Protoplast fusion of beta-glucosidase-producing Aspergillus niger strains.

Protoplast fusion, induced by polyethylene glycol and Ca2+, was carried out between two auxotrophic strains of Aspergillus niger. The fusion frequency ranged from 6.2 x 10(-2) - 9.1 x 10(-2). After induced haploidization of a diploid, various segregants showing combinations of the parental genetic markers were isolated. Unlike diploids, haploid segregants exhibited greater variations in their morphology and beta-glucosidase activities. One segregant showed a 2.5-fold increase in beta-glucosidase activity over those of the parents. Thus, this method appears promising for creating new recombinant strains of A. niger with improved beta-glucosidase activities.