3 h oganomycin b r 3 h r 4 oh etc the esterase derived from yeasts belonging to the genus torulopsis which can be employed in the present fermentation production step is an enzyme capable of hydrolysing the ester bond at the 3 side chain of said cephamycin compounds of formula ii material containing the aforementioned esterase may be in any form carrying the same and examples of such material are micro organisms carrying the esterase immobilized esterase etc as a result of investigation on various microorganisms isolated from the soil the present inventors have found that the aforementioned esterase which can hydrolyse the 3 side chain ester of cephamycin compounds of formula ii is present in a genus of yeast one suitable yeast strain has various properties as follows vegetative cells are spherical or oval sometimes protractile in various media the size is 3 0 to 10 u03bcm u00d7 2 0 to 5 u03bcm with oval cells and 3 to 11 u03bcm with spherical ones vegetative propagation occurs by multipolar budding formations of pseudomycelia chlamydospore oidispore budding spore etc are absent but a trace of pseudomycelia like formation sometimes occurs neither ascospores nor balistospores are formed 2 culturing properties cultured at 25 u00b0 c for 3 to 14 days the medium is somewhat turbid as a whole and colored pale pink to light orange neither skin nor precipitate is formed generation of gas is not observed colonies are smooth glossy colored pale orange to light orange and rise to a hemispherical shape on.