Bacterial Cellulose Nanowhiskers Research Articles

Grafting bacterial cellulose nanowhiskers into whey protein/essential oil film composites: Effect on structure, essential oil release and antibacterial properties of films

The development of bio-based primary packaging is imperative to improve food safety and quality, along with mitigating the environmental pollution resulting from the increasing production of packaging wastes. Whey protein concentrate (WPC) has received significant attention as an alternative raw material for edible films production, whereas an area of many ongoing researches has been the inclusion of bio-based compounds to formulate functional edible films. This study elaborated the development of WPC edible films fortified with different essential oils (EO) to assess antimicrobial activity against gram-positive (Staphylococcus aureus and Listeria monocytogenes) and gram-negative (Salmonella enteritidis and Pseudomonas aeruginosa) food-borne pathogens. Subsequently, the effect of grafting bacterial cellulose nanowhiskers (BCNW) in film composites was evaluated for WPC/oregano EO (WPC/OEO) films, which showed the highest antibacterial activity. Notably, increasing the concentration of grafted BCNW entailed a proportional increase on the inhibitory activity. In specific, antibacterial activity increased up to 80% when 10% BCNW was grafted in WPC/OEO films. Inclusion of BCNW and homogenous distribution of OEO into the film blend was pointed out through Raman analysis. In addition, AFM and SEM analysis revealed that inclusion of BCNW and OEO into the film matrix led to the formation of rough films with pores. This structural change enhanced the release capacity of OEO, that was further confirmed through a release kinetic experiment. This study indicated that BCNW addition positively affected whey protein films properties, thereby envisaging the potential development of sustainable food packaging materials with tailor-made properties.

Green Biodegradable Polylactide-Based Polyurethane Triblock Copolymers Reinforced with Cellulose Nanowhiskers

A novel series of biodegradable polylactide-based triblock polyurethane (TBPU) copolymers covering a wide range of molecular weights and compositions were synthesized for potential use in biomedical applications. This new class of copolymers showed tailored mechanical properties, improved degradation rates, and enhanced cell attachment potential compared to polylactide homopolymer. Triblock copolymers, (TB) PL-PEG-PL, of different compositions were first synthesized from lactide and polyethylene glycol (PEG) via ring-opening polymerization in the presence of tin octoate as the catalyst. After which, polycaprolactone diol (PCL-diol) reacted with TB copolymers using 1,4-butane diisocyanate (BDI) as a nontoxic chain extender to form the final TBPUs. The final composition, molecular weight, thermal properties, hydrophilicity, and biodegradation rates of the obtained TB copolymers, and the corresponding TBPUs were characterized using 1H-NMR, GPC, FTIR, DSC, and SEM, and contact angle measurements. Results obtained from the lower molecular weight series of TBPUs demonstrated potential use in drug delivery and imaging contrast agents due to their high hydrophilicity and degradation rates. On the other hand, the higher molecular weight series of TBPUs exhibited improved hydrophilicity and degradation rates compared to PL-homopolymer. Moreover, they displayed improved tailored mechanical properties suitable for utilization as bone cement, or in regeneration medicinal applications of cartilage, trabecular, and cancellous bone implants. Furthermore, the polymer nanocomposites obtained by reinforcing the TBPU3 matrix with 7% (w/w) bacterial cellulose nanowhiskers (BCNW) displayed a ~16% increase in tensile strength, and 330% in % elongation compared with PL-homo polymer.

Whey protein films reinforced with bacterial cellulose nanowhiskers: Improving edible film properties via a circular economy approach

Edible films were developed using whey protein concentrate (WPC) and a natural bio-polymer, namely bacterial cellulose (BC). BC was produced via fermentation from orange peels and subsequently acid-hydrolyzed to obtain BC nanowhiskers (BCNW) with high crystallinity (XRD analysis). Morphology of BCNW was analyzed by SEM, TEM, and AFM. WPC/BCNW film composites, containing different amounts of BCNW (0.5–15%, w/w) were developed and characterized. WPC/BCNW film composite was analyzed by Raman spectroscopy, indicating the successful incorporation and the homogenous distribution of BCNW into the WPC film matrix. Mechanical characterization showed that BCNW behaved as a reinforcing filler in the WPC film, increasing tensile strength and Young’s modulus by 32% and 80%, respectively. In addition, water vapor permeability was reduced by 33.9% upon the addition of 0.5% BCNW. This study presented a sustainable approach towards the production of WPC films with improved tensile and water barrier properties, suggesting its potential application as a packaging material.

Nanocatalyst doped bacterial cellulose-based thermosensitive nanogel with biocatalytic function for antibacterial application

Reactive oxygen species (ROS) for treating bacterial infection is an alternative strategy to overcome the drawbacks such as bacterial resistance of commonly used antibiotics. Nanocatalysts have been proved highly effective in regulating intracellular ROS level due to their intrinsic enzymes-mimicking ability. Herein, we prepared a carbon-based nanozyme doped with copper atoms with peroxidase mimetic activity to catalyze the decomposition of bio-safety dosage of H2O2 to highly reactive OH radicals for antibacterial treatment. Furthermore, we designed the thermo-responsive nanogels consisting of bacterial cellulose nanowhiskers as the carrier of the nanozyme. The obtained nanogels displayed remarkable intelligent response to temperature change with sol-gel transition temperature of ~33 °C and in situ gel forming ability. Moreover, the nanogels exhibited excellent biocompatibility in vitro, along with remarkable antibacterial efficacy which could inactivate 6.36 log of S. aureus and 6.01 log of E. coli in 3 h, respectively. The findings provide a novel strategy for advancing the development of nanocatalysts-based responsive biomaterials for treating bacterial infections.

Characterization of bio-nanocomposite films based on gelatin/polyvinyl alcohol blend reinforced with bacterial cellulose nanowhiskers for food packaging applications

Bacterial cellulose nanowhiskers (BCNW) were synthesized from Komagataeibacter xylinus (strain K2G30; UMCC 2756) using sulfuric acid hydrolysis and incorporated into a gelatin-polyvinyl alcohol (GL/PVA) blend film matrix. The effect of BCNW content (1–10 wt% of biopolymer) on the microstructural, mechanical, optical, and water barrier properties of bio-nanocomposites was studied. Transmission electron microscopy showed that BCNW had a needle shape morphology with an average length of 600 nm and an average width of 30 nm. The crystallinity index of BCNW was 94.7% using X-ray diffraction. Scanning electron microscopy (SEM) illustrated good miscibility between GL/PVA blend film matrix and BCNW up to 7.5 wt%. Fourier-transform infrared spectroscopy in the attenuated total reflection mode showed molecular interactions between functional groups of the GL/PVA blend film matrix and BCNW. The incorporation of BCNW up to 7.5% into the GL/PVA blend reduced the water vapor transmission rate and water vapor permeability by about 22% and 14%, respectively, while tensile strength, elongation at break, and elastic modulus increased by about 21.5%, 41% and 19%, respectively (p < 0.05). Films transparency was not affected by the addition of BCNW (p > 0.05) suggesting that the BCNW were dispersed uniformly at the nanoscale. All films were colorless (ΔE*<2) with low opacity value (<2) comparable to synthetic plastics. Overall, the characterization of functional properties revealed that GL/PVA blend film reinforced with BCNW could be used as an environmentally friendly packaging material to partially replace or reduce the use of current petroleum-based packaging materials.

Synthesis and characterization of cellulose nanowhisker‐reinforced‐poly(ε‐caprolactone) scaffold for tissue‐engineering applications

ABSTRACTPoly(ε‐caprolactone) (PCL) is a bioresorbable and biocompatible polymer with assorted medical applications. However, remarkable hydrophobicity and nonosteoconductivity have stood as a barrier to limit its applications. The present study aims to modify the bulk characteristics of PCL to develop a polymeric scaffold with adequate structural and mechanical properties to support regenerated tissues. For this purpose, functionalized bacterial cellulose nanowhiskers (BCNW‐g‐βCD‐PCL2000) are synthesized. Reinforcing PCL matrix with 4 wt % of the nanowhiskers resulted in a bionanocomposite with promoted bulk properties. Compared to neat PCL, the obtained bionanocomposite shows improvements of 115 and 51% in tensile strength and Young's modulus, respectively; 20% increase in hydrophilicity; 7% increase in degradation rate; and 6% decrease in crystallinity. Gas foaming/combined particulate leaching technique is used to develop highly porous structures of 86–95% porosity with interconnected macropores of mean pore diameters of 250–420 μm. Porous scaffolds showed compression modulus values of 5.3–9.1 MPa and would have promising applications in regenerative medicine. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48481.

Issue Highlights

The Canadian Journal of Chemical EngineeringVolume 97, Issue 10 p. 2575-2575 Issue HighlightsFree Access Issue Highlights First published: 12 September 2019 https://doi.org/10.1002/cjce.23281AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Experimental methods in chemical engineering: Micro-reactors-p. 2578 Arturo Macchi, Patrick Plouffe, Gregory S. Patience and Dominique M. Roberge The bulk chemical industry continues to build bigger plants but micro-reactors represent a paradigm shift in manufacturing: they contribute to process intensification—productivity an order of magnitude (and more) greater in a smaller footprint—with sub-millimetre lateral dimensions that reduce heat and mass transfer boundary layers. We propose a toolbox concept to select reactor types in order to optimize reactive conditions and then scale up, with relative confidence, through the clinical phases of pharmaceuticals. Research in the field is concentrated into five clusters: catalysis and kinetics; nano-particles; systems and microfluidics; chemistry and organic synthesis; and mass transfer and micro-channels.1 Experimental methods in chemical engineering: X-ray photoelectron spectroscopy-XPS-p. 2588 Josianne Lefebvre, Federico Galli, Claudia L. Bianchi, Gregory S. Patience and Daria C. Boffito X-ray photoelectron spectroscopy (XPS) identifies the elemental composition, empirical formula, chemical state, and electronic state of solid surfaces to a depth of 1-10 nm. With an atomic sensitivity of 0.1%, any exposure to ambient air contaminates the surface. X-ray beams irradiate solids held at 0.1 μPa and produce spectra of electrons where the intensity relates to concentration and position to an element's orbital and chemical environment. Research clusters that apply the technique include: nanoparticles and thin films; catalysis and oxidation; nanocomposites and graphene; photocatalysis and TiO2; and adsorption and aqueous solutions.2 Functionalized bacterial cellulose nanowhiskers as long-lasting drug nanocarrier for antibiotics and anticancer drugs-p. 2594 Mohamed M. Khattab and Yaser Dahman Biocompatible and nontoxic drug-nanocarriers based on a functionalized bacterial cellulose nanowhisker (BCNC-g-βCD) were developed. Compared to a pristine nanowhisker, the obtained drug-nanocarriers showed promising potential for conjugating higher payloads of antibiotic and anticancer drugs ranging from 495 ± 14 to 810 ± 17 μg/mg. In addition, the drug release profiles showed that 75-90% of drug payloads were released over 5-5.5 days in sustained and controlled manners with reduced initial blasts. Moreover, promoted drug release profiles were pragmatic in an acidic pH of 6.4 at 37°C, which mimics the tumour environment. The obtained observations demonstrate versatile medical applications for the obtained nanocarriers in localized and long-lasting drug delivery.3 Impeller power draw during turbulent operation in solid-liquid suspensions-p. 2662 Kevin J. Myers, Eric E. Janz, Tianxin Bao and M. Molly Heigel Measurements with six impeller types in solid-liquid suspensions indicate that power draw in the turbulent regime is approximately proportional to suspension density when the solids are distributed throughout the liquid; however, the accuracy of this approach is limited, with clear differences between impellers. Power draw increases are less than density increases for impellers with large blade-trailing vortices and are equal to or greater than density increases for impellers with smaller blade-trailing vortices. The data is well described by linear relations between impeller power number and the density difference correlating parameter of Micheletti et al, with slope depending on impeller type.4 REFERENCES 1A. Macchi, P. Plouffe, G. S. Patience, D. M. Roberge, Can. J. Chem. Eng. 2019, 97, 2578. 2J. Lefebvre, F. Galli, C. L. Bianchi, G. S. Patience, D. C. Boffito, Can. J. Chem. Eng. 2019, 97, 2588. 3M. M. Khattab, Y. Dahman, Can. J. Chem. Eng. 2019, 97, 2594. 4K. J. Myers, E. E. Janz, T. Bao, M. M. Heigel, Can. J. Chem. Eng. 2019, 97, 2662. Volume97, Issue10October 2019Pages 2575-2575 ReferencesRelatedInformation

Functionalized bacterial cellulose nanowhiskers as long‐lasting drug nanocarrier for antibiotics and anticancer drugs

A nano drug carrier based on sustainable and biocompatible nanocellulose was developed for use in prolonged drug releases. The grafting of β‐cyclodextrin (βCD) on bacterial cellulose nanowhiskers (BCNC) using citric acid (CA) as a green linker was performed. This led to the formation of functionalized BCNC‐grafted‐βCD (BCNC‐g‐βCD). Broad‐spectrum antibiotic Ciprofloxacin (CIP) and anticancer drugs Doxorubicin (DOX) and Paclitaxel (PTX) were used as model drugs. These model drugs were conjugated to BCNC‐g‐βCD to form the drug‐nanocarrier systems (BCNC‐g‐βCD‐drug). The change in the nanowhiskers’ surface chemistry, morphology, and crystallinity was characterized by FTIR, solid‐state 13C NMR, scanning electron microscopy (SEM), atomic force microscopy (AFM), and x‐ray diffraction (XRD). The functionalized nanowhiskers showed a significant increase in the drug payloads, which ranged from 495 ±4–810 ±7 μg/mg, along with a radical improvement in the drug release profiles. For all of the developed drug‐conjugated nanocarriers, the initial burst releases were reduced effectively. The observed drug releases showed a sustained and controlled manner, with cumulative releases of 75–90 % over 5–5.5 days. Nevertheless, an improved drug release performance was observed in the acidic pH of 6.4 that mimicked extracellular tumor cells. In vitro drug release data were fitted zero‐order kinetic model with drug release constants (K0) of 0.68, 0.74, and 0.79 μg drug/h (at pH 6.4 and 37 °C) for BCNC‐g‐βCD‐CIP, BCNC‐g‐βCD‐DOX, and BCNC‐g‐βCD‐PTX nanosystems, respectively. The observed higher payloads along with the slow releases of drugs from the developed nanocarrier suggests its promising potential for reducing the frequent daily dosing and minimizing systemic toxicity of loaded drugs.

Rapid synthesis of high strength cellulose–poly(vinyl alcohol) (PVA) biocompatible composite films via microwave crosslinking

ABSTRACTThe present study describes microwave (MW)‐assisted rapid synthesis of biocompatible poly(vinyl alcohol) (PVA) composite films that demonstrate synergy between reinforcement and crosslinking. Bacterial cellulose (5% w/w) nanowhiskers (reinforcement) and tartaric acid 35% (w/w) (crosslinker) are incorporated in PVA to prepare crosslinked cellulose–PVA composite films. The properties of thus prepared crosslinked cellulose–PVA composite films are compared with samples crosslinked with conventional hot air oven heating (CH). Crosslinking by both of the methods reduces water absorption of PVA by around an order of magnitude and improves its thermal stability. An increase in strength from 42 (PVA) to 172 MPa and 159 MPa for MW and CH crosslinked samples, respectively is also observed. Although composites prepared using MW and CH show similar properties, MW takes only 14 min compared to 2 h in case of CH. Notably, the prepared composites demonstrate hemocompatibility and cytocompatibility, and may also be explored for biomedical applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47393.

Development of Polyvinyl Alcohol Based High Strength Biocompatible Composite Films

In the present work, the development of high strength biocompatible polyvinyl alcohol (PVA) based composite films using citric acid (CA) as a crosslinker and bacterial cellulose nanowhiskers (BCNW) as nanofiller is reported. The interfacial binding between nanoreinforcement (BCNW) and polymer (PVA) is modified by covalently binding them by citric acid. These composite films demonstrate a highest tensile strength of 132 MPa in comparison to PVA (37 MPa). The composite also shows 10‐fold reduction in water swelling percentage and better thermal properties compared to PVA. Hemocompatibility and biocompatibility assays show that the developed high strength composite is nontoxic to blood and is favorable for cell growth. With the aforementioned strength and biocompatibility, the composite for development for bioimplants is proposed. image

Improving the barrier properties of thermoplastic corn starch-based films containing bacterial cellulose nanowhiskers by means of PHA electrospun coatings of interest in food packaging

In the present study, property enhanced thermoplastic corn starch (TPCS) nanobiocomposites containing bacterial cellulose nanowhiskers (BCNW) prepared by melt mixing were characterized in terms of morphology, mechanical, optical and barrier properties. Improved barrier to water vapour and oxygen at high relative humidity (80%) was noticed, reaching the best performance at 15 wt% BCNW loading with a maximum drop of 46% and 95% for water and oxygen permeability, respectively. In a second approach, the optimized nanobiocomposites (containing 15 wt% BCNW) were successfully hydrophobized by coating them with electrospun poly(3-hydroxybutyrate) (PHB) or electrospun PHB-BCNW fibres. To this end, hybrid electrospun PHB fibres reinforced with highly dispersed crystalline BCNW in solutions concentrations up to 15 wt% were directly electrospun onto both sides of TPCS nanobiocomposites containing 15 wt% BCNW. Similar coated structures prepared without BCNW were developed and characterized for comparative purposes. The methodology used resulted in good adhesion between the layers, also leading to enhanced barrier performance. Interestingly, the incorporation of BCNW in one of the layers led to a decrease on the oxygen permeability values showing no significant differences between multilayer films incorporating BCNW whatever the layer where the BCNW were located. However, when comparing amongst the different multilayer samples containing BCNW, the greatest reduction in the water vapour permeability values was seen for multilayer structures incorporating BCNW in both, the TPCS inner layer and the PHB coating. This study has demonstrated the potential of the combination of both technologies (nanocomposites and multilayered design) in the development of food packaging materials based on corn starch with improved barrier properties.

Assessment of Ball Milling as a Compounding Technique to Develop Nanocomposites of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) and Bacterial Cellulose Nanowhiskers

The aim of this study was the assessment of high energy ball milling technique to develop poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanocomposites containing bacterial cellulose nanowhiskers (BCNW). Crystallization behaviour of PHBV/BCNW nanocomposites was studied under non-isothermal and isothermal conditions using differential scanning calorimetry. The changes in PHBV crystalline structure were also studied using X-ray diffraction. The results confirmed that BCNW acted as nucleating agents and, hence, favored the crystallization of the PHBV. The oxygen permeability of the nanocomposites was reduced by ~22 % when compared to that of the neat PHBV. This work provides a new insight into the development of polyhydroxyalkanoate composites by means of the high energy ball milling technique.

Synergistic effect of cellulose nanowhiskers reinforcement and dicarboxylic acids crosslinking towards polyvinyl alcohol properties

ABSTRACTIn the presented work, a significant increase in the tensile strength of the PVA composite material is reported. The obtained best value of 122 MPa and 14.6% swelling shows the excellent synergistic effect of both crosslinker and reinforcement material. The composite films were prepared by simple mechanical dispersion of reinforcement material, bacterial cellulose nanowhiskers (BCNW) into PVA solution followed by crosslinking with diacids, succinic acid (SuA), and adipic acid (AdA). The effect of aliphatic carbon chain length of crosslinker on thermal, mechanical, and water uptake properties is evaluated and discussed in detail. Neat PVA had the strength of 37.3 MPa. With 5% reinforcement of BCNW, that is, without crosslinking, it exhibited 97% increase, that is, 74.5 MPa. With crosslinking of 15 mmol of SuA and AdA PVA films for 2 h had excellent thermal properties with swelling percentage of 19 and 26.6% and tensile strength of 103 and 67 MPa, respectively. The best result obtained was for 5% BCNW–PVA films crosslinked with 15 mmol SuA. These results were explained on the basis of synergetic crosslinking and extended hydrogen bonding between PVA and reinforcement material. The composite films can be used as biological implants, a membrane for pervaporation and filtration system, etc. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2515–2525

Nanofibrous microspheres prepared from bacterial cellulose nano-whiskers as potential cell microcarriers

Nanofibrous microspheres prepared from bacterial cellulose nano-whiskers as potential cell microcarriers

Production of bacterial nanobiocomposites of polyhydroxyalkanoates derived from waste and bacterial nanocellulose by the electrospinning enabling melt compounding method

ABSTRACTThis work reports on the characterization of nanocomposites fully synthesized by bacteria, consisting of polyhydroxybutyrate‐co‐hydroxyvalerate (PHBV) matrices reinforced with bacterial cellulose nanowhiskers (BCNW). Two PHBV grades, with 9% HV (PHBV9) and 16% HV (PHBV16), were synthesized using food industry waste feedstocks and compared with a 3% HV commercial grade (PHBV3). Whereas PHBV3 presented a high barrier performance but excessive brittleness, PHBV9 and PHBV16 showed a more ductile behavior and reduced barrier properties. Subsequently, BCNW were incorporated into the PHBVs by a high‐throughput electrospinning technique to produce master‐batch formulations with relatively high nanofiller concentrations. The hybrid ultrathin fibers showed homogeneous morphologies and greater thermal stability than the pure PHBV fibers. Nanocomposites were then produced by melt mixing PHBVs with the hybrid fibers. Despite the low compatibility between the extremely hydrophilic BCNW and the hydrophobic PHBVs, the nanofiller was highly dispersed and provided a reduction in oxygen permeability of the PHBV3 matrix without relevant modifications in mechanical performance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42486.

Melt polycondensation to improve the dispersion of bacterial cellulose into polylactide via melt compounding: enhanced barrier and mechanical properties

Nanocomposites of polylactide (PLA) and bacterial cellulose nanowhiskers (BCNW) with improved properties were obtained through melt compounding. Prior to melt processing, and with the aim of improving BCNW dispersion, lactic acid oligomers (OLLA) were in situ polymerized in the presence of the nanofiller (both freeze-dried and partially hydrated). This in situ polymerization reaction enhanced the compatibilization between hydrophilic cellulose and hydrophobic PLA, even leading to chemical grafting of the OLLA onto the surface of BCNW, when this was used in a partially hydrated form. The optimized dispersion attained through this pre-incorporation strategy was confirmed by comparison with materials obtained through direct melt compounding of PLA with BCNW. Differential scanning calorimetry experiments showed that although cellulose content had not effect on melting temperatures, the degree of crystallinity was significantly affected. Addition of grafted BCNW also resulted in improved mechanical properties increasing the elastic modulus and tensile strength up to 52 and 31 %, respectively, mainly ascribed to the promotion of filler–filler and filler–matrix interactions. Moreover, the developed nanocomposites showed improvements in the water and oxygen barrier properties (measured at 80 % RH), respectively, which make them attractive for food packaging applications. This could be explained by well-dispersed nanocrystals acting as blocking agents within the polymeric matrix, reducing the diffusion through the nanocomposite films and, hence, the water and oxygen permeability. Therefore, this work offers a new route for incorporating well dispersed nanocellulose within a hydrophobic PLA matrix, overcoming the dispersion problems that this entails, especially when working with melt compounding methods.

Antimicrobial Poly(lactic acid)-Based Nanofibres Developed by Solution Blow Spinning.

The present study reports on the development of hybrid poly(lactic acid) (PLA) fibres loaded with highly crystalline bacterial cellulose nanowhiskers (BCNW) by the novel solution blow spinning method. Furthermore, fibres with antimicrobial properties were generated by incorporating carvacrol and THC as antimicrobial agents and the biocide effect against Listeria monocytogenes was studied. Initially, PLA blow spun fibres containing BCNW were optimized in terms of morphology and thermal properties. The addition of BCNW was seen to significantly increase the viscosity and surface tension of solutions, restricting the capacity to form fibres for concentrations greater than 30 wt.-% BCNW. 15 wt.-% BCNW was selected as the optimum nanofiller loading as it led to the most uniform fibres morphology, with BCNW homogeneously distributed along the fibres' axis. Subsequently, carvacrol and THC were incorporated into the fibres to confer them with antimicrobial properties, although the hydrophobic PLA matrix did not provide an efficient release of the antimicrobials. Thus, hydrophilic substances were added in order to trigger the antimicrobials release through water sorption mechanisms. The addition of the BCNW filler was not seen to significantly increase the antimicrobial capacity of the fibres by itself and, hence, gelatin was added to help promoting further the hydrophylicity and biocide performance of the fibres. Nevertheless, for the more hydrophilic THC, the biocide capacity of the fibres with gelatin was accentuated further by the presence of the BCNW.

Preparation and properties of a novel porous poly(lactic acid) composite reinforced with bacterial cellulose nanowhiskers

In this work, rod-like bacterial cellulose nanowhisker (BCNW) was produced by sulfuric acid hydrolysis and then a porous polylactic acid (PLA) composite reinforced with 5 wt% BCNW was prepared by solvent casting and freeze drying. The morphology of BCNW and BCNW/PLA composite was observed by TEM and SEM. In addition, mechanical properties, wettability, and water absorption of the composite were examined. It is demonstrated that the incorporation of BCNW in PLA improves the pore structure and porosity. The BCNW/PLA composite shows significantly higher water uptake and hydrophilicity with respect to PLA. Mechanical testing reveals significant improvements in tensile strength and modulus and compressive strength and a decrease in strain at break as compared to neat PLA. The porous BCNW/PLA composite may find applications in the fields of tissue engineering and drug delivery.

On the extraction of cellulose nanowhiskers from food by-products and their comparative reinforcing effect on a polyhydroxybutyrate-co-valerate polymer

The present work reports on the characterization of cellulose nanowhiskers (CNW) extracted from three different food by-products, i.e., wheat straw (WSCNW), Brewer’s spent grains (BGCNW) and olive pomace (OPCNW), by using an optimized hydrolysis method similar to that developed to extract bacterial cellulose nanowhiskers (BCNW). WSCNW and BGCNW were seen to present optimal properties, with aspect ratio, crystallinity and thermal stability values comparable to those of BCNW. Additionally, the optimized hydrolysis treatment led to extraction yields higher than those previously reported for food by-products. The CNW were subsequently incorporated into a commercial polyhydroxybutyrate-co-valerate polymer (PHBV) by solution casting, and the produced nanocomposites were characterized. Although the addition of BGCNW and WSCNW was advantageous in terms of mechanical performance in comparison with OPCNW, no significant enhancement of the pure PHBV mechanical properties was reported because of the low nanofiller loadings used and the inherent difficulty of achieving a high degree of dispersion by the casting method. Interestingly, BGCNW and WSCNW presented reduced moisture sensitivity as compared with BCNW, leading to greater barrier performance and resulting in oxygen permeability reductions up to 26 % with WSCNW and 44 % with BGCNW.

A New Method for Developing Industrially Viable Nanocrystalline Cellulose-based Nanocomposites via Melt Compounding

Due to their high crystallinity and aspect ratio, bacterial cellulose nanowhiskers (BCNW) represent an appealing choice for the development of fully biobased nanocomposite materials with high barrier performance. However, their strong tendency to self-associate, together with their highly hydrophilic character, has restricted the production of nanocomposites containing cellulose nanowhiskers by industrial processing techniques such as melt compounding. This article presents an overview of the latest published results carried out within our group and also in other relevant literature, which have led to the development of an efficient strategy for the incorporation of highly dispersed BCNW by melt compounding through the use of electrohydrodynamic processing as a vehicle for the pre-incorporation of relatively high loadings of BCNW. First, a method for the production of highly crystalline and thermally stable BCNW was developed. These BCNW were incorporated into electrospun fibers, optimizing the process in terms of nanofiller dispersion and degree of incorporation. Finally, these hybrid fibers were used as masterbatches for the production of melt compounded nanocomposites, comparing their morphology and barrier properties with the conventional method of adding freeze-dried nanowhiskers. Th is method was proven to be effective for both hydrophilic and hydrophobic matrices and, thus, it provides a feasible route for the development of high barrier biobased materials.