| γ-Linolenic acid (GLA) is an essential fatty acid for human beings, which belongs tooctadecatrienoic acid. Currently, most GLA commercially available was extracted fromwild plants while the limitation of sources and outputs lead to high production costs. As aresult, more and more attentions are paid on low cost production of γ-linolenic acidrecently. Based on previous laboratory researches, this study mainly focused on relativeparameters for FR3fermentation in10L fermenter and5t fermentation tank. Specifically,the process of mycelium lipid subcritical extraction, the physical and chemical propertiesof gamma-linolenic acid as well as its effect as antioxidant were also been studied. Thisthesis aimed to obtain low-cost γ-linolenic acid from Cunninghamella echinulata FR3cultured in potato slurry.The optimal fermentation parameters for FR3in10L fermenter were obtained asfollows: pH5.0, cultured temperature of25℃, stirring speed of100r/min, aeration rate of500L/h.30%Glucose solution was continuously added from the third day afterinoculation till the end of fermentation so that the total sugar addition remained5%in the7thday to get final results of34.64g/L biomass, lipid yield of10.86g/L with1270mg/Lof GLA, the production were increased by25.10%,35.54%,71.16%respectively thanbefore optimized. After the study of scale-up, we concluded that the optimal aeration ratewas180m3/h, and the initial pH for5t fermenter at50L strain fermenter and500Lamplication fermenter was seted at5.0. Then20%glucose solution was feed continuouslythrough filter. so that the total amount of sugar reached5%in the7thday. Thus the finalbiomass amount, lipid yield and GLA yield for FR3reached34.54g/L,10.45g/L, and1236mg/L respectively, similar as the product level of10L fermenter.The optimumconditions of butane subcritical extraction with mycelium harvested from fermenter wereconducted and the results were as follows:(1) Hot pressing pretreatment process:mycelium moisture content of8.36%and the hot pressing temperature of70°C to get2mmexpeller cake.(2) Subcritical extraction process: extraction liquid ratio, temperature andtime were0.075,44°C and11.3h, respectively. The maximum production was32.56mgγ-linolenic acid per gram of mycelium under this condition. The stability analyses of GLA as well as antioxidation experiments have indicatedthat high temperature, UV and light would adversely affect the γ-linolenic acid in the oil.Natural antioxidant such as VCand rosemary extract showed certain inhibition to fatoxidation reaction. And among the national standard dosage range, the effect ofantioxidation was positive correlated with the amount of antioxidants.In summary, this thesis advanced an economical way to achieve low-cost GLAthrough microbial fermentation on reactor level and provided several important technicalparameters which are beneficial to the industrialized production of GLA. |
