Breeding Of Oleaginous Yeasts

Microbial oils, referring to oils produced by microorganisms with carbohydrate source(carbohydrates,hydrocarbons and ordinary fats), nitrogen sources and inorganic chemicals, were called single cell oil as well. Currently fats resouces mainly came from animails, plants, and petroleum. With the depletion of fossil resources and the progress of biotechnology, industrial oils were bound to a variety of ways. Microbial oils, as a new oil resouces has attracted wide attention. The exploitation and utilization of microbial oils enriched in traditional oils production technology, and provided a new way for oil production.In this thesis, comparing three extraction methods to determine the oil content, thermal-acid method with advanced efficiency was adopted. The best extraction conditions were optimized by single factor and orthogonal experiments. The results were as follows: aether 12 mL and petroleum ether 12mL, hydrochloric acid concentration 4 mol/L, hydrochloric acid volume 10mL, processing time by hydrochloric acid 8min, alcohol volume 10mL.In this thesis, high-yielding strain UD-71 was got by UV and DES compound mutation. The biomass 18.67g/L and the lipid content 63.2 percent were obtained after 96 hours flask culturing of UD-71. These values were obvious higher than the original strain. As time going on, these were no distinct changes on the yield.The conditions of fermentation were optimized by single factor and orthogonal experiments. The optimal fermentation conditions were as follows: glucose as carbons scource at 100 g/L, 0.8g/L KNO₃, 2.5g/L corn steep liquor, KH₂PO₄ 1g/L, MgSO₄·7H₂O 0.5g/L, MnSO₄ 0.3g/L; initial pH7.5, temperature 28℃, inoculation amount 10%(V/V), rotation speed of rocking bed 180 r/min, broth's volume in shake flask 30mL/250mL. Lipid productivity reached 18.2g/L. The biomass was up to 30g/L. In this thesis, factors that affect fatty acids composition were investigated. The results showed that low temperature was benefit to unsaturated fatty acids production. Production of polyunsaturated fatty acids can increase when the initial pH in neutral and alkaline range. Unsaturated fatty acids content can be up to 76.28 percent when rotation speed of rocking bed was 200r/min. Fe²⁺,Mg²⁺,Zn²⁺ and Mn²⁺ were helpful to unsaturated fatty acids production. The content of polyunsaturated fatty acids was increased when medium supplemented with soybean oil, peanut oil, glycerin and butyl alcohol .