Long-chain dicarboxylic acids from plant oils

Scheme of omega-oxidation of alkanes or monocarboxylic acids to long-chain dicarboxylic acids with subsequent possible degradation by beta-oxidation (according to Eschenfeldt W.H. et al. 2003 and Mauersberger S. et al 1992).
Stoffwechselweg der ω-Oxidation in Candida tropicalis
Metabolic pathway of ω oxidation in Candida tropicalis for the synthesis of long-chain dicarboxylic acids from fatty acids.

Long-chain dicarboxylic acids – Intermediates for plastics

Long-chain dicarboxylic acids (C>12) are interesting intermediates for the synthesis of plastics with new properties. For example, dicarboxylic acids are used in the production of polyamides and polyesters. However, these are chemically complex to synthesize. Alternatively, long-chain dicarboxylic acids can be produced biotechnologically from the renewable raw material rapeseed oil. In rapeseed oil, fatty acids are bound to glycerine. After cleavage, the free fatty acids can be converted, for example, from yeasts of the genus Candida to dicarboxylic acids.

Synthesis and degradation of dicarboxylic acids

The synthesis of long-chain dicarboxylic acids in microorganisms takes place via ω oxidation, which is described for some yeasts such as Candida tropicalis or Yarrowia lipolytica. In the course of three enzymatic reactions, fatty acids are oxidized to dicarboxylic acids. The microorganisms also possess the biochemical degradation pathway for mono- and dicarboxylic acids, the so-called β oxidation, which prevents the accumulation of dicarboxylic acids in naturally occurring yeasts.

Development of fermentation strains and processes

© Fraunhofer IGB
Fermentation in a 42-litre reactor.

At Fraunhofer IGB, new fermentation strains for the conversion of fatty acids into dicarboxylic acids are to be provided, which are easier to handle than the well-known pathogenic strain C. tropicalis due to their apathy. To provide new production strains, newly identified microorganisms are used as whole cell catalysts in an integrated process for the conversion of fatty acids in order to achieve the highest possible dicarboxylic acid yield.

On the other hand, selected strains are genetically modified to enable dicarboxylic acid accumulation. These recombinant strains are also currently being investigated for their suitability as production strains. Furthermore, the possible applications of vegetable oils for the production of dicarboxylic acids that do not compete with the food industry are investigated.

Results to date and outlook

42-litre bioreactor (left) for the cultivation of yeast strains (right) for the production of long-chain dicarboxylic acids.

By developing different fed-batch processes with microorganisms of the genus Candida, dicarboxylic acid concentrations of up to 100 g/L from oleic acid have already been achieved. At the same time, we are investigating other microorganisms to provide new and easier to handle production strains that enable the highest possible dicarboxylic acid yield.

Fraunhofer IGB is currently working on the genetic modification of a Pichia strain. By targeted knock-out of genes of the beta-oxidation pathway, the degradation of the dicarboxylic acids formed in this strain is to be prevented and the dicarboxylic acid yield is to be increased by increased activation of genes of the omega-oxidation pathway. The aim is to provide a microbiologically harmless production strain for dicarboxylic acid formation.

The process was developed using rapeseed oil derivatives and oleic acid as examples, but can in all probability be transferred to oils that are not used in the food sector. In a second approach, selected strains are genetically modified to ensure dicarboxylic acid synthesis. These recombinant strains are also currently being investigated for their suitability as production strains.

Range of services

  • We offer fermentations to provide samples of 1,18-octadecendioic acid produced by Candida sp.
  • In addition, we have know-how in the area of strain development and can carry out appropriate metabolic engineering at your request.