The aim of the study was to obtain Fil^- mutants (unable to transform from yeast cells to filamentous forms) of Y. lipolytica A-101-1.31 strain induced by UV irradiation. Previous studies suggest that such mutants can be more effective and stable during continuous CA production. At 20% UV survival level of cells, Fil^- mutants frequency was 0.35%. The total 15 smooth colony forming mutants were isolated on YM agar but only 7 of them characterized by good stability; the Fil⁺ revertants did not appear during culturing up to 45 generation. The acet^- mutation in those strains responsible for high citrate fermentation purity was well sustained. Assimilation profiles of different carbon sources were identical that those showed by parent strains. Only one of mutants produced CA as efficiently as the parent strain.

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