Fast Selection And Fermentation Condition Of High-yielding Mutant Strains Of Cunninghamella Echinulata Producing Gamma-linolenic Acid (GLA)

γ -Linolenic acid(GLA) is one kind of essential polyunsaturated fatty acid (PUFA) in the human body with important physiological functions to human body. Compared with the method of chemical synthesis and extracting from plant seeds and animal fats, microbial fermentation has its unique advantage, therefore, it is necessary to breed a high-yielding strain and to find out its optimum fermentation condition.A high-yielding mutant Cunninghamella echinulata C23 producing γ-linolenic acid was successfully obtained when the original strain Cunninghamella echinulata C₀ was treated by 5-FU and UV, and by the screening method of resisting maleic hydrazide and 15℃ low temperature. The index of fermentation of mutant C₂₃ was mensurated by the basic fermentation in 250-mL flask.The biomass reached 24.70g/L,lipid yield reached 10.73g/L, and GLA in total lipid reached 12.30%,GLA yield reached 1.32g/L, increasing 35.7%, 147.4%,236.4%,45.7% and 388.9% respectively compared with original C₀.Single factor experiments and orthogonal experiments were done by 250-mL flask, 5-L fermentor and 50-L fermentor to optimize the fermentation conditon for mutant C₂₃ producing GLA, and the lipid was extracted by supercritical CO₂.The result is that glucose and NH4NO3 are optimum carbon source and nitrogen source respectively, the original concentration of glucose and NH4NO3 in fermentation culture medium is 100g/L and 4g/L respectively, mutant C₂₃ was inoculated into 5-L fermentor by 10⁶spores/mL, and after 48h the seeds were inoculated into 50-L fermentor by 10% inoculums. When ventilation rate was 30L/min,stirring rate was 300r/min, the pH value of liquid media maintained 5.5, and the 15g/(L.d)glucose was fed in 60h,84h,108h of fermentation;thefermentation temperature was 28℃ for first132h,and then the temperature dropped to 20°C and lasted for 48h,and finally the temperature dropped to 15°C and lasted for 12h.The biomass, lipid yield and 7-linolenic acid yield of mutant C23 reached 49.88 g/L, 22.45 g/L and 3.03 g/L respectively.