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 tothe generation of highly dangerous reactive oxygen species (ROS), which may cause the dete-rioration of cell metabolism and damage cellular components. The antioxidants produced byalgae alleviate the harmful effects of ROS. While the enhancement of antioxidant productionin blue green algae under stress has been reported, the antioxidant response to changes inpH levels requires further investigation. This study presents the effect of pH changes on theantioxidant 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 chlorophylla and carotenoids (10.6 and 2.4 mg/g DW, respectively) was recorded at pH 8.5. The highestphenolic content (12.1 mg gallic acid equivalent (GAE)/g DW) was recorded at pH 9.5. Themaximum production of total phycobiliprotein (159 mg/g DW) was obtained at pH 9.0. Theantioxidant activities of radical scavenging activity, reducing power and chelating activitywere highest at pH 9.0 with an increase of 567, 250 and 206% compared to the positive con-trol, respectively. Variation in the activity of the antioxidant enzymes superoxide dismutase(SOD), catalase (CAT) and peroxidase (POD) was also reported. While the high alkaline pHmay favor the overproduction of antioxidants, normal cell metabolism and membrane func-tion is unaffected, as shown by growth and chlorophyll content, which suggests that theseconditions are suitable for further studies on the harvest of antioxidants from S. platensis.