8-46: Obtaining Spathaspora passalidarum adapted strains with high ethanol productivity in AFEX hydrolysate by directly Adaptation and high throughtput screening

The ascomycetous yeast Spathaspora passalidarum has the native ability to co-ferment sugars such as cellobiose, glucose and xylose that are found in hemicellulosic hydrolysates.  A series of S. passalidarum cultures were adapted to growth in a variety of hydrolysates over the period of three months.  We tested each population for its fermentation ability, and identified adapted strain HS6, which is able to ferment ammonia fiber expansion (AFEX) treated corn stover hydrolysate faster than nine other adapted strains or the wild-type strain.  The HS6 culture was subjected to selection on agar plates containing 25% AFEX hydrolysate, and approximately 60 of the isolated colonies were chosen for high throughput screening.  Strain HS6-F2 showed ~50% increase in both sugar utilization rate and ethanol productivity compared to the parental HS6.  The best fermentation result was production of 30 g/L of ethanol in less than 96 hour by adapted strains HS6-F2 and HS6-D11 from AFEX hydrolysate containing 1.8 g/L of acetic acid and 3.5 g/L of lactic acid. The average ethanol yield from HS6-F2 and HS6-D11 was 0.39 g/g and the productivity was 0.353 g/L•h.