Influence of culture temperature on the growth, biochemical composition and fatty acid profiles of six Antarctic microalgae

The growth, biochemical composition and fatty acid profiles of six Antarctic microalgae cultured at different temperatures, ranging from 4, 6, 9, 14, 20 to 30 degrees C, were compared. The algae were isolated from seawater, freshwater, soil and snow samples collected during our recent expeditions to Casey, Antarctica, and are currently deposited in the University of Malaya Algae Culture Collection (UMACC). The algae chosen for the study were Chlamydomonas UMACC 229, Chlorella UMACC 234, Chlorella UMACC 237, Klebsormidium UMACC 227, NaviculaUMACC 231 and StichococcusUMACC 238. All the isolates could grow at temperatures up to 20 degrees C; three isolates, namely Navicula UMACC 231 and the two Chlorella isolates ( UMACC 234 and UMACC 237) grew even at 30 degrees C. Both Chlorella UMACC 234 and Stichococcus UMACC 238 had broad optimal temperatures for growth, ranging from 6 to 20 degrees C (mu = 0.19 - 0.22 day(-1)) and 4 to 14 degrees C (mu = 0.13 - 0.16 day(-1)), respectively. In contrast, optimal growth temperatures for Navicula UMACC 231 and Chlamydomonas UMACC 229 were 4 degrees C (mu = 0.34 day(-1)) and 6 - 9 degrees C (mu = 0.39 - 0.40 day(-1)), respectively. The protein content of the Antarctic algae was markedly affected by culture temperature. All except Navicula UMACC 231 and Stichococcus UMACC 238 contained higher amount of proteins when grown at low temperatures ( 6 - 9 degrees C). The percentage of PUFA, especially 20: 5 in Navicula UMACC 231 decreased with increasing culture temperature. However, the percentages of unsaturated fatty acids did not show consistent trend with culture temperature for the other algae studied.