Oxygen transfer effects in β‐lactamase fermentation by Bacillus licheniformis in a glucose‐based defined medium

Abstract

AbstractThe effects of oxygen transfer on the β‐lactamase production by Bacillus licheniformis were investigated in a glucose‐based defined medium. The experiments were conducted in 3.0 dm3 batch bioreactor systems at three different air inlet (QO/VR = 0.2, 0.5 and 1.0 vvm) and agitation rates (N = 250, 500 and 750 min−1). During the fermentation, the concentrations of the cell, glucose, by‐products, ie organic and amino acids, oxygen transfer coefficients (KLa), yield coefficients, specific rates and oxygen uptake rates (OUR) were determined, in addition to β‐lactamase activities. The highest β‐lactamase activity was obtained at QO/VR = 0.5 vvm and N = 500 min−1 and at QO/VR = 0.2 vvm and N = 500 min−1 conditions, as ca A = 90 U cm−3. The highest cell concentration was obtained as CX = 0.67 kg m−3 at QO/VR = 0.5 vvm and N = 750 min−1 and at QO/VR = 0.2 vvm and N = 750 min−1 conditions. The values of KLa increased with increasing agitation and aeration rates and varied between 0.007 and 0.044 s−1, and the OUR varied between 0.4 and 1.6 mol m−3 s−1. With increasing QO/VR and/or N, the Damköhler number (ie the oxygen transfer limitation) decreased owing to the increase in mass transfer coefficients (KLa). The highest instantaneous yield of cell on substrate (YX/S) and yield of cell on oxygen (YX/O) values were respectively obtained at 0.5 vvm and 500 min−1 conditions at t = 2 h as YX/S = 0.72 kg kg−1 and YX/O = 1.49 kg kg−1. The highest instantaneous yield of substrate on oxygen (YS/O) was obtained at 0.5 vvm and 750 min−1 conditions at t = 20 h as YS/O = 8.07 kg kg−1. Copyright © 2005 Society of Chemical Industry