A diazotrophic cyanobacterium Nostochopsis lobatus was evaluated for enhanced production of biomass, pigments and antioxidant capacity. N. lobatus showed potentially high antioxidant capacity (46.12 mu M AEAC) with significant improvement under immobilized cell cultures (87.05 mu M AEAC). When a mixture of P and Fe was supplemented, biomass, pigments, nutritive value and antioxidant capacity increased substantially at pH 7.8. When considered separately, P appeared to be a better supplement than Fe for the production of biomass. chlorophyll and carotenoids. However, for phycocyanin, phycoerythrin, nutritive value and antioxidant capacity, Fe appeared more effective than P. Our study indicates N. lobatus to be a promising bioresource for enhanced production of nutritionally rich biomass, pigments and antioxidants. The study also suggests that P and Fe are potentially effective supplements for scale-up production for commercial application. (c) 2007 Elsevier Ltd. All rights reserved.