[Show abstract][Hide abstract] ABSTRACT: The kinetic study of Arthrospira platensis extracellular polymeric substances (EPS) production under different trophic modes-photoautotrophy (100 μmol photons m(-2) s(-1)), heterotrophy (1.5 g/L glucose), and mixotrophy (100 μmol photons m(-2) s(-1) and 1.5 g/L glucose)-was investigated. Under photoautotrophic and heterotrophic conditions, the maximum EPS production 219.61 ± 4.73 and 30.30 ± 1.97 mg/L, respectively, occurred during the stationary phase. Under a mixotrophic condition, the maximum EPS production (290.50 ± 2.21 mg/L) was observed during the early stationary phase. The highest specific EPS productivity (433.62 mg/g per day) was obtained under a photoautotrophic culture. The lowest specific EPS productivity (38.33 mg/g per day) was observed for the heterotrophic culture. The effects of glucose concentration, light intensity, and their interaction in mixotrophic culture on A. platensis EPS production were evaluated by means of 32 factorial design and response surface methodology. This design was carried out with a glucose concentration of 0.5, 1.5, and 2.5 g/L and at light levels of 50, 100, and 150 μmol photons m(-2) s(-1). Statistical analysis of the model demonstrated that EPS concentration and EPS yield were mainly influenced by glucose concentration and that conditions optimizing EPS concentration were dissimilar from those optimizing EPS yield. The highest maximum predicted EPS concentration (369.3 mg/L) was found at 150 μmol photons m(-2) s(-1) light intensity and 2.4 g/L glucose concentration, while the highest maximum predicted EPS yield (364.3 mg/g) was recorded at 115 μmol photons m(-2) s(-1) light intensity and 1.8 g/L glucose concentration.
Full-text · Article · Jun 2012 · Folia Microbiologica
[Show abstract][Hide abstract] ABSTRACT: The aim of this work was to evaluate the cytotoxicity of Arthrospira platensis Extracellular Polymeric Substances
(EPS) for colon cancer and kidney cell lines. Results showed that EPS were free from cytotoxic effects. A variety of
solvents were assessed for their ability to extract the bioactive ingredients from EPS. Methanol gave the highest
yield (75.75%) than other solvents. The extracts were tested for activities against a collection of Gram+/- bacteria.
The methanol extract exhibited a more potent activity than the other organic extracts, whereas the aqueous extract
was active against Staphylococcus epidermis (Gram+) and Salmonella typhimurium (Gram-). Finally, The extracts
were also tested for the antioxidant activity, using the Trolox Equivalent Antioxidant Activity assay. The methanol
extract displayed a moderate antioxidant activity (TEAC = 0.027 mg/ml). The HPLC analysis of this extract
revealed two distinct peaks: 8.1 kDa (8.31 min) and 4.1 kDa (8.54 min).
Full-text · Article · Jul 2011 · Brazilian Archives of Biology and Technology