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The aim of the present study was to compare bioethanol production from wet exploded corn stover (WECS) and loblolly pine (WELP) hydrolyzed with in-house and commercial enzymes and fermented separately (SHF) and simultaneously (SSF). In-house enzymes produced from Trichoderma reesei, RUT-C30 and a novel fungal strain, Aspergillus saccharolyticus were loaded as 5 and 15 FPU/g glucan and supplemented with 10 and 30 CBU/g glucan, respectively. For hydrolysis and fermentation, slurries of WECS and WELP at 5 and 10% (w/w) solids loading (SL) were utilized. Saccharomyces cerevisae was used for ethanol fermentation at 33°C. Maximally, 15.6 g/L and 13.4 g/L (corresponding to theoretical ethanol yield of 76% and 67%, respectively) were achieved in SSF process from WECS and WELP, respectively at 5% SL and 15 FPU/g glucan loading of in-house enzymes. Ethanol concentrations in all cases were higher for SSF compared to SHF under same conditions. A cross comparison of SSF with commercial enzymes (Celluclast 1.5 L + Novozym 188) showed highest ethanol concentration of 17.3 g/L and 15.4 g/L (corresponding to theoretical ethanol yield of 84% and 77%, respectively) from WECS and WELP, respectively at 5% SL and 15 FPU/g glucan. These findings demonstrated that in-house enzymes were comparable to commercial enzymes as these fungi produced other lignocellulolytic enzymes beyond cellulase and hence enhanced the overall enzyme activity.

The aim of this work was to investigate the optimal process conditions leading to high glucose yield (over 80 %) after wet explosion (WEx) pretreatment and enzymatic hydrolysis. The study focused on determining the "sweet spot" where the glucose yield obtained is optimized compared to the cost of the enzymes. WEx pretreatment was conducted at different temperatures, times, and oxygen concentrations to determine the best WEx pretreatment conditions for the most efficient enzymatic hydrolysis. Enzymatic hydrolysis was further optimized at the optimal conditions using central composite design of response surface methodology with respect to two variables: Cellic® CTec2 loading [5 to 40 mg enzyme protein (EP)/g glucan] and substrate concentration (SC) (5 to 20 %) at 50°C for 72 h. The most efficient and economic conditions for corn stover conversion to glucose were obtained when wetexploded at 170°C for 20 min with 5.5 bar oxygen followed by enzymatic hydrolysis at 20 % SC and 15 mg EP/g glucan (5 filter paper units) resulting in a glucose yield of 84 %.

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