconacetobacter xylinus is a plant-associated bacterium best studied for its cellulose production. Bacterial cellulose is important in facilitating plant-microbe interactions but little is known about the effect that exogenous phytohormones have on bacterial cellulose synthesis or the growth of G. xylinus. We characterized the growth, development and effect on pellicle characteristics caused by exogenous indole-3- acetic acid (IAA), gibberellic acid (GA), abscisic acid (ABA) and zeatin (Z) over a range of concentrations (1 nM to 100 µM). These phytohormones are plant growth regulators known to be involved plant development including fruit ripening and stress tolerance. Each of these hormones stimulated G. xylinus growth and influenced its pellicle characteristics. Exogenous IAA had the greatest effect on G. xylinus pellicles. Growth in IAA produced thin pellicles with very little cellulose. In general, pellicle wet weight was inversely proportional to the bacterial cellulose yield when cultures were grown in the presence of ABA, suggesting ABA influenced pellicle density and hydration. The crystallinity index, CI (IR) of cellulose produced in the presence of each phytohormone over a variety of concentrations was determined by Fourier transform infrared spectroscopy. The observed effect on cellulose crystallinity was concentration and hormone dependent. GA caused the greatest alterations in crystallinity with the highest CI (IR)=0.94 at 1 µM and the lowest CI (IR)=0.47 at 500 nM. Endogenous production of hormones by G. xylinus was investigated by high performance liquid chromatography of extracts prepared from both cell pellets and culture supernatants. We found G. xylinus synthesized GA, ABA and Z but did not produce IAA. [ABSTRACT FROM AUTHOR]

Gluconacetobacter xylinus is a plant-associated bacterium best studied for its cellulose production. Bacterial cellulose is important in facilitating plant-microbe interactions but little is known about the effect that exogenous phytohormones have on bacterial cellulose synthesis or the growth of G. xylinus. We characterized the growth, development and effect on pellicle characteristics caused by exogenous indole-3- acetic acid (IAA), gibberellic acid (GA), abscisic acid (ABA) and zeatin (Z) over a range of concentrations (1 nM to 100 μM). These phytohormones are plant growth regulators known to be involved plant development including fruit ripening and stress tolerance. Each of these hormones stimulated G. xylinus growth and influenced its pellicle characteristics. Exogenous IAA had the greatest effect on G. xylinus pellicles. Growth in IAA produced thin pellicles with very little cellulose. In general, pellicle wet weight was inversely proportional to the bacterial cellulose yield when cultures were grown in the presence of ABA, suggesting ABA influenced pellicle density and hydration. The crystallinity index, CI (IR) of cellulose produced in the presence of each phytohormone over a variety of concentrations was determined by Fourier transform infrared spectroscopy. The observed effect on cellulose crystallinity was concentration and hormone dependent. GA caused the greatest alterations in crystallinity with the highest CI (IR)=0.94 at 1 μM and the lowest CI (IR)=0.47 at 500 nM. Endogenous production of hormones by G. xylinus was investigated by high performance liquid chromatography of extracts prepared from both cell pellets and culture supernatants. We found G. xylinus synthesized GA, ABA and Z but did not produce IAA. [ABSTRACT FROM AUTHOR]

Abstract: Thin stillage (TS), a wastewater from rice wine distillery can well sustain the growth of Gluconacetobacter xylinus for production of bacterial cellulose (BC). When used as a supplement to the traditional BC production medium (Hestrin and Schramm medium), the enhancement of BC production increased with the amount of TS supplemented in a static culture of G. xylinus. When TS was employed to replace distilled water for preparing HS medium (100%TS–HS medium), the BC production in this 100%TS–HS medium was enhanced 2.5-fold to a concentration of 10.38g/l with sugar to BC conversion yield of 57% after 7 days cultivation. The cost-free TS as a supplement in BC production medium not only can greatly enhance the BC production, but also can effectively dispose the nuisance wastewater of rice wine distillery. [Copyright &y& Elsevier]

Gluconacetobacter xylinus, a gram-negative bacterium that synthesizes and extrudes a cellulose nanofiber in SH media moves in random manners, resulting in 3D-network structure of the secreted nanofibers termed a pellicle. In this study, the bacterial movement was successfully regulated to be in a waving manner when cultured on ordered templates made of chitin. Interestingly, by addition of more cellulose into the chitin ordered templates, the waving pattern was getting close to a linear or straight manner. Real time video analysis and other visualization techniques clarified that the regulation of the moving manners was due to the interfacial interaction between the secreted nanofibers and the template surfaces. Furthermore, the changing of the pattern due to the cellulose content in the ordered templates appeared to depend on the magnitude of the interaction between the template and nanofibers. This regulated autonomous deposition of the fibers will build patterned 3D-structure with unique properties on the surface of the templates, leading to a novel type of nanotechnology using biological systems with biomolecular nano-templates to design 3D-structures. [ABSTRACT FROM AUTHOR]

Abstract: An extensive matrix of different growth conditions including media, incubation time, inoculum volume, surface area and media volume were investigated in order to maximize the yield of bacterial cellulose produced by Gluconacetobacter xylinus, which will be used as reinforcement material to produce fully biodegradable composites. Crystallinity was shown to be controllable depending on the media and conditions employed. Samples with significant difference in crystallinity in a range from 50% to 95% were produced. Through experimental design, the yield of cellulose was maximized; primarily this involved reactor surface area design, optimized media and the use of mannitol being the highest cellulose-producing carbon source. Increasing the volume of the media did achieve a higher cellulose yield, however this increase was not found to be cost or time effective. [Copyright &y& Elsevier]

Determine the effect of sucrose on the productivity of BC by Gluconacetobacter xylinus IFO 13693 in static condition. Materials and methods, The synthesis of bacterial cellulose (BC) by Gluconacetobacter xylinus was carried out in a discontinuous static culture at room temperature, in the presence of sucrose as the main carbon source at initial concentrations of 0.8 to 7.6% (p/v). The residual concentrations of BC, sucrose, glucose and fructose were measured every week. The Microcal Origin 6.0®. Software used to determine the kinetics of hydrolysis of sucrose and formation of cellulose and the coefficient of performance of the product Results. In the fourth week the BC values were between 32.5 to 39.5 g/L for the different concentrations of sucrose. The kinetics for the hydrolysis of sucrose fits the Michaelis-Menten model, with a Vmax of 0.0002 mol L-1 h-1 and Km of 0.018 M. The production of BC follows the model proposed by Marx-Figini and Pion, with a value of the slope (kc) between 0.0018 and 0.0024 h-1 for different initial concentrations of sucrose. The yield coefficients have values of 0.8 to 2.4 g of BC produced / g of sucrose consumed. Conclusions. The hydrolysis of sucrose, fructose consumption and glucose is reflected in cellulose synthesis. The hydrolysis of sucrose and production of BC fit the Michaelis-Menten model and the model proposed by Marx-Figini and Pion, respectively. Finally, the performance depends on the concentration of sucrose [ABSTRACT FROM AUTHOR]

Abstract: This study reinvestigated the synthesis of cellulose in vitro with a well-known cellulose-producing bacterium, Gluconacetobacter xylinus. Alkylmaltoside detergents, which are more frequently used in recent structural biological researches, are uniquely used in this study to solubilize cellulose-synthesizing activity from the cell membrane of G. xylinus. Activity comparable to that previously reported is obtained, while the synthesized cellulose is crystallized into a non-native polymorph of cellulose (cellulose II) as well as the previous studies. In spite of this failure to recover the native activity to synthesize cellulose I microfibril in vitro, the product is a polymer with a degree of polymerization greater than 45 as determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). It was thus concluded that the established protocol can solubilize cellulose-synthesizing activity of G. xylinus with polymerizing activity. [Copyright &y& Elsevier]

Abstract: In this study the effects of growth times and culture mediums on the structural characteristics of bacterial cellulose have been investigated. Bacterial cellulose (BC) nanofibers were synthesized by Gluconacetobacter xylinus. BC pellicles were compared using SEM, FT-IR and X-ray diffraction techniques. The crystallinity index (CrI) and crystallite size (CrS) were calculated based on X-ray measurements. Three growth times (7, 14 and 21 days) and three culture mediums (A, B and C) were applied. SEM micrographs showed that increasing growth time up to 7 days improves the microfibril branches crossing to each other and the number of bundles. However, further increase in growth time (21 days) results in decrease in the microfibril network. On the other hand the hydrogen and C–H bonds were developed by the increase in growth time. In conclusion, BC synthesized in medium B for 7 days had superior properties in terms of CrI, CrS and microfibril networks. [Copyright &y& Elsevier]

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]