Improved synthesis of medium chain triacylglycerol catalyzed by lipase based on use of supercritical carbon dioxide pretreatment

The esterification reaction of glycerol and caprylic acid catalyzed by immobilized lipase has been investigated in the present work quantifying the intensification benefits based on the use of supercritical carbon dioxide pretreatment. Factors influencing the progress of enzymatic reaction such as the pretreatment conditions, reaction time, reaction temperature, molar ratio of the two reactants, type of enzyme and its loading were varied to establish the effect on the progress of reaction. Optimum conditions for pretreatment using supercritical CO2 were established as time of 1 h, pressure of 100 bars and temperature of 50 degrees C. Use of pretreatment under optimized conditions resulted in a conversion of free fatty acids to tricaprylin as 97.3% in 6 h of reaction time at 50 degrees C and molar ratio of 4:1 (caprylic acid: glycerol), which was three times higher as compared to the conventional approach (without any pretreatment) performed under same conditions. Two types of immobilized biocatalysts as Novozyme 435 and Lipozyme RM were used and it was established that Novozyme 435 showed better catalytic activity as compared to Lipozyme RM, though importantly both were active even in the presence of supercritical carbon dioxide used as pretreatment. Reuse of both the enzymes up to 15 cycles with supercritical carbon dioxide pretreatment did not affect the activity significantly. The quality analysis of the synthesized product was performed using various physiochemical tests based on the determination of acid value and peroxide value. Overall, it has been established that use of supercritical carbon dioxide pretreatment was more efficient and enhanced the rate of synthesis of tricaprylin significantly as compared to conventional approach. Understanding into effect of reaction and pretreatment parameters also enabled in maximizing the intensification benefits.