14-26: Novel fungal xylanolytic accessory enzymes improve digestibility of pretreated lignocellulosic biomass

In addition to challenges imposed by various biomass types and pretreatment methods, inefficiency in enzymatic saccharification is widely regarded as the most critical impediment to commercializing second-generation biofuels and chemicals. This challenge is due mainly to high enzyme cost. Although research has demonstrated remarkable synergies between cellulases, hemicellulases, ligninases and non-hydrolytic cell wall enhancing proteins, commercial cellulases are yet to be optimal for direct industrial application. One way to circumvent this challenge is to exploit synergistic activities between cellulases and fungal xylanolytic accessory enzymes, namely xylanases, acetylxylan esterases, arabinofuranosidases and xylosidases.

Our approach involves mining the steadily-increasing number of sequenced fungal genomes for new xylanolytic enzymes. Promising genes were cloned and expressed in native or recombinant host systems, particularly Aspergillus niger. Crude and purified protein targets were tested for enhancement of commercial cellulases at low loadings (2%) of various chemically-treated biomass types in microtitre plate format. The digestibility of various pretreated samples was estimated via BCA reducing sugar and glucose assays among other techniques. Three xylanolytic enzymes derived from A. niger, myceliophthora thermophila and Thielavia terrestris were identified as promising candidates for the enhancement of chemically-treated biomass hydrolysis by cellulases.