Loading...
8 results
Search Results
Now showing 1 - 8 of 8
- Microplastics reduce microalgal biomass by decreasing single-cell weight: the barrier towards implementation at scalePublication . Mendonça, Ivana; Cunha, César; Kaufmann, Manfred; Faria, Marisa; Cordeiro, NereidaMicroplastics (MPs) are a widespread environmental threat, especially to aquatic and urban systems. Water quality is vital for biomass production in microalgal-based industries. Here, industrially relevant microalgae Tetraselmis suecica, Scenedesmus armatus, and Nannochloropsis gaditana were exposed to PS- and PE-MPs (polystyrene and polyethylene, re spectively – 10-20 μm) contaminated waters (5 and 10 mg/L). Following industrial empirical and ecotoxicological pro cedures, the production period was established as four days (exponential growth phase). 27-long day experiments were conducted to determine the chronic effects of MPs contamination in microalgal biomass yields. MPs induced different responses in cell density: T. suecica decreased (up to 11 %); S. armatus showed no changes; and N. gaditana increased (up to 6 %). However, all three microalgae exhibited significant decreases in biomass production (up to 24, 48, and 52 %, respectively). S. armatus exposed to PS-MPs and N. gaditana exposed to PE-MPs were the most im pacted regarding biomass production. The decrease in biomass yield was due to the reduction in single-cell weight (up to 14, 47, and 43 %), and/or the production of smaller-sized cells (T. suecica). In response to chronic exposure, microalgae showed signs of cell density adaptation. Despite cell density normalizing, biomass production was still re duced compared to biomass production in clean water. Computational modelling highlighted that MPs exposure had a concentration-dependent negative impact on microalgae biomass. The models allow the evaluation of the systematic risks that MPs impose in microalgal-based industries and stimulate actions towards implementing systems to contain/ eliminate MPs contamination in the waters used in microalgae production.
- Solving urban water microplastics with bacterial cellulose hydrogels: leveraging predictive computational modelsPublication . Mendonça, Ivana; Sousa, Jessica; Cunha, César; Faria, Marisa; Ferreira, Artur; Cordeiro, NereidaThe 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 floc culation 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
- Bacterial cellulose biopolymers: the sustainable solution to water-polluting microplasticsPublication . Faria, Marisa; Cunha, César; Gomes, Madalena; Mendonça, Ivana; Kaufmann, Manfred; Ferreira, Artur; Cordeiro, NereidaMicroplastics (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 mainte nance procedures are environmentally damaging and unsustainable. Following the need to develop sustainable filtration frameworks for MPs water removal, years of R&D 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 effi ciencies 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.
- Microalgal-based biopolymer for nano- and microplastic removal: a possible biosolution for wastewater treatmentPublication . Cunha, César; Silva, Laura; Paulo, Jorge; Faria, Marisa; Nogueira, Natacha; Cordeiro, NereidaThe increasing water pollution caused by the presence of nano- and microplastics has shown a need to pursue solutions to remediate this problem. In this work, an extracellular polymeric substance (EPS) producing freshwater Cyanothece sp. strain was exposed to nano- and microplastics. The bioflocculant capacity of the biopolymer produced was evaluated. The influence of different concentrations (1 and 10 mg L-1) of polystyrene nano- and microplastics in the extracellular carbohydrates and in the EPS production was studied. The presence of nano- and microplastics induced a negative effect on the microalgal growth (of up to 47%). The results show that the EPS produced by Cyanothece sp. exhibits high bioflocculant activity in low concentrations. Also, the EPS displayed very favourable characteristics for aggregation, as the aggregates were confirmed to consist of microalga, EPS and both the nano- and microplastics. These results highlight the potential of the microalgal-based biopolymers to replace hazardous synthetic flocculants used in wastewater treatment, while aggregating and flocculating nano- and microplastics, demonstrating to be a multi-purposed, compelling, biocompatible solution to nano- and microplastic pollution.
- Ecotoxicological and biochemical effects of environmental concentrations of the plastic-bond pollutant dibutyl phthalate on Scenedesmus sp.Publication . Cunha, César; Paulo, Jorge; Faria, Marisa; Kaufmann, Manfred; Cordeiro, NereidaPhthalate esters are highly present in aquatic plastic litter, which can interfere with the biological processes in the wildlife. In this work, the commonly found freshwater microalga Scenedesmus sp. was exposed to environmental concentrations (0.02, 1 and 100 μg L-1) and to a higher concentration (500 μg L-1) of dibutyl phthalate (DBP), which is an environmental pollutant. The growth, pH variation, production of photosynthetic pigments, proteins and carbohydrates were evaluated. The main inhibition effect of DBP on the microalgal growth was observed in the first 48 h of the exposure (EC50: 41.88 μg L-1). A reduction in the photosynthetic pigment concentration was observed for the 0.02, 1 and 100 μg L-1 conditions indicating that the DBP downregulated the growth rate and affected the photosynthetic process. A significant increase in protein production was only observed under 500 μg L-1 DBP exposure. The extracellular carbohydrates production slightly decreased with the presence of DBP, with a stronger decrease occurring in the 500 μg L-1 condition. These results highlight the environmental risk evaluation and ecotoxicological effects of DBP on the production of biovaluable compounds by microalgae. The results also emphasize the importance of assessing the consequences of the environmental concentrations exposure as a result of the DBP dose-dependent correlation effects.
- Marine vs freshwater microalgae exopolymers as biosolutions to microplastics pollutionPublication . Cunha, César; Faria, Marisa; Nogueira, Natacha; Ferreira, Artur; Cordeiro, Nereida Maria AbanoMicroalgae can excrete exopolymer substances (EPS) with a potential to form hetero-aggregates with microplastic particles. In this work, two freshwater (Microcystis panniformis and Scenedesmus sp.) and two marine (Tetraselmis sp. and Gloeocapsa sp.) EPS producing microalgae were exposed to different microplastics. In this study, the influence of the microplastic particles type, size and density in the production of EPS and hetero-aggregates potential was studied. Most microalgae contaminated with microplastics displayed a cell abundance decrease (of up to 42%) in the cultures. The results showed that the formed aggregates were composed of microalgae and EPS (homo-aggregates) or a combination of microalgae, EPS and microplastics (hetero-aggregates). The hetero-aggregation was dependent on the size and yield production of EPS, which was species specific. Microcystis panniformis and Scenedesmus sp. exhibited small EPS, with a higher propension to disaggregate, and consequently lower capabilities to aggregate microplastics. Tetraselmis sp. displayed a higher ability to aggregate both low and high-density microplastics, being partially limited by the size of the microplastics. Gloeocapsa sp. had an outstanding EPS production and presented excellent microplastic aggregation capabilities (adhered onto the surface and also incorporated into the EPS). The results highlight the potential of microalgae to produce EPS and flocculate microplastics, contributing to their vertical transport and consequent deposition. Thus, this work shows the potential of microalgae as biocompatible solutions to water microplastics treatment.
- Nannochloropsis gaditana grown outdoors in annular photobioreactors: operation strategiesPublication . Nogueira, Natacha; Nascimento, Francisco J.A.; Cunha, César; Cordeiro, NereidaMicroalgae are a topic of intense research due to their potential applications in bio-based economy. However, sustainable commercial production is still overpriced due to high cultivation costs, harvesting and dewatering processes. In the present study, trials were conducted with the aim to improve daily operation strategies related to microalgae harvesting processes that did not compromise biomass productivity or the biochemical composition of the cultivated microalgae. Two experimental trials were performed in outdoor tubular annular photobioreactors to evaluate the effects of harvesting and medium dilution time (sunrise vs sunset) on Nannochloropsis gaditana biomass productivity, lipid and fatty acid content. Results showed that harvesting time had no significant effect on cell concentration and biomass productivity. Harvesting and medium dilution time did not affect lipid content. However, lipid content in samples collected at sunset was significantly higher than in samples collected at sunrise for both experimental treatments. The fatty acids profiles were mainly composed by polyunsaturated fatty acids, followed by mono-unsaturated fatty acids and saturated fatty acids. Regardless of medium dilution time, harvesting at sunset indicated that lipidic production (higher polyunsaturated fatty acids and lower saturated fatty acids) was favored without affecting the biomass productivity. The current study showed harvesting in the afternoon is a viable option for large production units that use semi-continuous strategy, without compromising biomass cell and lipid productivity.
- The effect of microplastics pollution in microalgal biomass production: a biochemical studyPublication . Cunha, César; Lopes, Joana; Paulo, Jorge; Faria, Marisa; Kaufmann, Manfred; Nogueira, Natacha; Ferreira, Artur; Cordeiro, NereidaMicroplastics (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.