Mass culture, biomass production and antioxidant activities of two microalgae, Arthospira platensis and Chlorella vulgaris, and a fern, Azolla pinnata

Algae have widely been used in aquaculture as feedstuff and additives. Pharmaceutically, algae are used as nutritional supplements for treating many ailments in humans as they are considered a traditional food. The present study was carried out to optimise the culture medium for the growth and biomass production of two microalgae, Arthospira platensis (Spirulina) and Chlorella vulgaris (Chlorella), and the fern, Azolla pinnata (Azolla), under laboratory conditions. After 30 days of mass culture, the biomass production of A. platensis was found to be maximum in Zarrouk's medium (3.0 g/L dry wt.) than that of BG11 medium (2.02 g/L dry wt.). For C. vulgaris, the maximum growth was found in Conway's medium (2.86 g/L dry wt.) than that of Bold's basal medium (1.98 g/L dry wt.). In the case of A. pinnata, it was recorded to be 0.745 kg/L (dry wt.) in the Cow dung, followed by red soil (0.684 kg/L dry wt.) and urea (0.646 kg/L dry wt.). These algae and the fern possessed antioxidant activities, such as scavenging DPPH, ABTS and superoxide radicals, reducing power and inhibiting ascorbate autoxidation. Among these, the overall antioxidant activity was the best with Spirulina, followed by Chlorella and Azolla. These algae and the fern even can be grown in every household at a small scale level as and when required. Based on our previous study, it is concluded that microalgae, Spirulina and Chlorella can be consumed by humans as they are sources of protein and fibre if they are grown hygienically, and also can be used as food sources for fishes, prawns and other aquatic animals, and livestock also along with Azolla.