Gene manipulation by protoplast fusion and penicillin production by Penicillium chrysogenum.

Hybrids have been obtained by protoplast fusion of nitrate-nonutilizing cnx- and acetate-nonutilizing fac- mutants of Penicillium chrysogenum strains 4/95 and 26/818, respectively. Induced haplodization of the hybrids allowed the recovery of stable segregants, which were screened for penicillin production. The penicillin-producing segregants showed a wide range of titers that reached for a certain mutant to 290-390% increase above the parent strains.