Comparative study on Bio-diesel Content in Micro-algal Biomass

Abstract

Biodiesel content of the six selected algal strains was highest in Chlorococcum sp. (44.59%) followed by Closterium sp. (42%), Oedogonium sp.(40.82%), Oscillatoria sp.(37.52%), Pithophora sp.(37.5%) and Cladophora sp. (21.66%). Biomass (after oil extraction) was maximum (46g) in Cladophora sp. and minimum (26g) in Oscillatoria sp.. Sediment (glycerine, water and pigments) was higher in Pithophora sp. (25.92g) and lower in Oedogonium sp. (8.17g). The pH range of bio-diesel and byproducts of the selected strains is 7.0-7.4 and 10.7-12, respectively; whereas the Optical Density (OD) range of bio-diesel and byproduct were 0.8-0.95 and 0.8-1, accordingly. In vitro culture of six different algal strains (viz. Oedogonium sp., Oscillatoria sp., Chlorococcum sp., Closterium sp., Cladophora sp. and Pithophora sp.) were established in three different algal media (viz BBM, Fogg's medium and Chu medium). Among them, Chlorococcum sp., Closterium sp. and Pithophora sp. exhibited optimum growth (μ= 0.04 d-1) in all media. Net growth rate (μ= 0.03 d-1) were same incase of the rest three strains in all mediums. Among three media biomass yield of Cholorococcum sp. was best in BBM (51.01g±0.01) followed by Fogg's medium (50.20g ±0.01) and Chu medium (49.20g ± 0.02). Yield of rest of the five selected strains e.g. Closterium sp. (50.45±0.03), Cladophora sp. (29.97±0.02), Oedogonium sp.(31.75±0.03),Oscillatoria sp. (29.01±0.02) and Pithophora sp. (49.75±0.02) was also highest in BBM. Suitable pH in BBM for growth of all strains was found to be 6.5 while in Fogg's and Chu media the best performance were observed at pH 7.2. As evident, Chlorococcum sp. contains highest biodiesel content (44.59%) and is highest biomass gaining and fast growing (biomass= 51.01g ±0.01 and growth rate, μ= 0.04 d-1) green algae commonly found in the northern region of Bangladesh may be recommended as a potential source of commercial bio-diesel production. Biodiesel content of Closterium sp. (42%), Oedogonium sp.(40.82%) indicate these two strains are also potential for biodiesel extraction.