AbstractIn search of an optimal system for extractive fermentation of an organic acid, fermentations of lactic, citric, and acetic acids were studied in a broth saturated with an organic solvent and in a broth‐organic solvent two‐liquid phase system. Among the 13 solvents tested, only long‐chain hydrocarbons, perfluorodecalin, and methyl oleate were found to be nontoxic to the cells ofL. delbrueckiiin two‐liquid phase systems. However, a distinction was made between toxicity due to dissolved solvent molecules and that due to a separate solvent phase. Thus, cells ofL. delbrueckii,which were not inhibited in n‐dodecanol‐saturated broth, but inhibited in a two‐phase system, were successfully protected by immobilization in carrageenan beads. The same solvent however, partially inhibited the growth ofA. nigerandA. acetiwhen present at saturated levels in the broth. The effect of tridodecylamine on lactic acid fermentation in a two‐liquid phase system was investigated in view of enhancing the acid extraction. Since extraction of an acid is favored by low pH, an extractive fermentation of an acid is practical for microorganisms that can grow at pH展开▼
