Study On Enzymatic And Comprehensive Utilization Of Soybean Oil Deodorizer Distillate

Soybean oil deodorizer distillate(SODD)is a by-product produced during refining and deodorization of soybean oil,which mainly contains free fatty acids(FFA),glycerides and tocopherols,sterols and squalene and other natural active substances.Bioactive compounds have rich nutritional value,and have high utilization value in food,cosmetics,health products and other fields.The annual output of soybean oil deodorized distillate in China is 60,000 to100,000 tons.Due to the limitation of processing technology,the direct disposal of deodorizer distillate will increase the burden of the environment and cause the waste of resources.Therefore,in this paper,using SODD as raw material,a self-made immobilized lipase YM1 with high methanol tolerance,good operation and high stability was used to catalyze the methyl esterification.And FFA and triglycerides in SODD were converted into fatty acid methyl ester(FAME)with lower molecular free range.FAME and bioactive compounds were separated by molecular distillation technology,purification of biodiesel and enrichment of tocopherols,squalene and sterols to realize the comprehensive utilization of SODD.The main research results obtained were as follows:(1)Raw material analysis of soybean oil deodorized distillate: By ultrahigh pressure liquid chromatography time of flight mass spectrometry(UPLC-MS-TOF),the glyceride content was around 33.06% and FFA content in SODD was 45% and SODD contained unsaturated fatty acid triglycerides(TAG)as high as 89.11%,the highest content was TAG(16:0 / 18:2 / 18:2),reaching 18.10%,and then were 13.13% for TAG(16 :0 / 18:1 / 18:2)and12.66% for TAG(18:2 / 18:2 / 18:3)respectively.A RP-HPLC method for simultaneous detection and accurate quantification of five bioactive compounds was established.Phenomenex C18 reverse liquid chromatography column 00G-4375-E0 was selected and the chromatographic conditions were optimized.The mobile phase was methanol / isopropanol /formic acid(V/V/V): 9 / 1 / 0.001.The contents of α-tocopherol,δ-tocopherol,γ-tocopherol,β-sitosterol and squalene in SODD were 5.40 ± 0.01 mg/g,19.31 ± 0.32 mg/g,25.69 ± 0.21mg/g,18.12 ± 0.97 mg/g,and 15.53 ± 0.54 mg/g,respectively.(2)Study on the immobilization of lipase YM1.Taking esterification activity and protein adsorption as reference indexes,to explore the influence of different resins for lipase immobilization and optimize the immobilization conditions.The results showed that AP/D5753 was the best resin for immobilization.Under the conditions of enzyme/resin ratio of 40 mg/g,ionic strength of 100 mmol/L,p H of 7,and immobilized at 45℃ for 8 h,the esterification activity of the immobilized lipase YM1 was 3526.48 U/g,and the specific activity reached 130.51 mg/g.The immobilized lipase YM1 was physically characterized by Scanning Electron Microscopy(SEM)and Fourier Transform Infrared(FT-IR).The results showed that the free lipase YM1 was successfully immobilized onto AP/D5753 resin.And the storage stability of immobilized lipase YM1 was studied,after one year of storage in the 4°C refrigerator,the esterification activity of immobilized lipase YM1 was 3350 U/g,which was more than 95% of the initial esterification activity.Therefore,it has a broad application prospect.(3)The immobilized lipase YM1 catalyzed the methyl esterification of soybean oil deodorized distillate.First,the effects of immobilized lipase YM1 and commercial enzymes in catalyzing SODD methyl esterification were compared.The results showed that the immobilized lipase YM1 had better performance than other commercial lipases in the preparation of FAME from SODD.The production process of FAME catalyzed by immobilized lipase YM1 was investigated.Under the condition of 1:2 molar ratio,35U/g enzyme loading,temperature 35℃,FAME conversion rate reached 97.08%,exceed the minimum limit required by the EU EN14214 standards(96.5%).Meanwhile,the acid value decreased from 89.50 mg KOH/g to less than 2 mg KOH/g,and there was no loss of squalene and tocopherols.(4)FAME and bioactive compounds were separated by molecular distillation,and the evaporation temperature was optimized to 100℃.At this temperature,all FAME transferred to light phase,the recovery rate is more than 99%.The recovery rate of the bioactive compounds was 93.37%,and the enrichment of α-tocopherol,δ-tocopherol,γ-tocopherol,β-sitosterol and squalene were 4.31,3.90,3.92,1.81,and 3.09 times compared with their initial contents,respectively.Finally,FT-IR and Nuclear Magnetic Resonance(NMR)were used to characterize FAME after separation,and SODD was used as control.According to the determination of characteristic absorption peak,it was confirmed that the immobilized lipase YM1 did realize the transformation from SODD to FAME in the catalytic process.The comprehensive utilization of SODD was realized.In conclusion,a high methanol tolerance lipase was found and immobilized,and its application potential in catalytic esterification and transesterification was explored.The methyl esterification treatment of SODD with this enzyme is convenient for separation and purification,and at the same time,the active ingredients can be enriched,which provides a solution for realizing the effective utilization of SODD waste resources,and also provides a scientific basis and data basis for the technological upgrading of oil industry.