Optimization Techniques with FORTRAN

Recovery of carboxylic acids produced by fermentation

Comparative assessment of downstream processing options for lactic acid

Citric acid is a commodity chemical produced and consumed throughout The World. It is used mainly in the food and beverage industry, primarily as an acidulant. Although it is one of the oldest industrial fermentations, its World production is still in rapid increasing. Global production of citric acid in 2007 was over 1.6 million tones. Biochemistry of citric acid fermentation, various microbial strains, as well as various substrates, technological processes and product recovery are presented. World production and economics aspects of this strategically product of bulk biotechnology are discussed.

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Citric acid production.

Extraction of lactic acid by phosphonium ionic liquids

Lactic, malic, and citric acids are representatives of hydroxycarboxylic acids, and they are also important biotechnological products. Extraction equilibria of these acids in the system water-solution of trialkylamine in mixtures of 1-octanol/n-heptane at temperatures 25, 50, and 75°C have been measured. Mathematical models of diverse complexity are presented, and their goodness of fit is tested and mutually compared. The best fits display the models comprising the formation of three acid-amine complexes and the nonideality of organic phase. In the cases of lactic and malic acids the acid-amine complexes (1,1), (2,1), and (2,2) and in the case of citric acid the complexes (1,1), (1,2), and (2,3) have been included. The incorporation of dissociation in the aqueous phase and of its nonideality has been found to have little effect on the model accuracy. The effects of temperature and solvent composition on the extraction equilibria have been studied, and exponential relations for their prediction have been derived. All the three systems display sensitivity to both temperature and solvent composition. Accordingly the principles of temperature and diluent swings are applicable to the processes of extractive recovery and purification of the acids investigated

Amine Extraction of Hydroxycarboxylic Acids. 2. Comparison of Equilibria for Lactic, Malic, and Citric Acids

Extraction of citric acid with tertiary amine—third-phase formation

The extraction equilibria of aliphatic dicarboxylic acids with solutions of trialkylamine (TAA) in binary diluents were measured and compared. Oxalic, succinic, DL‐malic and D‐tartaric acids were used. Trialkylamine with C7–C9 carbon atom chains was dissolved in 1‐octanol, methyl‐isobutyl ketone (MIBK), and chloroform, or in their binary mixtures with n‐heptane. Physical extraction with pure active diluents also was measured. The contribution of physical extraction was significant only in the case of succinic and oxalic acids and with octanol‐1 and MIBK as diluents. In all systems, formation of the (1:1) acid:amine complex was found dominant at low aqueous‐phase equilibrium acid concentrations. The values of the respective equilibrium constants grew in the same order as the first dissociation constants of these acids. In the region of high acid concentrations, overloading of amine was observed, indicating formation of (2:1) and (3:1) complexes. Here, the extraction grew with increasing lyophilici...

Extraction Equilibrium of Dicarboxylic Acids with Tertiary Amine in Single and Binary Diluents

Tall oil soap as a waste product of the sulphate cellulose production process was treated by single-stage liquid-liquid extraction. The aim of this study was to compare yields of health beneficial matters contained in tall oil soap when several extraction solvents, recommended in literature, were used. Hexane, 1-methyl-4-(1-methylethenyl)-cyclohexene, 2-methylpropan-1-ol, hexan-1-ol, 4-methylpentan-2-one, 2-methoxy-2-methylpropane, and butyl ethanoate were tested. For hydrocarbons it was necessary to add a de-emulsifier into the system, which limits the formation of foams and stable emulsions. The highest yields of total phytosterols (78 %) and especially of β-sitosterol (100 %) were reached when butyl ethanoate was used. However, it was necessary to adjust pH of the treated raw material to approximately 7. The highest yields for feed where pH was not adjusted were obtained with 2-methylpropan-1-ol: 67 % of total sterols and 89 % of β-sitosterol. Disadvantages of most of the tested solvents included the formation of the undesirable solid interphase which could not be removed, partial solubility of the solvents in the water phase, their high boiling point and/or instability. These disadvantages prevent the use of these solvents in industrial applications; they also complicate the treatment of tall oil soap by liquid-liquid extraction or the regeneration of the used organic solvent.

Extraction of phytosterols from tall oil soap using selected organic solvents

The dependence of extraction equilibrium on pH of the aqueous phase was studied in the system: aqueous solution of D-tartaric acid - solution of trialkylamine (TAA) in binary diluent. TAA was a mixture of tertiary amines with C 7 -C 9 carbon chains, the binary diluent was a mixture of w=0.7 of n-octan-1-ol in n-heptane. Measurements were performed at three levels of equilibrium pH 2.0, 2.5 and 3.0, the pH value required being adjusted with aqueous sodium hydroxide solution. The range of pH values and of acid concentrations investigated was limited by the low solubility of the sodium hydrogentartrate forming. In the range of pH values examined an increase of acid extraction with increasing pH was found, if only free acid in the aqueous phase was taken into account. The results of the extraction at constant initial total acid molality and varying pH exhibited diverse trends according to the way of expressing the degree of extraction. All these effects could be explained by assuming that only the free, undissociated acid can be extracted.

Aleš Heyberger

Papers

Amine Extraction of Hydroxycarboxylic Acids. 2. Comparison of Equilibria for Lactic, Malic, and Citric Acids

Extraction of citric acid with tertiary amine—third-phase formation

Extraction Equilibrium of Dicarboxylic Acids with Tertiary Amine in Single and Binary Diluents

Extraction of phytosterols from tall oil soap using selected organic solvents

pH dependence of tartaric acid extraction