Process for producing optically active cephalosporin analogs

A process for producing optically active compounds of cephalosporin analogs represented by the formula (I) ##STR16## wherein R.sub.1 represents a substituted or unsubstituted, saturated or unsaturated six-membered carbocyclic or five-membered hexacyclic group, R.sub.2 represents a hydrogen or a protective group of carboxylic acid, Hal represents a halogen atom, the hydrogens at the 6- and 7-positions have cis configuration and X represents a hydrogen, a lower alkyl group, a hydroxy group, a carboxyl group or an amino group, which comprises reacting .alpha.,.alpha.-disubstituted carboxylic acid represented by the formula (II) ##STR17## (wherein R.sub.1 and X have the same significance as defined above) or a reactive derivative thereof and an optically inactive dl compound represented by the formula (III) ##STR18## (wherein R.sub.2 and Hal have the same significance as defined above) in the presence of (1) a microorganism having an ability of producing optically active compounds of the cephalosporin analog represented by the formula (I), from the .alpha.,.alpha.-disubstituted carboxylic acid or reactive derivative thereof and the compound represented by the formula (III) and belonging to the genus Pseudomonas, Xanthomonas, Escherichia, Aeromonas, Achromobacter, Arthrobacter, Acetobacter, Alcaligenes, Kluyvera, Gluconobacter, Clostridium, Comamonas, Corynebacterium, Sarcina, Staphylococcus, Spirillum, Bacillus, Falvobacterium, Brevibacterium, Protaminobacter, Beneckea, Micrococcus, Proteus, Mycoplana or Rhodopseudomonas, (2) the culture broth of said microorganism, (3) matter recovered from the culture broth of said microorganism capable of causing the production of said optically active compounds or (4) an enzyme produced by said microorganism capable of causing the production of said optically active compounds.