Pa. Holden et al., TOLUENE DIFFUSION AND REACTION IN UNSATURATED PSEUDOMONAS-PUTIDA BIOFILMS, Biotechnology and bioengineering, 56(6), 1997, pp. 656-670
Biofilms are frequently studied in the context of submerged or aquatic
systems. However, much less is known about biofilms in unsaturated sy
stems, despite their importance to such processes as food spoilage, te
rrestrial nutrient cycling, and biodegradation of environmental pollut
ants in soils. Using modeling and experimentation, we have described t
he biodegradation of toluene in unsaturated media by bacterial biofilm
s as a function of matric water potential, a dominant variable in unsa
turated systems. We experimentally determined diffusion and kinetic pa
rameters for Pseudomonas putida biofilms, then predicted biodegradatio
n rates over a range of matric water potentials. For validation, we me
asured the rate of toluene depletion by intact biofilms and found the
results to reasonably follow the model predictions. The diffusion coef
ficient for toluene through unsaturated P. putida biofilm averaged 1.3
x 10(-7) cm(2)/s, which is approximately two orders of magnitude lowe
r than toluene diffusivity in water. Our stud ies show that, at the sc
ale of the microbial biofilm, the diffusion of toluene to biodegrading
bacteria can limit the overall rate of biological toluene depletion i
n unsaturated systems. (C) 1997 John Wiley & Sons, Inc.