AbstractA model of oxygen absorption in microbiological systems of zero order reaction rate is proposed. The partial differential equation was solved to predict the profile of the oxygen concentration boundary layer next to a gas‐liquid interface. Generally speaking, the presence of microbial cells always helps to increase the oxygen absorption rate over that of physical absorption. Only when the microbiological reaction is slow as judged by the fact that the reaction time,tr, is much larger than the diffusion time,tD, can one rightfully approximate the oxygen absorption in microbiological suspensions by physical absorptio