Fermentation Conditions and Media Optimization for Isocitric Acid Production from Ethanol by Yarrowia lipolytica.

Isocitric acid exists in the form of four stereoisomers, of which only the threo-Ds-form (ICA) is a natural active compound, an intermediate of Krebs cycle, and suitable for nutritional and pharmaceutical use. In this paper, we propose a method for ICA production from ethanol by yeast Yarrowia lipolytica. The effects of temperature, pH of the medium, and aeration on the growth of the producer Y. lipolytica VKM Y-2373 and synthesis of ICA were studied. An optimal fermentation regime, which ensures a good growth of the producer and directed synthesis of the target product, was determined. The producer is advised to carry out cultivation at 29°C and various pH of the medium and the oxygen concentration (pH 5 and pO2 20-25% (of saturation) during the growth period and pH 6 and pO2 50-55% (of saturation) during the acid formation) on a nutrient medium containing an increased content of zinc (0.6 mg/L), iron (1.2 mg/L), and 30 mM itaconic acid (inhibitor of isocitrate lyase-the key enzyme of ICA metabolism) should also be introduced into the nutrition medium. Such fermentation production mode provides 90.5 g/L ICA with process selectivity of 80%, mass yield (YICA) of 0.77 g/g, and energy yield (ηICA) of 0.278 g/g.

The effect of oxalic and itaconic acids on threo-Ds-isocitric acid production from rapeseed oil by Yarrowia lipolytica.

The effect of oxalic and itaconic acids, the inhibitors of the isocitrate lyase, on the production of isocitric acid by the wild strain Yarrowia lipolytica VKM Y-2373 grown in the medium containing rapeseed oil was studied. In the presence of oxalic and itaconic acids, strain Y. lipolytica accumulated in the medium isocitric acid (70.0 and 82.7 g/L, respectively) and citric acid (23.0 and 18.4 g/L, respectively). In control experiment, when the inhibitors were not added to the medium, the strain accumulated isocitric and citric acids at concentrations of 62.0 and 28.0 g/L, respectively. Thus, the use of the oxalic and itaconic acids as additives to the medium is a simple and convenient method of isocitric acid production with a minimum content of citric acid.

The peculiarities of succinic acid production from rapeseed oil by Yarrowia lipolytica yeast.

The process of succinic acid (SA) production represents the combination of microbial synthesis of α-ketoglutaric acid from rapeseed oil by yeast Yarrowia lipolytica VKM Y-2412 and subsequent decarboxylation of α-ketoglutaric acid by hydrogen peroxide to SA that leads to the production of 69.0 g l(-1) of SA and 1.36 g l(-1) of acetic acid. SA was isolated from the culture broth filtrate in a crystalline form. The SA recovery from the culture filtrate has certain difficulties due to the presence of residual triglycerides of rapeseed oil. The effect of different methods of the culture filtrate treatment and various sorption materials on the coagulation of triglycerides was studied, and as a result, the precipitation of residual triglycerides by acetone was chosen. The subsequent isolation procedures involved the decomposition of H2O2 in the filtrate followed by filtrate bleaching and acidification with a mineral acid, evaporation of filtrate, and SA extraction with ethanol from the residue. The purity of crystalline SA isolated from the culture broth filtrate achieved 97.6-100 %. The product yield varied from 62.6 to 71.6 % depending on the acidity of the supernatant.