Abstract: The original strain Mortierella isabellina As3.3410 was treated by microwave and ultraviolet. Mutated strains were screened by acetyl salicylic acid and low temperature (15°C). A high-yield strain named as A35-4 was successfully selected. The biomass of this strain was 17.9 g/L, oil content was 67.8%, oil production was 12.12 g/L, polyunsaturated fatty acids (PUFAs) content was 20.2%, and production of PUFAs was 2.46 g/L, which increased 32.6%, 49.8%, 98.69%, 14.0%, and 125.7% compared with the original A0 stain, respectively. The continuous slope transmission experiments confirmed that the strain had a good genetic stability. The study is beneficial for cloning high efficiency genes for PUFAs and producing PUFAs in this stain, and lays the ground work for creation of transgenic plants containing high levels of PUFAs.

Key words: microwave irradiation, UV irradiation, Mortierella isabellina, resistance screening