Recombinant E. coli host cells that comprise recombinant DNA expression
vectors that drive expression of methylmalonyl CoA mutase from Propionibacterium
shermanii or Streptomyces cinnamonensis as well as Propionibacterium
shermanii epimerase can produce S-methylmalonyl CoA, a required substrate for
the production of polyketides by most modular polyketide synthases and is not present
in wild-type E. coli host cells.