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A growing number of studies has shown that the exposure to microplastics (MPs) of different polymeric compositions can induce diverse adverse effects towards several aquatic species. The vast majority of such studies has been focused on the effects induced by the administration of MPs made by polystyrene (PS; hereafter PS-MPs). However, despite the increase in the knowledge on the potential toxicity of PS-MPs, there is a dearth of information concerning their role in affecting energy resources and/or their allocation. The present study aimed at exploring the impact of 21-days exposure to three concentrations (0.125, 1.25 and 12.5 μg mL

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.

The prevalence of microplastics (MPs) in both urban and aquatic ecosystems is concerning, with wastewater treatment plants being considered one of the major sources of the issue. As the focus on developing sustainable solutions increases, unused remnants from bacterial cellulose (BC) membranes were ground to form BC hydrogels as potential bioflocculants of MPs. The influence of operational parameters such as BC:MPs ratio, hydrogel grinding, immersion and mixing time, temperature, pH, ionic strength, and metal cations on MPs flocculation and dispersion were evaluated. A response surface methodology based on experimental data sets was computed to understand how these parameters influence the flocculation process. Further, both the BC hydrogel and the hetero-aggregation of MPs were characterised by UV-Vis, ATR-FTIR, IGC, water uptake assays, fluorescence, and scanning electron microscopy. These highlights that the BC hydrogel would be fully effective at hetero-aggregating MPs in naturally-occurring concentrations, thereby not constituting a limiting performance factor for MPs' optimal flocculation and aggregation. Even considering exceptionally high concentrations of MPs (2 g/L) that far exceed naturally-occurring concentrations, the BC hydrogel was shown to have elevated MPs flocculation activity (reaching 88.6%: 1.77 g/L). The computation of bioflocculation activity showed high reliability in predicting flocculation performance, unveiling that the BC:MPs ratio and grinding times were the most critical variables modulating flocculation rates. Also, short exposure times (5 min) were sufficient to drive robust particle aggregation. The microporous nature of the hydrogel revealed by electron microscopy is the likely driver of strong MPs bioflocculant activity, far outperforming dispersive commercial bioflocculants like xanthan gum and alginate. This pilot study provides convincing evidence that even BC remainings can be used to produce highly potent and circular bioflocculators of MPs, with prospective application in the wastewater treatment industry.

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

Microplastics (MPs) are widely spread throughout aquatic systems and water bodies. Given that water quality is one of the most important parameters in the microalgal-based industry, it is critical to assess the biochemical impact of short- and long-term exposure to MPs pollution. Here, the microalga Phaeodactylum tricornutum was exposed to water contaminated with 0.5 and 50 mg L-1 of polystyrene (PS) and/or polymethyl methacrylate (PMMA). Results show that the microalgal cultures exposed to lower concentrations of PS displayed a growth enhancement of up to 73% in the first stage (days 3-9) of the exponential growth phase. Surprisingly, and despite the fact that long-term exposure to MPs contamination did not impair microalgal growth, a steep decrease in biomass production (of up to 82%) was observed. The production of photosynthetic pigments was shown to be pH-correlated during the full growth cycle, but cell density-independent in later stages of culturing. The extracellular carbohydrates production exhibited a major decrease during long-term exposure. Still, the production of extracellular proteins was not affected by the presence of MPs. This pilot laboratory-scale study shows that the microalgal exposure to water contaminated with MPs disturbs its biochemical equilibrium in a time-dependent manner, decreasing biomass production. Thus, microalgal industry-related consequences derived from the use of MPs-contaminated water are a plausible possibility.

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.

Submitted by António Freitas (amsf@uma.pt) on 2021-04-15T20:40:03Z No. of bitstreams: 1 Polylactic acid nano chitosan composite fibers and their morphological, physical characterization for the removal of cadmium.pdf: 5096005 bytes, checksum: 7c5c2155f86a01e74f93df42c793eefe (MD5) Made available in DSpace on 2021-04-15T20:40:03Z (GMT). No. of bitstreams: 1 Polylactic acid nano chitosan composite fibers and their morphological, physical characterization for the removal of cadmium.pdf: 5096005 bytes, checksum: 7c5c2155f86a01e74f93df42c793eefe (MD5) Previous issue date: 2020 info:eu-repo/semantics/publishedVersion

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.

The lipophilic extracts from the storage root of 13 cultivars of sweet potato (Ipomoea batatas (L.) Lam.) were evaluated by gas chromatography-mass spectrometry with the aim to valorize them and offer information on their nutritional properties and potential health benefits. The amount of lipophilic extractives ranged from 0.87 to 1.32% dry weight. Fatty acids and sterols were the major families of compounds identified. The most abundant saturated and unsaturated fatty acids were hexadecanoic acid (182-428 mg/kg) and octadeca-9,12-dienoic acid (133-554 mg/kg), respectively. β-Sitosterol was the principal phytosterol, representing 55.2-77.6% of this family, followed by campesterol. Long-chain aliphatic alcohols and α-tocopherol were also detected but in smaller amounts. The results suggest that sweet potato should be considered as an important dietary source of lipophilic phytochemicals.

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.