Isolation of α-glucosidase suppression transformants on aspergillus niger

We have already cloned an extracellular a-glucosidase gene from Aspergillus niger with oligonucleotide probe synthesized on the basis of the peptide sequences determined previously. The DNA sequence revealed an open reading frame of 895 amino acids split by three introns. We are attempting to construct an A. niger strain deficient in the α-glucosidase enzyme activity, which would be useful for the glucoamylase production without contamination by the industrially undesirable α-glucosidase. For destruction of the α-glucosidase gene, we try to make transformations. A cloned partial α-glucosidase gene was introduced into Aspergillus niger, and transformants with suppressed α-glucosidase activity were isolated. The transformants were cultured on YPD medium which contained Hygromycin B at 30°C. The activity of α-glucosidase of the suppressed transformants was compared to that of wild type activity. As shown by southern-hybridization, we detected that the transformant was a heterocaryon.