Study On The Preparation Of Medium-chain Monoglycerides From Camphor Tree Seed Kernel Oil Transformed By Enzymatic Method

The medium-chain monoglycerides was esterified by a fatty acid molecule of6-12carbon atoms (such as octane acid, decane acid, dodecanoic acid) and a glycerol molecule. The camphor tree seed kernel oil was the ideal material to produce medium-chain monoglycerides because it is rich in decane acid (54.09%) and dodecanoic acid (39.62%). Compared with the long-chain monoglycerides, the medium-chain monoglycerides has stronger emulsifying ability and better antimicrobial properties. Thus it has a wide range of applications in the field of food, cosmetics, pharmaceutical, mechanical and chemical. At present, medium-chain monoglycerides was prepared in organic solvent system through the synthesis of chemical methods. These methods not only are money-consuming, energy-consuming, reaction conditions-demanding, but with a bit of organic solvent residues in the products, limiting its application in food, pharmaceutical and other high security level field.In this paper, the synthesis of medium-chain monoglycerides was achieved by catalyzing camphor tree seed oil and glycer using lipase in solvent-free micro-water phase. The yield rate of medium-chain monoglyceride was taken as measurement index, and the synthesis conditions and processes for production of medium-chain monoglycerides was optimized based on single factor experiments and orthogonal experiments. The comparative study of the catalytic ability of three kinds of single lipase (lipase form porcine pancreas, lipase from candida antarctica, lipase from aspergillus niger) and composite lipases was used to analyze its impact on the yield rate of medium-chain monoglycerides. TLC was adopted for the analysis of the components in product and for the separation and purification of medium-chain monoglycerides. The chemical structure and composition of the medium-chain monoglycerides in product were analyzed by gas chromatography and mass spectrometry.The results of the preparation of medium-chain monoglycerides from camphor seed kernel oil catalyzed by single lipase showed that in the appearance of lipase from procine pancreas as the catalyst, the optimal conditions for the production of medium-chain monoglycerides were as follows:reaction temperature47℃, enzyme dosage220mg, molar ratio of glycerol to oil4.3:1, initial water dosage35μL, reaction time30h. Under the optimized circumstances, the yield of medium-chain monoglycerides was53.42%±0.05%. In the appearance of lipase form candida antarctica as the catalyst, the suitable conditions were as follows:reaction temperature25℃, enzyme dosage2.2g, molar ratio of glycerol to oil4.0:1, initial water dosage26μL, reaction time47h. Under this circumstance, the yield of medium-chain monoglycerides was36.94%±0.06%. In the appearance of lipase form aspergillus niger as the catalyst, the suitable conditions were as follows: reaction temperature36℃, enzyme dosage1200mg, molar ratio of glycerol to oil4.8:1, initial water dosage34μL, reaction time27h. Under this optimized circumstances, the yield of medium-chain monoglycerides was40.26%±0.04%.The results of the preparation of medium-chain monoglycerides from camphor seed kernel oil catalyzed by the composite lipases showed that in the appearance of lipase from procine pancreas and candida antarctica as the composite catalyst, the suitable conditions were as follows:reaction temperature35℃, enzyme dosage for lipase form porcine pancreas200mg and lipase from candida antarctica125mg, molar ratio of glycerol to oil4.0:1, initial water dosage25μL, reaction time50h. Under the optimized conditions, the yield of medium-chain monoglycerides was52.89%±0.13%. Keep the same reaction conditions, the yield of medium-chain monoglycerides only fluctuated between52.80%and53.25%in the addition of lipase from aspergillus niger. In the appearance of lipases from porcine pancreas and aspergillus niger as the composite catalyst, the suitable conditions were as follows: reaction temperature30℃, enzyme dosage for lipase from porcine pancreas200mg and lipase from aspergillus niger500mg, molar ratio of glycerol to oil4.0:1, initial water dosage30μL, reaction time30h. Under the optimized circumstances, the yield of medium-chain monoglycerides was52.92%±0.29%. Keep the same reaction conditions, the yield of medium-chain monoglycerides reduced from53%±0.17%to51%±0.14%in the addition of the lipase from candida antarctica. In the appearance of lipase from candida antarctica and aspergillus niger as the composite catalyst, the suitable conditions were as follows:reaction temperature35℃, enzyme dosage for lipase from candida antarctica1800mg and lipase from aspergillus niger900mg, molar ratio of glycerol to oil4.0:1, initial water dosage30μL, reaction time25h. Under such conditions, the yield of medium-chain monoglycerides was49.31%±0.06%. Keep the same reaction conditions, the yield of medium-chain monoglycerides increased from50.38%±0.13%to56.80%±0.09%in the addition of the lipase from porcine pancreas.The results of the separation and purification by TLC showed that in the appearance of the single lipase and the composite lipases as the catalyst, the products were mainly camphor tree seed oil and the medium-chain monoglycerides.The comparison of the infrared spectra structure between camphor seed kernel oil and its products showed that the products contained a large area of-OH stretching vibration peak, which was not contained in the camphor tree seed oil. It Showed that the products must contain a large number of the medium-chain monoglycerides. The analysis of medium-chain monoglycerides in products by GC-MS detection showed that the medium-chain monoglycerides mainly consist of decane acid monoglyceride and dodecanoic acid monoglyceride.