17-06: Ethanol production from lignocellulosic hydrolysates by genome shuffled strains of Scheffersomyces stipitis

Two genome-shuffled strains of Scheffersomyces (Pichia) stipitis, GS301 and GS302, with improved tolerance to hardwood spent sulphite liquor (HW SSL), were tested for fermentation performance on a steam-pretreated enzymatically hydrolyzed poplar hydrolysate supplied by Mascoma Canada (formerly SunOpta Bioprocess Inc.), a steam pretreated poplar hydrolysate supplied by Forest Products Laboratory, UBC and a kraft dissolving pulp mill pre-hydrolysate supplied by FPInnovations, using high initial cell density inocula. The sugars and acetic acid concentrations ranged from 2.2 to 6.8% and 0.43 to 0.95% (w/v), respectively, in the hydrolysates tested.  In the Mascoma hydrolysate, GS301 and GS302 completely utilized glucose in 96 to 114 h and xylose in 264 h while producing maximum ethanol levels (1.2 to 1.4%, w/v) in 144 h. In contrast, glucose and xylose were incompletely utilized by the WT. In the UBC hydrolysate, the two genome shuffled strains completely utilized glucose and xylose in 48 to 72 h and 192 h, respectively, and produced 0.39 to 0.42% (w/v) of ethanol while the WT utilized glucose slowly and incompletely utilized xylose even after 12 days. In the kraft dissolving pulp mill pre-hydrolysate, GS301 and GS302 completely utilized glucose and xylose in 42 to 48 h and 138 to 186 h, respectively and produced 0.8 to 0.9% (w/v) of ethanol. In contrast, the WT strain incompletely utilized glucose and was unable to utilize xylose after 8 days. The WT did not produce ethanol in any of the hydrolysates tested.