| Popis: |
Isoamyl monochloroacetate ( i -AmOCIAc) inhibited the growth of sake yeast. AOF10, which is resistant to isoamyl monofluoroacetate and has low esterase activity toward isoamyl acetate ( i -AmOAc), also showed resistance to i -AmOClAc. Monochloroacetic acid formed by an esterase through the hydrolysis of i -AmOClAc was more effective at glycolysis inhibition than i -AmOClAc. Forty five mutants resistant to i -AmOClAc were isolated from a parental haploid strain (HL-69) derived from sake yeast. Three had less than 20% of the original activity of the esterase. All mutants fermented sake mash as well as the parent strain, HL-69, and accumulated 1.3 to 1.7-fold the levels of i -AmOAc and 1.8 to 2.4-fold the levels of isobutyl acetate accumulated by HL-69. Surprisingly one mutant (CL-90), which accumulated 1.7-fold the amount of i -AmOAc and 1.3-fold the amount of ethyl acetate, exhibited increased alcohol acetyltransferase (EC 2.3.1.84) activity (1.6-fold). Esterase patterns were also examined by gel electrophoresis and activity staining. Changes in the intensity of the strongest band ( EST2 ) were closely related to the activity of the esterase toward i -AmOAc. |
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