Harvesting Chlorella variabilis Biomass Using Moringa oleifera Seed-induced Sedimentation

Aim: To evaluate the efficacy of using Moringa oleifera seed powder, filtered cold water extract, and autoclaved cold water extract to induce sedimentation of Chlorella variabilis NIES 2541 cells without pH adjustment.

Place and Duration of Study: Department of Plant Science and Biotechnology, University of Nigeria, Nsukka between October, 2017 and July, 2018.

Methodology: Three sets of dry seeds of Moringa oleifera were prepared namely: (a) powdered seed, (b) Cold water extract of the seed which was prepared by soaking powdered seeds in cold water for 30 minutes, and filtering the extract through cheese cloth, and (c) autoclaved extract which was prepared by autoclaving the extract obtained from (b) for 20 minutes at 121°C. Chlorella variabilis was cultivated in BG11 medium and different concentrations of these Moringa seed samples were added to the culture broth, mixed and allowed to sediment. The sedimentation rates were monitored at 30 minutes intervals by taking samples from the top and measuring the optical density at 680 nm.

Results: In all the three cases, the rate of sedimentation increased with increase in the concentration of the Moringa seed used. In comparison with seed powder, use of cold water extract resulted in significant decrease in the sedimentation rate (P<0.05). However, more than 60% sedimentation was achieved by addition of extract from 10 g/l seed powder and incubating for only 30 minutes. Autoclaving the extract did not result in significant decrease in the efficacy of sedimentation (P>0.05). More than 70% sedimentation of Chlorella variabilis culture with an optical density of 3.5 was achieved in 30 minutes by addition of 7 g/l of autoclaved seed extract.

Conclusion: Although using Moringa seed powder resulted in the highest rate of cell sedimentation, autoclaved seed extract can still be used for efficient harvesting of Chlorella variabilis.