116 Chapter 5 The large scale production of organic acids by micro-organisms Overview In this chapter we shall look at the use of micro-organisms to produce organic acids of ommercial importance. Although all of the examples to be mentioned are relatively imple chemically, they are interesting in that they are metabolically diverse. Some are genuine end products of metabolism, while others are compounds considered to be entral metabolites in all living cells. These central metabolites are normally present in relatively small, constant amounts. However, some micro-organisms can b persuaded"to produce enormous yields of these metabolites The first part of this chapter the Introduction, will identify some of the organic acids roduced by micro-organisms and highlight those which are of commercial interest. The products considered in this chapter are metabolites of the tricarboxylic acid (tCa) cycle or oxidative derivatives of glucose. Since most of the biological commerical processes involve interference with the metabolism of micro-organisms, we present a section discussing relevant pathways together with the control mechanisms involved The industrial production of the most commercially important organic acid, citric adid, is then considered in depth. Finally, we outline the biochemistry, formation and downstream processing of other TCA cycle intermediates(malic acid, fumaric acid) and oxidation products of glucose(itaconic acid, gluconic acid and its derivatives) 5.1 Introduction organic acid We must first indicate exactly what is meant by the term'organic acid in the context of efiniton this Chapter. Inevitably it will be far more restricted in scope than the literal definition, which essentially means'any organic compound which is acidic adids whig ve one or more examples in each of the categories below of organic 1) Acids of non-carbohydrate origin which are produced by all living systems 2) Acids continuously produced by all living systems 3) Acids of carbohydrate origin which are constantly produced by living systems and are not considered as waste products. 4)Acidic examples of continuously produced waste products Acceptable answers to part 1)include amino acids and fatty acids or specific examples of each, such as glycine or stearic acid respectively. The obvious answer for part 2)is the central metabolite Pyruvate, though all of the acids of the TCA cycle would be appropriate Answers to part 3)include the principal acid of the hexose monophosphate116 Chapter 5 The large scale production of organic acids by m icro-org an isms Overview In this Chapter we shall look at the use of mim~~rganisms to produce organic acids of commercial importance. Although all of the examples to be mentioned are relatively simple chemically, they are interesting in that they are metabolically diverse. Some are genuine end products of metabolism, while others are compounds considered to be central metabolites in all living cells. These central metabolites are normally present in relatively small, constant amounts. However, some micro-organisms can be "persuaded" to produce enormous yields of these metabolites. The first part of this Chapter, the Introduction, will identdy some of the organic acids produced by micro-organisms and highlight those which are of commercial interest. The products consided in this chapter are metabolites of the tricarboxylic acid UCA) cycle or oxidative derivatives of glucose. Since most of the biological coITLmerical processes involve interference with the metabolism of micro-organisms, we present a section discussing relevant pathways together with the control mechanisms involved. The industrial production of the most commercially important organic acid, citric acid, is then considered in depth. Finally, we outline the biochemistry, formation and downstream processing of other TCA cycle intermediates (malic acid, fumaric acid) and oxidation products of glucose (itaconic acid, gluconic acid and its derivatives). 5.1 Introduction organic acid definmon We must first indicate exactly what is meant by the tern 'organic acid' in the context of this Chapter. Inevitably it will be far more restricted in scope than the literal definition, which essentially means 'any organic compound which is acidic'. n acids which are produced by living cells? 1) Acids of non-carbohydrate origin which are produced by all living systems. 2) Adds continuously produced by all living systems. 3) Acids of carbohydrate origin which are constantly produced by living systems and are not considered as waste products. 4) Acidic examples of continuously produced waste products. Amptable answers to part 1) include amino acids and fitly acids or specific examples of each, such as glycine or stearic acid mpectively. The obvious answer for part 2) is the central metabolite pyruvate, though all of the acids of the TCA cycle would be appropriate. Answers to part 3) include the principal acid of the hexose monophosphate Can you give one or more examples in each of the categories below of organic