Abstract
Co-utilization of xylose and glucose and subsequent fermentation using Saccharomyces
cerevisiae could enhance ethanol productivity. Directed engineering approaches have met
with limited success due to interconnectivity of xylose metabolism with other intrinsic,
hidden pathways. Therefore, random approaches like protoplast fusion were used to
reprogram unidentified mechanisms.
Saccharomyces cerevisiae LN, the best hexose fermenter, was fused with xylose
fermenting Pichia stipitis NCIM 3498. Protoplasts prepared using glucanex were fused under
electric impulse and fusants were selected using 10% ethanol and cycloheximide (50 ppm)
markers. Two fusants, 1a.23 and 1a.30 showing fast growth on xylose and tolerance to 10%
ethanol, were selected. Higher extracellular protein expression observed in fusants as
compared to parents was corroborated by higher number of bands resolved by twodimensional analysis.
Overexpression of XYL1, XYL2, XKS and XUT4 in fusants as compared to S.
cerevisiae LN as observed by RT-PCR analysis was substantiated by higher specific activities
of XR, XDH and XKS enzymes in fusants. During lignocellulosic hydrolysate fermentation,
fusants could utilize glucose faster than the parent P. stipitis NCIM 3498 and xylose
consumption in fusants was higher than S. cerevisiae LN.
Publisher Correction: Strain Improvement of Native Saccharomyces cerevisiae LN ITCC 8246 Strain Through Protoplast Fusion to Enhance Its Xylose Uptake
