RESUMO
An Acremonium chrysogenum strain improvement program based on the transformation with cephalosporin biosynthetic genes was carried out to enhance cephalosporin C production. Best results were obtained with cefEF and cefG genes, selecting transformants with increased cephalosporin C production and lower accumulation of biosynthetic intermediates. Phleomycin resistant transformants, designated B1 and C1, showed a single copy random integration event, higher levels of cefEF transcript and, according to immunoblotting analyses, higher amounts of deacetylcephalosporin C acetyltransferase (DAC-AT) protein than their parental strains. Moreover, DAC-AT activity was higher in the transformants. Plasmids carrying geneticin resistance markers based on the nptII gene from Tn5 and the aphI gene from Tn903 were constructed to transform again B1 and C1, showing that the cassette Pgdh-nptII-trpC was able to confer geneticin resistance to A. chrysogenum and demonstrating that geneticin is a helpful selection marker.
