S111: Oxidoreductase activity of GH61 enzymes acts synergistically with cellobiose dehydrogenase or small molecule activators to promote enzymatic degradation of lignocellulosic biomass

Hydrolysis of lignocellulosic biomass offers a vast, renewable resource of monosaccharides which can be fermented to produce ethanol for fuel, as well as other valuable chemicals.  Research over the past decade on enzymatic hydrolysis of lignocellulosic material has resulted in dramatic lowering of the enzyme dosage required for hydrolysis, which has had an enabling effect on the industry.  One remarkable finding was that addition of a crude fermentation broth from Thielavia terrestris to a Trichoderma reesei enzyme preparation resulted in a 2-fold lowering of the protein required for hydrolysis.  This led to the discovery that certain proteins from previously classified glycoside hydrolase family 61 (GH61s) were responsible for this hydrolysis boosting effect.  The reason for this boosting was largely unknown, as structural and biochemical assay analysis did not reveal glycoside hydrolase properties.  More recently, we have shown that GH61s in combination with cellobiose dehydrogenase (CDH) shows remarkable synergy with cellulases for cleavage of crystalline and amorphous cellulose, and the products include both oxidized and non-oxidized oligosaccharides.  We have shown that small molecules, such as gallic or ascorbic acid, can activate GH61s, promoting GH61 activity on cellulose.  These findings suggest that GH61s operate on cellulose with a mechanism involving oxidoreductive steps, rather than a conventional glycoside hydrolysis.  In addition, we have shown through proteomics of T. terrestris that both CDH and GH61s appear to be induced under cellulose growth conditions, which when combined with biochemical results may suggest a biological role for this enzyme combination in the breakdown of lignocellulosic biomass.