This study was designed to evaluate the e ect of oxygen transfer from gas phase to liquid phase on pigment production in Monascus ruber NBRC 32318 cultured in a liquid medium composed mainly of rice starch. The cells were cultured in 500-mL ba ed Erlenmeyer asks either by varying the shaking speed from 40 to 200 rpm with a xed culture volume of 100 mL or by varying the culture volume from 50 to 250 mL with a xed shaking speed of 120 rpm. Maximum pigment concentration was obtained at a shaking speed of 160 rpm and a culture volume of 100 mL. Cell mass concentration and pigment concentration, evaluated using the volumetric liquid-phase mass transfer coe cient (kLa) of oxygen, con rmed that both parameters increased with increase in kLa, but reached a plateau when kLa was more than 100 h 1.