TECHNOLOGY FOCUS - BIOTECHNOLOGY - Recombinant method (claimed): The host cell (D1) is prepared using recombinant method. Preferred Host cell: The recombinant host cell (D1) has an elevated expression or activity compared to the parent host cell it is derived from of 4-hydroxybutyrate dehydrogenase, 4-hydroxybutyrate CoA-transferase and/or 4-hydroxybutyryl-CoA synthetase or the engineered host cell (D2), further being transformed with nucleic acid encoding 4-hydroxybutyrate dehydrogenase, 4-hydroxybutyrate CoA-transferase and/or 4-hydroxybutyryl-CoA synthetase. The recombinant host cell (D1) has an elevated expression or activity compared to the parent host cell it is derived from of at least one of the enzymes selected from the following group, or the engineered host cell (D2), further is transformed with nucleic acid encoding at least one enzyme of the following group, where the group consists of enzymes with 4-hydroxybut-2-enoate ammonia lyase and 4-hydroxybut-2-enoate reductase activity. In the recombinant host cell (D1) or (D2), the expression or activity of at least one, preferably all of the enzymes of at least one of the following groups (a) and (b): (a) butyryl-CoA dehydrogenase, butyraldehyde dehydrogenase, and butanol dehydrogenase; and (b) butyryl-CoA dehydrogenase and butyrate CoA-transferase is elevated or the engineered host cell is transformed with (a) nucleic acid encoding at least one, preferably all of the enzymes of at least one of the groups. The enzyme is expressed from (a) nucleic acid introduced into the host cell. The host cell is selected from a microorganism, a plant cell and an animal cell (preferably kingdom of bacteria, archea, yeast and fungi, especially genus of Clostridium and Escherichia, Pseudomonas, Bacillus, Saccharomyces, Pichia, Clostridium, Corynebacterium and Aspergillus, particularly Escherichia coli. The host cell produces 2-ketoglutarate. Preferred Method: In the method, the host cell is cultured under anaerob conditions. Preferred Components: The nucleic acid comprises at least one nucleic acid selected from 29 nucleic acid sequence as given in the specification, for e.g. nucleic acid sequence containing 2808 nucleotide base-pairs (SEQ ID NO: 1), containing 1167 nucleotide base-pairs (SEQ ID NO: 7), containing 3696 nucleotide base-pairs (SEQ ID NO: 15), containing 1266 nucleotide base-pairs (SEQ ID NO: 29), containing 2577 nucleotide base-pairs (SEQ ID NO: 51), as given in the specification, or at least one nucleic acid encoding an enzyme with the same activity and having at least 40% sequence identity to the amino acid sequence selected from 28 amino acid sequence as given in the specifications, for e.g. amino acid sequence containing 933 amino acids (SEQ ID NO: 2), containing 289 amino acids (SEQ ID NO: 10), containing 548 amino acids (SEQ ID NO: 20), containing 421 amino acids (SEQ ID NO: 30), containing 390 amino acids (SEQ ID NO: 58), as given in the specifications. EXAMPLE - No suitable example given.