Extracting long-chain fatty acids from a fermentation medium

Several solvents were evaluated for extracting free long-chain FA (LCFA) from a fermentation medium. Chloroform, chloroform/methanol (1:1), hexane, and hexane/methyl tertbutyl ether (MTBE) (1 :1) were evaluated as alternative extraction solvents. Parameters considered for optimizing LCFA recoveries included pH and ionic strength. Maximal LCFA recoveries were obtained by adding 2 mL of the hexane/MTBE (1:1) solvent mixture, 80 muL of 50% H2SO4, and 0.05 g NaCl to 1 mL of the aqueous sample and mixing for 15 min at 200 rpm. This method quantified saturated LCFA [capric acid (C-10:0) to stearic acid (C-18:0)] and unsaturated LCFA with 18 carbons [linoleic acid (C-18:2) and oleic acid (C-18:1)] with a 98 to 100% recovery. Caproic (C-6:0) and caprylic (C-8:0) acids were characterized by 27 and 76% recoveries, respectively.