KINETIC-STUDIES OF BIODEGRADATION OF INSOLUBLE COMPOUNDS BY CONTINUOUS DETERMINATION OF OXYGEN-CONSUMPTION

Continuous determination of oxygen consumption by electrolytic respiro metry has been experimented as a means to stud! the biodegradation kin etics of scarcely soluble environmental pollutants. The substrates use d were the polycyclic aromatic hydrocarbons (PAH), naphthalene, phenan threne, anthracene fluoranthene and pyrene. The definition of an appro priate mode of PAH supply, either as crystals or more generally as a s olution in a water non-miscible solvent, was found essential for yield ing reproducible biodegradation kinetics. In these conditions, for all compounds tested, oxygen determination was found suitable for quantit ative evaluation of PAH biodegradation and formation of biomass and so luble metabolites, The study of biodegradation kinetics with this meth odology showed that a first phase of exponential growth could be chara cterized in most cases, followed by a phase of limited growth. Possibl e mechanisms involved in insoluble substrate uptake are discussed, Dur ing exponential growth, the bacteria utilized (although not necessaril y exclusively) the PAH solubilized in the aqueous medium.