To improve itaconic acid production level, the glyceraldehyde dehydrogenase gene (gpdA) and the gene encoding a fungal hemoglobin domain (hbd1) were cotransformed with the pyrG + marker into the selected host AB 1.13 CAD 10.1. To select improved itaconic acidproducing co-transformants, 14 gpdA and 23 hbd1 transformants were screened in 96 well micro-titer plate using reference medium [4]. Three strains from each HBD and GPD differing most strongly from CAD 10.1 were selected
and analyzed for the presence for extra hbd1 or gpdA gene copies by Southern Blot analysis (Figure 1B).