DIBENZOTHIOPHENE BIODEGRADATION BY A PSEUDOMONAS SP IN MODEL SOLUTIONS

The presence of a fatty acid and an n-alkane may affect the biodegrada tion rate of aromatic sulphur compounds such as dibenzothiophene (DBT) . A fatty acid (hexadecanoic acid) may form micellar structures favour ing DBT bioavailability. n-Alkanes, such as n-dodecane or n-hexadecane , form a film around the aromatic sulphur molecule as a consequence of solvation, thus increasing DBT bioavailability. The mass-transfer rat e from the solid to the aqueous phase controls the DBT biodegradation rate when DBT is the only carbon source. Diffusional coassimilation an d microbial hydrophobic effects are rate-limiting steps in DBT biodegr adation in the presence of aliphatic compounds. Diffusion depends on t he DBT concentration in n-alkane, while cometabolism is associated wit h different n-alkane biodegradation rates. Through the definition of b iodesulphurization selectivity and biodesulphurization efficiency, our investigations have shown that a selective aerobic biodesulphurizatio n process is possible by using an unselective biocatalyst, such as a P seudomonas sp.