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Genetic study of auxotrophic and resistant mutants of Aspergillus niger and their glucoamylase production

Márcia Masiero; Renato Bonatelli Junior

Departamento de Genética e Evolução, Instituto de Biologia, UNICAMP, Caixa Postal 6109,13081 Campinas, SP, Brasil. Send correspondence to R.B.J.

ABSTRACT

Auxotrophic and resistant mutants have been isolated from an Aspergillus niger glucoamylase-producing strain. A resistant mutant, mgrA₂ (malachite green), and the auxotrophic mutants, metA₁ (methionine) and mysA₁ (methionine or cysteine) were the only ones not to show significantly lower yields compared to the parental strain. Production levels of heterozygous diploids indicated that lower yields observed in the other mutants might be due to pleiotropic effects. Four linkage groups have been identified by means of heterozygous diploid segregation. The gene mgrA₂ was shown to be recessive and etbA₅ (resistance to ethidium bromide), semi-dominant. The latter could be used for gene order determination in linkage group I.

Keywords: Auxotrophic; Resistant mutants; Aspergillus niger; Glucoamylase.

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