反应详情

Pichia stipitis is known to ferment D-xylose to ethanol more efficiently than other native yeasts previously described (Prior, et al., Process Biochemistry 24(1), 21-32 (1989)). The Pichia stipitis that had been deposited at the USDA's ARS Culture Collection (deposit accession number NRRL Y-7124) was recently renamed Scheffersomyces stipitis (Kurtzman and Suzuki, Mycoscience 5(2), 2-14 (2010)) and is particularly useful because it has strong NADH-linked, as opposed to NADPH-linked, aldose reductase activity providing for a more favorable cofactor balance in the conversion of xylose to xylulose (Bruinenberg, et al., Applied Micro. and Biotech. 19, 256-260 (1984)). S. stipitis strain NRRL Y-7124 ferments hexoses and xylose to economically recoverable concentrations of ethanol exceeding 40 g/L with almost no accumulation of xylitol byproduct (Slininger, et al., Biotechnology Letters 7, 431-436 (1985); Slininger, et al., Biotechnology and Bioengineering 35, 727-731 (1990a); Slininger, et al., Annals of the New York Academy of Science 589, 25-40 (1990b)). In nutritionally optimized media, this S. stipitis strain is able to produce over 70 g/L ethanol in 40 hours (1.75 g/L/h) from 150 g/L sugars at a yield of 0.41±0.06 g/g and an ethanol productivity of 1.6 g/L/h in high density fermentations (6 g/L cells) (Slininger, et al. (1985); Slininger, et al., Applied Microbiology and Biotechnology 72, 1285-1296 (2006); Slininger, et al., Biotechnology and Bioengineering 108(8), 1801-1815 (2011)). Given appropriate nitrogen levels, it is also relatively resistant to fermentation inhibitors ethanol, furfural, and hydroxymethylfurfural (HMF) (Slininger, et al., Biotechnology and Bioengineering 102(3):778-790 (2009)). Scheffersomyces stipitis is one of the most viable native pentose-fermenting yeasts available for commercial scale-up, as reviewed by Agbogbo and Coward-Kelly (Biotechnology Letters 30, 1515-1524 (2008)) who point to the need to improve sugar uptake rate in biomass hydrolyzates, including reducing the effects of diauxy and improving ethanol and inhibitor tolerance. Thus, there is a need for novel strains of S. stipitis which are tolerant of diverse lignocellulosic hydrolyzates.

1. customThe Pichia stipitis that had been deposited at the USDA's ARS Culture Collection (deposit accession number NRRL Y-7124)