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As. Pac. J. Mol. Biol. & Biotech., Dec 2002 Vol. 10 (2) : 109-117

Influence of Irradiance and Inoculum Density on the Pigmentation of Spirulina platensis

Wan-Loy Chu1, Siew-Moi Phang2*, K. Miyakawa3** and T. Tosu4

1International Medical University, Sesama Centre-Plaza Komanwel, Bukit Jalil, 57000 Kuala Lumpur, Malaysia
2Institute of Biological Sciences, University of Malaya, 50603 Kuala Lumpur, Malaysia
3Dainippon Ink & Chemicals Inc., Food and Food Additives Division, 3-7-20 Nihonbashi, Chuo-ku, 103-0011 Tokyo, Japan
4Siam Algae Co. Ltd., 19 Moo 4, Bangna-Trad Road (Km 24), T. Bangsaothong, King Amphur Bangsaothong, Samutprakarn 11540, Thailand

Abstract.

The effects of irradiance and inoculum density on the growth and pigmentation, especially carotenoid composition of Spirulina (Arthospira) platensis UMACC 160 were investigated. The cultures were grown at three irradiance levels (50, 105 and 160 µmol m-2 s-1) using two inoculum densities (OD620= 0.2 and 2.0). Biomass and pigment contents throughout the growth cycle were determined. The low-density inoculum cultures attained higher specific growth rates (µ) based on dry weight (0.54 day-1) than the high-density inoculum cultures (0.26 day-1). For the low-density inoculum cultures, specific growth rate (µ) increased with increasing irradiance. Maximum biomass attained under the various culture conditions reached 1363 mg dry weight L-1. The contents of phycocyanin, chlorophyll a and carotenoids varied markedly, ranging from 1.1 - 127.0, 7.2 - 32.2 and 3.30 - 12.19 mg g-1 dry weight respectively. The highest yield of phycocyanin (919 mg L-1) was attained by the low-density inoculum cultures grown at the lowest irradiance, while the highest yield of carotenoids (8.50 mg L-1) was attained by the high-density inoculum cultures grown at the highest irradiance, both at stationary phase. The carotenoids consisted of β-carotene (5.50 mg g-1 dry weight), myxoxanthophyll (4.62 mg g-1 dry weight), zeaxanthin (2.52 mg g-1 dry weight) and oscillaxanthin (1.14 mg g-1 dry weight); the content of each constituent varied with culture age and irradiance, and was dependent on the inoculum density used. Irradiance, inoculum density and culture age are three important factors to be considered for optimisation of pigment production by S. platensis.

Keywords: β-carotene, carotenoids, chlorophyll a, irradiance, phycocyanin, Spirulina platensis

*Author for Correspondence.
Mailing address: Institute of Biological Sciences, University of Malaya, 50603 Kuala Lumpur, Malaysia.
Fax: +603-79568940 Tel: +603-79674610  E-mail: phang@um.edu.my
**Present Address: Micro Gaia, Inc., 535 Lipoa Parkway, Suite 151, Kihei, Maui, Hawaii 96753, USA