Study Of High-yield PUFAs Mortierella Isabellina Strain Breeding And Fermentation Production

PUFAs can maintain membrane structure; inhibit cardiovascular diseases, inflammatory reaction and cancer cell growth; stimulate brain development; reduce weight; improve animal farrowing and survival rate and so on. PUFAs are widely used in food, medicine, aquaculture, cosmetics and other industries. Mortierella isabellina as one of the most widely studied strains, is the most potential microbiological resource to realize industrialization produce extensively; but the low-yield PUFAs of Mortierella isabellina hindered the development of extensive industrialization production. In order to improve the yield of PUFAs in Mortierella isabellina, the following contents were systematically studied in the research:screening the high-yield PUFAs strain; establishing the optimal extraction procedure of microbial oil; optimizing the culture medium composition and fermentation conditions. And the following research results were obtained mainly:1. The high production strain of PUFAs was rational screened by ultraviolet and NTG using the acetylsalicylic acid in this study, finally a mutant named NO.1-112was obtained, which has high growth vigor and whose biomass concentration satisfy further fermentation to produce PUFAs. The biomass of the strain was24.71g/L, the yield of oil was20.02g/L and the PUFAs production was4.67g/L, which were202.45%、580.06%and267.72%higher than that of the initial strain, respectively and genetic stability.2. In the study, the extraction conditions of ultrasound-assisted acid-heating extraction and ultrasonic/microwave assisted extraction of microbial oil from Mortierella isabellina was investigated using mathematical statistics and the optimal extraction conditions were established, respectively. Through comparison of the two extraction procedures, the ultrasonic/microwave assisted extraction of microbial oil was definitized as the optimum extraction method. The optimum extraction conditions of ultrasonic/microwave assisted extraction were as follows:microwave power of400W; microwave time of3.7min; ultrasonic time of40.5min; ultrasonic power of498W; material to solvent ratio of1:12.3(w/v) and ultrasonic temperature was manipulated at30℃, respectively. Under the optimal conditions, the extraction rate of microbial oil from NO.1-112was up to92.24%, and the yield of SCO was up to178.73±0.17mg/g (wet cell)(P<0.05) which was1.65-fold the yield of SCO before optimizing.3. On the basis of single-factor test, Box-Benhnken design was used to optimize the medium composition and fermentation conditions. The optimized medium was composed of2g/L KH2PO4and sodium citrate;116g/L glucose,10.8g/L of the mixture of yeast extract and peanut meal at3:1(w/w); supplement with Ca2+30.8mg/L and Mg2+96.8mg/L, respectively. Under the optimum medium condition, the yield of PUFAs was6.27g/L. The optimized fermentation condition was as follows:initial pH,6.36; culture temperature,28℃; inoculation amount,10%; liquid medium volume,117mL/500mL and rotation speed,200r/min. Under the optimum fermentation condition, the yield of PUFAs was up to7.03g/L.