High Pressure-Induced Changes of Physico-Chemical Properties and Mutagenesis in Aspergillus Oryzae

In order to study the pressure-induced changes of biological and physiochemical properties in fungi, Aspergillus Oryzae was treated with high pressure at 0.1~400 MPa for 20 min, and their viability and modality, as well as the activity of protease and amylase were determined. The result showed that high pressure induced obvious changes in the viability and modality of Aspergillus Oryzae. The activities of protease and amylase in Aspergillus Oryzae showed a specific regular pattern upon high pressure treatment. In the pressure range of 0.1~200 MPa, the protease activities decreased, but enhanced gradually in the range of 200~400 MPa. The protease activity was larger than control strain after treatment fungi with 300 MPa or higher, and reached the maximal at 400 MPa. The activity of amylase also decreased with pressure in the range of 0.1~100 MPa and gradually enhanced in the range of 100~200 MPa, and subsequently decreased again at the range of 200~400 MPa. The activity of amylase is highest in the treatment with 200 MPa, and same as control strain at 400 MPa. A fine mutant strain of fungi, HP300a, was obtained after treatment with 300 MPa. HP300a has a series of excellent characteristic: quick growth, more spores, higher activity of protease, and is rarely polluted by other strains. In addition, several indexes of soy sauce brewaged by HP300a were much better than that by control strains.