Synthesis Of Phytosterol Esters By Lipase

Phytosterols exist naturally in a wide variety of vegetable oils, nuts, and seeds. In recent years, phytosterols have attracted significant attention due to their structural similarity to cholesterol and to their ability to effectively lower both total serum cholesterol (TC) and low-density lipoprotein cholesterol (LDLC) by inhibiting the adsorption of cholesterol through the small intestine. However, the high melting point and low solubility in both water and edible oils have greatly limited the further use of phytosterols in food products. To overcome this problem, phytosterol esters of fatty acids have been derived from phytosterols and are considered suitable for addition to food products as they maintain all of the excellent properties contained in the original phytosterol. And phytosterol ester is one of the functional food ingredients recommended by the International Life Sciences Institute. In this work, phytosterol and oleic acid were used for synthesizing phytosterol ester by Yarrowia lipolytica lipase Ylip2. And the phytosterol ester with high purity was obtained by removing the excess oleic acid. The main content were as following:1. The synthesis of phytosterol ester in a solvent-free system by free lipase. The optimized reaction conditions were 1:3 mole ratio of phytosterol and oleic acid and 18000 U/g substrate lipase loading amount, and the phytosterol conversion was reached 91.1% at 50? for 110h. However, the viscosity of this system was high. To overcome this problem, the fluid dynamics the impeller paddles were calculated. The anchor impeller and the four narrow-leaf axial impeller were selected for mixing the system simultaneously. Finally, the phytosterol conversion was 93.1% for 102h.2. The construction of a computer-aided water activity bio-reactor. The phytosterol oleate was synthesized either without controlling the water activity or controlling the water activity at 10,15,25, or 40%. After optimizing, optimal water activity (15% rh) was determined to synthesize phytosterol esters in a solvent-free system. And the lipase can be reused 5 batches in a 5L bio-reactor under the controlled water activity.3. Lipase immobilized on celite for the synthesis of phytosterol ester in a water activity controlled reactor. The optimized reaction conditions were 1:3 mole ratio of phytosterol and oleic acid,18000 U/g substrate lipase loading amount and 15% rh water activity, and the phytosterol conversion was 97.4% at 55? for 70h. The immobilized lipase can be reused 10 times in 5L reactor, and 9840g phytosterol oleste was obtained.4. Synthesis of phytosterol oleate via substrate pretreatment by the immobilized lipase. After pretreating the substrate at 75? for 30min, the phytosterol conversion was increased to 96.2% for 42.5h. The operation of adding phytosterol multiple time can further shorten the reaction time to 35h. The oleic acid content was decreased from 60.07% to 10.62%, and the lower loeic acid content was more convenient for purifying phytosterol oleate.5. Countercurrent centrifugal extraction for phytosterol ester purification. The follow rate light and heavy phase was 5 and 2 ml/min, the stirred rate was 3500 rpm and the temperature was 30? with methanol as the extracted reagent. The obtained phytosterol ester content was 99.45% after extracting 5 times, and the acid value (0.55mg KOH/g product) was accorded with the national standard. The phytosterol ester yield was 81.6% for this process.6. The phytosterol ester was purified by molecular distillation and the color was removal by extraction. For the process of molecular distillation, the evaporator temperature was 120?, the vacuum degree 0.001mbar and the capacity 286g/h. After purified phytosterol ester, methanol was used to decrease the product's color. Finally, the acid value (0.58mg KOH/g product) was accorded with the national standard, and the phytosterol ester yield was 98.2% for this process. And this process was the most suitable program for purifying phytosterol ester. Additional, the sensory, physical and chemical parameter, and the microbial index were accorded with the national standard of the produced phytosterol...