Mutation and selection of high squalene production yeast Pseudozyma sp. induced by carbon-ions beam irradiation and its electrotransfor-mation

In order to improve the yield of squalene, using Pseudozyma sp. SD301 as the starting strain, we selected the mutant strain with high squalene yield by carbon-ions (¹²C⁶⁺) beam irradiation technology, and optimized the electrotransformation conditions of the mutant strain. We used 100 μmol·L⁻¹ H₂O₂ as the screening pressure. When the carbon heavy ion beam irradiation dose was 120 Gy, the mutant PS120 was obtained with higher squalene yield than the original strain. After 3 days of culture, the squalene yield of the mutant reached 1.33 g·L⁻¹ and the squalene mass reached 41.31 mg·g⁻¹. The green fluorescent protein EGFP was used as the characterization marker to optimize the electrotransformation conditions of PS120. The results of enzyme digestion, electrophoresis and sequencing show that the gene encoding EGFP could be successfully transferred into PS120 cells under 900 V voltage. The high-level expression of EGFP protein in PS120 cells was further confirmed by laser confocal microscope.