Production Of Arachidonic Acid By Fermentation Of Mortierella Alpina

Arachidonic acid(ARA) is one of the three most important fatty acids which are necessary for the body development. Furthermore, arachidonic acid is also the direct precursor of some physiologically important hormones, such as prostaglandins and leukotrienes in mammals, and plays a vital role in the growth process in human and animal development. Arachidonic acid has important commercial value in food, medicine, cosmetics and agriculture and many other fields. Production of arachidonic acid using microbial fermentation method has the advantage of high yield, low cost, no seasonal and climate influence and so on. So compared with the traditional tissue extraction method, the former get more extensive application. ARA has been widely studied in the food, medical, cosmetics, pharmacology, agricultural and many other fields.In this thesis, Mortierella alpina was used as the study object. The main medium components and fermentation conditions in shake-flask were optimized. Five liter fermentor amplification and an aging strategy were carried out and they turned out to be very efficient for ARA production. The main conclusions were as follows:Single factor and orthogonal design were applied to investigate effects of different nutrients and conditions for arachidonic acid fermentation by M. alpina. Results indicated corn and soybean meal were perfect for fungal growth and lipid accumulation. Dissolved oxygen played an important role in fungal growth and ARA formation. Addition of n-hexadecane could greatly improve rheology of fermentation broth and enhance DO value. Optimal concentration of n-hexadecane was 6%(v/v). The temperature-shift strategy was applied and fermentation period was shortened by two days. Arachidonic acid yield got its maximum(13.6 g/L) when medium comprised of(g/L): corn meal 66, soybean meal 54, KH2PO4 3, Mg SO4 1, Na2SO4 2.Mortierella alpina possessed excellent ability of using starch-based materials to produce arachidonic acid, while the production remained to be verified when it was cultured in a fermentor. This study focused on fermentation and cell aging strategy to reduce production cost. Starch liquefaction was applied to improve media rheology and dissolved oxygen. Results indicated that the best mixing speed and ventilation is 200 r/min, 1:1(v/v). The study also found that the optimal temperature and aging time was 20 ℃, 5 d respectively. Cell aging can effectively reduce the production cost while maintaining production. Arachidonic acid production reached 11.7 g/L when the optimal fermentation and cell aging strategy was employed, which allowed large-scale production of arachidonic acid using raw crop meals.