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- Microalgal-based industry vs. microplastic pollution: Current knowledge and future perspectivesPublication . Mendonça, Ivana; Faria, Marisa; Rodrigues, Filipa; Cordeiro, NereidaMicroalgae can play a crucial role in the environment due to their efficient capture of CO2 and their potential as a solution for a carbon-negative economy. Water quality is critical for the success and profitability of microalgal based industries, and understanding their response to emergent pollutants, such as microplastics (MPs), is essential. Despite the published studies investigating the impact of MPs on microalgae, knowledge in this area remains limited. Most studies have mainly focused on microalgal growth, metabolite analysis, and photosyn thetic activity, with significant discrepancies in what is known about the impact on biomass yield. Recent studies show that the yield of biomass production depends on the levels of water contamination by MPs, making it necessary to reduce the contamination levels in the water. However, present technologies for extracting and purifying water from MPs are limited, and further research and technological advancements are required. One promising solution is the use of bio-based polymer materials, such as bacterial cellulose, which offer biode gradability, cost-effectiveness, and environmentally friendly detoxifying properties. This review summarises the current knowledge on MPs pollution and its impact on the viability and proliferation of microalgae-based industries, highlights the need for further research, and discusses the potential of bio-solutions for MPs removal in microalgae-based industries.
- 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
- Efficacy of bacterial cellulose hydrogel in microfiber removal from contaminated waters: A sustainable approach to wastewater treatmentPublication . Rodrigues, Filipa; Faria, Marisa; Mendonça, Ivana; Sousa, Edward; Ferreira, Artur; Cordeiro, NereidaMicrofibers (MFs), the dominant form of microplastics in ecosystems, pose a significant environmental risk due to the inadequacy of existing wastewater treatments to remove them. Recognising the need to develop sus tainable solutions to tackle this environmental challenge, this research aimed to find an eco-friendly solution to the pervasive problem of MFs contaminating water bodies. Unused remnants of bacterial cellulose (BC) were ground to form a hydrogel-form of bacterial cellulose (BCH) and used as a potential bioflocculant for poly acrylonitrile MFs. The flocculation efficiency was evaluated across various operational and environmental fac tors, employing response surface methodology computational modelling to elucidate and model their impact on the process. The results revealed that the BCH:MFs ratio and mixing intensity were key factors in flocculation efficiency, with BCH resilient across a range of environmental conditions, achieving a 93.6 % average removal rate. The BCH's strong retention of MFs released only 8.3 % of the MFs, after a 24-hour wash, and the flocculation tests in contaminated wastewater and chlorinated water yielded 89.3 % and 86.1 % efficiency, respectively. Therefore, BCH presents a viable, sustainable, and effective approach for removing MFs from MFs-contaminated water, exhibiting exceptional flocculation performance and adaptability. This pioneer study using BCH as a bioflocculant for MFs removal sets a new standard in sustainable wastewater treatment, catalysing research on fibrous pollutant mitigation for environmental protection.
- 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.
- Nutrient deprivation stimulates soluble extracellular polymeric substances: physiological and biochemical responses in the cyanobacterium Cyanocohniella rudolphiaPublication . Rodrigues, Filipa; Mendonça, Ivana; Faria, Marisa; Mougin, Karine; Gómez Pinchetti, Juan Luis; Ferreira, Artur; Cordeiro, Nereida; Gonçalves Rodrigues, Ana Filipa; Silva Mendonça, Ivana Rita da; Faria, Marisa Camacho Gonçalves; cordeiro, nereidaThe effect of macro- and micronutrient deprivation on the cyanobacterium Cyanocohniella rudolphia (BEA 0786B) over 180 days (without medium renewal) was evaluated to intensify the production of soluble extracellular polymeric substances (S-EPS). Growth, pH, cell-free medium viscosity, S-EPS content (phenol‑sulfuric acid assay), Alcian Blue staining, and biochemical/structural markers were monitored to assess EPS release and extracellular matrix dynamics. Progressive nutrient depletion induced a shift from biomass growth toward extracellular-matrix investment. Microcolony formation observed around day 45 preceded a sustained high- production phase, with pronounced matrix densification evident by approximately day 75. Apparent viscosity increased in parallel with S-EPS accumulation and showed a strong correlation with extracellular carbohydrate concentration (R 2 = 0.86), supporting its use as an operational, non-destructive proxy for S-EPS. Alcian Blue staining qualitatively confirmed the presence of acidic polysaccharides. Quantitatively, S-EPS concentrations increased from 0.1 to 0.8 g L 1 , accompanied by an increase in apparent viscosity from 24.7 to 34.7 mPa⋅s. Morphological and spectroscopic analyses indicated a predominantly carbohydrate-rich extracellular matrix with an increasing protein contribution over time. As an exploratory proof of concept, unprocessed S-EPS present in the spent culture medium enabled LAP- initiated photochemical formation of Au and Ag nanoparticles at 365 nm, with S-EPS acting as a stabilising and co-reducing matrix and conferring pH-responsive optical behaviour. This indicates a practical route toward integration into EPS-rich matrices to engineer stimuli-responsive coatings and biomaterials. Overall, this study demonstrates that prolonged nutrient deprivation without medium renewal is an effective strategy to intensify S- EPS accumulation in C. rudolphia and that apparent viscosity provides a practical in-process parameter for monitoring production and supporting direct valorisation of spent culture medium in saline bioprocesses.
- Towards scalable production of bound extracellular polymeric substances (B-EPS): autoclave hydrothermal extraction coupled with solvent-free ultrafiltrationPublication . Mendonça, Ivana; Rodrigues, Filipa; Marisa Faria; Gómez Pinchetti, Juan L.; Ferreira, Artur; Cordeiro, Nereida; Silva Mendonça, Ivana Rita da; Gonçalves Rodrigues, Ana Filipa; Faria, Marisa Camacho Gonçalves; cordeiro, nereidaBound extracellular polymeric substances (B-EPS) are extracellular polysaccharides tightly attached to cyanobacterial and microalgal cell surfaces, representing a high-value class of biopolymers with industrial potential. Selective extraction is technically challenging due to strong adhesion to the cell wall and poten tial co-extraction of soluble EPS. Conventional methods can be chemically aggressive and may involve high energy and/or solvent inputs, making solvent-free extraction routes desirable. In this work, four hydrothermal extraction techniques (reflux, autoclave, ultrasonic bath, and microwave) were evaluated for their ability to recover B-EPS from the marine cyanobacterium Chroococcus submarinus (BEA 1200B), followed by a harmonised ultrafiltration step. Each method was assessed for extraction efficiency and its impact on bulk descriptors (inorganic carry-over, ATR-FTIR, zeta potential, and thermal profiles) and mor phology. Among the methods tested, autoclave extraction demonstrated the highest performance, yield ing up to 2.5 times more B-EPS than the other methods and showing reduced inorganic carry-over after purification. Across all methods, the purified B-EPS fractions exhibited broadly comparable bulk profiles under the applied analytics. Response Surface Methodology (RSM) applied to the autoclave system ident ified temperature and extraction time as key variables; optimal conditions (biomass-to-solvent ratio 1:20 (w/v), 130 °C, 16 min) enabled >90% recovery. Coupling autoclave extraction with solvent-free ultrafiltra tion avoids solvent precipitation and the use of hazardous reagents, enabling desalting and removal of low-molecular-weight components. Using a photosynthetic marine strain supports seawater cultivation and biogenic CO2 uptake, aligning the workflow with carbon-mitigation goals.
- Industrial Production of Microalgae with Microplastic Contaminated Waters. Effects and biosolutionsPublication . Mendonça, Ivana Rita da Silva; Cordeiro, Nereida Maria Abano; Kaufmann, Manfred JosefCurrently, microplastics (MPs) pose one of the most pressing environmental and urban issues, and aquatic systems are particularly vulnerable to these particles. Among the major sources of the problem are wastewater treatment plants. Biomass production relies heavily on water quality in microalgal-based industries. Therefore, industrially exploited microalgae, Tetraselmis suecica, Scenedesmus armatus and Nannochloropsis gaditana, were cultivated in PS- and PE-MPs contaminated waters (5 and 10 mg/L). Simulating industrial procedure, production began 4 days before stationary phase, and chronic effects were assessed with 27-day long experiments. Both MPs induced species-specific algae density: T. suecica inhibited (up to 11%), S. armatus no significant changes and N. gaditana increased (up to 6%). However, all presented significant decrease in biomass yield (up to 24, 48 and 52%, respectively) - by a reduction in single cell weight (up to 14, 47, and 43%), and/or the production of smaller cells (e.g., T. suecica). Although chronic exposure showed adaptation signs in algae density, reduction in biomass production is still evident (up to 19, 49, and 35%). RSM revealed that microalgal biomass production using MPs contaminated waters is concentration-dependent. With growing interest in developing sustainable solutions, unused remnants of bacterial cellulose membranes were ground to form BC hydrogels as potential bioflocculants of MPs. BC hydrogel’s viability in removing MPs from MPs-contaminated water was assessed for different environmental and operational conditions. BC hydrogel unveiled a very high flocculation rate (80.42%), most likely driven by the hydrogel’s microporous nature. RSM showed BC hydrogel:MPs ratio and grinding times as the most critical variables modulating flocculation rates. Also, short exposure times (5 min) were sufficient to drive robust particle aggregation. These findings suggest that BC hydrogel could be an alternative to synthetic flocculants in wastewater remediation processes.