Experimental Study of Biodegradation of Ethanol and Toluene Vapors

2.2.6 Pseudomonas
It is well known that bacteria belonging to the genus Pseudomonas utilize a
large number and variety of compounds as carbon and energy sources (Stanier et al.,
1966). While toluene is not readily degraded by all microorganisms, several strains of
Pseudomonas putida have demonstrated a toluene-degrading ability (Gibson et al.,
1970; Vecht et al., 1988; Keuning and Jager, 1994; Romine and Brockman, 1996;
Reardon et al., 1994, 2000; Kim and Jaffe, 2000; Brown et al., 2000). Reardon et
al.(1994) measured the kinetics of toluene biodegradation by Pseudomonas putida F1
(PpF1) and the maximum growth rate of PpF1 on toluene was found to be 0.86 h -1 .
Reardon et al. (2000) also reported the kinetics of PpF1 growing on mixtures of
benzene, toluene, and phenol. Toluene significantly inhibited the biodegradation rate of
benzene and phenol. Brown et al. (2000) have reported toluene removal from aqueous
streams in a cyclical bioreactor using Pseudomonas putida (ATCC 23973), which is the
same strain used in this study. Liquid toluene was added to the self-cycling fermentor
by diffusion across a silicone membrane.
2.3 Modeling of Microbial Growth
2.3.1 Monod Model
Microbial growth is the result of both replication and change in cell size. In a
suitable nutrient medium, organisms extract nutrients from the medium and convert
them into biological compounds. A typical bacterial growth curve in a batch culture
appears in the following order: lag phase, exponential phase, stationary phase, and death
phase (Shuler and Kargi, 2002). The lag phase starts with inoculation of the
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