Author(s)

A Cejkova, J Masak, V Jirku, A Fialova & D Moenandar

Abstract

The level of phenol hydroxylase in Candida maltosa - the key activity for efficient aromatic compounds biodegradation A. Cejkova, J. Masak, V. Jirku, A. Fialova & D. Moenandar Department of Fermentation Chemistry and Bioengineering, Institute of Chemical Technology, Prague, Czech Republic. Abstract The yeast Candida maltosa, biodegrader of aromatic compounds, was obtained from a soil sample long-term contaminated with phenol-like and other aromatic compounds, using modified methodology of aerobic enrichment and consequent yeast (single species) isolation. We showed that the phenol hydroxylase in C. maltosa (phenol 2-monooxygenase, EC 1.14.13.7), the key enzyme for the decomposition of some aromatic compounds, is inducible. This work is focused on the possibility to exploit the inducibility of phenol hydroxylase in order to enhance the biodegradation potential of this microorganism. The changes in the determined phenol hydroxylase activity in vivo are dependent on the substrate type (phenol, catechol, resorcinol, p-cresol benzoic acid), substrate concentration and on the growth phase of the microorganism. The substrate specificity and the influence of environmental conditions (pH, temperature, etc.) on activity of an isolated enzyme were determined. The best inducer was phenol (ca 1 g/l). Enzyme activity was very low in the cultivation with p-cresol as a sole C-source. Optimization of phenol addition, as a growth substrate, allowed the successful biodegradation of p-cresol presented in a medium. We have shown that humic acids positively modulate the level of phenol hydroxylase activity. Application of these compounds in the reactor cultivation enhanced the total biodegradation activity of C. maltosa for phenol- like substances. The reached results indicated that optimization of composition and concentration of C-sources and/or addition humic acids (non-toxic compounds)

Keywords