LI Ying,LEE Xiangjun,GUO Jianfeng,FENG Jingjing,XU Chenshuai,BAI Yujie,GUO Shiwei,WANG Fang
Palmitoleic acid (C16:1n7, POA), a 16-carbon ω-7 monounsaturated functional fatty acid, has been demonstrated a variety of beneficial properties to human health and a wide range of applications in nutrition, medical and chemical industries. Lipozyme® RM IM (Rhizomucor Miehei lipase), a Sn-1,3 specific lipase, was used to catalyze the hydrolysis of seabuckthorn fruit oil and produce monoglycates rich in palmitoleic acid. The fruit oil of seabuckthorn was used as the research object, the dosage of enzyme taking 10% wt.% oil, the influence of water/oil ratio, pH value and reaction temperature to hydrolysis rate were investigated, and then the response surface methodology was applied for optimizing the process conditions. Further, the relationship between the hydrolysis rate and the content of monoacylglycerol was studied under the optimal hydrolysis conditions. The result indicated that the optimal combined condition is as follows: the reaction temperature is 55°C, the pH is 7, the water-oil quality ratio is 1:1. The hydrolysis rate achieved 79.59% within 12 h in the condition above. Under the optimal conditions, the hydrolysis rate was positively correlated with the content of monoester, and the correlation coefficient was 0.999 within the first 10 h of the reaction. The hydrolysis rate was 66.76% at 10 h, and the content of monoglyceride reached the highest of 61.11%. Hereafter, the hydrolysis of monoglyceride began if the reaction continued. The content of palmitoleic acid increased from 27.11% to 40.84%, and that of linoleic acid increased from 4.51% to 33.34%, so the total amount of the two functional fatty acids reached 74.18%. Enzymatic hydrolysis can be an effective way to improve the function of seabuckthorn fruit oil.
To obtain high purity of 1,3-Dioleoyl-2-palmitoylglycerol (OPO), an important structured triglyceride for infant formula, a facile method was established. Tripalmitin (PPP) was firstly synthesized, and then OA was incorporated into the sn -1 and 3 position of the PPP glycerol backbone by acidolysis catalyzed using sn -1,3 regiospecific lipases. Two kinds of widely used immobilized sn -1,3 regiospecific lipases, Lipozyme TL IM and Lipozyme RM IM, were investigated in both solvent ( n -hexane) and solvent-free system. The results showed that Lipozyme TL IM and Lipozyme RM IM were suitable for solvent system and solvent-free system respectively. Other reaction conditions (enzyme load, substrate molar ratio, temperature, reaction time) were optimized. The palmitic acid (PA) at the sn -2 position of the obtained triacylglycerols (TAGs) under optimized conditions were 92.92% and 86.62%, and OPO contents in the final products were 32.34% and 40.23% in the solvent and solvent-free system respectively. Special emphasis was given to test the reusability of the two immobilized lipases, results showed that Lipozyme TL IM was almost non-reusable, while Lipozyme RM IM could keep its activity for at least 15 times (about 60 h). These results provide a guide for the industrial production of high purity OPO by facile method.
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