Abstract
Novozym® 435, an immobilized lipase from Candida antarctica B. (CALB), was used as a biocatalyst for the synthesis of high purity medium chain diacylglycerol (MCD) in a bubble column reactor. In this work, the properties of the MCD produced were characterized followed by determining its practical application as an emulsifier in water-in-oil (W/O) emulsion. Two types of MCDs, namely, dicaprylin (C8-DAG) and dicaprin (C10-DAG), were prepared through enzymatic esterification using the following conditions: 5% Novozym® 435, 2.5% deionized water, 60°C for 30 min followed by purification. A single-step molecular distillation (MD) (100–140°C, 0.1 Pa, 300 rpm) was performed and comparison was made to that of a double-step purification with MD followed by silica gel column chromatography technique (MD + SGCC). Crude C8-DAG and C10-DAG with DAG concentration of 41 and 44%, respectively, were obtained via the immobilized enzyme catalyzing reaction. Post-purification via MD, the concentrations of C8-DAG and C10-DAG were increased to 80 and 83%, respectively. Both MCDs had purity of 99% after the MD + SGCC purification step. Although Novozym® 435 is a non-specific lipase, higher ratios of 1,3-DAG to 1,2-DAG were acquired. Via MD, the ratios of 1,3-DAG to 1,2-DAG in C8-DAG and C10-DAG were 5.8:1 and 7.3:1, respectively. MCDs that were purified using MD + SGCC were found to contain 1,3-DAG to 1,2-DAG ratios of 8.8:1 and 9.8:1 in C8-DAG and C10-DAG, respectively. The crystallization and melting peaks were shifted to higher temperature regions as the purity of the MCD was increased. Dense needle-like crystals were observed in MCDs with high purities. Addition of 5% C8-DAG and C10-DAG as emulsifier together in the presence of 9% of hydrogenated soybean oil produced stable W/O emulsion with particle size of 18 and 10 μm, respectively.
Highlights
Diacylglycerol (DAG) is made up of two fatty acids esterified to a glycerol backbone
It can be proposed that the higher DAG yield acquired under short reaction time in this work was ascribed to the usage of a bubble column reactor (BCR) which was more suitable for esterification processes compared to the stirred tank reactor due to the viscous nature of the substrate mixture
In this work, immobilized lipase Novozym R 435 was successfully employed to catalyze the esterification between glycerol and fatty acids to produce C8-DAG (41%) and C10-DAG (44%) in a bubble column reactor during a short period of time (30 min)
Summary
Diacylglycerol (DAG) is made up of two fatty acids esterified to a glycerol backbone. 70% of the DAG exists in the form of 1,3-DAG while 1,2-DAG mainly occurs as intermediates from metabolism (Wang et al, 2010) These two isomers differ in terms of the binding positions of the fatty acid acyl groups and hydroxyl groups on the glycerol skeleton and among these isomers, 1,3-DAG is more thermodynamically stable. Chemical method is often being employed in the industry, this process involves the use of high reaction temperatures at 220–260◦C. This is a major drawback as it causes degradation of the thermosensitive polyunsaturated fatty acids, lipid oxidation, and development of undesirable odor, rancidity and color change in the end product. Synthesis of DAG through the enzymatic pathway has started to gain popularity for its mild reaction temperatures and low energy consumption (Liu et al, 2016)
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