The Study Of Regulating Arachidonic Acid Biosynthesis By Mortierella Alpina

Arachidonic Acid(ARA)belongs to the omega-6 series of polyunsaturated fatty acids,is a direct precursor of various eicosanoic acid derivatives.ARA also plays an important role in the physiological processes of many diseases.ARA’s extensive application and good developmental prospect make it a product with great commercial value.Nowadays,high medium cost limits industrial ARA production,so improving ARA production and reducing production cost are what it matters to stay competitive for producers.In this paper,the Mortierella alpina M30 was used as the research object,organic nitrogen sources and DO were further studied to regulate ARA synthesis,and to provide references for lowering industrial ARA production cost.The results are as follows:(1)Firstly,the fermentation medium of Mortierella alpina was optimized by response surface analysis and the concentration of glucose,yeast extract,sodium nitrate,potassium dihydrogen phosphate and magnesium sulfate heptahydrate each was 60.0 g/L,10.1 g/L,3.4 g/L,3 g/L,0.5 g/L,ARA oil production reached 3.66 g/L,while the optimized medium carbon source utilization increased by 35.7%.Secondly,several organic nitrogen sources were studied to evaluate their influences on ARA synthesis and a suitable organic nitrogen source compounding(SBM:YE=1:4)was obtained.The production cost reduced by 15.95%while the ARA production increased by 3.8%while fermenting with this compounding.At last,the contents of amino nitrogen,total phosphorus and amino acid components of yeast extract soybean meal and corn steep liquor were determined.Via cluster analysis and variance analysis,the key components influencing ARA production in organic nitrogen source were obtained:tyrosine and methionine.(2)A dissolved oxygen control strategy was established for M.alpina fermentation and the suitable M.alpina morphology was determined for ARA synthesis.Studies on key parameter DO showing that the best fit K_La was 62.57±1.28.Moreover,reasearch on scale of the 10L tank identified the critical oxygen concentration of the fungus to 17.2%.The effects of different air distributor on fermentation was also studied and the result showed that air distributor which could generate more,smaller bubbles can improve the level of dissolved oxygen in the medium,thus promoting the synthesis of ARA.Then the researcher on relationship between M.alpina’s morphology and ARA yield was carried out,and the results indicated that the addition of 0.5g/L 200-300 mesh neutral aluminium oxide particles could make M.alpina maintain at the most suitable morphology-the pinnate structure with loose core.Summing up the above,the yield of ARA reached 4.14 g/L,which was higher than that of the control group(3.61 g/L)by 14.68%.(3)The dissolved oxygen control strategy was applied to 30 L multi-parameter fermentator,and the fermentation process was optimized through multi-parameter analysis to promote ARA synthesis effectively.Dynamic change of process parameters(OUR,CER,K_La|)were analyzed combining with glucose sonsumption and fatty acid composition to obtain the preferable pilot-scale fermentation conditions.The foam control and feeding process were optimized with ventilation of 1-1.5vvm and stirring speed of 200-300rpm,ARA production reached 4.59 g/L,which was 25.41%higher compared to the control group.Researchs above effectively regulate and promote ARA synthesis,and provide theoretical and experimental basis for reducing production cost in ARA’s industrial production.