Abstract
Microalgae and their metabolites can be influenced by their environment, effects that can be investigated in a laboratory by modifying the composition of the cultivation medium. In this study, pH was varied around (4-10), temperature (10-45 degrees C), and sodium nitrate (0-5 g/L) concentration to assess the performance of Chlorella sp. and Oedogonium sp., which were isolated from water bodies from the Lahore district of Pakistan. A decreased algal growth rate was paralleled by an increase in the lipid levels. In dried samples of Chlorella sp. the lipid increased from 42% under optimal growth conditions to 73% in samples grown under nitrogen deficiency at 20 degrees C in a cultivation medium adjusted to pH 4. A similar result was found in cultures of Oedogonium sp. while the lipid content increased from 40 to 69%. These two algal strains were further esterified for biodiesel production and fuel properties were analyzed. In both algae, C16 and C18 fatty acids increased preferentially under stress. This was paralleled by improved fuel properties of the produced biodiesel. It can be suggested that microalgal lipid compositions enhanced by acclimatization to sub-optimal environmental conditions opens a new opportunity for the production of cost-effective biodiesel.
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