Transformation of Aspergillus oryzae with a dominant selectable marker

A novel transformation system using a bleomycin resistance marker with chemosensitizers for Aspergillus oryzae

Aspergillus oryzae is resistant to many kinds of antibiotics, which hampers their use to select transformants. In fact, the fungus is resistant to over 200microg/ml of bleomycin (Bm). By enhancing the susceptibility of A. oryzae to Bm using Triton X-100 as a detergent and an ATP-binding cassette (ABC) pump inhibitor, chlorpromazine, to the growing medium, we established a novel transformation system by Bm selection for A. oryzae. In a medium containing these reagents, A. oryzae showed little growth even in the presence of 30microg Bm/ml. Based on these findings, we constructed a Bm-resistance expression cassette (BmR), in which blmB encoding Bm N-acetyltransferase from Bm-producing Streptomyces verticillus was expressed under the control of a fungal promoter. We obtained a gene knockout mutant efficiently by Bm selection, i.e., the chromosomal ligD coding region was successfully replaced by BmR using ligD disruption cassette consisted of ligD flanking sequence and BmR through homologous recombination.

Production of alkaline protease by a genetically engineered Aspergillus oryzae U1521

The production of alkaline protease of Aspergillus oryzae U1521 was examined in liquid culture. In a culture of defatted soybean only, it gave satisfactory enzyme yields at 584,000 U/g defatted soybean. When various carbohydrates were supplemented, enzyme production was significantly increased. An increase in production by lactose was the most marked. Enrichment with casitone or casein increased productivity, but not cornsteep solid. Media formulation (g/L) of defatted soybean 10, lactose 5, casitone 1, and KH(2)PO(4) 5 enhanced alkaline protease production by A. oryzae U1521 to a maximum of 1,410,000 U/g defatted soybean. Scaling-up experiments indicated the flask-scale results could be reproduced at 40 g of substrate in 5-L fermenter. The enzyme activity was maximum between pH 8-9 and at a temperature of 45 degrees C.