Search

Microplastics (MPs) pollution has become one of our time's most consequential issue. These micropolymeric particles are ubiquitously distributed across all natural and urban ecosystems. Current filtration systems in wastewater treatment plants (WWTPs) rely on non-biodegradable fossil-based polymeric filters whose maintenance procedures are environmentally damaging and unsustainable. Following the need to develop sustainable filtration frameworks for MPs water removal, years of RD lead to the conception of bacterial cellulose (BC) biopolymers. These bacterial-based naturally secreted polymers display unique features for biotechnological applications, such as straightforward production, large surface areas, nanoporous structures, biodegradability, and utilitarian circularity. Diligently, techniques such as flow cytometry, scanning electron microscopy and fluorescence microscopy were used to evaluate the feasibility and characterise the removal dynamics of highly concentrated MPs-polluted water by BC biopolymers. Results show that BC biopolymers display removal efficiencies of MPs of up to 99%, maintaining high performance for several continuous cycles. The polymer's characterisation showed that MPs were both adsorbed and incorporated in the 3D nanofibrillar network. The use of more economically- and logistics-favourable dried BC biopolymers preserves their physicochemical properties while maintaining high efficiency (93-96%). These polymers exhibited exceptional structural preservation, conserving a high water uptake capacity which drives microparticle retention. In sum, this study provides clear evidence that BC biopolymers are high performing, multifaceted and genuinely sustainable/circular alternatives to synthetic water treatment MPs-removal technologies.

Nanocomposites composed of poly(glycidyl methacrylate) (PGMA) and bacterial cellulose (BC) were prepared by the in-situ free radical polymerization of glycidyl methacrylate (GMA) inside the BC network. The resulting nanocomposites were characterized in terms of structure, morphology, water-uptake capacity, thermal stability and viscoelastic properties. The three-dimensional structure of BC endowed the nanocomposites with good thermal stability (up to 270 °C) and viscoelastic properties (minimum storage modulus = 80 MPa at 200 °C). In addition, the water-uptake and crystallinity decreased with the increasing content of the hydrophobic and amorphous PGMA matrix. These nanocomposites were then submitted to post-modification via acid-catalysed hydrolysis to convert the hydrophobic PGMA into the hydrophilic poly(glyceryl methacrylate) (PGOHMA) counterpart, which increased the hydrophilicity of the nanocomposites and consequently improved their water-uptake capacity. Besides, the post-modified nanocomposites maintained a good thermal stability (up to 250 °C), viscoelastic properties (minimum storage modulus = 171 MPa at 200 °C) and porous structure. In view of these results, the PGMA/BC nanocomposites can be used as functional hydrophobic nanocomposites for post-modification reactions, whereas the PGOHMA/BC nanocomposites might have potential for biomedical applications requiring hydrophilic, swellable and biocompatible materials. published

Bacterial cellulose (BC) has recently been the subject of a considerable amount of research, not only for its environmentally friendly biosynthesis, but also for its high potential in areas such as biomedicine or biomaterials. A symbiotic relationship between a photosynthetic microalga, Chlamydomonas debaryana, and a cellulose producer bacterium, Komagataeibacter saccharivorans, was established in order to obtain a viable and active biofilm. The effect of the growth media composition ratio on the produced living material was investigated, as well as the microalgae biomass quantity, temperature, and incubation time. The optimal temperature for higher symbiotic biofilm production was 30 &deg, C with an incubation period of 14 days. The high microalgae presence, 0.75% w/v, and 60:40 HS:BG-11 medium (v/v) induced a biofilm microalgae incorporation rate of 85%. The obtained results report, for the first time, a successful symbiotic interaction developed in situ between an alkaline photosynthetic microalga and an acetic acid bacterium. These results are promising and open a new window to BC living biofilm applications in medical fields that have not yet been explored.

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

Bacterial cellulose/polyaniline (BC/PANi) blends present a great potential for several applications. The current study evaluates the impact of using different BC matrixes (drained, freeze-dried and regenerated) and different synthesis conditions (in situ and ex situ) to improve the inherent properties of BC, which were monitored through FTIR-ATR, EDX, XRD, SEM, AFM, swelling, contact angle measurement and IGC. The employment of in situ polymerization onto drained BC presented the most conductive membrane (1.4 × 10−1 S/cm). The crystallinity, swelling capacity, surface energy and acid/base behavior of the BC membranes is substantially modified upon PANi incorporation, being dependent on the BC matrix used, being the freeze-dried BC blends the ones with highest crystallinity (up to 54%), swelling capacity (up to 414%) and surface energy (up to 75.0 mJ/m2). Hence, this work evidenced that the final properties of the BC/PANi blends are greatly influenced by both the BC matrixes and synthesis methods employed.

The use of non-wood fibers in the paper industry has been an economical and environmental necessity. The application of dry-strength agents has been a successful method to enhance the strength properties of paper. The experimental results evidencing the potential of chitosan and cationic starch utilization in bagasse paper subjected to hot water pre-extraction has been presented in this paper. The research analyzes the surface properties alterations due to these dry-strength agents. Inverse gas chromatography was used to evaluate the properties of surface chemistry of the papers namely the surface energy, active sites, surface area as well as the acidic/basic character. The results of the study revealed that the handsheets process causes surface arrangement and orientation of chemical groups, which induce a more hydrophobic and basic surface. The acid-base surface characteristics after the addition of dry-strength agents were the same as the bagasse handsheets with and without hot water pre-extraction. The results showed that the dry-strength agent acts as a protecting film or glaze on the surfaces of bagasse paper handsheets.

In this work, a simple and green route to the synthesis of the bacterial nanocellulose-calcium carbonate (BNC/CaCO3) hybrid bionanocomposites using one-step in situ biosynthesis was studied. The CaCO3 was incorporated in the bacterial nanocellulose structure during the cellulose biosynthesis by Gluconacetobacter xylinus PTCC 1734 bacteria. Hestrin-Schramm (HS) and Zhou (Z) culture media were used to the hybrid bionanocomposites production and the effect of ethanol addition was investigated. Attenuated total reflection Fourier transform infrared spectroscopy, field emission scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, inverse gas chromatography and thermogravimetric analysis were used to characterize the samples. The experimental results demonstrated that the ethanol and culture medium play an important role in the BNC/CaCO3 hybrid bionanocomposites production, structure and properties. The BNC/CaCO3 biosynthesized in Z culture medium revealed higher O/C ratio and amphoteric surface character, which justify the highest CaCO3 content incorporation. The CaCO3 was incorporated into the cellulosic matrix decreasing the bacterial nanocellulose crystallinity. This work reveals the high potential of in situ biosynthesis of BNC/CaCO3 hybrid bionanocomposites and opens a new way to the high value-added applications of bacterial nanocellulose.

Biodegradable nanocomposite films were prepared by incorporation of cellulose nanofibrils (CNF) into alginate biopolymer using the solution casting method. The effects of CNF content (2.5, 5, 7.5, 10 and 15 wt %) on mechanical, biodegradability and swelling behavior of the nanocomposite films were determined. The results showed that the tensile modulus value of the nanocomposite films increased from 308 to 1403 MPa with increasing CNF content from 0% to 10%; however, it decreased with further increase of the filler content. Incorporation of CNF also significantly reduced the swelling percentage and water solubility of alginate-based films, with the lower values found for 10 wt % in CNF. Biodegradation studies of the films in soil confirmed that the biodegradation time of alginate/CNF films greatly depends on the CNF content. The results evidence that the stronger intermolecular interaction and molecular compatibility between alginate and CNF components was at 10 wt % in CNF alginate films.

In this work, the effects of hot water pre-extraction of depithed bagasse on the soda pulping and surface properties were studied. The conditions of hot water pre-extraction were: maximum temperature 170 °C, heat-up time 90 min, time at maximum temperature 10 min, and solid to liquor ratio (S:L) 1:8. Consequently, the pre-extracted and un-extracted bagasse chips were subjected to soda pulping at 160 °C for 1 h with 11, 14 and 17% active alkali charge and an S:L of 1:5. The results showed that the hot water pre-extraction increased bagasse surface texture porosity by hemicellulose degradation. Therefore, the delignification was faster for pulping of pre-extracted samples. At a certain charge of alkali, pre-extracted samples showed higher screened yield and lower Kappa number. For instance, at 17% alkali charge, pre-extracted bagasse gave 11.3% higher pulp yield compared with the un-extracted ones. Inverse gas chromatography (IGC) results showed that the hot water pre-extraction changed the active sites on the bagasse surface, decreasing the dispersive energy and the basicity character, and affected the particle morphology. The pulping process decreased the hydrophobicity and the basicity of the bagasse surface. The surfaces of un-extracted and pre-extracted bagasse pulps had similar properties but different morphology. The pulps present higher surface area and permeability with more reactive capacity.

The effect of saponin on the surface properties of banana fibres was studied by Inverse Gas Chromatography (IGC). Parameters including the dispersive component of the surface energy, surface heterogeneity, surface area, as well as acid–base surface properties were determined for saponin modified banana micro and nanofibres. These parameters show a more extensive saponin coating on the nanofibres with a network formation which is explained by the higher reactivity of nanofibres due to the higher surface energy, specific interaction and higher surface area presented by the nanofibres. The energetic profile indicates that both micro and nanofibres coated with saponin interact with the same, or similar, energy active sites. Saponin treatment reduces considerably the surface area of the fibres, with the consequent decrease in the monolayer capacity. The interaction with the polar probes clearly indicates that saponin treatment creates new polar active sites for specific interactions in both samples. However, the treatment increases predominately the basicity of the fibre surface with more relevance to the nanofibres. This behaviour will lead to better polymer/fibre interaction during composite preparation.