Mutation breeding of ethanol-producing yeast Saccharomyces cerevisiae by low-energy nitrogen ion implantation and UV rays

The ethanol-producing yeast Saccharomyces cerevisiae was induced by N⁺ implantation with an output power of 18 keV and a dose of 400 × 10¹⁴ cm^-2, depending on the survival and mutation rates. The UV exposure time was 60 s. Under optimized conditions, the strain achieved the highest positive mutation and lethality rates. A mutant strain SC-N9015 was selected; the ethanol yield of this strain was 15.53%, whereas that of the parental strain was 14.65%. Further, evaluation of ethanol yield over successive generations indicated the hereditary stability of the mutations. The study shows that the combination of low energy N⁺ implantation with UV rays is an efficient method for mutation breeding of S. cerevisiae. (authors)