Statistical optimization of the growth factors for Chaetoceros neogracile using fractional factorial design and central composite design.

Statistical experimental designs; involving (i) a fractional factorial design (FFD) and (ii) a central composite design (CCD) were applied to optimize the culture medium constituents for production of a unique antifreeze protein by the Antartic microalgae Chaetoceros neogracile. The results of the FFD suggested that NaCl, KCl, MgCl 2 , and Na 2 SiO 3 were significant variables that highly influenced the growth rate and biomass production. The optimum culture medium for the production of an antifreeze protein from C. neogracile was found to be Kalle's artificial seawater, pH of 7.0±0.5, consisting of 28.566 g/l of NaCl, 3.887 g/l of MgCl 2 , 1.787 g/l of MgSO 4 , 1.308 g/l of CaSO 4 , 0.832 g/l of K 2 SO 4 , 0.124 g/l of CaCO 3 , 0.103 g/l of KBr, 0.0288 g/l of SrSO 4 , and 0.0282 g/l of H 3 BO 3 . The antifreeze activity significantly increased after cells were treated with cold shock (at -5°C) for 14 h. To the best of our knowledge, this is the first report demonstrating an antifreeze-like protein of C. neogracile.