Mechanical Properties Of Bacterial Cellulose Research Articles

Review on the strategies for enhancing mechanical properties of bacterial cellulose

Review on the strategies for enhancing mechanical properties of bacterial cellulose

Improved degradability and mechanical properties of bacterial cellulose grafted with PEG derivatives

New functional materials based on bacterial cellulose (BC) grafted with poly(ethylene glycol) PEG derivatives for food packaging applications and a facile method for assessing the degradation rates of the final materials are presented. Two types of materials were obtained by grafting the BC films (BCF), respectively lyophilized BC pellicles (BCL) with three PEG derivatives of different molecular weights through radical polymerization. The BC based polymer materials were characterized by SEM, FT-IR, contact angle measurements, and TGA. Tensile tests and DMA analysis were used to compare the two types of materials in terms of shear-modulus, tensile strength and performance giving suitable information for food packaging applications. A new degradation evaluation method, that we propose herein, offers quantitative information about the degradation process in contrast with the SEM analysis, primarily used in literature, which is not decisive in all cases because it characterizes only small parts of the sample. The degradation rates evidenced that the PEG derivatives of higher molecular weight grafted on the surface of BCF led to an acceleration of the degradation process compared with the pristine samples. A good correlation was obtained between the samples analyzed by SEM after the degradation process and their degradation rates were mathematically determined.

Bio-materials for sustainable textile-based sensing applications

The paper is devoted to the production of biodegradable nonwovens (films) based on bacterial cellulose, the study of its physical and mechanical properties and the possibility of designing garments made from this fabric. As a result of the research, samples of bacterial cellulose films of different thicknesses were obtained, the relationship between changes in film thickness and cultivation time was established, the structure of biodegradable films was determined, the values of microfibrils forming them were revealed, and the physical and mechanical properties of bacterial cellulose were studied. A comparative analysis of the obtained biomaterials with commercial samples of composite eco-materials was carried out using synthetic leather made from Mexican cactus waste. The data collected is valuable for further research in the design of eco-friendly and biodegradable materials for both casual wear and textiles, as well as smart biomaterials for the engineering of sustainable textile-based sensors.

The influence of alkaline treatment on the mechanical and structural properties of bacterial cellulose

The unique mechanical properties of hydrated bacterial cellulose make it suitable for biomedical applications. This study evaluates the effect of concentrated sodium hydroxide treatment on the structural and mechanical properties of bacterial cellulose hydrogels using rheological, tensile, and compression tests combined with mathematical modelling. Bacterial cellulose hydrogels show a concentration-dependent and irreversible reduction in shear moduli, compression, and tensile strength after alkaline treatment. Applying a poroelastic biphasic model to through-thickness compressive stress-relaxation tests showed the alkaline treatment to induce no significant change in axial compression, an effect was observed in the radial direction, potentially due to the escape of water from within the hydrogel. Scanning electron microscopy showed a more porous structure of bacterial cellulose. These results show how concentration-dependent alkaline treatment induces selective weakening of intramolecular interactions between cellulose fibres, allowing the opportunity to precisely tune the mechanical properties for specific biomedical application, e.g., faster-degradable materials.

BACTERIAL CELLULOSE AS A BASE MATERIAL IN BIODIGITAL ARCHITECTURE (BETWEEN BIO-MATERIAL DEVELOPMENT AND STRUCTURAL CUSTOMIZATION).

1. ABSTRACT Recently, developing sustainable architectural materials from renewable resources is gaining great interest. This interest is intended to alleviate the drawbacks of petroleum-based materials and their contribution in the escalation of CO2 emissions causing the current environmental deterioration. Achieving sustainability through developing efficient architectural materials have been always conditioned by technological advancements and economic potential. This has affected the architectural design and construction sectors, especially in times of disasters or economic crisis, resulting in paralysis in the architectural construction and material development. These effects were caused by the capitalization and centralization of architectural construction industries. The recent trend of self-sufficiency that had first emerged in environmental activities supporting recycling, environmental purification and conservation, oxygen, food, and electricity production, has extended to cover more sophisticated products, such as wearables, gadgets and architecture. Achieving self-sufficiency in architecture is of interest to multidisciplinary researchers who focus on developing both self-sufficient systems and materials as the two main components of the built environment. Developing architectural materials aims to provide cheap, recycled, renewable, environmentally friendly, durable and sustainable building material regardless of the possibility of the autonomous production of these materials on a popular democratic basis. Architectural building materials production was always and still is considered a massive industry that is centralized in major firms and LTDs, limiting the architectural construction process to the availability of major economic capacity. This centralization had its merits in forcing forward large-scale economies and vitalizing the architectural design and construction market, but only on the large scale; however, this centralization shows its drawbacks every time in disasters or economic crisis, causing almost total paralysis in the construction industry due to economic impotence caused by different reasons. Moreover, the centralization of the building and construction industry have affected developing communities, causing economic drawbacks and creating a ripple-like crisis in housing. In this paper, the authors propose the self-sufficiency approach in the development and production of sustainable architectural material from abundant and renewable microbial agents, in order to democratize and popularize material production on a domestic and personalized basis. The current work presents Bacterial Cellulose (BC) as a structural and membrane material in different architectural elements and applications, developed through simple and domestically applied procedures in order to create distributed and self-sufficient productive units for architectural materials production. The current study aims specifically at the easiness and simplification of the production practices and procedures of the biopolymers, and specifically bacterial cellulose for encouraging and establishing the popularization of self-sufficient production units of these renewable and abundant biopolymers. In this regard, the current study is part of the ongoing research on enhancing the mechanical properties of bacterial cellulose in order to use it for structural applications, that will be further developed in terms of medium optimization, bacterial cellulose production efficiency analysis, and material mechanical and physical properties testing. The following sections will contain a literature review on the chemical base and physical/mechanical properties of biopolymers including bacterial cellulose, followed by the experimental work conducted in this paper to develop bacterial cellulose as an architectural material. The results were further analyzed through formal and structural customization proposing possible applications in architectural design.

A Review on Production, Characterization and Application of Bacterial Cellulose and Its Biocomposites

Bacterial cellulose (BC) can be produced by an agitated or static fermentation process in presence of suitable media. Groups of microorganisms such as fungi, bacteria, and algae are responsible for the synthesis of BC. Under agitated cultivation, BC yield is enhanced as compared to static cultivation. BC is pure cellulose, so it can easily interact with hydrophilic or hydrophobic biopolymers. In this review paper, we have discussed the preparation and characterization of BC reinforced biopolymer (polylactic acid, cellulosic fibers, agar, and Mater-Bi) based biocomposites and biopolymer (natural rubber, chitosan, polycaprolactone, hydroxyapatite) reinforced BC-based biocomposites related research carried out in last 2 decades. The high moisture content of BC results in reduced compatibility to most hydrophobic biopolymers as compared to hydrophilic biopolymers. Mechanical properties of BC before and after reinforcement were compared as it is important parameters in the production of green composites with targeted application in tissue engineering, wound dressing, dental implants, artificial blood vessels, surgical mesh, bone fillings, heart valve, and artificial cartilage. This review paper will help in exploring various applications of BC-based biocomposites in addition to several parameters that affect the production of BC.

Characterization of Bacterial Cellulose Produced by Acetobacter xylinum Strain LKN6 Using Sago Liquid Waste as Nutrient Source.

<b>Background and Objective:</b> Bacterial Cellulose (BC) is an exopolysaccharide produced by bacteria with unique structural and mechanical properties and is highly pure compared to plant cellulose. This study aimed to produce novel bacterial cellulose using sago liquid waste substrate and evaluate its characteristics as a potential bioplastic.<b>Materials and Methods:</b> Production of BC by static batch fermentation was studied in sago liquid waste substrate usingAcetobacter xylinumLKN6. The BC structure was analyzed by Scanning Electron Microscopy (SEM) and Fourier Transform infrared spectroscopy (FT-IR). Mechanical properties were measured include tensile strength, elongation at break, elasticity (Young's modulus) and Water Holding Capacity (WHC). <b>Results:</b> The BC yield from sago liquid waste as a nutrients source was achieved 12.37 g L<sup>1</sup> and the highest BC yield 14.52 g L<sup>1</sup> in sago liquid waste medium with a sugar concentration of 10% (w/v) after 14 days fermentation period. The existence of bacterial cellulose is proven by FT-IR spectroscopy analysis based on the appearance of absorbance peaks, which are C-C bonding, C-O bonding, C-OH bonding and C-O-C bonding and represents the fingerprints of pure cellulose. The mechanical properties of BC from sago liquid waste were showed a tensile strength of 44.2-87.3 MPa, elongation at break of 4.8-5.8%, Young's Modulus of 0.86-1.64 GPa and water holding capacity of 85.9-98.6 g g<sup>1</sup>. <b>Conclusion:</b> The results suggest that sago liquid waste has great potential to use as a nutrient source in the production of bacterial cellulose and BC's prospect as the bioplastic.

Production enhancement of bacterial cellulose nanofiber using local Komagataeibacter xylinus SB3.1 under static conditions

Bacterial cellulose (BC) is a nanostructured material mainly produced by Gluconacetobacter. The excellent physicochemical and mechanical properties of BC have made it become regarded as a kind of highly functional biopolymer in the application fields of bio-medicine, cosmetics and food industry. However, application of bacterial cellulose faced one of the main big problems in industry, viz., low productivity. Herein, this work was undertaken with a view to enhance the BC production using Komagataeibacter xylinus SB3.1 under static condition through study the effective culture parameters that played a vital role in nanofiber production. Various parameters were investigated including, carbon and nitrogen sources, inoculum size, pH, temperature, and incubation time. Chemical and physical characterizations were investigated using state-of-art tools e.g. FTIR, XRD and SEM. Results revealed the successful production of BC nanofibers through using Komagataeibacter xylinus SB3.1 under static condition as obviously indicated from SEM image. FTIR and XRD affirmed both chemical structure and crystallographic nature of cellulose I of the produced nanofibers. In the seek of improvement, the maximum yield production of BC reached 6.54 g/l at optimum conditions including the use of mannitol and yeast extract as a sole carbon and nitrogen source during incubation period for 8 days at 30 ◦C with 8% inoculum size. These findings emphasize the potential use of a new locally isolated Komagataeibacter xylinus SB3. in production of BC nanofibers as cellulose type I with enhanced crystallinity index up to 82% occurred at optimum conditions which reveals to the increase in the fiber production 3.3 folded times than others with unoptimized condition under the same stationary conditions of growth. This also opens up the window for utilizing the domestic isolated Acetobacter bacteria in industrial manufacturing with potential features.

Effect of pH Buffer and Carbon Metabolism on the Yield and Mechanical Properties of Bacterial Cellulose Produced by Komagataeibacter hansenii ATCC 53582.

Bacterial cellulose (BC) is widely used in the food industry for products such as nata de coco. The mechanical properties of BC hydrogels, including stiffness and viscoelasticity, are determined by the hydrated fibril network. Generally, Komagataeibacter bacteria produce gluconic acids in a glucose medium, which may affect the pH, structure and mechanical properties of BC. In this work, the effect of pH buffer on the yields of Komagataeibacter hansenii strain ATCC 53582 was studied. The bacterium in a phosphate and phthalate buffer with low ionic strength produced a good BC yield (5.16 and 4.63 g/l respectively), but there was a substantial reduction in pH due to the accumulation of gluconic acid. However, the addition of gluconic acid enhanced the polymer density and mechanical properties of BC hydrogels. The effect was similar to that of the bacteria using glycerol in another carbon metabolism circuit, which provided good pH stability and a higher conversion rate of carbon. This study may broaden the understanding of how carbon sources affect BC biosynthesis.

The Influence of Electrolyte Solutions on the Mechanical Properties of Bacterial Cellulose

The mechanical characteristics of bacterial cellulose (one of the most promising cellulose-based nanomaterials) fundamentally depend on its moisture content. It has been found that the effect of aqueous solutions of alkali metal chlorides on its strength and deformation properties is determined by the mobility of water molecules in the near coordination spheres of cation hydration shells.

Physicochemical Mechanics of Bacterial Cellulose

Bacterial cellulose is a product of the vital activity of some types of bacteria. In contrast to plant cellulose, it is characterized by high purity, strength, and elasticity. Together with nontoxicity and biocompatibility, these properties make bacterial cellulose to be applicable in biotechnology, medicine, and production of composites as a reinforcing component. The nanoscopic sizes of the structural units of bacterial cellulose provide it with a large specific surface area and, as a consequence, a pronounced dependence of many properties of a material on surface interactions with an environment. This review is devoted to discussing the structure and mechanical properties of bacterial cellulose, with especial attention being focused on its behavior in the presence of water and aqueous solutions. “Bacteria make no mistakes…” S. Gandlevskii

Microbially-derived nanofibrous cellulose polymer for connective tissue regeneration

Among a vast array of biomaterials investigated for tissue engineering applications, bacterial cellulose (BC) has not been evaluated in depth, despite the material's strong potential of applicability in the field of biotechnology. In this study we investigate the effect of sugar concentration and culture duration on physical and mechanical properties of BC. BC was grown in culture media with different glucose concentrations (weight percent) of 1.25%, 2.50%, 5.00%, 10.00%, 15.00% and also in media with fructose concentration of 5.00%. The swelling ratio of harvested BC sheets did not change significantly with concentration of glucose or the type of sugar (fructose vs glucose). Swelling ratio did not change significantly with culture duration either. Cellulose production rate was significantly higher (p < 0.05) at 5.00%wt. glucose concentration compared to other groups. Ultimate tensile strength (309.3 ± 32.8 MPa) and Young's modulus (3.1 ± 0.6 GPa) of BC sheets harvested from the medium with 5.00%wt. glucose concentration were the highest among all treatment groups. Bacterial removal process and testing condition (wet/dry) did not affect the mechanical performance of the bacterial cellulose significantly. X-ray diffraction data demonstrated higher crystallinity for samples cultured in media with 5.00%wt. glucose concentration. Viability/cytotoxicity, proliferation, and cells' metabolic activities demonstrated BC to be biocompatible. Cells attached, spread, and proliferated with time on bacterial cellulose. Results of this study showed 5.00 wt% glucose concentration is the optimum concentration of sugar in media to produce BC with highest strength and modulus compared to other concentration. High mechanical strength along with biocompatibility present bacterial cellulose as an invaluable material for use in tissue engineering of load bearing connective tissues such as tendons and ligaments.

Controlled mercerization of bacterial cellulose provides tunability of modulus and ductility over two orders of magnitude

Effects of mercerization process on plant-based cellulose is well studied in the literature whereas the effects of mercerization on mechanical properties of bacterial cellulose is not investigated. In this work bacterial cellulose (BC) was mercerized in NaOH solution with different molar concentrations of 0, 1.50, 1.75, 2.00, 2.13, 2.25, 5.00, 7.00 and 10.00 M. The BC samples shrunk substantially with increasing NaOH concentration. At the same concentration, NaOH treatment resulted in significantly larger shrinkage than KOH treatment. Mercerization of BC samples in 7 M NaOH resulted in an order of magnitude increase in elongation from 5.4 ± 1.6% to 50.8 ± 5.7% along with about 30-fold reduction in Young's modulus. Mercerized samples in 4 M NaOH had maximum toughness among all groups at a value of 64.0 ± 15.8 MJ m−3. Changes in BC crystalline structure from cellulose I to cellulose II were characterized and confirmed semiquantitatively by using X-ray diffraction (XRD) and Raman spectroscopy. Results of this work demonstrated mercerization as a method to tune the mechanical properties of BC precisely. Mercerized BC as a biocompatible material with tunable mechanical properties shows potential to be utilized in tissue engineering and regenerative medicine in the future.

Struktur dan Sifat Mekanik Film Bacterial Cellulose dengan Disintegrasi Mekanis

Film structure was greatly affected to mechanical properties of Bacterial Cellulose (BC). An engineering effort on Bacterial Cellulose Fibers (BCF) structure was changing the size and distribution of BC fiber through mechanical disintegrator process using a High Speed Blender (HSB). This study aimed to show the effect of disintegrator to the structure and mechanical properties of BCF film. The method used in this study is a synthesis of BCF from fermentation from pineapple peel waste with incubation of Acetobacter xylinum ( A. xylinum ) for 14 days. BC pellicle was soaked by using 1% NaOH for 24 hours then distrusted using the HSB with code speed variation of L (18000 rpm), M (21000 rpm), and H (26000 rpm) for 5 min. Then film formed by a casting method and dried in the oven at a temperature of 60 °C for 8 hours. The study result showed that the morphology of BCF formed pores, the crystallinity decreased so the tensile strength was decreased by 94%. The results of this study are expected to provide engineering information on the BCF structure potentially for filters and for sensors. DOI: http://dx.doi.org/10.17977/um024v3i22018p055

Mechanical properties of bacterial cellulose synthesised by diverse strains of the genus Komagataeibacter

Bacterial cellulose (BC) has several current and potential future uses in the food industry because of its ability to form hydrogels with distinctive properties. The texture of BC hydrogels is determined by both the cellulose fibre network and the internal dispersed water. In this study, mechanical properties of hydrated BC synthesised by six different strains of Komagataeibacter genus were investigated with regards to their extensibility, compressive strength, relaxation ability, viscoelasticity and poroelasticity. The stress/strain at failure and Young's modulus were assessed by uniaxial tensile testing. The compressive strength, relaxation ability and viscoelasticity were measured via a series of compression and small amplitude oscillatory shear steps. A poroelastic constitutive modelling simulation was used to investigate the mechanical effects of water movement. The morphology of the BC fibril network under compression was observed via scanning electron microscopy. Results showed that the mechanics of BC were highly dependent on the cellulose concentration, as well as the morphology of the fibril network. BC synthesised by ATCC 53524 was the most concentrated (0.71 wt%), and exhibited high tensile properties, stiffness and storage moduli; whereas comparatively low mechanical properties were noted for BC produced by ATCC 700178 and ATCC 10245, which contained the lowest cellulose concentration (0.18 wt%). Small deformation responses (normal stress, G′) scaled with cellulose concentration for all samples, whereas larger deformation responses (Young's modulus, poroelasticity) depended on both cellulose concentration and additional factors, presumably related to network morphology. Increasing concentration and compressive coalescence of fibres in the integrated BC network reduced both the relaxation of the normal stress and the movement of water. This research aids the selection of bacterial strains to modulate the texture and mechanical properties of hydrated BC-based food systems.

Improved thermal and mechanical properties of bacterial cellulose with the introduction of collagen

Composite films comprised of bacterial cellulose (BC) and collagen (COL) were developed using BC hydrogel membranes as the base material and COL as the reinforcing material. Glutaraldehyde (GT) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC·HCl) were then used as cross-linking agents to prepare cross-linked BC/COL composite films by a wet chemical method. The effects of chemical cross-linking on the thermal and mechanical properties of composite films were investigated in detail. The COL molecules were adsorbed and deposited inside of 3D nanofiber networks of BC, coated on the surface of BC fibers. Chemical bonds formed between BC molecules, and between BC and COL molecules after cross-linking. Compared with BC, the obtained composite films showed 57.9 and 70.8% improvement in tensile strength after being cross-linked by GT and EDC·HCl, respectively. Cross-linking also enhanced the thermal stability of the specimens.

Oriented bacterial cellulose-soy protein based fully ‘green’ nanocomposites

Bacterial cellulose (BC) nanofibrils are considered as promising biodegradable fiber-reinforcement for polymeric composites because of their excellent tensile properties. However, commonly obtained randomly-oriented web-like form of BC nanofibrils impedes achieving their full potential as reinforcement. In the present study, a facile and scalable method has been developed to orient the nanofibrils through a controlled stretching of BC hydrogel. An optimum hydrogel-stretching at the cross-head speed of 0.05 mm/min and strain ratio of 1.2 showed substantial improvements in the orientation and mechanical properties of BC. Degree of orientation, apparent Young's modulus and fracture stress of the dried BC were increased by 117, 103 and 85%, respectively. Consequently, a BC-reinforced soy protein isolate based fully ‘green’ composites (BC-SPI composites) were prepared by using vacuum-assisted SPI resin impregnation into BC hydrogel and then stretching the resin impregnated BC hydrogel. The stretched BC-SPI green composites, after drying and curing, showed significant improvement in their tensile properties due to higher BC nanofibrillar orientation. This study opens up new possibilities for direct fabrication of lightweight and mechanically robust ‘green’ composites that can replace traditional non-degradable composites and reduce carbon footprint significantly.

Effect of down-stream processing parameters on the mechanical properties of bacterial cellulose

Bacterial cellulose (BC), a biodegradable polymer with high degree of crystallinity, produced by Gluconacetobacter xylinus, was used as reinforcement in biocomposites. The downstream process parameters involved in the preparation process of BC have important influence on its mechanical properties. The effect of some key processing parameters such as treatment temperature, drying stages, type of treatment solvent and pressure on biocellulose sheets was investigated during drying in order to modify the parameters responsible in mechanical properties. The rise in treatment temperature and drying processes of BC sheets showed about 8 and 11 % reduction in tensile strength, respectively. The addition of NaOH solutions during the treatment reduced the tensile strength of BC sheets sharply, though an increase in NaOH concentration produced treated samples with higher tensile modulus. The use of optimum NaClO solution as a cheap treatment solvent led to an increase of about 10–11 % in the mechanical properties of BC. A pressure increase during drying stage improved the tensile strength of biocellulose sheets by 7 % and resulted in highly enhanced tensile modulus of BC samples. The production process (microbial fermentation) and structural features (porous web-shaped structure) provide an ideal scenario for synthesis of BC composites. A number of schemes have been introduced to synthesize BC composites with different materials. Among these schemes, the initial addition of materials to BC culture media, the treatment of BC with solutions and suspensions, and the dissolution of BC in solvents are the most commonly used techniques.

Mechanical and structural property analysis of bacterial cellulose composites

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.

Bacterial cellulose and bacterial cellulose-vaccarin membranes for wound healing

Bacterial cellulose (BC) and bacterial cellulose-vaccarin (BC-Vac) membranes were successfully produced in large scale. BC was synthesized by Gluconacetobacter xylinum. BC-Vac membranes were prepared by immersing BC in vaccarin solution. The surface morphologies of BC and BC-Vac membranes were examined by a scanning electron microscope (SEM) and an atomic force microscopy (AFM). The images showed that BC-Vac exhibited the characteristic 3D nanofibrillar network of BC matrix but there was adhesion between fibers. The mechanical properties of BC and BC-Vac membranes were evaluated and the results indicated that the adding of drug vaccarin into the BC membranes increased the malleability indicated by the increment in elongation at break compared with BC. Fourier transform infrared spectroscopy (FTIR) analysis was conducted to confirm the incorporation of vaccarin in BC-Vac and investigate the hydroxyl interactions between BC and drug vaccarin. Cell viability and cell attachment studies demonstrated that BC and BC-Vac membranes had no cytotoxicity and could be a good carrier for cell growth. The wound healing performance was examined in vivo by rat skin models. Histological observations revealed that wounds treated with BC-Vac epithelialized and regenerated faster than treated with BC. Therefore, BC-Vac was considered as a potential candidate for wound dressing materials.