The mechanism and kinetic model for glycerolysis by 1,3 position specific lipase from Rhizopus arrhizus

doi:10.1016/j.bej.2005.03.009

Biochemical Engineering Journal

Volume 25, Issue 1, August 2005, Pages 39-45

https://doi.org/10.1016/j.bej.2005.03.009 Get rights and content

Abstract

Hydrolysis and glycerolysis of l,3-palimitin-2-olein (POP) was studied and mechanism of glycerolysis was discussed. The results showed that the glycerolysis is a complicated process including hydrolysis, esterification and isomerization of monoglycerides (MG) and diacylglycerols (DG). At first 5 h of glycerolysis, hydrolysis dominates the process and then esterification and isomerization will take place. A new mechanism and kinetic model based on hydrolysis, esterification and isomerization were established to correct all reactions in glycerolysis. The average relative error between experimental data and simulated results is 8.37%. The kinetic model can be used to predicate the results of glycerolysis at different molar ratios of POP to glycerol. The relative errors between the results predicted and experimental data are lower that 10%, which means that the kinetic model can be used to describe for glycerolysis of triglycerides.

Introduction

Glycerolysis of triacylglycerol can produce many useful products such as monoglycerides (MG) and diacylglycerols (DG), which have wide applications in food, cosmetics and pharmaceuticals [1]. The glycerolysis carried out by a lipase has got attention due to its mild reaction conditions and position specific products such as 2-monoglycerol by 1,3 specific lipase [2]. Yamane and his co-workers studied the production of MG by a glycerolysis with a lipase from Pseudomons fluoresc and their results showed that the conversion was strongly dependent on reaction temperature [3], [4]. The 60–90% conversion could be obtained below critical temperature.

Millqvist et al. used 1,3 specific lipase from Rhizopus to produce 2-monoglyceride and high conversion (92%) was obtained [2]. Glycerolysis by different systems, such as two-phase system [5] and reverse micelles system [6], have also been reported.

Although a lot of applications of glycerolysis by lipase catalysis have been seen, until now a few were concerned with the mechanism and kinetic model on glycerolysis. Boswinkl et al. suggested acyl migration in monoglycerol synthesis to explain formation of 2-monoolein [7]. The result showed that the acyl migration rate was strongly dependent on the acyl chain length. Peng et al. suggested a mechanism including hydrolysis, esterification and interesterification for glycerolysis [8]. However, this model is rather complicated and there is no experimental data to support it. Heisler et al. studied the glycerolysis of tripalmitin by 1,3 lipase, and found the isomerization of 1,2-dipalmitin into 1,3-dipalmitin [9]. He presented a two-step mechanism for glycerolysis. The first step is hydrolysis of dipalmitin and then an isomerization of 2-monopalmitin into 1-monopalmitin happens. But the detailed mechanism and kinetics of glycerolysis have not been discussed.

Lykidis et al. [10] and Dandik et al. [11] studied the kinetics of hydrolysis of triacylglyerol by a lipase. All these models are a two-step mechanisms, triacylglycerols were firstly hydrolyzed to 1,2 diacylglycerol, then the diacylglycerol was subsequently converted into 2-monoacylglycerol. Kinetics of interesterification of triacylglycerol has also been reported and a Ping–Pong model was presented [12]. Until now, to the best of our knowledge, the mechanism and kinetics of glycerolysis have not been reported. In this paper, the mechanism was studied and a new kinetic model for glycerolysis was established.

Section snippets

Materials

Rhizopus arrhizus strain was stored in our laboratory. Chinese vegetable tallow (CVT) was purchased from Nanjing Grain and Oil Company (Nanjing, China). Glycerol and other chemicals without special mention were of analytical grade.

Acetonitrile and methylene chloride of HPLC grade were obtained from Caledon Laboratories Ltd. (Georgetown, Ont., Canada). Acetic acid was of analytical grade from Beijing Chemicals Factory (Beijing, China).

The following reference standards were purchased from Sigma

Mechanism of glycerolysis

To show mechanism of glycerolysis, hydrolysis of POP was firstly studied as shown in Fig. 1. From Fig. 1A, some oleic acids were formed in hydrolysis. Most MGs are 2-monoolein and small amount of 1-monoolein and 1-monopalmitin (Fig. 1B). The DG mainly consisted of 1-palmitin-2-olein, while 1-palmitin-3-olein content is very low, indicating that the lipase from R. arrhizus is 1,3 position specific.

Glycerolysis of POP by free solvent system is shown in Fig. 2. At first 5 h of reaction, hydrolysis

Conclusions

Glycerolysis is a complicated process including hydrolysis, esterification and isomerization of MG and DG. At first 5 h of glycerolysis, hydrolysis dominated the process and then esterification and isomerization took place. A new mechanism and kinetic model based hydrolysis, esterification and isomerization were established to correct all these reactions. The simulated relative errors are lower than 10%. The kinetic model can be used to predict the results of glycerolysis at different molar

Acknowledgments

The authors want to express their thanks for the supports from ‘973’ Project (2003CB716002), Nature Science Foundation of China (20136020), (20325622), (50373003), Nature Science Foundation of Beijing (2032013), National Key Technology Program (2004BA71B08-02) (2004BA411B05), and ‘863’ High-Tech Program (2002AA514030) and Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institutions of MOE, Key Project of MOE (704010), PR China.

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The mechanism and kinetic model for glycerolysis by 1,3 position specific lipase from Rhizopus arrhizus

Abstract

Introduction

Section snippets

Materials

Mechanism of glycerolysis

Conclusions

Acknowledgments

Enzyme Microb. Technol.

Process Biochem.

Enzyme Microb. Technol.

J. Am. Oil Chem. Soc.

J. Jpn. Oil Chem. Soc.

J. Am. Oil Chem. Soc.

Biotechnol. Bioeng.