Production of emulsan in a fermentation process using soybean oil (SBO) in a carbon–nitrogen coordinated feed

Abstract

A fermentation process for the microbial production of an amphipatic lipopolysaccharide, emulsan, has been established using a triglyceride carbon source in a coordinated carbon-nitrogen feed strategy. The polysaccharide was produced by the Acinetobacter strain at a productivity of about 0.5 g emulsan/L h while utilizing only the fatty acids (FA) portion of the triglycerides or free fatty acids that were fed into the medium.A useful correlation between the utilization of the fatty acids and the consumption of the nitrogen was found and employed for the practical feed strategy using an appropriate C--N ratio (7.7 g C/g N) of the soybeanoil (SBO) (carbon source) to the ammonium hydroxide base (nitrogen source). Either the pH control or the supervising computer system could accomplish the adequate balanced feed in to the fermentor. Lipolysis slowdown was overcome by switching from a triglyceride carbon source to a free fatty acids one. A yield of about 0.2 g emulsan/g fatty acids was obtained and a final concentration of over 20 g/L was reached. The polymeric product was found to be partially associated with the cell-oil complexes in the fermentation broth unless the oily carbon source was efficiently exhausted. A fedbatch fermentation that employed a shift of the carbon source feed from triglycerides to free fatty acids appeared to be an appropriate and feasible way of producing the polymer.