Development of self-assembled bacterial cellulose–starch nanocomposites

Recent Progress in Polysaccharide-Based Materials for Energy Applications: A Review

In recent years, polysaccharides have emerged as a promising alternative for the development of environmentally friendly materials. Polysaccharide-based materials have been mainly studied for applications in the food, packaging, and biomedical industries. However, many investigations report processing routes and treatments that enable the modification of the inherent properties of polysaccharides, making them useful as materials for energy applications. The control of the ionic and electronic conductivities of polysaccharide-based materials allows for the development of solid electrolytes and electrodes. The incorporation of conductive and semiconductive phases can modify the permittivities of polysaccharides, increasing their capacity for charge storage, making them useful as active surfaces of energy harvesting devices such as triboelectric nanogenerators. Polysaccharides are inexpensive and abundant and could be considered as a suitable option for the development and improvement of energy devices. This review provides an overview of the main research work related to the use of both common commercially available polysaccharides and local native polysaccharides, including starch, chitosan, carrageenan, ulvan, agar, and bacterial cellulose. Solid and gel electrolytes derived from polysaccharides show a wide range of ionic conductivities from 0.0173 × 10-3 to 80.9 × 10-3 S cm-1. Electrodes made from polysaccharides show good specific capacitances ranging from 8 to 753 F g-1 and current densities from 0.05 to 5 A g-1. Active surfaces based on polysaccharides show promising results with power densities ranging from 0.15 to 16 100 mW m-2. These investigations suggest that in the future polysaccharides could become suitable materials to replace some synthetic polymers used in the fabrication of energy storage devices, including batteries, supercapacitors, and energy harvesting devices.

Edible, strong, and low-hygroscopic bacterial cellulose derived from biosynthesis and physical modification for food packaging

BACKGROUND

The pervasive presence of plastic packaging has led to significant environmental contamination due to excessive reliance on petrochemicals and the inherent non-biodegradability of these materials. Bacterial cellulose (BC) films present a viable alternative for food packaging applications, owing to their environmentally friendly synthesis process, non-toxic nature, robust mechanical strength, and biodegradability. However, the high hygroscopicity of such bio-based materials has limited their widespread adoption, as it results in diminished strength and barrier properties. In this study, a novel approach for creating edible, transparent, robust, and high-barrier BC-based composite packaging was proposed through biosynthesis with the incorporation of soy protein isolate and the physical interpenetration of calcium alginate-polyethylene glycol as a composite coating.

RESULTS

The finding demonstrated that the synthesized bio-based composite material exhibits stability in water, high optical transparency, complete oil resistance, and full degradability within 1 to 2 months. Furthermore, the composite material displayed enhanced mechanical properties in both dry and wet conditions, with a tensile strength of approximately 84 MPa, outperforming commercially available kraft paper and low-density polyethylene.

CONCLUSIONS

Soy protein isolate established a rigid, coherent, and homogeneous network with BC fibrils, thereby augmenting mechanical properties. Calcium alginate can be effectively combined with BC, utilizing polyethylene glycol as a binder and plasticizer, to generate a densely packed structure with reduced hygroscopicity. This bio-based composite material demonstrated considerable potential for application in food packaging and other value-added sectors as a substitute for non-degradable plastics. © 2023 Society of Chemical Industry.

A Review on Reinforcements and Additives in Starch-Based Composites for Food Packaging

The research of starch as a matrix material for manufacturing biodegradable films has been gaining popularity in recent years, indicating its potential and possible limitations. To compete with conventional petroleum-based plastics, an enhancement of their low resistance to water and limited mechanical properties is essential. This review aims to discuss the various types of nanofillers and additives that have been used in plasticized starch films including nanoclays (montmorillonite, halloysite, kaolinite, etc.), poly-saccharide nanofillers (cellulose, starch, chitin, and chitosan nanomaterials), metal oxides (titanium dioxide, zinc oxide, zirconium oxide, etc.), and essential oils (carvacrol, eugenol, cinnamic acid). These reinforcements are frequently used to enhance several physical characteristics including mechanical properties, thermal stability, moisture resistance, oxygen barrier capabilities, and biodegradation rate, providing antimicrobial and antioxidant properties. This paper will provide an overview of the development of starch-based nanocomposite films and coatings applied in food packaging systems through the application of reinforcements and additives.

Use of brewer's residual yeast for production of bacterial nanocellulose with Gluconacetobacter hansenii

Bacterial nanocellulose (BNC) has attained elevated interest due to its versatile structure and high resistance characteristics. Accordingly, efforts have been made in order to reduce its production costs, such as the employment of its by-products as a nutrient broth to yield the microorganism. Residual brewer's yeast is an excellent recourse, due to its high nutritional value and availability. Therefore, research which aimed to contribute to the development of a low cost, efficient and biosustainable technology for BNC production with Gluconacetobacter hansenii was carried out. BNC was obtained from residual brewer's yeast hydrolysate at pH 7.0 and five days of incubation at 30 °C in static culture. The hydrolysate was characterized by the amount of sugars, fatty acids, total proteins and ash content. Subsequently, BNC obtained was characterized in terms of yield, carbon conversion ratio, hydrodynamic size, crystallinity, morphology, Fourier-transform infrared spectroscopy, and surface analysis. Residual brewer's yeast hydrolysate proved to be efficient in BNC production via gluconeogenesis with consumption of alanine, threonine and glycerol, obtaining 1.9 times the yield of the chemically defined broth adopted as standard. Additionally, properties observed in the obtained BNC were equal to those obtained from conventional chemical medium. The research contributed to bacterial nanocellulose production using by-products from the brewing industry.

Development of a layered bacterial nanocellulose-PHBV composite for food packaging

BACKGROUND

Most of the current materials used in food packaging are synthetic and non-degradable, raising environmental issues derived from the accumulation of plastics in landfills/waterways. The food industry increasingly needs eco-friendly sustainable materials that meet food-packaging requirements. Bacterial nanocellulose (BNC), a biopolymer obtained by fermentation, offers very good mechanical properties and the ability to carry and deliver active substances. However, its water-vapor permeability is too high for food-packaging applications. In this work, a layered biodegradable composite based on BNC and polyhydroxyalkanoate (PHBV) was produced, attempting to improve its overall barrier properties. Polyhydroxyalkanoate is a biopolymer with high degree of hydrophobicity and biodegradability, and is also obtained by fermentation. Wet BNC membranes produced by static culture were plasticized by impregnation of solutions of either glycerol (BNC_gly ) or polyethylene glycol (M_W 600) (BNC_PEG ). The plasticized BNC was then coated with PHBV solution dissolved in formic acid, and oven dried at 148 °C.

RESULTS

Overall, PHBV coating on plasticized BNC reduced water vapor permeability significantly (from 0.990 to 0.032 g.μm.m^-2 .day^-1 .Pa^-1 ) under 50% relative humidity. It increased the hydrophobicity (contact angle from 10-40° to 80-90°) but decreased the stiffness (from 3.1 GPa to 1.3 Gpa) of the composite.

CONCLUSIONS

Overall, the mechanical and barrier properties of the layered composite obtained were considered suitable for food-packaging applications. The plasticizing (with glycerol or polyethylene glycol) of BNC significantly improved the mechanical performance and the PHBV coating reduced the water affinity (vapor and liquid state) on BNC. © 2022 Society of Chemical Industry.

Effect of TiO2 Nanoparticles and Extrusion Process on the Physicochemical Properties of Biodegradable and Active Cassava Starch Nanocomposites

Biodegradable polymers have been strongly recognized as an alternative to replace traditional petrochemical plastics, which have become a global problem due to their long persistence in the environment. In this work, the effect of the addition of titanium dioxide nanoparticles (TiO₂NP) on the morphology, physicochemical properties and biodegradation under industrial composting conditions of cassava starch-based nanocomposites obtained by extrusion at different screw speeds (80 and 120 rpm) were investigated. Films performed at 120 rpm (S₁₂₀ and S₁₂₀-TiO₂NP) showed completely processed starch and homogeneously distributed nanoparticles, leading to much more flexible nanocomposites than those obtained at 80 rpm. The incorporation of TiO₂NP led to an increase in storage modulus of all films and, in the case of S₁₂₀-TiO₂NP, to higher strain at break values. From the Kohlrausch-Williams-Watts theoretical model (KWW), an increase in the relaxation time of the nanocomposites was observed due to a decrease in the number of polymer chains involved in the relaxation process. Additionally, S₁₂₀-TiO₂NP showed effective protection against UV light, greater hydrophobicity and faster biodegradation in compost, resulting in a promising material for food packaging applications.

In situ regulation of bacterial cellulose networks by starch from different sources or amylose/amylopectin content during fermentation

Bacterial cellulose (BC) is a promising biopolymer, but its three-dimensional structure needs to be controllable to be used in multiple fields. BC has some advantages over other types of cellulose, not only in terms of purity and properties but also in terms of modification (in situ modification) during the synthesis process. Here, starches from different sources or with amylose/amylopectin content were added to the growth medium to regulate the structural properties of BC in-situ. The obtained BC membranes were further modified by superhydrophobic treatment for oil-water separation. Starches alter the viscosity of the medium, thus affecting bacterial motility and cellulose synthesis, and adhere to the microfibers, limiting their further polymerization and ultimately altering the membrane porosity, pore size, and mechanical properties perpendicular to the BC fibril layer direction. The average pore diameter of the BC/PS membrane increased by 1.94 times compared to the initial BC membrane. The chemically modified BC/PS membrane exhibited super-hydrophobicity (water contact angle 167°), high oil-water separation flux (dichloromethane, 23,205 Lm^-2 h^-1 MPa^-1), high separation efficiency (>97%). The study provides a foundation for developing methods to regulate the network structure of BC and broaden its application.

Use of Industrial Wastes as Sustainable Nutrient Sources for Bacterial Cellulose (BC) Production: Mechanism, Advances, and Future Perspectives

A novel nanomaterial, bacterial cellulose (BC), has become noteworthy recently due to its better physicochemical properties and biodegradability, which are desirable for various applications. Since cost is a significant limitation in the production of cellulose, current efforts are focused on the use of industrial waste as a cost-effective substrate for the synthesis of BC or microbial cellulose. The utilization of industrial wastes and byproduct streams as fermentation media could improve the cost-competitiveness of BC production. This paper examines the feasibility of using typical wastes generated by industry sectors as sources of nutrients (carbon and nitrogen) for the commercial-scale production of BC. Numerous preliminary findings in the literature data have revealed the potential to yield a high concentration of BC from various industrial wastes. These findings indicated the need to optimize culture conditions, aiming for improved large-scale production of BC from waste streams.

Efficacy of Bacterial Nanocellulose in Hard Tissue Regeneration: A Review

Bacterial nanocellulose (BNC, as exopolysaccharide) synthesized by some specific bacteria strains is a fascinating biopolymer composed of the three-dimensional pure cellulosic nanofibrous matrix without containing lignin, hemicellulose, pectin, and other impurities as in plant-based cellulose. Due to its excellent biocompatibility (in vitro and in vivo), high water-holding capacity, flexibility, high mechanical properties, and a large number of hydroxyl groups that are most similar characteristics of native tissues, BNC has shown great potential in tissue engineering applications. This review focuses on and discusses the efficacy of BNC- or BNC-based biomaterials for hard tissue regeneration. In this review, we provide brief information on the key aspects of synthesis and properties of BNC, including solubility, biodegradability, thermal stability, antimicrobial ability, toxicity, and cellular response. Further, modification approaches are discussed briefly to improve the properties of BNC or BNC-based structures. In addition, various biomaterials by using BNC (as sacrificial template or matrix) or BNC in conjugation with polymers and/or fillers are reviewed and discussed for dental and bone tissue engineering applications. Moreover, the conclusion with perspective for future research directions of using BNC for hard tissue regeneration is briefly discussed.

Sandwich panel biocomposite of thermoplastic corn starch and bacterial cellulose

Inadequate disposition and long period for degradation of Petroleum-derived polymers promote damages in the environment, which could be minimized by the use of biodegradable polymers such as starch and cellulose. Films of thermoplastic corn starch (TPS) and bacterial cellulose (BC) were used to produce sandwich panel biocomposite. RXD, SEM and FTIR were used to verify the transformation of TPS from native corn starch. TPS/BC is flexible and transparent, but it is less transparent that TPS and BC due to its multilayer format. TPS/BC presented similar thermal events to TPS and BC samples and thermal stability similar to TPS. The FTIR spectrum of the TPS/BC showed bands observed in the BC and TPS spectra. BC, TPS and TPS/BC showed faster water absorption in the initial stage reaching a stability at about 50 h and presenting Fickian behavior. TPS/BC showed lower water absorption and a good adhesion between the phases observed by SEM images, which can be associated to hydrogen interactions in the interface improving mechanical properties. TPS/BC showed an increase of about 3.6 times in the tensile strength compared to TPS, indicating that BC is a good reinforcement for TPS.

Mirror effect in atomic force microscopy profiles enables tip reconstruction

In this work, the tip convolution effect in atomic force microscopy is revisited to illustrate the capabilities of cubic objects for determination of the tip shape and size. Using molecular-based cubic nanoparticles as a reference, a two-step tip reconstruction process has been developed. First, the tip-to-face angle is estimated by means of an analysis of the convolution error while the tip radius is extracted from the experimental profiles. The results obtained are in good agreement with specification of the tip supplier even though the experiments have been conducted using real distribution of nanoparticles with dispersion in size and aspect ratio. This demonstrates the reliability of our method and opens the door for a more accurate tip reconstruction by using calibration standards.

Nanocellulose Bio-Based Composites for Food Packaging

The food industry is increasingly demanding advanced and eco-friendly sustainable packaging materials with improved physical, mechanical and barrier properties. The currently used materials are synthetic and non-degradable, therefore raising environmental concerns. Consequently, research efforts have been made in recent years towards the development of bio-based sustainable packaging materials. In this review, the potential of nanocelluloses as nanofillers or as coatings for the development of bio-based nanocomposites is discussed, namely: (i) the physico-chemical interaction of nanocellulose with the adjacent polymeric phase, (ii) the effect of nanocellulose modification/functionalization on the final properties of the composites, (iii) the production methods for such composites, and (iv) the effect of nanocellulose on the overall migration, toxicity, and the potential risk to human health. Lastly, the technology readiness level of nanocellulose and nanocellulose based composites for the market of food packaging is discussed.

Antibacterial Activity of Bacterial Cellulose Loaded with Bacitracin and Amoxicillin: In Vitro Studies

The use of bacterial cellulose (BC) in skin wound treatment is very attractive due to its unique characteristics. These dressings’ wet environment is an important feature that ensures efficient healing. In order to enhance the antimicrobial performances, bacterial-cellulose dressings were loaded with amoxicillin and bacitracin as antibacterial agents. Infrared characterization and thermal analysis confirmed bacterial-cellulose binding to the drug. Hydration capacity showed good hydrophilicity, an efficient dressing’s property. The results confirmed the drugs’ presence in the bacterial-cellulose dressing’s structure as well as the antimicrobial efficiency against Staphylococcus aureus and Escherichia coli. The antimicrobial assessments were evaluated by contacting these dressings with the above-mentioned bacterial strains and evaluating the growth inhibition of these microorganisms.

Fabrication and In-Vivo Study of Micro-Colloidal Zanthoxylum acanthopodium-Loaded Bacterial Cellulose as a Burn Wound Dressing

Bacterial cellulose (BC) is a biopolymer commonly used for wound dressing due to its high biocompatible properties either in-vitro or in-vivo. The three-dimensional fiber structure of BC becomes an advantage because it provides a template for the impregnation of materials in order to improve BC's properties as a wound dressing, since BC has not displayed any bioactivity properties. In this study, micro-colloidal Zanthoxylum acanthopodium (MZA) fruit was loaded into BC fibers via an in-situ method. Z. acanthopodium is known to have anti-inflammatory, antioxidant and antimicrobial activities that can support BC to accelerate the wound healing process. The FTIR, XRD and SEM analysis results showed that the loading process of MZA and the composite fabrication were successfully carried out. The TGA test also showed that the presence of MZA in BC fibers decreased Tmax composite from BC, from 357.8 to 334.5 °C for BC-MZA3. Other aspects, i.e., water content, porosity, hemocompatibility and histology studies, also showed that the composite could potentially be used as a wound dressing.

A Novel Multilayer Composite Membrane for Wound Healing in Mice Skin Defect Model

To develop a wound dressing material that conforms to the healing process, we prepared a multilayer composite (MC) membrane consisting of an antibacterial layer (ABL), a reinforcement layer (RFL), and a healing promotion layer (HPL). Biocompatible zein/ethyl cellulose (zein/EC) electrospun nanofibrous membranes with in situ loaded antibacterial photosensitizer protoporphyrin (PPIX) and healing promotion material vaccarin (Vac) were, respectively, chosen as the ABL on the surface and the HPL on the bottom, between which nonwoven incorporated bacterial cellulose (BC/PETN) as the HPL was intercalated to enhance the mechanical property. Photodynamic antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa was confirmed by the enlarged inhibition zones; meanwhile, satisfactory biocompatibility of the HPL was verified by scanning electronic microscopy (SEM) of L929 cells cultured on its surface. The potential effects on wound healing in a mice skin defect model of the MC membranes were also evaluated. The animal experiments demonstrated that the wound healing rate in the MC group was significantly increased compared with that in the control group (p < 0.05). Histopathological observation revealed an alleviated inflammatory response, accompanied with vascular proliferation in the MC group. The MC membranes significantly promoted wound healing by creating an antibacterial environment and promoting angiogenesis. Taken together, this MC membrane may act as a promising wound dressing for skin wound healing.

Microscopic and spectroscopic characterization of rice and corn starch

Starch granules from rice and corn were isolated, and their molecular mechanism on interaction with α-amylase was characterized through biochemical test, microscopic imaging, and spectroscopic measurements. The micro-scale structure of starch granules were observed under an optical microscope and their average size was in the range 1-100 μm. The surface topological structures of starch with micro-holes due to the effect of α- amylase were also visualized under scanning electron microscope. The crystallinity was confirmed by X-ray diffraction patterns as well as second-harmonic generation microscopy. The change in chemical bonds before and after hydrolysis of the starch granules by α- amylase was determined by Fourier transform infrared spectroscopy. Combination of microscopy and spectroscopy techniques relates structural and chemical features that explain starch enzymatic hydrolysis which will provide a valid basis for future studies in food science and insights into the energy transformation dynamics.

Preparation and Applications of the Cellulose Nanocrystal

Cellulose widely existed in plants and bacteria, which takes important effect on the synthesis of macromolecule polymer material. Because of its great material properties, the cellulose nanocrystal (CNC) showed its necessary prospect in various industrial applications. As a renewable future material, the preparation methods of the CNC were reviewed in this paper. Meanwhile, the important applications of CNC in the field of composites, barrier film, electronics, and energy consumption were also mentioned with brief introductions. The summarized preparations and considerable applications provided operable ideas and methods for the future high-end and eco-friendly functional composites. Suggestions for potential applications were also discussed.

Natural Polysaccharide Nanomaterials: An Overview of Their Immunological Properties

Natural occurring polymers, or biopolymers, represent a huge part of our planet biomass. They are formed by long chains of monomers of the same type or a combination of different ones. Polysaccharides are biopolymers characterized by complex secondary structures performing several roles in plants, animals, and microorganisms. Because of their versatility and biodegradability, some of them are extensively used for packaging, food, pharmaceutical, and biomedical industries as sustainable and renewable materials. In the recent years, their manipulation at the nanometric scale enormously increased the range of potential applications, boosting an interdisciplinary research attempt to exploit all the potential advantages of nanostructured polysaccharides. Biomedical investigation mainly focused on nano-objects aimed at drug delivery, tissue repair, and vaccine adjuvants. The achievement of all these applications requires the deep knowledge of polysaccharide nanomaterials' interactions with the immune system, which orchestrates the biological response to any foreign substance entering the body. In the present manuscript we focused on natural polysaccharides of high commercial importance, namely, starch, cellulose, chitin, and its deacetylated form chitosan, as well as the seaweed-derived carrageenan and alginate. We reviewed the available information on their biocompatibility, highlighting the importance of their physicochemical feature at the nanoscale for the modulation of the immune system.

Nanoskin® to treat full thickness skin wounds

This experimental study evaluated 40 guinea pigs that received Nanoskin®. A full thickness skin rectangle measuring 2x4 cm was removed from the median dorsal region and the wound was covered by a 2X2 cm fragment of uncoated Nanoskin® graft (uncoated group) or Nanoskin® coated with gelatin (coated group) and sutured in the caudal region and a 2x2 cm fragment of autologous skin sutured in the cranial aspect of the surgical wound served a control. The animals were examined daily by ectoscopy and euthanized at 7, 30, 90 and 180 days postoperatively. Immediately after euthanasia, the operated area was shaved, documented with photos and removed, and prepared for morphological, morphometric and ultrastructural exam. It was found that the full thickness skin wound healed in a centripetal pattern. The healing process was similar between groups, with a more pronounced inflammatory reaction initially that gradually decreased over time. The conclusion is that the uncoated Nanoskin® or Nanoskin® coated with gelatin is a good material to treat full thickness skin wound. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res B Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 724-732, 2019.

A Novel In Situ Self-Assembling Fabrication Method for Bacterial Cellulose-Electrospun Nanofiber Hybrid Structures

Self-assembling fabrication methodology has recently attracted attention for the production of bio-degradable polymer nanocomposites. In this research work, bacterial cellulose/electrospun nanofiber hybrid mats (BC/CA-ENM) were formed by incorporating cellulose acetate electrospun nanofiber membranes (CA-ENMs) in the fermentation media, followed by in situ self-assembly of bacterial cellulose (BC) nanofibers. ENMs exhibit excessive hydrophobicity, attributed to their high crystallinity and reorientation of hydrophobic groups at the air/solid interfaces. We aimed to improve the hydrophilic and other functional properties of ENMs. As-prepared nanohybrid structures were characterized using SEM and FTIR. SEM results revealed that in situ self-assembling of BC nanofibers onto the electrospun membrane's surface and penetration into pores gradually increased with extended fermentation periods. The surface hydrophilicity and water absorption capacity of as-prepared hybrid mats was also tested and analyzed. Hybrid mats were observably more hydrophilic than an electrospun membrane and more hydrophobic compared to BC films. In addition, the incorporation of CA electrospun membranes in the culture media as a foundation for BC nanofiber growth resulted in improved tensile strength of the hybrid nanocomposites compared to ENMs. Overall, the results indicated the successful fabrication of nanocomposites through a novel approach, with samples demonstrating improved functional properties.

Comparison of the analytical methods (solid state NMR, FT-IR, PXRD) in the analysis of the solid drug forms with low concentration of an active ingredient - 17-β-estradiol case

The application of various techniques (FT-IR, PXRD, ssNMR) in the analysis of solid dosage forms with low concentration of an API (17-β-estradiol hemihydrate, EBHH) was tested. PXRD analysis of Estrofem Mite tablets (EMT) confirmed the presence of the main crystalline excipient, α-lactose monohydrate. In the PXRD pattern of EMT the strong background from polycrystalline excipients, i.e. hydroxypropylmethylcellulose and corn starch was observed. FT-IR spectra were characterized by the broad peaks in the 3000-3600cm^-1 region of the OH stretching modes coming from multiple hydrogen bonds that are present in the structures of the excipients (α-lactose monohydrate, corn starch) and API. The only technique which unambiguously confirmed the presence of an API in the EMT was solid state NMR. Despite the tabletting process each of the EMT component retained its characteristic features like relaxation time and T_1ρ^I. Due to the possibility of the manipulation in the experimental registration parameters like recycle delay (RD), evolution time (τ) and contact time (CT) it was possible to perform multiple experiments on the same sample of EMT. The most valuable were the inversion recovery CP experiments in which, by setting the proper values of τ, it was possible to selectively observe the signals of the chosen component of the drug formulation. In this study the great potential of solid state NMR in the analysis of solid dosage forms, as the unique technique that combines the possibility of selective observation of the chosen signals with the non destructive character that enables further analysis of the same sample, was confirmed.

Production and Status of Bacterial Cellulose in Biomedical Engineering

Bacterial cellulose (BC) is a highly pure and crystalline material generated by aerobic bacteria, which has received significant interest due to its unique physiochemical characteristics in comparison with plant cellulose. BC, alone or in combination with different components (e.g., biopolymers and nanoparticles), can be used for a wide range of applications, such as medical products, electrical instruments, and food ingredients. In recent years, biomedical devices have gained important attention due to the increase in medical engineering products for wound care, regeneration of organs, diagnosis of diseases, and drug transportation. Bacterial cellulose has potential applications across several medical sectors and permits the development of innovative materials. This paper reviews the progress of related research, including overall information about bacterial cellulose, production by microorganisms, mechanisms as well as BC cultivation and its nanocomposites. The latest use of BC in the biomedical field is thoroughly discussed with its applications in both a pure and composite form. This paper concludes the further investigations of BC in the future that are required to make it marketable in vital biomaterials.

Synthesis of carboxymethylcellulose/starch superabsorbent hydrogels by gamma-irradiation

Background

Superabsorbent hydrogels show a large potential in a wide array of applications due to their unique properties. Carboxymethylcellulose (CMC) is a commercially available water-soluble cellulose derivative of major interest in the hydrogel synthesis. High-energy irradiation allows the chemical crosslinking without the use of crosslinking agents, while the introduction of other natural or synthetic polymers offers a convenient way to modify the gels. In this study we examined the effect of the addition of starch, a low-cost renewable polysaccharide, on the properties of carboxymethylcellulose-based hydrogels.

Results

Superabsorbent gels were prepared by gamma irradiation from aqueous mixtures of carboxymethylcellulose and starch. The partial replacement of CMC with starch improved the gel fraction, while a slight increase in the water uptake was also observed. However, very high starch content had a negative impact on the gelation, resulting in a decrease in gel fraction. Moreover, higher solute concentrations were preferred for the gelation of CMC/starch than for pure CMC. Hydrogels containing 30% starch showed the best properties: a water uptake of ~350 g_water/g_gel was achieved with ~55% gel fraction synthesized from 15 w/w% solutions at 20 kGy. Heterogeneous gel structure was observed: the starch granules and fragments were dispersed in the CMC matrix. The swelling of CMC/starch gels showed a high sensitivity to the ionic strength in water due to the CMC component. However, the mixed gels are less sensitive to the ionic strength than pure CMC gels.

Conclusions

The introduction of starch to carboxymethylcellulose systems led to improved properties. Such gels showed higher water uptake, especially in an environment with high electrolyte concentration. CMC/starch hydrogels may offer a cheaper, superior alternative compared to pure cellulose derivative-based gels depending on the application.

In Situ Self-Assembled Nanocomposites from Bacterial Cellulose Reinforced with Eletrospun Poly(lactic acid)/Lipids Nanofibers

The goal of this study is to explore a new strategy to improve the mechanical and hydrophobic properties of bacterial cellulose (BC) mats. The present work is the first to report the preparation of in situ self-assembled BC nanocomposites using electrospun hydrophobic poly(lactic acid) (PLA) or PLA/lipids (PLA/Lip) nanofiber mats as foundation for BC nanofiber growth. Adding electrospun PLA mats to the BC culture media led to a two-fold increase in toughness with a 52% increase in elongation of the nanocomposites with regard to BC. The incorporation of electrospun PLA and PLA/Lip nanofiber mats lowered the moisture regain and water vapor transmission of BC nanocomposites relative to pure BC mats. The interfacial bonding between the individual components of a nanocomposite is a key factor for the improvement of composite strength, stiffness, and barrier properties; thus additional strategies to improve interaction between hydrophilic BC and hydrophobic PLA fibers need to be explored.

Production and characterization of bacterial cellulose membranes with hyaluronic acid from chicken comb

The bacterial cellulose (BC), from Gluconacetobacter hansenii, is a biofilm with a high degree of crystallinity that can be used for therapeutic purposes and as a candidate for healing wounds. Hyaluronic acid (HA) is a constitutive polysaccharide found in the extracellular matrix and is a material used in tissue engineering and scaffolding for tissue regeneration. In this study, polymeric composites were produced in presence of hyaluronic acid isolated from chicken comb on different days of fermentation, specifically on the first (BCHA-SABT0) and third day (BCHA-SABT3) of fermentation. The structural characteristics, thermal stability and molar mass of hyaluronic acid from chicken comb were evaluated. Native membrane and polymeric composites were characterized with respect to their morphology and crystallinity. The optimized process of extraction and purification of hyaluronic acid resulted in low molar mass hyaluronic acid with structural characteristics similar to the standard commercial hyaluronic acid. The results demonstrate that the polymeric composites (BC/HA-SAB) can be produced in situ. The membranes produced on the third day presented better incorporation of HA-SAB between cellulose microfiber, resulting in membranes with higher thermal stability, higher roughness and lower crystallinity. The biocompatiblily of bacterial cellulose and the importance of hyaluronic acid as a component of extracellular matrix qualify the polymeric composites as promising biomaterials for tissue engineering.

Monitoring molecular dynamics of bacterial cellulose composites reinforced with graphene oxide by carboxymethyl cellulose addition

Broadband Dielectric Relaxation Spectroscopy was performed to study the molecular dynamics of dried Bacterial Cellulose/Carboxymethyl Cellulose-Graphene Oxide (BC/CMC-GO) composites as a function of the concentration of CMC in the culture media. At low temperature the dielectric spectra are dominated by a dipolar process labelled as a β-relaxation, whereas electrode polarization and the contribution of dc-conductivity dominate the spectra at high temperatures and low frequency. The CMC concentration affects the morphological structure of cellulose and subsequently alters its physical properties. X-ray diffractometry measurements show that increasing the concentration of CMC promotes a decrease of the I_α/I_β ratio. This structural change in BC, that involves a variation in inter- and intramolecular interactions (hydrogen-bonding interactions), affects steeply their molecular dynamics. So, an increase of CMC concentration produces a significantly decrease of the β-relaxation strength and an increase of the dc-conductivity.

Emerging trends in eco-compliant, synergistic, and hybrid assembling of multifunctional polymeric bionanocomposites

The quest to develop eco-benign polymeric hybrid materials arose out of the need to protect the environment from the harmful effects of synthetic petroleum polymeric waste and meet the specific needs of industries such as oil and gas, aerospace, automotives, packaging, electronics biomedicals, pharmaceuticals, agricultural, and construction. This has resulted in synergistic hybrid assembling of natural fibers, polymers, biopolymers, and nanoparticles. Bionanocomposites based on inorganic nanoparticle reinforced biofiber, polymers and biopolymers, and polysaccharides such as chitosan, alginate, and cellulose derivatives, and so on, exhibiting at least a dimension at the nanometer scale, are an emerging group of nanostructured hybrid materials. These hybrid bionanocomposites exhibit structural and multifunctional properties suitable for versatile applications similar to polymer nanocomposites. Their biocompatibility and biodegradability provide opportunities for applications as eco-benign green nanocomposites. This review presents state-of-the-art progress in synergistic nanotechnological assembling of bionanocomposites relative to processing technologies, product development, and applications.