Influence of high biomass concentrations on alkane solubilities

Alkane solubilities were measured experimentally for high-density biomass. The resulting Henry's law constants for propane were found to decrease significantly for both dense yeast suspensions and an actual propane-degrading biofilm consortium. At the biomass densities of a typical biofilm, propane solubility was about an order of magnitude greater than that in pure water. For example, a dense biofilm had a propane Henry's law constant of 0.09 ± 0.04 atm m³ mol^-1 compared to 0.6 ± 0.1 atm m³ mol^{- 1} measured in pure water. The results were modeled with mixing rules and compared with octanol-water mixtures. Hydrogels (agar) and salts decreased the alkane solubility. By considering a theoretical solubility of propane in dry biomass, estimates were made of intrinsic Henry's law constants for propane in pure yeast and biomass, which were 13 ± 2 and 5 ± 2 atm kg biomass mol^-1 for yeast and biofilm consortium, respectively. (C) 2000 John Wiley and Sons, Inc.