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Acid Fermentation in Water‐Organic Solvent Two‐Liquid Phase Systems
Author(s) -
Bar Raphael,
Gainer John L.
Publication year - 1987
Publication title -
biotechnology progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 129
eISSN - 1520-6033
pISSN - 8756-7938
DOI - 10.1002/btpr.5420030208
Subject(s) - chemistry , fermentation , solvent , lactic acid , dodecanol , chromatography , extraction (chemistry) , citric acid , acetic acid , organic acid , microorganism , organic chemistry , bacteria , biology , genetics
In 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 of L. delbrueckii in 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 of L. 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 of A. niger and A. aceti when 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 < pK a , such as A. aceti and A. niger. The amine was found to be toxic to L. delbrueckii above a concentration of 222 mM, and at a level of 50%v, it was deleterious to all cell microorganisms tested, either free or gel entrapped.