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Orientador(es)
Resumo(s)
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.
Descrição
Palavras-chave
Cyanocohniella rudolphia Soluble EPS (S-EPS) Nutrient deprivation Starvation phase Viscosity proxy Spent-medium valorisation . Faculdade de Ciências Exatas e da Engenharia
Contexto Educativo
Citação
Rodrigues, F., Mendonça, I., Faria, M., Mougin, K., Pinchetti, J. L. G., Ferreira, A., & Cordeiro, N. (2026). Nutrient deprivation stimulates soluble extracellular polymeric substances: physiological and biochemical responses in the cyanobacteria Cyanocohniella rudolphia. Algal Research, 104600.
Editora
Elsevier BV