Irpex lacteus CCBAS Fr. 238 617/93 v1.0
Irpex lacteus by María Jesús Martinez, Centro de Investigaciones Biológicas, Madrid, Spain
Irpex lacteus by María Jesús Martinez, Centro de Investigaciones Biológicas, Madrid, Spain

Irpex lacteus is a white-rot basidiomycete inhabiting the world´s temperate areas whose colonies are often found on dead branches, stumps, logs or trunks of deciduous trees. It has been classified as a member of family Polyporaceae whose taxonomy has not yet been definitely established. Because of its interesting enzymatic systems that so far have not been investigated in detail, I. lacteus has been proposed for use in a wide spectrum of biotechnological applications: biodegradation of organic pollution, water and soil bioremediation, pretreatment of lignocellulosic substrates to improve sugar recoveries for bioethanol production, and production of industrially applicable enzymes.

Interest in the fungus was aroused by recognizing its potential to degrade lignocellulosics. I. lacteus is able to degrade cellulose by the action of a large machinery of exocellulases and endoglucanases and, simultaneously, hemicellulose is broken down by endo-1,4-β-xylanases and acetyl xylan esterases, and pectins by rhamnogalacturonan hydrolases.

The significant proteolytic potential of I. lacteus was connected to pepsin-like aspartic proteases. Biotechnological applicability of the enzymes of I. lacteus was further demonstrated in the case of a commercial fibrolytic enzyme preparation and in the synthesis of chiral cyclic secondary alcohols. The secretome of I. lacteus can thus be of interest for use in pretreatment of lignocellulosic materials or for an enzymatic hydrolysis improvement through the preparation of optimized enzyme cocktails.

I. lacteus emerged also as a species with a remarkable pollutant toxicity resistance and biodegradation capacity including some specific aromatic-ring cleavage strategies. Its application in various bioreactor cultures and in soil remediation was helped by its ability to colonize lignocellulosic materials used as the carriers on which the fungus can be immobilized. In addition, this fungus produces a new dye-decolorizing peroxidase able to display a synergistic action with cellulases during the hydrolysis of wheat straw, increasing significantly the fermentable glucose recoveries from this substrate. This extraordinary capacity is mainly the result of a high metabolic versatility and secretory potential of this fungus suggesting wide biotechnological applications.