Biodegradation of different molecular-mass polyphenols derived from olive mill wastewaters by Geotrichum candidum

The decolourisation of fresh and stored olive mill wastewaters (OMW) and the biodegradation of three groups (F1, F2 and F3) of phenolic compounds by Geotrichum candidum were investigated. Separated phenolic compounds derived from natural OMW ultrafiltration using membranes with a cutoff 2 and 100 kDa. G. candidum growth on fresh OMW decreased pH and reduced COD and colour of 75% and 65%, respectively. However, on the stored-black OMW a failure of COD and colour removal were observed. G. candidum activity on this later substrate was enhanced by the addition of a carbon source easily metabolised, misleading an improvement of the COD reduction and decolourization that reached 58% and 48%, respectively. Growth of G. candidum in the presence of F2 or F3 polyphenolic fractions induced high decolourisation and depolymerisation of phenolic compounds. Whereas, very week decolourisation and biodegradation were observed with F1 fraction. Moreover, the highest levels of lignin peroxidase (UP) and manganese peroxidase (MnP) activities were obtained in the presence of F2 fraction. These results showed that increasing of molecular-mass of aromatics led to an increase in levels of depolymerisation, decolourisation and COD removal by G. candidum culture. (C) 2008 Published by Elsevier Ltd.