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KMID : 0545119930030040232
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Journal of Microbiology and Biotechnology
1993 Volume.3 No. 4 p.232 ~ p.237
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Genetically Engineered Yeast by Heterologous Transformation and Intergeneric Two-Step Protoplast Fusion for Ethanol Fermentation
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Kim, Young Ho
Lee, Jae Ran/Seu, Jung Hwn
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Abstract
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A strain of yeast which can convert starch directly to ethanol was developed by the intergeneric protoplast fusion between Schwanniomyces alluvius possessing a amylase as well as glucoamylase with debranching activity and FSC-14-75 which previously had been formed from a heterologous transformation and subsequent intergeneric protoplast fusion. Fusants were selected on minimal medium after protoplasts of auxotrophic mutant of S. alluvius fused with heat-treated protoplasts of FSC-14-75 in the presence of 30%(w/v) PEG and 20mM CaCl_2. The fusion frequency was in the range of 10^-6 order. All fusants tested were intermediate types of parental strains for carbon compound assimilation, and their cell volumes were approximately 1.1 times larger than FSC-14-75 and 1.8 times larger than S. alluvius. The fusants were unable to sporulate like FSC-14-75, while S. alluvius could sporulate. In flask scale the most promising fusant, FSCSa-R10-6, produced 7.83%(v/v) and 10.17%(v/v) ethanol from 15% and 20% of liquefied potato starch, respectively, indicating that the fermetation efficiency of each case increased 1.2 times and 1.6 times than that of FSC-14-75. The elution pattern on DEAE-cellulose chromatography showed that FSCSa-R10-6 has four distinct amylase peaks of which two peaks originated from S. alluvius and the other two from FSC-14-75. These results suggest that the enhanced fermentation efficiency of the fusant might be due to almost-complemented parental amylases.
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