Xianfeng Fu,Jianyong Zheng,Xiangxian Ying,Hongde Yan,Zhao Wang
A novel ultraviolet (UV) spectrophotometric method for evaluating lipase transesterification activity in organic solvents is described. The model reaction was lipase-catalyzed transesterification between p -nitrophenyl palmitate (pNPP) and n -butanol in n -hexane at 30 °C. The conversion of pNPP to p -nitrophenol was monitored by measuring UV absorbance changes at 310 nm. Seven commercial lipases were tested using this method, and the results were similar to those obtained using gas chromatography . The UV spectrophotometric method was used to investigate the kinetics of the Lipozyme TL IM-catalyzed reaction of pNPP, and the correlation between synthetic activity and biocatalyst concentration was determined. The method was also used to investigate the Lipozyme TL IM-catalyzed transesterification properties, namely solvent effect, acyl acceptor specificity, alcohol tolerance, optimum reaction temperature, and thermostability.
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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