COMPOSITION AND ACCUMULATION OF SECONDARY CAROTENOIDS IN CHLOROCOCCUMSP

A locally isolated Chlorococcum sp. could accumulate astaxanthin and i ts esters as secondary carotenoids. The secondary carotenoids could re ach a concentration of 5.2 mg g(-1) d. wt, and were located in the cyt oplasm and chloroplast as globules. Cells grew best at pH 8.0 and 30 d egrees C, at which the growth rate was about 0.066 h(-1) Acidic condit ion (pH 5.5 and 6.5) and slightly elevated temperature (35 degrees C) enhanced the cellular accumulation of astaxanthin. Outdoor studies ind icated that Chlorococcum sp, grew well in a tubular photobioreactor. I n medium containing 2 mM and 10 mM NH4CI, the cellular contents of tot al secondary carotenoids and astaxanthin reached similar levels (5.0 m g g(-1) d. wt and 2.0 mg g(-1) d. wt, respectively) in the 15 days of cultivation, while the yields of total secondary carotenoids and astax anthin in 10 mM NH4CI were higher (45 mg L-1 and 18 mg L-1, respective ly). The advantages of tolerance to high temperature and extreme pH va lues, relative fast growth rate and ease of cultivation in an outdoor system suggest that Chlorococcum sp. could be a potential candidate fo r mass production of secondary carotenoids in particular astaxanthin.