Fungal screening for biological removal of extractives from Eucalyptus globulus wood

Wood extractives cause production troubles during pulp and paper manufactur e. The potentiality of fungal strains for biotechnological removal of extra ctives from Eucalyptus globulus Labill. wood is evaluated here. First, a su rvey of fungi present in eucalypt woodlands in western Spain was carried ou t, and 90 species, including fungi strictly associated with eucalypt trees, were collected. Then, a total of 33 basidiomycetes, 21 ascomycetes, and 19 conidial fungi (including some strains from culture collections) were comp ared in terms of their capacity to decrease the acetone extract of eucalypt wood. High extractive removal (50-70% of initial content) was obtained wit h Ophiostoma, Mollisia, and Pleurotus species, as well as with Funalia trog ii (Berk. in Trog) Bond. & Singer, Melanotus hepatochrous (Berk.) Singer, a nd Paecilomyces sp. Microscopic observation of the degraded wood revealed a correlation between extractive degradation and removal of spherical deposi ts in wood rays. Moreover, when extractive biodegradation was analyzed by g as chromatography - mass spectrometry it was found that some of the basidio mycetes were able to remove both free and esterified sitosterol (75-100% de gradation by Poria subvermispora Pilot, Phlebia radiata Fr., F. trogii, and Bjerkandera adusta (Willd.) P. Karsten), which has been identified as a ma jor constituent of pitch deposits in eucalypt pulps, whereas the action of ascomycetes was mainly limited to hydrolysis of the sitosterol esters.