19576: Assessing the function of CDH and CDH-like hemoproteins in the degradation of lignocellulosic biomass in the fungus Myceliophthora thermophila C1

Dyadic develops the filamentous fungus Myceliophthora thermophila C1, an ascomycete which was previously classified as Chrysosporium lucknowense as a proprietary protein expression platform for the efficient production of enzyme mixtures for the complete degradation of lignocellulosic biomass.  Recently, re-sequencing of the C1 genome has been completed and approximately 10.000 genes were identified by automated annotation. At present, this knowledge is being exploited to improve the performance of C1 production strains and the enzyme mixtures produced by dedicated genetic manipulation. The annotated genome of C1 revealed an impressive number of carbohydrate active enzymes and oxidative enzymes, including a number of cellobiose dehydrogenases (CDHs). CDHs are extracellular flavocytochromes that catalyze the oxidation of cellobiose and have been linked to the degradation of lignocellulosic materials in basidomycetes as well as asccomycetes. One of the C1-CDHs was found to be a class IIa enzyme containing a C-terminal cellulose binding domain (CBM). A second CDH belonged to class IIb , lacking such a CBM. A third CDH was identified that, surprisingly, lacked the N-terminal heme domain. Interestingly, in addition to these three CDHs, a number of small extracellular enzymes was found that are homologous to the CDH heme domain. The function of the CDHs and these small CDH-like hemoproteins in relationship with the GH61 oxidohydrolases, which are also abundantly present in C1, in the degradation of lignocellulosic materials is discussed.