TLC screening of thraustochytrid strains for squalene production
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Screenings of thraustochytrids (Labyrinthulomycetes) have been conducted for 176 strains isolated from various sites in the Asian region to investigate what type of species and strains accumulate high levels of squalene. Thin layer chromatography (TLC) screening for squalene production revealed that 38 strains were rated as “+” (high), 29 as “±” (medium), and 109 as “−” (low). Further, high performance liquid chromatography analysis strongly supported the TLC screening results. Besides the 18W-13a strain of Aurantiochytrium sp., which was previously recognized as a squalene-rich strain, several strains produced squalene at approximately 1 g L−1 of culture volume. Squalene production was strongly related to locality, colony color, and phylogenetic clade. Most strains with “+” squalene spots were isolated from Okinawa, a subtropical region of Japan, while the strains with “±” and “−” squalene spots were isolated from wide geographical regions from tropical to subarctic. Approximately half the strains with orange colonies on GTY medium plates produced a high amount of squalene, whereas the other strains with different colors showed less or no squalene spots on TLC. All the squalene-rich strains were assigned to the Aurantiochytrium clade. Overall, our results suggest that (1) the thraustochytrids show tendentious locality in terms of squalene production, (2) a relationship exists between the metabolic synthesis of carotenoid pigments and squalene production, and (3) the Aurantiochytrium clade may have evolved to accumulate squalene.
KeywordsThraustochytrid Aurantiochytrium Squalene TLC
We are especially grateful to Dr. Nanda Kyaw Thu of the University of Tsukuba for his technical assistance in DNA purification on gel and cutting of PCR products. Thanks are also due to Dr. Masahiro Koide, Dr. Mayumi Erata and Dr. Yoshihisa Hirakawa of the University of Tsukuba and Dr. Ryoji Shimamura and Mr. Keiji Ikeda of NEWBIC (New Business Incubation Co. Ltd.) for their help in collecting or maintaining thraustochytrids. We would like to express our sincere gratitude to the members of Watanabe-Kaya Laboratory of the University of Tsukuba for their kind support. This research is supported by JST CREST funding and the MEXT Special Funds Program.
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