Bisphenol A removal by the Chlorophyta Picocystis sp.: optimization and kinetic study.

The Chlorophyta Picocystis sp. isolated from a Tunisian household sewage pond appears promising for effective removal of Bisphenol A (BPA). Efficient and cost-effective technology for contaminants remediation relies on a tradeoff between several parameters such as removal efficiency, microorganism growth, and its tolerance to contaminant toxicity. This article demonstrates the optimum conditions achieving the highest removal rates and the minimal growth inhibition in batch cultures of Picocystis using response surface methodology. A central composite face-centered (CCF) design was used to determine the effects on removal and growth inhibition of four operating parameters: temperature, inoculum cell density, light intensity, and initial BPA concentration. Results showed that the maximal BPA removal was 91.36%, reached the optimal culture conditions of 30.7 °C, 25 × 105 cells ml-1 inoculum density, 80.6 µmol photons m-2 s-1 light intensity, and initial BPA concentration of 10 mg l-1. Various substrate inhibition models were used to fit the experimental data, and robustness analysis highlighted the Tessier model as more efficient to account for the interaction between Picocystis and BPA and predict removal efficiency. These results revealed how Picocystis respond to BPA contamination and suggest that optimization of experimental conditions can be effectively used to maximize BPA removal in the treatment process.HighlightsSurface response methodology was applied for optimization of BPA removal by the Chlorophyta Picocystis sp.Temperature, light intensity, inoculum cell density and initial BPA concentration were selected as factors that may affect BPA removal and microalgae growth.The optimal conditions for the maximum BPA removal and minimum growth inhibition were 30.7 °C; 80.6 µmol photons m-2 s-1; 25 × 105 cells ml-1 and 10 mg l-1 BPA.Teissier model was selected to fit the kinetic of BPA removal by Picocystis with R2 = 0.92.

Biodegradation of diclofenac by two green microalgae: Picocystis sp. and Graesiella sp.

The aim of the present study was to provide an integrated view of algal removal of diclofenac (DCF). Two isolated microalgal strains Picocystis sp. and Graesiella sp. were cultivated under different DCF concentrations and their growth, photosynthetic activity and diclofenac removal efficiency were monitored. Results showed that DCF had slight inhibitory effects on the microalgal growth which did not exceed 21% for Picocystis and 36% for Graesiella after 5 days. Both species showed different patterns in terms of removal efficiency. In presence of Picocystis sp., the amounts of removed DCF were up to 73%, 43% and 25% of 25, 50 and 100 mg L-1 respectively; whereas only 52%, 28% and 24% were removed in the presence of Graesiella at same DCF tested concentrations. DCF removal was insured mainly by biodegradation. To better reveal the mechanism involved, metabolites analyses were performed. Two DCF biodegradation/biotransformation products were detected in presence of Picocystis. This study indicated that Picocystis performed a satisfactory growth capacity and DCF removal efficiency and thus could be used for treatment of DCF contaminated aqueous systems.

Effect of Bisphenol A on the extremophilic microalgal strain Picocystis sp. (Chlorophyta) and its high BPA removal ability.

Bisphenol A (BPA) effects and removal by an alkaliphilic chlorophyta, Picocystis, were assessed. BPA at low concentrations (0-25 mg L-1) did not inhibit the Picocystis growth and photosynthesis during 5 days of exposure. At higher BPA concentrations (50 and 75 mg L-1), the growth inhibition did not exceed 43%. The net photosynthetic activity was dramatically reduced at high BPA concentrations while, the PSII activity was less affected. The exposure to increasing BPA concentrations induced an oxidative stress in Picocystis cells, as evidenced by increased malondialdehyde content and the over-expression of antioxidant activities (ascorbate peroxydase, gluthation-S-transferase and catalase). Picocystis exhibited high BPA removal efficiency, reaching 72% and 40% at 25 and 75 mg L-1 BPA. BPA removal was ensured mainly by biodegradation/biotransformation processes. Based on these results, the extended tolerance and the high removal ability of Picocystis make her a promising specie for use in BPA bioremediation.