Production Of Polyunsaturated Fatty Acids From Corn Sugar By Mortierella Spp

With Mortierella alpina 3.12824 as the starting strain and corn sugar as the carbon source,the fermentation process and extraction process of Mortierella alpina for producing polyunsaturated fatty acids were optimized through single factor experiments and orthogonal experiments,and the oil yield of the strain was further improved through aging process.Finally,refine the extracted oil and find the optimal degumming and deacidification conditions,including:（1）Determine the optimal conditions for shake flask fermentation of Mortierella alpina through single factor experiments and orthogonal experiments.Research has shown that when the mass concentration of carbon source corn sugar is 80.0 g/L,nitrogen source yeast extract is 12.0 g/L,KH₂PO₄is 3.8 g/L,Na NO₃is 3.4 g/L,and Mg SO₄·7H₂O is 0.5g/L,the order of four factors affecting biomass is culture days>culture temperature>liquid loading>p H,and the order of four factors affecting oil production is culture days>liquid loading>culture temperature>p H.The optimal fermentation conditions are liquid loading of 200 m L/L,fermentation time of 7 days,fermentation temperature of 25℃,and p H 6.5.Under these conditions,the biomass of the strain and oil production reach 26.05g/L and 9.37 g/L,respectively.The oil produced by Mortierella alpina was analyzed by gas chromatography.The composition was palmitic acid（C16:0）,stearic acid（C18:0）,oleic acid（C18:1）,linoleic acid（C18:2）,octadecatrienoic acid（C18:3）,arachidonic acid（C20:3）,arachidonic acid（C20:4）,eicosane acid（C22:0）.The content of unsaturated fat acid C18:1,C18:2,C18:3,C20:3,C20:4 in the oil was 17.72%,5.73%,0.75%,5.83%,39.93%,the total content exceeds 69.00%,of which the content of polyunsaturated fatty acids C18:2,C18:3,C20:3,C20:4 exceeds 52.00%,and the content of ARA is the most abundant,reaching 39.93%.（2）Through single factor experiments,the fermentation temperature and aeration ratio of Mortierella alpina fermentation tank were investigated.After obtaining the optimal fermentation conditions,one-time and constant rate feeding methods were used to further optimize the fermentation conditions.The study showed that the culture medium consisted of carbon source corn sugar concentration of 80.0 g/L,nitrogen source yeast extract concentration of 12.0 g/L,KH₂PO₄3.8 g/L,Na NO₃3.4 g/L,and Mg SO₄·7H₂O 0.5 g/L,fermentation temperature 25℃,aeration ratio 1:1,constant rate feeding method fermentation for 7 days,the biomass and oil production of Mortierella alpina reached their maximum values,33.5 g/L and 13.16 g/L,respectively.（3）Design single factor experiments and orthogonal experiments to determine the optimal extraction conditions for the extraction of oil from Mortierella alpina.In order to further improve the oil production,the optimal aging time and temperature of Mortierella alpina were determined through single factor experiments.Research has shown that the main and secondary order of the three factors affecting the extraction rate of Mortierella alpina is liquid-solid ratio>temperature>time.The optimal process parameters are liquid-solid ratio of 20:1,extraction time of 9 hours,and extraction temperature of 75℃.Under these conditions,the oil extraction rate of Mortierella alpina is 39.25%.The aging process of alpine Mortierella mycelium was studied using the optimal Soxhlet extraction process.The results showed that the filtered and non dried mycelium could be used as the optimal aging process.The optimal aging time was 6 days,and the optimal aging temperature was 20℃.Under this condition,the oil yield could be 11.25 g/L,which was20.06%higher than the oil yield of the non aged mycelium of 9.37 g/L.（4）A study was conducted on the refining conditions of the extracted high mountain Mortierella oil.The optimal conditions for degumming and deacidification of the high mountain Mortierella oil were determined through single factor experiments and orthogonal experiments.The study showed that the three main and secondary factors affecting the degumming of crude oil were:the amount of phosphoric acid solution added>the degumming temperature>the amount of water added.The optimal degumming conditions were as follows:the amount of phosphoric acid solution added accounted for0.9%of the oil weight,the amount of water added accounted for 6.0%of the oil weight,and the gelation temperature was 60℃,Using the optimal degumming conditions,the degumming rate can reach 81.56%.The main and secondary order of the three factors affecting the deacidification of the degummed oil from Mortierella alpina is deacidification temperature>super alkali content>deacidification time.The optimal deacidification conditions are:deacidification temperature 60℃,super alkali content 0.3%oil weight,deacidification time 50 minutes.Using the optimal deacidification conditions,the deacidification rate can reach 81.54%.