Purification and characterization of a native lytic polysaccharide monooxygenase fromThermoascus aurantiacus

Lytic polysaccharide monooxygenases (LPMOs) have emerged as key proteins for depolymerization of cellulose. These copper-containing enzymes oxidize C-1 and/or C-4 bonds in cellulose, promoting increased hydrolysis of the oxidized cellulose chains. The LPMO fromThermoascus aurantiacus, a thermophilic ascomycete fungus, has been extensively studied and has served as a model LPMO. A method was developed to purify the LPMO from culture filtrates ofT. aurantiacusalong with its native cellobiohydrolase and endoglucanase. The activity of the purified LPMO was measured with a colorimetric assay that established theT(opt)of the native LPMO at 60 degrees C. Purification of the components of theT. aurantiacuscellulase mixture also enabled quantification of the amounts of cellobiohydrolase, endoglucanase and LPMO present in theT. aurantiacusculture filtrate, establishing that the LPMO was the most abundant protein in the culture supernatants. The importance of the LPMO to activity of the mixture was demonstrated by saccharifications with Avicel and acid-pretreated corn stover.