초록
<P><B>Background</B></P><P>Thermophilic fungi have attracted increased interest for their ability to secrete enzymes that deconstruct biomass at high temperatures. However, development of thermophilic fungi as enzyme producers for biomass deconstruction has not been thoroughly investigated. Comparing the enzymatic activities of thermophilic fungal strains that grow on targeted biomass feedstocks has the potential to identify promising candidates for strain development. <I>Thielavia terrestris</I> and <I>Thermoascus aurantiacus</I> were chosen for characterization based on literature precedents.</P><P><B>Results</B></P><P><I>Thermoascus aurantiacus</I> and <I>Thielavia terrestris</I> were cultivated on various biomass substrates and culture supernatants assayed for glycoside hydrolase activities. Supernatants from both cultures possessed comparable glycoside hydrolase activities when incubated with <B>artificial</B> biomass substrates. In contrast, saccharifications of ionic liquid pretreated switchgrass (<I>Panicum virgatum</I>) revealed that <I>T. aurantiacus</I> enzymes released more glucose than <I>T. terrestris</I> enzymes over a range of protein mass loadings and temperatures. Temperature-dependent saccharifications demonstrated that the <I>T. aurantiacus</I> proteins retained higher levels of activity compared to a commercial enzyme mixture sold by Novozymes, Cellic CTec2, at elevated temperatures. Enzymes secreted by <I>T. aurantiacus</I> released glucose at similar protein loadings to CTec2 on dilute acid, ammonia fiber expansion, or ionic liquid pretreated switchgrass. Proteomic analysis of the <I>T. aurantiacus</I> culture supernatant revealed dominant glycoside hydrolases from families 5, 7, 10, and 61, proteins that are key enzymes in commercial cocktails.</P><P><B>Conclusions</B></P><P><I>T. aurantiacus</I> produces a complement of secreted proteins capable of higher levels of saccharification of pretreated switchgrass than <I>T. terrestris</I> enzymes. The <I>T. aurantiacus</I> enzymatic cocktail performs at the same level as commercially available enzymatic cocktail for biomass deconstruction, without strain development or genetic modifications. Therefore, <I>T. aurantiacus</I> provides an excellent <B>platform</B> to develop a thermophilic fungal system for enzyme production for the conversion of biomass to biofuels.</P>