Final Thesis

Crystallization of organic acids from fermentation broth

Key Info

Basic Information

Fluid Process Engineering
Forschungspraktikum for Biotechnologen
Focus/Key Topic:


Organic acids such as acetic acid, citric acid or vitamin C play an important role in the food industry and can be produced by fermentation. They then have to be separated from the aqueous fermentation broth in the purest form possible and in an energy-efficient manner. As a low-energy process that is gentle on the fabric and at the same time ensures high product purity, the crystallization process is often the method of choice. The fermentation broth is a complex solution with many secondary components that affect the solubility of the acid to be crystallized. In addition, an increasing viscosity of the solution in the progressing process makes the separation of the acid more difficult. This can result in a delay in crystallization, since the supersaturation of the solution cannot be broken down quickly enough and the solid-liquid equilibrium is not always achieved in the process. The aim of this work is to increase the yield during crystallization. For this purpose it is necessary to experimentally determine the equilibrium behavior of the acid by carrying out solubility tests of the acid in the fermentation medium at different temperatures. In order to quantify the effects of the increased viscosity on the delay in crystallization, experiments on kinetics and viscosity measurement should be carried out. Finally, the knowledge of equilibrium and kinetics should be applied in order to achieve the highest possible crystal yield with suitable operating parameters.