Isolation and screening of microalgal species, native to Zimbabwe, with potential use in biodiesel production

Microalgae are increasingly being preferred as sustainable biomass feedstock for biofuels production due to their high growth rate and lipid yield. However, optimal production requires the use of economical native microalgal species which are well adapted to local climatic and ecological conditions. Therefore, this study's main objective was to isolate and select local microalgal species for prospective biofuels production. Serial dilution and streak plate techniques were used to isolate four species: Chlorella, Scenedesmus, Oscillatoria and Microcystis from Manyame River, Zimbabwe. The isolates were evaluated for their biomass and lipid productivity under artificial lighting (8:16 h light/dark cycle) and a temperature of 25 +/- 3 degrees C. Lipid quantification was done gravimetrically, using hexane as an extraction solvent. Each isolate's performance was compared against that of an imported Chlorella vulgaris strain. Amongst the isolates, Chlorella sp. exhibited a highly competitive growth rate of 0.26 d(-1) and lipid yield of 37.16% dry cell weight. In comparison, the imported C. vulgaris had a growth rate of 0.226 d(-1) and lipid yield of 35.74% dry cell weight. Although findings suggest that the native Chlorella sp. is the ideal candidate, growth enhancement and genetic engineering techniques may be used to further improve its biomass and lipid yield.