Nineteen bacteria were tested for growth on paraffin wax as the sole source of carbon. Paraffin wax is a solid mixture of hydrocarbons including n-alkanes ranging from C18H38 to C37H 76. Of the nineteen bacteria tested, four bacteria (Arthrobacter paraffineus ATCC 19558, Mycobacterium OFS, Pseudomonas fluorescens Texaco and Rhodococcus IS01) grew well on paraffin wax. However, only one, Rhodococcus IS01, was found to rapidly and completely degrade a mixture of paraffin wax liquefied with hexadecane using the Self-Cycling Fermentation (SCF) technology. This strain was able to degrade n-alkanes ranging from dodecane to heptatriacontane as well as highly branched hydrocarbons such as pristane and hepta-methyl-nonane. Kinetic studies performed with Rhodococcus IS01 growing on mixtures of n-alkanes showed that the hydrocarbons were degraded in ascending order of chain length: shortest to longest chain. The short lag period between the biodegradation of the different n-alkanes suggested that the growth of Rhodococcus IS01 on mixtures of n-alkanes followed some form of diauxie. Further kinetic studies were conducted growing Rhodococcus IS01 on individual and various mixtures of n-alkanes; these showed that the initial first-order oxidation constant decreased with increasing chain length. This trend is suspected to be due to an enzyme specificity constraint rather than to a mass transfer limitation. In addition, it was also observed that the maximum specific growth rate constant (mumax) increased with increasing n-alkane chain length. Rhodococcus IS01 was also found to produce a cell-associated biosurfactant.

Cooper, D. G. (Advisor)