Experimental Study of Biodegradation of Ethanol and Toluene Vapors

3.4.3 Batch Growth
The batch growth experiments were carried out to study the growth rates of P.
putida (ATCC 23973) on different substrates, however toluene was stripped too quickly
from the bioreactor to carry out batch growth experiments (Brown et al., 2000).
Therefore, bioremediation kinetics on ethanol or benzyl alcohol was determined from
batch growth experiments.
A volume of 1.5 L of media was added to the bioreactor. The reactor, complete
with the nutrient media, was sterilized at a temperature of 121 o C for 45 minutes. The
inoculum was prepared in shaking flasks using the same chemical as the growth
substrate (see Section 3.2.3 for preparation procedure). A certain amount of the selected
substrate was added into the bioreactor to reach the desired initial concentration then
75-150 mL of inoculum was aseptically transferred from the shake flask into the
bioreactor.
The media in the bioreactor thus contained either ethanol or benzyl alcohol at
known initial concentrations. The temperature was controlled at 25.0 °C. In order to
maintain efficient mixing in the reactor, and to gain sufficient oxygen supply from the
air stream, an agitation rate of 450 rpm and an air flowrate of 0.4 L/min was set for all
experiments. These operating conditions were based on the results from air stripping
and mass transfer experiments. Samples of approximately 10 mL were taken at specific
time intervals through the liquid sample port. Three to four mililitres of these samples
were immediately analyzed for biomass concentration, and a 5 mL sample was
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