ACQUISITION OF DATA FROM ONLINE LASER TURBIDIMETER AND CALCULATION OFSOME KINETIC VARIABLES IN COMPUTER-COUPLED AUTOMATED FED-BATCH CULTURE

Output signals of a commercially available on-line laser turbidimeter exhibit fluctuations due to air and/or CO2 bubbles. A simple data proc essing algorithm and a personal computer software have been developed to smooth the noisy turbidity data acquired, and to utilize them for t he on-line calculations of some kinetic variables involved in batch an d fed-batch cultures of uniformly dispersed microorganisms. With this software, about 10(3) instantaneous turbidity data acquired over 55 s are averaged and convert it to dry cell concentration, X, every minute . Also, volume of the culture broth, V, is estimated from the averaged output data of weight loss of feed solution reservoir, W, using an el ectronic balance on which the reservoir is placed. Then, the computer software is used to perform linear regression analyses over the past 3 0 min of the total biomass, VX, the natural logarithm of the total bio mass, In(VX), and the weight loss, W, in order to calculate volumetric growth rate, d(VX)/dt, specific growth rate, mu [=dln(VX)/dt] and the rate of W, dW/dt, every minute in a fed-batch culture. The software u sed to perform the first-order regression analyses of VX, In(VX) and W was applied to batch or fed-batch cultures of Escherichia coli on min imum synthetic or natural complex media. Sample determination coeffici ents of the three different variables (VX, In(VX) and W) were close to unity, indicating that the calculations are accurate. Furthermore, gr owth yield, Y-X/S, and specific substrate consumption rate, q(sc), wer e approximately estimated from the data, d(VX)/dt and dW/dt in a 'bala nced' fed-batch culture of E. coli on the minimum synthetic medium whe re the computer-aided substrate-feeding system automatically matches w ell with the cell growth.