Breeding Of Lipid Yeast And Study On Fermentation Products

At present, animal and vegetable oil can not meet with the demands of people nowdays by the develoment of population. Microbial oil is a new kind of resources after animal and vegetable oil, a lot of which are rich in polyunsaturated fatty acids which can lower the Serum Cholesterol. So they play important role in the health of human being, which aslo are raw materials of the biodiesel development. So the exploitation of microbial oil possess realistic sense in health foods satisfing lipids insufficiency of people.In this thesis, high-yielding strains of Candida Yeast-2 were got in the condition of UV and MW complex mutagenesis and protoplast mutation from candida yeast. And we studied the optimum conditions for ferment offerring technic foundation of the exploitation of yeast oil. We found out this mutation strain have obviously improvement than starting strain, the biomass of which improve 41%, and the absorbency of which improve 42%. And the lipid content improve 5.2%. The experiment display that A4 strains have the potential of industrialisation. In addition, we optimized the fermentation conditions of lipid yeast using multi-criteria cross experiment. The optimized liquid fermentation mediums were as follows: 0.05% MnCl₂, 0.04% FeSO₄, 0.3% (NH₄)₂SO₄, 2% C6H6O, pH 6.5 at 120 r/min and 30℃in 4 d, and the content of lipids improved 11% comparing with 36% before. At last, the fermentation products of yeast oil and the methods of yeast fat urea inclusion complex of extraction of unsaturation acids of yeast oil were studied, testing lipid content, protein content and lipase activities etc. The methods show good effects just needing simple conditions, and have the characteristic of calling easily back the solvents, suiting for extraction of unsaturation acids of microorganism. So, the optimum conditions of extracting unsaturated fatty acids by urea inclusion complex was the ratio of urea and fatty acids(3:1), refluxing time (30 min) and the cooling temperature ( 0℃). In this conditions, the extracting rate reach to 33%.