A high-ethyl caproate-producing strain, Saccharomyces cerevisiae strain 3703-7, was isolated from cerulenin-resistant mutants of sake yeast. The strain produced a large amount of ethyl caproate when it was grown on a 15% glucose concentration and at 25C. A much higher yield of ethyl caproate was produced from sucrose or fructose than from glucose added as a substrate. On the other hand, glucose concentration and growth temperature were not effective for the production of ethyl caproate by the parent strain 3703. From these results, it was suggested that strain 3703-7 produces ethyl caproate, ethyl acetate, and isoamyl acetate from the apple pomace extract containing sugars composed of glucose, fructose, and sucrose. The strain 3703-7 was grown in the apple pomace extract containing 6. 4% and 10. 4% sugars at 25C. Ethyl caproate was produced in a much larger amount in the 10. 4% than the 6. 4% sugars. After 8 days of incubation in the pomace extract containing 10. 8% sugars at 25C, 5. 23%of ethanol was produced, and the production amounts of ethyl caproate, ethyl acetate and isoamyl acetate were 3. 12 ppm, 7. 13 ppm, and 0. 45 ppm, respectively. The distilled liquor had the flavor of alcohol containing 32. 3% ethanol, possessing a sweet aroma typical of ethyl caproate in addition to an apple flavor.

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The properties of mutant glucoamylases（GlaBs） from Aspergillus oryzae H-1 and G-4 strains with a high level of GlaB activity were compared with those of native GlaBs from parental strains. Amino acid compositions of both mutant GlaBs were different from those of native GlaBs, with a particular decrease in Ser residue of mutant GlaBs. Moreover, N-linked suger chains of native and mutant GlaBs were considered a complex or hybrid type, and not a high mannose type. Because N-linked sugar chain of each GlaB mainly consisted of galactose and N-acetylglucosamine, there was little mannose. Since a little more galactose and N-acetylglucosamine combined per mannose were found in the N-linked suger chains of mutant GlaBs than of native GlaBs, this suggested that each N-linked sugar chain length of mutant GlaBs was possibly shorter. Native GlaBs were not deglycosylated with Endoglycosidase H, while both mutant GlaBs were deglycosylated. This result suggests N-linked suger chain structures of both mutant GlaBs changed from a complex type in native GlaBs to a hybrid type. In circular dichroism spectra analysis, Tm values of GlaBs from H-1 and G-4 strains were approximately 53℃ both, and thus similar to Tm of native GlaBs. Therefore, the thermostability of mutant GlaBs was shown as not being affected by mutation.

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