Microbiological process for the preparation of heteroaromatic carboxylic acids using Alcaligenes faecalis

A microbiological process for the preparation of a heteroaromatic carboxylic acid or one of its physiologically tolerated salts of the formulae I or II:

• ##STR7## wherein R.sub.1 and R.sub.2 are identical or different and each denotes a hydrogen or halogen atom, and X denotes a nitrogen atom or CH--, comprising converting a heteroaromatic nitrile of the formulae III or IV:
• ##STR8## as substrate, wherein R.sub.1 and R.sub.2 have the above stated meanings, comprising the steps of:
• a) culturing a microorganism having all the identifying characteristics of Alcaligenes faecalis (DSM 6335) in the presence of the inducer, 2-cyanopyridine, and a carbon source selected from the group consisting of a dicarboxylic acid, a tricarboxylic acid and a carbohydrate;
• b) reacting the substrate III or IV with the cultured microorganism, wherein the biotransformation is carried out under anaerobic conditions when compounds of the formula I are desired, and under aerobic conditions when compounds of the formula II are desired;
• c) recovering the carboxylic acid I or II;
• and
• d) converting the carboxylic acid I or II, where appropriate, into the corresponding physiologically tolerated salt.