Enhancement of the Growth of Marine Microalga Chlorella sp. from Mixotrophic Perfusion Cultivation for Biodiesel Production

W. Choi, S. Oh, C. Lee, Y. Seo, C. Song, J. Kim and H. Lee

Abstract
For biodiesel production, marine alga Chlorella sp. was grown by continuously perfusing 35–40 °C warm waste seawater in a 14 L photobioreactor. The temperature of the culture system was maintained at minimum of 25 °C at 1.0 L h–1 of perfusion rate with no other heating systems. Under mixotrophic conditions with only 1 g L–1 of glucose, a maximum cell concentration of 7.1 (gdry mass L–1) was observed for over 95 days cultivation while 3.3 (gdry mass L–1) of maximum cell concentration was maintained for autotrophic growth. The highest total lipid production was also obtained as w = 21.6 % with w = 50 % of palmitic and oleic acids, which would be a proper composition for biodiesel. The specific lipid production rate remained relatively constant until the end of the perfusion cultivation while it decreased in latter periods of batch cultivation. In general, the perfusion process shows a better performance because of the continuous supply of fresh medium and high accumulation of biomass. These results prove that this unique recycling system can be employed where geographically the temperature is a more critical factor for outdoor mass cultivation.

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Keywords
Chlorella sp., mixotrophic, lipid production, biodiesel, photobioreactor