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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.
- 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.
- 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.