Extraction optimization using response surface methodology and evaluation of the antioxidant and antimicrobial potential of polyphenols in Scenedesmus sp. and Chlorella sp.

Microalgae are considered natural alternatives to replace synthetic antioxidants. The extraction of polyphenols from Scenedesmus sp. and Chlorella sp. was optimized by employing a central composite design. The effect of solvent nature (ethanol, methanol, and ethyl acetate), extraction temperature (4–80 °C), and extraction time (0.1–4 h) were investigated with an ultrasound-assisted system. Total phenolic compound (TPC) extraction was higher at the combination of methanol, 4 °C, and 4 h for Scenedesmus and methanol, 80 °C, and 4 h for Chlorella. Microalgae were cultivated in BG11 and BG11 + 40% olive mill wastewater (OMUF) media. The extracts were analyzed for their total polyphenol content and antioxidant and antimicrobial activities. The estimation results of models and experimental results indicated a high consistency when cultivating microalgae in BG11 medium. Polyphenols extracted from microalgae cultured with 40% (OMUF) possess significantly high antioxidant and antimicrobial activities. Hence, Scenedesmus sp. and Chlorella sp. showed a capability to grow in the presence of ultrafiltered OMW and produce high added-value compounds.