Use of continuous-culture techniques for determining the growth kinetics of a celluloytic Thermoactinomyces sp.

In order to better understand the kinetics of cellulose degradation by Thermoactinomyces sp., continuous-culture experiments were performed utilizing the various intermediates of cellulose degradation as the feed substrates. Steady-state data from the glucose runs suggest that this organism has a growth yield of 0.42 g cell/g glucose, and a specific maintenance of 0.24 g glucose/g cell/hr. The Monod equation did not seen to model the growth well, since a plot of 1/D vs. 1/S gave a maximum specific growth rate that was even lower than one of the steady-state dilution rates. A dynamic washout experiment suggested a maximum specific specific growth rate of 0.36 hr^?1 and indicated that glucose is only slightly growth inhibitory as the inhibition constant, K_i, is 19 g glucose/liter. An equation for substrate concentration for washout conditions was derived. This equation predicted the transient glucose concentration relatively well. A fill-and-draw technique was investigated for determination of the growth parameters. It was not successful because of difficulties in contamination and accurately monitoring the dissolved oxygen in the small highly agitated vessel. However, the technique could be useful in studying the growth characteristics of sludge in a waste treatment system where contamination is not a worry. One could cover the medium surface and use a nonsterilizable dissolved oxygen probe of high sensitivity membrane to overcome these difficulties.