Process for the fermentative production of cephalosporin

A process for preparing a cephalosporin of the formula

• wherein R0 is hydrogen or C1-3 alkoxy;
• Y is CH2, O, S or an oxidized form of S;
• and
• R1 is selected from the group consisting of H, OH, halogen, C1-3 alkoxy, C1-5 alkyl which is saturated or unsaturated, branched or straight, said alkyl being optionally substituted and optionally containing one ore more heteroatoms, C5-8 cycloalkyl, said cycloalkyl being optionally substituted and optionally containing one or more heteroatoms, optionally substituted aryl, optionally substituted in heteroaryl, and optionally substituted benzyl;
• which comprises
• (a) extracting an N-substituted cephalosporin into an organic solvent from a fermentation broth of a cephalosporin producing microorganism, said fermentation having been conducted in the presence of a dicarboxylic acid cephalosporin N-side chain precursor, to obtain an organic solvent extract containing the N-substituted cephalosporin:
• (b) back-extracting the N-substituted cephalosporin into an aqueous phase, thus obtaining an aqueous phase containing said N-substituted cephalosporing and
• (c) treating said aqueous phase containing N-substituted cephalosporin with a dicarboxylate acylase to convert said N-substituted cephalosporin into the compound of formula (I);
• and
• (d) optionally isolating said compound of formula (I) by crystallization;
• wherein the fermentation broth extracted in step (a) or the aqueous phase containing N-substituted cephalosporin or the compound formula (I) in step (c) is incubated at a pH lower than 4 and a temperature of 60° C. or higher.