Variation of photoautotrophic fatty acid production from a highly CO 2 tolerant alga, C hlorococcum littorale , with inorganic carbon over narrow ranges of p H

Photoautotrophic fatty acid production of a highly CO 2 ‐tolerant green alga Chlorococcum littorale in the presence of inorganic carbon at 295 K and light intensity of 170 µmol‐photon m −2  s −1 was investigated. CO 2 concentration in the bubbling gas was adjusted by mixing pure gas components of CO 2 and N 2 to avoid photorespiration and β‐oxidation of fatty acids under O 2 surrounding conditions. Maximum content of total fatty acid showed pH‐dependence after nitrate depletion of the culture media and increased with the corresponding inorganic carbon ratio. Namely, [HCO 3 − ]/([CO 2 ]+ n [CO 3 2 −]) ratio in the culture media was found to be a controlling factor for photoautotrophic fatty acid production after the nitrate limitation. At a CO 2 concentration of 5% (vol/vol) and a pH of 6.7, the fatty acid content was 47.8 wt % (dry basis) at its maximum that is comparable with land plant seed oils. © 2015 American Institute of Chemical Engineers Biotechnol. Prog ., 31:1053–1057, 2015