Transformation of the thermophilic fungus Humicola grisea var. thermoidea and overproduction of Humicola glucoamylase

Abstract

The thermophilic fungus Humicola grisea var. thermoidea was successfully transformed using a bleomycin-phleomycin resistance gene linked to regulatory sequences from Aspergillus nidulans. Transformation was achieved using the lithium acetate method with young mycelia, and transformants were obtained at a frequency of 0.5-2 per μg of plasmid DNA. Vector DNA used in transformations was integrated in the genome of Humicola in varying patterns and copy number, and transformants were mitotically stable. Extra copies of an Humicola gla1 gene encoding glucoamylase (GAM) were introduced into the genome of several Humicola strains by transformation, with the result that some transformants produced almost 3-fold more GAM in comparison to the untransformed parental strains. © 1992 Springer-Verlag.