Abstract:
Diatoms are primary producers in aquatic ecosystems. Water from aquaculture
ponds is rich in nutrients essential for diatom growth. In this research, marine diatom Amphora
subtropica BUUC1502 was cultured to determine the conditions that yielded the highest growth
and fucoxanthin concentration using water from shrimp pond. It was found that the cultivation of
A. subtropica BUUC1502 using F/2 growth medium mixed with water from shrimp pond at 4:1
volume ratio (25% shrimp pond water by volume) yielded the highest cell number density (352 ´
104 cells/mL) and fucoxanthin concentration (3.37 mg/L). This condition was subsequently used
to determine the effects of light intensity and nutrient. The optimal light intensity was determined
at 200 µmole/m2/s, yielding cell number density and fucoxanthin concentration of 134 ´
104 cells/mL and 3.19 mg/L, respectively. For the nutrient study, the cultivation of A.
subtropica BUUC1502 using F/2 medium containing 3-folds silica and shrimp pond water (25%)
yielded higher cell number density (262 ´ 104 cells/mL) and fucoxanthin (6.06 mg/L) than other
conditions. From the results obtained, it was apparent that light intensity and silicate
concentration are important factors affecting growth and fucoxanthin production. Moreover, the
cultivation in 15 L photobioreactor was conducted. After adjusting the light intensity to
compensate with longer light path, it was found that, at the light intensity of 68 µmole/m2/s, the
cultivation of A. subtropica BUUC1502 using the mixture of F/2 medium (3-folds silicate) and
shrimp water pond (25%) produced the cell number density and fucoxanthin concentration of 134
´ 104 cells/mL and 5.53 mg/L, respectively. In conclusion, water from shrimp pond had the
potential to support growth of marine diatom, reduce the amount of nutrient discharge into the
natural water resources, and decrease operational expense of diatom cultivation.