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Isolation and genetic analysis of Aspergillus niger mutants with reduced extracellular glucoamylase
Gisela Umbuzeiro ValentI; Maria Regina CalilII; Renato Bonatelli JuniorII
ISetor de Microbiologia - CETESB, Avenida Prof. Frederico Hermann Jr., 345, 05489 São Paulo, SP, Brasil
IIDepartamento de Genética e Evolução, IB - UNICAMP, Caixa Postal 6109, 13081 Campinas, SP, Brasil. Send correspondence to R.B.J.
ABSTRACT
Mutants with impaired production of extracellular glucoamylase were isolated at a high frequency (2% of survivors) from an Aspergillus niger strain treated with UV light. These were designated as low glucoamylase producers (lgp, up to 30% of the parental yield) and medium producers (mgp, a 35 to 50% decrease in enzyme level). All the mutants were shown to be recessive; one strain segregated two unlinked genes. Complementation tests, and segregation from heterozygous diploids, suggested at least three to four unlinked genes, each able to impair glucoamylase production. There is evidence of a single structural gene for glucoamylase in A. niger. Therefore, as production of extracellular enzymes is normally the final result of several steps at intracellular and membrane levels, including regulation of enzyme synthesis, we suggest intergenic interaction that controls extracellular enzyme accumulation and that mutation in any of these genes would result in impaired production.
Keywords: Aspergillus niger.
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