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In this paper, we perform a systematic analysis of the structural organization of bacterial cellulose (BC). We report four types of organization of the BC mass, produced by Gluconacetobacter hansenii that occur depending on cultivation conditions. Two of those, particularly, plywood type one and layers of micro-sized tubes were observed and described for the first time. In spherical BC particles (pellets), we found the layered structure that had previously been reported for planar geometry only. We suggest a model explaining why layers form in BC films and attempt to reveal the impact of different factors on the BC microscale morphology. We assume that the main factor that has direct impact on the type of structure formed is the rate of BC mass accumulation., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest, (Copyright © 2020 Elsevier Ltd. All rights reserved.)

In this work, we report a convenient method of grafting non-leachable bioactive amine functions onto the surface of bacterial cellulose (BC) nanofibrils, via a simple silylation treatment in water. Two different silylation protocols, involving different solvents and post-treatments were envisaged and compared, using 3-aminopropyl-trimethoxysilane (APS) and (2-aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPS) as silylating agents. In aqueous and controlled conditions, water-leaching resistant amino functions could be successfully introduced into BC, via a simple freeze-drying process. The silylated material remained highly porous, hygroscopic and displayed sufficient thermal stability to support the sterilization treatments generally required in medical applications. The impact of the silylation treatment on the intrinsic anti-bacterial properties of BC was investigated against the growth of Escherichia coli and Staphylococcus aureus. The results obtained after the in vitro studies revealed a significant growth reduction of S. aureus within the material., (Copyright © 2019. Published by Elsevier Ltd.)

Including additives in the culture media during bacterial cellulose (BC) biosynthesis is a traditional method to produce BC-based nanocomposites. This study examines a novel fermentation process, which is to co-culture Gluconacetobacter hansenii (G. hansenii) with Escherichia coli (E. coli) under static conditions, to produce BC pellicles with enhanced mechanical properties. The mannose-rich exopolysaccharides (EPS) synthesized by E. coli were incorporated into the BC network and affected the aggregation of co-crystallized microfibrils without significantly changing the crystal sizes of BC. When co-culturing G. hansenii ATCC 23769 with E. coli ATCC 700728, which produced a low concentration of EPS at 3.3 ± 0.7 mg/L, the BC pellicles exhibited a Young's modulus of 4,874 ± 1144 MPa and a stress at break of 80.7 ± 21.1 MPa, which are 81.9% and 79.3% higher than those of pure BC, respectively. The growth dynamics of the two co-cultured strains suggested that the production of BC and EPS were enhanced through co-culturing fermentation., (Copyright © 2019. Published by Elsevier Ltd.)

Bacterial cellulose (BC) has been gaining importance over the past decades as a versatile material that finds applications in diverse industries. However, a secured supply is hindered by the slow production rate and batch-to-batch variability of the yield. Here, we report a rational approach for characterising the BC production process using Design of Experiment (DoE) methodology to study the impact of different parameters on desired process attributes. Notably, we found that the carbon source used for bacterial growth significantly impacts the interplay between the process variables and affects the desired outcomes. We therefore, propose that the highest priority process outcome in this study, the yield, is a function of the carbon source and optimal reactor design. Our systematic approach has achieved projected BC yields as high as ∼40 g/L for Gluconacetobacter hansenii 53582 grown on sucrose as the carbon source compared to the widely reported yields of ∼10 g/L., (Copyright © 2018. Published by Elsevier Ltd.)

Pecan nutshell is an abundant waste with a high content of carbohydrates. According to its chemical composition, pecan nutshell could be used as carbon source for Gluconacetobacter entanii, a bacterium that produces cellulose with high purity and nanometric characteristics. Bacterial cellulose (BC) was obtained from a static culture medium using pecan nutshell as carbon source and saccharose as control. Results showed that the pecan nutshell could be used as carbon source for production of BC. The cellulose yield ranged around 2.816 ± 0.040 g/L for 28 days. The morphological, structural and chemical properties of the cellulose produced were similar to those reported for others BC. The spectroscopic characterization indicated the chemical functionalization of BC and the reduction of its crystallinity. The production of BC with G. entanii using pecan nutshell as carbon source, is the first report. The BC could have potential use in chemical functionalization and in the preparation of biocomposites., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

In this work, for the first time bacterial cellulose (BC) hydrogel membranes were used for the fabrication of antimicrobial cellulosic nanocomposites by hydrothermal deposition of Cu derivative nanoparticles (i.e.Cu(0) and CuxOy species). BC-Cu nanocomposites were characterized by FTIR, SEM, AFM, XRD and TGA, to study the effect of hydrothermal processing time on the final physicochemical properties of final products. XRD result show that depending on heating time (3-48h), different CuxOy phases were achieved. SEM and AFM analyses unveil the presence of the Cu(0) and copper CuxOy nanoparticles over BC fibrils while the surface of 3D network became more compact and smother for longer heating times. Furthermore, the increase of heating time placed deleterious effect on the structure of BC network leading to decrease of BC crystallinity as well as of the on-set degradation temperature. Notwithstanding, BC-Cu nanocomposites showed excellent antimicrobial activity against E. coli, S. aureus and Salmonella bacteria suggesting potential applications as bactericidal films., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Films with antioxidant activity were prepared by combining chitosan (CH) and epigallocatechin-3-gallate (EGCG) with nano-bacterial cellulose (BC) as a reinforcement agent. Results showed that BC addition improved the qualities of films jeopardized by EGCG. Fourier Transform Infrared (FTIR) spectroscopy analysis confirmed that there were intermolecular interactions among BC, CH and EGCG though hydrogen bonding. Consequently, BC addition increased the crystallinity and thermal stability of CH-BC5/10-EGCG15/30 films analyzed by X-ray diffraction (XRD) and thermogravimetric (TGA) analysis. BC addition also significantly decreased water solubility (WS), from 26.54% to 20.80%, increased tensile strength (TS), from 18.71 to 44.17MPa, and increased elongation at break (EAB), from 2.72% to 7.34%. Moreover, BC and EGCG had high affinity for each other, as BC addition lowered the release of EGCG from CH films with a higher ABTS radical scavenging ability. Therefore, BC can be used as a sustained release carrier of EGCG in antioxidant active films., (Copyright © 2017. Published by Elsevier Ltd.)

Bacterial cellulose (BC) exhibits unique properties including high mechanical strength and high crystallinity. Improvement in the mechanical properties of BC is sought for many applications ranging from food to structural composites to biomedical materials. In this study, different additives including carboxymethyl cellulose (CMC), pectin, gelatin, cornstarch, and corn steep liquor were included in the fermentation media to alter the BC produced. Three different concentrations (1%, 3% and 5%) were chosen for each of the additives, with no additive (0%) as the control. The produced BC was then analyzed to determine tensile and compression modulus. Amongst the tested additives, BC produced in media containing 3% (w/v) pectin had the maximum compressive modulus (142kPa), and BC produced in media containing 1% (w/v) gelatin exhibited the maximum tensile modulus (21MPa). Structural characteristics of BC and BC-additive composites were compared using X-Ray diffraction (XRD). The crystal size and crystallinity of BC was reduced when grown in the presence of CMC and gelatin while pectin only decreased the crystallite size. This suggested that CMC and gelatin may be incorporated into the BC fibril structure. The field emission scanning electron microscopy (FESEM) images showed the increased micro-fibril aggregation in BC pellicles grown in the presence of additives to the culture media., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The current study was intended to produce bio-cellulose through a cell-free system developed by disrupting Gluconacetobacter hansenii PJK through bead-beating. Microscopic analysis indicated the complete disruption of cells (2.6 × 10(7) cells/mL) in 20 min that added 95.12 μg/mL protein, 1.63 mM ATP, and 1.11 mM NADH into the medium. A liquid chromatography mass spectrometry/mass spectrometry linear trap quadrupole (LC-MS/MS LTQ) Orbitrap analysis of cell-lysate confirmed the presence of all key enzymes for bio-cellulose synthesis. Under static conditions at 30 °C, microbial and cell-free systems produced 3.78 and 3.72 g/L cellulose, corresponding to 39.62 and 57.68% yield, respectively after 15 days. The improved yield based on consumed glucose indicated the superiority of cell-free system. Based on current findings and literature, we hypothesized a synthetic pathway for bio-cellulose synthesis in the cell-free system. This approach can overcome some limitations of cellulose-producing cells and offers a wider scope for synthesizing cellulose composites with bactericidal elements through in situ synthesizing approaches., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

A novel method to synthesize highly crosslinked bacterial cellulose (BC) is reported. The glyoxalization is started in-situ, in the culture medium during biosynthesis of cellulose by Gluconacetobacter medellensis bacteria. Strong crosslinked networks were formed in the contact areas between extruded cellulose ribbons by reaction with the glyoxal precursors. The crystalline structure of cellulose was preserved while the acidic component of the surface energy was reduced. As a consequence, its predominant acidic character and the relative contribution of the dispersive component increased, endowing the BC network with a higher hydrophobicity. This route for in-situ crosslinking is expected to facilitate other modifications upon biosynthesis of cellulose ribbons by microorganisms and to engineer the strength and surface energy of their networks., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Bacterial cellulose (BC) synthesized by Gluconacetobacter sucrofermentans CECT 7291 seems to be a good option for the restoration of degraded paper. In this work BC layers are cultivated and purified by two different methods: an alkaline treatment when the culture media contains ethanol and a thermal treatment if the media is free from ethanol. The main goal of these tests was the characterization of BC layers measured in terms of tear and burst indexes, optical properties, SEM, X-ray diffraction, FTIR, degree of polymerization, static and dynamic contact angles, and mercury intrusion porosimetry. The BC layers were also evaluated in the same terms after an aging treatment. Results showed that BC has got high crystallinity index, low internal porosity, good mechanical properties and high stability over time, especially when purified by the alkaline treatment. These features make BC an adequate candidate for degraded paper reinforcement., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

This study characterized the cellulosic and non-cellulosic exopolysaccharides (EPS) produced by four Gluconacetobacter strains. The yields of bacterial cellulose and water-soluble polysaccharides were dependent on both carbon source and Gluconacetobacter strain. The carbon substrate also affected the composition of the free EPS. When galactose served as an exclusive carbon source, Gluconacetobacter xylinus (G. xylinus) ATCC 53524 and ATCC 700178 produced a distinct alkaline stable crystalline product, which influenced the crystallization of cellulose. Gluconacetobacter hansenii (G. hansenii) ATCC 23769 and ATCC 53582, however, did not exhibit any significant change in cellulose crystal properties when galactose was used as the carbon source. Microscopic observation further confirmed significant incorporation of EPS into the cellulose composites. The cellulosic network produced from galactose medium showed distinctive morphological and structural features compared to that from glucose medium., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Gluconacetobacter diazotrophicus is a nitrogen-fixing bacterium that has been found colonizing several plants. This acid-tolerant bacterium produces phytohormones that promote plant growth and is also able to grow in high-sugar concentrations. It has been demonstrated that exopolysaccharides (EPS), which are produced by strain Pal5 of G. diazotrophicus, play an important role in plant infection. We have investigated the structure of the EPS, which was produced by a strain of Pal5 grown in liquid medium containing mannitol as the sole carbon source. The results reveal an EPS with Glc, Gal, Man in a molar ratio of 6:3:1, respectively. NMR spectroscopy and chemical derivatization have revealed that the EPS structure has 4-O-substituted units of β-glucose, 3-O-substituted units of β-galactose and 2-O-substituted units of α-mannose. Glucose and galactose units linked at C6 were also found. The structure proposed herein is different from EPS produced by other species of Gluconacetobacter published to date., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

A strain producing bacterial cellulose (BC) screened from rotten mandarin fruit was identified as Gluconacetobacter intermedius CIs26 by the examination of general taxonomical characteristics and 16S rDNA sequence analysis. Furthermore, Fourier transform infrared (FT-IR) spectrum showed that pellicle produced by strain CIs26 was composed of glucan, and had the same functional group as a typical BC. X-ray diffractometry (XRD) analysis indicated that the BC was type I in structure with crystallinity index of 75%. BC yields of strain CIs26 in Hestrin-Schramn (HS), citrus waste modified HS (CMHS) and citrus waste solution (CWS) mediums were 2.1 g/L, 5.7 g/L, and 7.2 g/L, respectively. It was shown that citrus waste could stimulate BC production of strain CIs26 efficiently. Based on the ability of utilization of citrus waste, this strain appeared to have potential in BC manufacture on an industrial scale., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

A bacterial strain isolated from the fermentation of Colombian homemade vinegar, Gluconacetobacter medellensis, was investigated as a new source of bacterial cellulose (BC). The BC produced from substrate media consisting of various carbon sources at different pH and incubation times was quantified. Hestrin-Schramm (HS) medium modified with glucose led to the highest BC yields followed by sucrose and fructose. Interestingly, the microorganisms are highly tolerant to low pH: an optimum yield of 4.5 g/L was achieved at pH 3.5, which is generally too low for other bacterial species to function. The cellulose microfibrils produced by the new strain were characterized by scanning and transmission electron microscopy, infrared spectroscopy X-ray diffraction and elemental analysis. The morphological, structural and chemical characteristics of the cellulose produced are similar to those expected for BC., (Copyright © 2012 Elsevier Ltd. All rights reserved.)