Airlift Photobioreactor High Cell Density Culture Of Chaetoceros Gracilis

Based on orthogonal test design, six major medium components, KH2PO4 , Na2SiO3,9H2O, NaHCO3, NaNO3, VB 1 and VB12, were optimized to be 0.02, 0.20, 0.15, 1.0, 2.7xlO-3and 1.5xlO-6g 1-1 for the culture of microalgae, Chaetoceros gracilis. This medium composition was validated thereafter by comparing the cell density achieved for SBM and f/2 media, which indicated 3.08 and 7.55 fold increases after 7 days' cultivations in 1000 ml scale culture bottles, respectively. The effects of pH and inoculation level were also investigated, and pH 7.8-8.6 and 7.5% seed inoculation were demonstrated to be suitable for both microalgae cell growth and practical application. Furthermore, 10 L scale bottle cultivation was designated and the cell densities of 0.72 and 0.86 g (d.w) 1-1 were achieved when the cultivations were operated at batch and feed-batch ways for 9 days, respectively, using the medium optimized above. Finally, 20 L airlift photobioreactor cultivation was initiated, and the operating parameters, including light strength, cultivation temperature and aeraion rate, were optimized through orthogonal tests. When light strength of 8 mW cm-2, temperature 23 &, and aeration rate 0.6 vvm were designated and batch cultivation was applied, as high as 1.13 g (d.w) 1-1 cell density was achieved after 5 days' cultivation and the microalgae productivity was calculated to be 0.226 g (d.w) 1-1 d-1 for this designated photobioreactor.