ACOI 58 and ACOI 1257, two different Portuguese strains of colonial green microalga Botryococcus bruanii Kutz obtained from Coimbra Collection of Algae (ACOI), were evaluated on their potential for biofuel production, which was assessed from batch culture in photobioreactors under indoors and outdoors conditions using pretreated waste water and semisynthetic culture media. In the experiments, the maximum specific growth rate achieved was 0.4 day-1 with doubling times ranging from 2 to 7 days in the fastest growing phase. However, both strains showed ability to absorb nutrients in waste water cultures, to grow and accumulate oil. The maximum lipid extraction on a dry matter basis was 36% in CHU media and 29% in waste water cultures, which revealed the promising potential of these B. braunii isolates to be used in biofuel production applications. This is also supported by the predominance of oleic (C18:1, 42 to 63%) and palmitic acid (C16:0, 8 to 18%) in the lipid extract, since the methyl esters of these fatty acids (FAME) are ideal for biodiesel production. In summary, although these strains of B. braunii have presented a typical growth for this species, they produced considerable lipid content and were able to grow in waste water and under outdoors conditions that warrants further investment in their study.
Key words: Microalga, Botryococcus braunii, wastewater, photobioreactors, biofuels.
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