title: Role of pH on antioxidants production by Spirulina (Arthrospira) platensis.
abstract: Algae can tolerate a broad range of growing conditions but extreme conditions may lead to the generation of highly dangerous reactive oxygen species (ROS), which may cause the deterioration of cell metabolism and damage cellular components. The antioxidants produced by algae alleviate the harmful effects of ROS. While the enhancement of antioxidant production in blue green algae under stress has been reported, the antioxidant response to changes in pH levels requires further investigation. This study presents the effect of pH changes on the antioxidant activity and productivity of the blue green alga Spirulina (Arthrospira) platensis. The algal dry weight (DW) was greatly enhanced at pH 9.0. The highest content of chlorophyll a and carotenoids (10.6 and 2.4mg/g DW, respectively) was recorded at pH 8.5. The highest phenolic content (12.1mg gallic acid equivalent (GAE)/g DW) was recorded at pH 9.5. The maximum production of total phycobiliprotein (159mg/g DW) was obtained at pH 9.0. The antioxidant activities of radical scavenging activity, reducing power and chelating activity were highest at pH 9.0 with an increase of 567, 250 and 206% compared to the positive control, respectively. Variation in the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) was also reported. While the high alkaline pH may favor the overproduction of antioxidants, normal cell metabolism and membrane function is unaffected, as shown by growth and chlorophyll content, which suggests that these conditions are suitable for further studies on the harvest of antioxidants from S. platensis.
authors.affiliation: Department of Biological Sciences, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada; Botany Department, Faculty of Science, Zagazig University, Zagazig, Egypt. Electronic address: mostafamsami@yahoo.com.
authors.forename: Mostafa Mahmoud Sami
authors.initials: MM
authors.lastname: Ismaiel
authors.affiliation: Botany Department, Faculty of Science, Zagazig University, Zagazig, Egypt.
authors.forename: Yassin Mahmoud
authors.initials: YM
authors.lastname: El-Ayouty
authors.affiliation: Department of Biological Sciences, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Michele
authors.initials: M
authors.lastname: Piercey-Normore
mesh_terms: D000975:Antioxidants / Q000737:chemistry / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry / Q000378:metabolism; D052979:Phycobiliproteins / Q000737:chemistry / Q000378:metabolism; D053545:Spirulina / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D010636:Phenols; D052979:Phycobiliproteins; D002734:Chlorophyll; D000077194:Chlorophyll A
keywords: Antioxidant enzymes; Antioxidants; Carotenoids; Phycocyanin; Radical scavenging activity; Total phenolic content