A native strain of the heterocytous cyanobacterium Trichormus variabilis VRUC 168 was mass cultivated in a low-cost photobioreactor for a combined production of Polyunsaturated Fatty Acids (PUFA) and Exopolymeric Substances (EPS) from the same cyanobacterial biomass. A sequential extraction protocol was optimized leading to high yields of Released EPS (REPS) and PUFA, useful for nutraceutical products and biomaterials. REPS were extracted and characterized by chemical staining, Reversed Phase-High-Performance Liquid Chromatography (RP-HPLC), Fourier Transform Infrared Spectroscopy (FT-IR) and other spectroscopic techniques. Due to their gelation property, REPS were used to produce a photo-polymerizable hybrid hydrogel (REPS-Hy) with addition of polyethylene glycol diacrylated (PEGDa). REPS-Hy was stable over time and resistant to dehydration and spontaneous hydrolysis. The rheological and functional properties of REPS-Hy were studied. The enzyme carrier ability of REPS-Hy was assessed using the detoxification enzyme thiosulfate:cyanide sulfur transferase (TST), suggesting the possibility to use REPS-Hy as an enzymatic hydrogel system. Finally, REPS-Hy was used as a scaffold for culturing human mesenchymal stem cells (hMSCs). The cell seeding onto the REPS-Hy and the cell embedding into 3D-REPS-Hy demonstrated a scaffolding property of REPS-Hy with non-cytotoxic effect, suggesting potential applications of cyanobacteria REPS for producing enzyme- and cell-carrier systems.

The large-scale cultivation of microalgae provides a wide spectrum of marketable bioproducts, profitably used in many fields, from the preparation of functional health products and feed supplement in aquaculture and animal husbandry to biofuels and green chemistry agents. The commercially successful algal biomass production requires effective strategies to maintain the process at desired productivity and stability levels. Hence, the development of effective early warning methods to timely indicate remedial actions and to undertake countermeasures is extremely important to avoid culture collapse and consequent economic losses. With the aim to develop an early warning method of algal contamination, the potentiometric E-tongue was applied to record the variations in the culture environments, over the whole growth process, of two unialgal cultures, Phaeodactylum tricornutum and a microalgal contaminant, along with those of their mixed culture. The E-tongue system ability to distinguish the cultures and to predict their growth stage, through the application of multivariate data analysis, was shown. A PLS regression method applied to the E-tongue output data allowed a good prediction of culture growth time, expressed as growth days, with R² values in a range from 0.913 to 0.960 and RMSEP of 1.97–2.38 days. Moreover, the SIMCA and PLS-DA techniques were useful for cultures contamination monitoring. The constructed PLS-DA model properly discriminated 67% of cultures through the analysis of their growth media, i.e., environments, thus proving the potential of the E-tongue system for a real time monitoring of contamination in microalgal intensive cultivation.

An isolate of the diatom Staurosirella pinnata is a promising platform for drug discovery due to its ability to produce bioactive metabolites. As previously shown, S. pinnata extracts exhibit bioactivities, with hydrophilic fractions showing selective cytotoxicity against human melanoma cells and lipidic fractions promoting thermogenesis in murine white adipocytes. In this work, we focused on the interaction between S. pinnata metabolism and light irradiance exposure to evaluate bioactivity targeting medulloblastoma cells. Cultures under standard, control, irradiance (80 µmol photons m⁻² s⁻¹) were exposed in the stationary phase to increased light intensities (200 and 600 µmol photons m⁻² s⁻¹) for 126 h. Growth, photosynthetic performance and metabolic profile were monitored, while the bioactivity of small-molecule fractions was assessed at the end. Exposure to 200 µmol photons m⁻² s⁻¹ significantly enhanced growth (92.6% increase in absorbances compared to the control), whereas 600 µmol photons m⁻² s⁻¹ induced growth inhibition (41.3% decrease in absorbances with respect to the control culture) and impaired photosynthesis. Metabolomic analysis revealed a shift from carbohydrate to lipid metabolism. Bioactivity assays showed that extracts from the highest irradiance exhibited cytotoxic effects on medulloblastoma cells, similar to the 80 µmol photons m⁻² s⁻¹ cultures on DAOY (68% vs. 82% of cell death induction levels, respectively), while intermediate irradiance did not show a significant effect in any of the tested cell lines. The results showed that different light intensities impact S. pinnata metabolism, demonstrating effects exploitable for drug discovery and the importance of investigating the impact of cultivation parameters in modulating S. pinnata bioactivity potential.

Cyanobacteria are considered green cell factories that produce high-value molecules for the pharmaceutical, food and colorants sectors. Despite their biotechnological potential, large-scale cyanobacteria bioprocesses generally remain limited by low yields and high costs. Low-intensity pulsed ultrasound (LIPUS) is a non-thermal, scalable technology demonstrated to enhance mass transfer and influence microbial activity, yet its impact on cyanobacteria is underexplored. In this study, we investigated the effect of pulsed US (40 kHz) on phycobiliproteins (PBPs) and ExoPolymeric Substances (EPS) production in Trichormus variabilis VRUC 168. Cultures were treated for 15 days with US after the onset of the stationary phase, under static and air-mixed conditions in a previously developed PBR. Results showed US treatment significantly increased released EPS (1.12 vs 0.27 g/L in control) and PBP yield (by 121 vs 13 mg/g in control). Aerated systems also responded positively, albeit with lower yields. These findings show that the UltraSounds can optimize cyanobacteria-based bioprocesses up to industrial-like conditions.