Abstract
Paraffins, mainly composed of long chain alkanes (LCA), pose a problem in the recovery of oil from fields producing paraffinic oil. This is due to the build up of paraffin deposits. Solidification and aggregation of LCA can cause serious problems in oil recovery due to the clogging of oil production pipes, deposits in the process equipments and sealing off pores in the reservoirs. Partial degradation, i.e. reduction in chain length of LCA present in such oils is likely to greatly increase its quality as well as enhance the recovery.
The approach presented in this paper is the development of biocatalytic processes involving bacteria capable of degrading LCA in situ. The project has focused on the identification of bacterial strains capable of LCA degradation and the search for and characterization of enzymes therein. One strain, identified as Acinetobacter sp. 6A2, was isolated by screening for strains capable of utilizing a paraffin with a melting point of 52-54°C. The strain was shown to be able to degrade alkanes with a chain length ranging from C10 to C40. Three enzyme systems have been identified showing overlapping alkane substrate specificities in this strain, two AlkM–type alkane hydroxylase homologues, AlkMa and AlkMb, and one system encoded by a gene given the name almA. AlkMa and AlkMb are involved in the degradation of C10 to C20 alkanes. AlmA, however, is involved in the degradation of LCA with a chain length of C30 to C40. This is confirmed in growth experiments of mutant strains. The AlmA enzyme is of particular interest as it is involved in the degradation of the more heavy wax components.
Efficiency and specificity of the enzyme systems are currently under investigation.
