Effect of Oxygen Mass Transfer between the Gas and Liquid Phases on the Production of Monascus Red Pigments by Monascus ruber

Abstract

This study was designed to evaluate the effect 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 baffled Erlenmeyer flasks either by varying the shaking speed from 40 to 200 rpm with a fixed culture volume of 100 mL or by varying the culture volume from 50 to 250 mL with a fixed 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 coefficient (k_La) of oxygen, confirmed that both parameters increased with increase in k_La, but reached a plateau when k_La was more than 100 h⁻¹.