FERMENTATION PROCESS MONITORING THROUGH MEASUREMENT OF AEROSOL RELEASE

Fermentation involves many complex biological processes, some of which can be difficult to monitor. In this study, aerosol measurement was e xplored as an additional technique for monitoring a batch aerobic ferm entation process using Escherichia coli strain W3110. Using this techn ique, a small aerosol extraction flow from the fermenter was continuou sly dried in-line and analyzed with an aerosol size spectrometer and a n aerosol photometer, used to measure the size-integrated aerosol conc entration. The results of the measurements demonstrated that the bacte rial growth rate and the aerosol number concentration changed in a sim ilar fashion: the effluent aerosol number concentration increased duri ng the exponential growth phase and subsequently decreased after the b acterial cell concentration had reached a stable level. This aerosol c oncentration increased sharply approximately 1 h after initiation of g rowth. Thus, this increase in aerosol concentration suggests that the release of aerosols changes as a function of the microbial product for mation activity. The products may change the theological properties of the liquid, especially if surface-active compounds are produced. The increase in aerosol concentration corresponds to a decrease in the val ues of the measured surface tension during the same time frame. Furthe rmore, the aerosol size spectrometer and the photometer showed similar time traces of the effluent aerosols. The size distributions of the s olid residues from the fermentation broth remained relatively constant , while the concentrations changed with the phase of fermentation. As the photometer is inexpensive, it appears promising as a convenient in strument for monitoring fermentation processes.