| This project investigated the feasibility of improving efficiencies of carbazole removal in hydrotreating with a biocatalytic pre-treatment step. The ideal biocatalyst was defined as one able to denitrogenate carbazole with minimal carbon mineralization and with activity selective for carbazole. Such biological activity had not previously been identified. Bacteria were isolated from creosote-contaminated soil and screened for this activity. One isolate, Sphingomonas sp. CP19, was investigated in detail. Its specific activity for carbazole transformation was 1.8μmo1 carbazole (mg dry cell weight-d) −1. Further characterization showed that this activity did not meet the specifications of the ideal biocatalyst. The coloured product that distinguished CP19 from other isolates was identified as an abiotic condensation product of 2-aminophenol. The accumulation of the condensation product from a biological oxidation product re-enforced the need for a suitable biocatalyst to completely denitrogenate carbazole. The formation of 2-aminophenol represents a newly identified step in the carbazole degradation pathway. |
