The evaluation of oleic acid alternatives for the biochemical production of 9-octadecenedioic acid

Abstract

Despite considerable foaming problems, oleic acid is still the most commonly used substrate for the biochemical production of 9-octadecenedioic acid (DCA). In this paper, the suitability of alternative substrates such as oleyl alcohol, methyl-, ethyl- and butyl oleate, was investigated. First, the toxicity of the alternative substrates to the fermenting yeast C. tropicalis ATCC20962 was determined for different substrate concentrations. It was found that the addition of up to 100 g L−1 of the ester and alcohol substrates showed no growth influence. Since alcohols are expected side products when using ester substrates, the toxicity of the corresponding released alcohols was also evaluated. Methanol and ethanol showed no effect on the growth up to 36 g L−1 and 55 gL−1 respectively, whereas a half maximum inhibitory concentration (IC50) of 1.4 g L−1 for butanol was found. Using 20 g L−1 oleic acid, oleyl alcohol, methyl oleate and butyl oleate as substrate showed a yield of 14 g L−1, 7 g L−1, 5 gL-1 and 0.9 g L-1 9-octadecenedioic acid respectively. A qualitative study showed that all four substrates were converted to 9-octadecenedioic acid. Oleic acid resulted in the highest yield whereas oleyl alcohol is the closest candidate for alternative DCA production.