S80: The fermentation production of long chain dicarboxylic acids

A Candida sp. isolate was obtained after screening of mutants on which ⁶⁰Co irradiation was carried out. The mutant strain exhibited fast process to oxidize and convert methyl laurate (CAS No. 111-82-0) to dodecanedioic acid. The nitrogen sources proved to be essential for efficiency of the conversion. Nitrate, ammonium and urea played an important role in the growth of cells but did not contribute to the diacid formation when dodecane was present. However, complex organic nitrogen sources such as molasses, yeast extract and corn steep liquor significantly helped conversion of methyl laurate to its corresponding diacid. The highest molar conversion ratio from methyl laurate to dodecanedioic acid has been more than 70% for a fermentation process of 120 hours, which was 30 hours shorter than the current manufacturing bioprocess using dodecane as the feedstock. In addition, the mutant accomplished the diacid conversion with dissolved oxygen (DO) 20% less in contrast with the current industrial strain, which suggested a more economical bioprocess. An optimized fermentation process has also been developed to prevent intensive foam from forming when methyl laurate was fed, which has been an obstacle for industrial application of a fatty acid or its ester as the feedstock. A trial bioconversion process to produce hexadecanedioic acid was also conducted using methyl palmate by the mutant isolate. The 5-day process achieved 55% molar conversion rate, which suggested a great potential of the strain, as well as the strategy, to produce various types of long chain DCAs.