Poster Presentations

Session Title: Biodegradation: Appetite for the Unusual
Presentation Date: Thursday, August 21, 2008
Poster Board Number: 0003

METHODS FOR ENHANCING THE PHENOL BIODEGRADATION BY RHODOCOCCUS ERYTHROPOLIS

A. Cejkova¹, J. Masak¹, V. Jirku¹, O. Schreiberova¹, T. Krulikovska¹, J. Szokol², M. Patek^2
1Institute of Chemical Technology in Prague, Dept. Fermentation Chemistry and Bioengineering, Prague, Czech Republic, ²Academy of Science of Czech Republic, Department of Microbiology, Prague, Czech Republic

The bacterial genus Rhodococcus possesses the ability to degrade large number of toxic and recalcitrant compounds. R. erythropolis CCM 2595 cells show non-inhibited capability to utilize phenol up to 0.3 /L. To increase this tolerance, the way of physiological adaptation, genetic modification, cell attachment, and application of humic additives was investigated. A recombinant strain with higher and stable level of phenol hydroxylase activity was constructed by cloning of the phenol hydroxylase operon pheA2A1R in the multicopy plasmid pSRK21.Growth and degradative function of suspended cells were tested using a laboratory bioreactor (operating volume of 2.0 L). Biofilm cultivation was carried out in aerated glass column reactor (250 x Ø 50 mm). Biomass growth, phenol utilization and phenol hydroxylase activity were monitored. Assaying hydrophobicity and XPS spectroscopy were used for characterization of cell surfaces. A half year (physiological) adaptation of R. erythropolis cells to gradually increased phenol concentration brought a derivative capable to tolerate 1.0 g/L of phenol. This strain and the recombinant R. erythropolis (pSRK21pheA2A1R) were compared both the cell surface composition / hydrophobicity and the capability to colonize hydrophobic (polypropylene) and hydrophilic (glass) carriers. R. erythropolis (pSRK21pheA2A1R) showed the fastest biofilm formation if a polypropylene carrier is used. In a continuously operated vessel such a reactor load performs also the highest phenol removal. Humic acids are able to cover the R. erythropolis cells. The enhancement of phenol tolerance and biodegradation rates of R. erythropolis exposed to the humic acids was observed as well.