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The results of kinetic studies of bacterial depyritization of HCl-kerogen concentrate of Aleksinac (Serbia) oil shale by the chemolithoautotrophic thionic bacteria Thiobacillus ferrooxidans under discontinuous laboratory conditions at various temperatures (0, 20, 28 and 37°C) at a pH of ca. 1.5 are presented in this paper. Low pH prevents the occurrence of the precipitation of iron(III)-ion hydrolysis products on the substrate particles and thereby reduces the process efficiency. Bacterial depyritization is developed as per kinetics of the first order. The activation energy which points to a successive mechanism of pyrite biooxidation, was computed from the Arrhenius plot. The biochemical kinetics indicators point to a high affinity of the bacteria toward pyrite but small values of Vmax, which are probably the result of decelerated metabolic processes due to the low pH value of the environment resp. the large difference of the pH between the external medium and the cell interior.

Aleksinac oil shale organic matter appeared to remain unchanged, according to ele-mental, IR, P-GC and P-GC-MS analytical characterization, after exposure to Bacillus circulans-Jordan desilicification for 30 days. These experiments indicate that siliceous bacteria may have potential as an alternative, biochemical agent for the isolation of native kerogen, and justify further efforts toward continuedevaluation of this advantageous process.