Developing Bioactive and Intelligent Biomaterials from Microalgae/Cyanobacteria for Sustainable Food Packaging

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Towards scalable production of bound extracellular polymeric substances (B-EPS): autoclave hydrothermal extraction coupled with solvent-free ultrafiltration

Publication . 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, nereida

Bound 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.

2026Artigo científico

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Nutrient deprivation stimulates soluble extracellular polymeric substances: physiological and biochemical responses in the cyanobacterium Cyanocohniella rudolphia

Publication . 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, nereida

The 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.

2026-04Artigo científico

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Palavras-chave

, Engineering and technology ,Engineering and technology/Industrial biotechnology

Entidade financiadora

Fundação para a Ciência e a Tecnologia, I.P.

Número da atribuição

2023.04389.BD