Enzymatic Preparation Of Epoxidized Oils In Natural Deep Eutectic Solvents And Its Application

Epoxidized oils have received extensive attention as a substitute for phthalate plasticizers.The biocatalytic method to replace the traditional chemical method to prepare epoxidized oils has received more and more attention.During the epoxidation reaction,hydrogen peroxide is widely used as an ideal clean oxygen source.However,the lipase is affected by hydrogen peroxide,and the peroxidase activity of the lipase is seriously lost or even inactivated.This greatly limits the industrial application of biocatalytic epoxidation.Natural deep eutectic solvents?NADES?has attracted widespread attention as a"green solvent".It has the advantages of simple preparation,no biological toxicity,biodegradability,etc.,and thus becomes an excellent substitute for traditional organic solvents,ionic liquids and other media.Moreover,studies have shown that NADES has a protective effect on the catalytic activity of the enzyme.Therefore,this paper selects NADES as the reaction media,partial glyceride lipase derived from Aspergillus oryzae?AOL?as catalyst,and enzymatically catalyzes epoxidation to efficiently prepare epoxidized soybean oil and epoxidized waste cooking oils.And separation and characterization of epoxidized products.Finally,the epoxidized products were applied as a plasticizer with the PVC material.The main findings of this paper are as follows:1.Expression and purification of lipase:Firstly,AOL lipase was expressed and purified by fermentation of a constitutive Pichia strain,and lipase AOL was prepared and its enzymatic properties were studied.Studies on the peroxidation activity of AOL showed that the optimum temperature of AOL was 50°C,the optimum pH was 6.0,and the optimum carboxylic acid substrate was octanoic acid.AOL catalyzes the formation of peroxyacids in situ by carboxylic acid.When octanoic acid is used as a substrate,the peroxidation activity of AOL is 13.1 U/mg.2.Lipase-catalyzed epoxidation of oils:The effects of different NADES on lipase-catalyzed epoxidation were compared,and the best NADES was selected as the reaction media for epoxidation.The choline chloride:sorbitol?1:1 molar ratio?system was found to be the best reaction media for lipase AOL.Epoxidized soybean oil was prepared by epoxidation of soybean oil under this system.The epoxidation process was optimized as follows:molar ratio of octanoic acid/H₂O₂/C=C double bond=0.3:1.5:1,choline chloride:sorbitol?1:1 molar ratio?content70.0%of the weight of hydrophilic phase,enzyme loading was 15 U/g of soybean oil,reaction temperature is 50 ^oC.Up to 96.8%conversion was successfully achieved under the optimized conditions.At the same time,under the optimal conditions,the methyl esterification product of the waste cooking oil was subjected to epoxidation treatment to obtain the corresponding epoxidized oils.3.Separation,characterization and application of epoxidized oils:The scale-up of the reaction system was performed under the above optimized conditions.After 12 h reaction,the yield of epoxidized soybean oil was as high as 95.9%.After separation of the two-liquid phase system?hydrophobic phase-hydrophilic phase?,the neutralization treatment was carried out,and the acid value of the epoxidized soybean oil was lowered to 0.45 mg KOH/g,and the iodine value was as low as 2.8 g/100 g?in terms of I₂?.Epoxidized soybean oil was mixed with epoxidized waste cooking oil?ESO-EWCOME?in different proportions,and then plasticized with a PVC material.The results show that compared with the traditional plasticizer DOP,the mechanical and mobility properties of ESO-EWCOME were improved.ESO-EWCOME overcomes the shortcomings of poor compatibility with PVC when ESO is used alone,and also realizes the recycling and reuse of catering waste oil,which has important strategic significance for green sustainable development.