Selection of a PAH-degrading consortium using TLP culture system.

PESSACQ J., BIANCHINI F.E., MORELLI I. S., DEL PANNO M.T.

Villa Carlos Paz, Córdoba, Argentina

Congreso; VI congreso de microbiologia general, SAMIGE.; 2009

Sociedad Argentina de Microbiologia General (SAMIGE)

Polycyclic aromatic hydrocarbons (PAH) are environmental pollutants mainly caused by industrial activity. Its low solubility in water and sequestration in soils and sediments contribute to their persistence in the environment. Two liquid phase (TLP) culture systems consist of an aqueous phase and a hydrophobic biocompatible and non-biodegradable phase. They have the potential to improve aqueous mass transfer of the poorly soluble compounds and control the availability of non-polar toxic compounds produced during the microbial development. They are self-regulated systems, so that the availability of the PAH in the aqueous phase is controlled by the partitioning ratio constant between the two phases and by the microbial metabolic activity. The aim of this study was to compare the PAH-degrading activity and bacterial diversity of PAH-degrading consortiums obtained using TLP system (20 ml silicone: 90 ml of mineral medium), with the conventional enrichment in mineral medium (MML). Both systems were supplied with 500 mg/l phenanthrene and pyrene. As initial inoculum a chronically contaminated soil of a petrochemical zone was used. In both systems five successive cultures were done every 30 days of incubation at 28°C. Before each subculture the density of PAH degrading bacteria was determined and predominant strains were isolated. The TLP systems showed an increase in PAH-degrading bacterial counts during the two firsts subculture, after that their kept relatively stable. On the other hand, the MML systems reached the higher PAH-degrading counts during the first subculture, after that the PAH-degrading counts decreased significantly during the successive subcultures. The PAH elimination in the 5th subculture was 89.8% and 55.5% for phenanthrene and pyrene respectively in TLP system and was only 6% for both PAH in MML system. The bacterial compositions of the 5th consortiums were analyzed by PCR-DGGE, showing the TLP system the most diversity composition. These results showed that the selection of PAH-degrading consortium in a TLP system preserve the bacterial diversity with a greater efficiency of PHA elimination.