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Über dieses Buch

Solvent Extraction in Biotechnology deals with the reco- very and purification of primary and secondary metabolites by solvent extraction. In the first part the reaction engineering principles: definitions, thermodynamic fundamentals, and system models, the kinetics of mass transfer between two phases without and with chemical reaction as well as extraction equipment, which are important for downstream processing in biotechnology, are considered in detail. The special part of the book describes the recovery of low-molecular metabolites: alcohols, acids and antibiotics with organic solvents, carrier-modifier-solvent systems, supercritical gases as well as with liquid membrane techniques. Several practical examples are given for the recovery of different metabolites as well as for the calculation of the extraction processes necessary for equipment design. Besides solvent extraction, novel separation techniques with liquid membrane, microemulsion and reversed micelles are also presented. This book will introduce the biochemical engineer and process engineer to the recovery of products from complex cultivation broths by modern techniques of solvent extraction and help them with process design.



1. Introduction

Cultivation media for microorganisms consist of carbon-, nitrogen-, phosphate-sources and nutrient salts with trace elements and vitamins. In laboratories, synthetic media with well-defined composition can be used. In industrial production, complex media consisting of agricultural (by)products and wastes (molasses, pharma medium, cornsteep liquor, yeast extract, soybean meal, peanut flour, cottonseed meal, fish meal, etc.) with poorly defined composition are employed. During the cultivation and production process, the medium components are consumed and converted into other compounds. The aim of the downstream processing is the recovery and purification of the valuable products from this complex fermentation broth.
Karl Schügerl

2. Reaction Engineering Principles

Equilibrium partitioning of nonelectrolytes between two immiscible phases is achieved, when the chemical potential of the solute is equal in the two phases
$${\mu _a} - {\mu _o},$$
where the potential in the aqueous phase is given by
$${\mu _a} = \mu _a^o + RT\ln {x_a}{\gamma _a}$$
and that of the organic phase by
$${\mu _o} = \mu _o^o + RT\ln {x_a}{\gamma _o}$$
Karl Schügerl

3. Extraction Equipment

In the chemical industry, three main types of extraction equipment are in use:
  • mixer-settler extractors
  • extraction columns and
  • centrifugal extraction equipment.
Karl Schügerl

4. Extraction of Metabolites

One usually distinguishes between primary and secondary metabolites. Primary metabolites are simple compounds which have direct connections to the metabolic pathway of the microorganisms. Therefore, close relationships exist between the growth rate and their production rate.
Karl Schügerl


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