Breeding Of High-Yield Strains Producing Function Oil And Primary Studies On Metabolism Regulation

Function oil as a kind of oil with special physiological functions can reduce cardiovascular diseases risk, promote organism cell growth and lipid metabolism, prevent senescence and cancer, and avoid allergic reactions and so on. Function oil is considered with a broad applications prospect in the field of biomedicine and medicine, functional foods and daily life. The research of functional oil from microorganism can resolve the shortage functional oil, limited source of producing, and the deficiency of demanding in human's daily diet. Mortierella isabellina as one of the most widely studied strains producing microbial lipids is the most potential microbiological resource to realize industrialization produce of function oil extensively. In order to improve the yield of function oil by Mortierella isabellina, the Mortierella isabellina As3.3410 was chosen as the starting strain. The following contents were systematically studied in the research: screening the high-yield function oil strains; optimizing the culture medium composition; establishing the optimal supercritical CO₂ fluid extraction procedure of function oil; the influence of adding exogenous factor to the metabolism of the strain producing function oil. And the following research results were obtained mainly:1. The high production strain of function oil was rational screened by ultraviolet- LiCl using the malonic acid and sesamol in this study, finally a mutant named ZL2-103 was obtained, it showed a good genetic stability by the experiment of genetics stability, and which has a strong capacity of producing function oil. The biomass of the strain was 25.73 g/L, the yield of oil was 20.38 g/L and the function oil production was 4.32 g/L, which later two were 111.19% and 285.71% higher than that of the initial strain, respectively.2. On the basis of single-factor test, Box-Benhnken design was used to optimize the fermentation medium composition of ZL2-103 and the optimum composition of fermentation medium were obtained: 107.40 g/L glucose, 8.71 g/L mixed nitrate, 91.87 mg/L MgSO4, 2.73 g/L KH2PO4, the nitrate was mixed by peanut meal and yeast extract at 1:3?w/w?, under the optimum fermentation medium, the yield of function oil was up to 5.21 g/L.3. Use the technique of supercritical CO₂ extraction?SFE-CO₂? inquiring into the extract condition of affecting the microbial oil extraction rate, based on single-factor experiments, Box-Benhnken design was used to optimize the key extract conditions and the optimum conditions were found: extractive pressure/Mpa =48, the extractive temperature /? = 44, dynamic extraction time/min =141, static extraction time/min =20, the particle size for processing is 60 mesh. Under above-mentioned conditions, the oil extraction ratio was up to 94.83%.The oil were extracted by Soxhlet extraction?SE?and SFE-CO₂, their physicochemical properties?acid value, peroxide value, saponification value, iodine value and refractive index?and composition of fatty acids were detected by chemical and GC-MS analysis methods, and fungal cells of biomass powder by SE and SFE-CO₂ were also analyzed by means of Scanning electron microscopy to observe the degree of breaking the cells wall, through the comprehensive comparison analysis, the conclusion are got: SFE-CO₂ is better than SE in extracting function oil, and the SFE-CO₂ is the optimal method for the function oil extracting.4. The effects of three kinds of exogenous factors on the production functional oils metabolism of bacterial strain ZL2-103 were investigated. The experiment result showed that 0.3% sodium acetate, 0.01% malic acid, 0.01% citric acid have the role in promoting to the accumulation of strain functional oils, and adding exogenous factors can achieve the highest yield of functional oil during the optimal fermention period.The yield of strain functional oils was 5.89g/L when 0.01% citric acid was added in the fouth fenmention day, 0.3% sodium acetate and 0.01% malic acid were added in the initial time of fermentation, which increased 15.26% than the control group.