Natural plant extracts as an economical and ecofriendly alternative for harvesting microalgae

The study investigated the ability of plant based natural coagulants from Azadirachta indica; Ficus indica; Moringa oleifera; Citrus sinensis; Punica granatum and Musa acuminata to harvest the microalgal biomass. Influence of eluent type (water and NaCl) and concentration (1-5 N) on coagulant extraction; coagulant dosage (1-5 g) and volume (20-100 ml); pH (6-12) and algal concentration (0.1-1 g l(-1)) on harvesting were analyzed. The results obtained were compared with alum and chitosan. FTIR and biochemical analysis confirmed the presence of bioactive compounds to aid coagulation. Biomass removal efficiency of 75.50% was obtained with M. oleifera extracts (8 mg ml(-1)) at pH 7.5-7.8, within 100 min. The harvesting efficiency increased to 95.76% when 4mgml(-1) M. oleifera extracts was combined with 0.75 mg ml(-1) chitosan. The life cycle and cost analysis acknowledged the eco-friendly coagulants as strong alternative for conventional coagulants used in microalgal harvesting, thereby improvising the overall bioprocess.