7-09: Development and characterization of thermophilic fungal enzyme cocktails for biomass saccharification

Thermophilic fungi have the potential to provide industrially relevant enzymes for converting biomass to biofuels.  Characterization of glycoside hydrolases secreted by thermophilc fungi is essential to identify novel enzymes for lignocellulose bioconversion and to uncover efficient hydrolytic mechanisms. Thermophilic fungal glycoside hydrolases tolerate high temperatures, often exhibiting temperature optima >70 °C.  In this work, thermotolerant and thermophilic fungi were cultivated using both intact and pretreated switchgrass as carbon sources.  Supernatant proteins were recovered for measurement of cellulase and hemicellulase activities using purified substrates.  Interestingly, different profiles were observed for the measured activities, which may correspond to observed efficiencies in biomass hydrolysis.  Enzymes were found to possess temperature optima between 60 – 75^oC and to maintain >60% activity in 10% (v/v) [C₂mim][OAc] when assayed for endoglucanase activity.  Supernatant protein from one thermophilic fungal isolate performed comparably to CTec2 (Novozymes) in the release of glucose from AFEX-, IL-, and dilute acid-pretreated switchgrass.  Proteomic analyses have identified critical enzymes utilized by fungal systems for efficient biomass saccharification.  Together, these results reveal great promise in using thermophilic fungi to develop fungal enzyme cocktails for biomass saccharification after pretreatment.