M. E. Mancera-López,^a M. T. Rodríguez-Casasola,^a E. Ríos-Leal,^a F. Esparza-García,^a B. Chávez-Gómez,^b R. Rodríguez-Vázquez,^a J. Barrera-Cortésa,*

^a CINVESTAV IPN, Depto. Biotecnología y Bioingeniería, Av. IPN 2508, Col. San Pedro Zacatenco, C.P. 07360, México D.F.
Tel.: +52 55 50613800/4380,
Fax: +52 55 50613313,
E-mail: jbarrera@cinvestav.mx
^b Instituto Mexicano del Petróleo. Depto Biotecnología, Eje Central Lázaro Cárdenas 152, Col. San Bartolo Atepehuacan, C.P. 07730, México D.F.

Abstract
Cultivable fungi and bacteria were isolated from two highly contaminated soils with total petroleum hydrocarbon (TPH) concentrations of 60,600 and 500,000 mg kg^–1. The aim of the study was to determine the capacity of these bacteria and fungi to degrade TPH, specifically the aliphatic hydrocarbon (AH) and polycyclic aromatic hydrocarbon (PAH) fractions, when cultivated in a mineral liquid culture (modified Rennie medium) together with a complex mixture of TPH as the unique source of carbon. Thirty-seven hydrocarbon-degrading strains were isolated, but only six strains showed a high ability to degrade PAHs, AHs and TPH. These strains were identified as Pseudomonas pseudoalcaligenes, Bacillus firmus, Bacillus alvei, Penicillium funiculosum, Aspergillus sydowii and Rhizopus sp., and they removed 79%, 80%, 68%, 86%, 81% and 67% of TPH, respectively. P. pseudoalcaligenes and P. funiculosum removed 75% of PAHs, while B. firmus and P. funiculosum removed 90% and 92% of AHs, respectively. The highest TPH removal was observed by P. funiculosum, which was isolated from the soil with a high TPH concentration. A. sydowii was also isolated from this soil; no reports were found regarding its capacity to remove PAHs, but it was able to degrade five- and six-ring aromatic compounds.

Keywords: Bacteria, bioremediation, fungi, polycyclic aromatic hydrocarbons, aliphatic hydrocarbons.