Enzyme-Catalyzed Synthesis and Kinetics of Ultrasonic-Assisted Methanolysis of Waste Choice White Grease for Fatty Acid Methyl Ester Production

Abstract

In this study, the effects of ultrasonic parameters (amplitude, cycle, and pulse) and major reaction factors (molar ratio and enzyme concentration) on the reaction kinetics of fatty acid methyl ester (FAME) generation from waste choice white grease (CWG) biocatalyzed by immobilized lipase [Candida antarctica lipase B (CALB)] were investigated. A yield of 98.2% was attained in 20 min at an ultrasonic amplitude (40%) at 5 kHz, fat/methanol molar ratio (1:4), and catalyst level of 6% (wt/wt of fat). The effect of ultrasonic mixing on the reaction kinetic of enzymatic transesterification was investigated using a Ping Pong Bi Bi kinetic model approach. Kinetic constants of the transesterification reaction were determined at different ultrasonic amplitudes (30, 35, 40, 45, and 50%) and enzyme concentrations (4, 6, and 8 wt % of fat) at a constant molar ratio (fat/methanol) of 1:6 and ultrasonic cycle of 5 kHz. The fitted curves of the kinetic mechanism showed a sigmoidal curve as a result of mass-transfer limitations, which controlled the process at the beginning of the reaction. The kinetic model results also revealed interesting features of ultrasound-assisted enzyme-catalyzed transesterification. The kinetic model approach described the whole methanolysis process accurately. At the ultrasonic amplitude of 40%, the reaction activities within the system seemed to have steadied after 20 min, which means that the reaction could proceed with or without ultrasonic mixing.

Ultrasonic Assisted Enzymatic Transesterification for Biodiesel Production

“…As can be observed in several studies, the frequency that has been applied does not exceed more than 50 kHz. As reported by Adewale et al, 12,51,53 the lowest frequency of 5 kHz gave an almost complete conversion of biodiesel. The study indicates that the frequencies of ultrasonics influence the dissemination of energy for mixing of the reaction medium.…”

“…The findings indicate that the time for biodiesel enzymatic transesterification can be shortened with application of the ultrasonic system. The shortest reaction time recorded is 20 min by Adewale et al. , However, a suitable ultrasonic system must be tuned so that the optimum yield of biodiesel can be obtained without disturbing the activity and stability of the enzyme. A suitable parameter for ultrasonics implemented in enzymatic transesterification is less than 100 kHz for frequency and not more than 50% for amplitude.…”

“…It was claimed that the molar ratio of oil to methanol was 1:4 for conventional way, while 1:3 was favored under the ultrasonic-assisted medium reaction. Adewale et al have recorded that the optimum molar ratio under the ultrasonic system was 1:4 oil to methanol and the yield was 98.2% biodiesel in 20 min. A similar amount of alcohol recorded in a study by Kumar et al was 1:4 oil to methanol needed to produce 84.5% biodiesel.…”

Production and characterization of biodiesel from canola oil through enzymatic transesterification

“…Besides, the formation of di-and monoacylglycerides is not considered since they are intermediate products, making the overall reaction simpler towards the generation of fatty acid methyl ester as the main products [26]. In the context of this reaction, canola oil (CO) as the triglyceride and methanol (M) will act as the substrates.…”

Enzyme-Catalyzed Production of Biodiesel as Alternative to Chemical- Catalyzed Processes: Advantages and Constraints

“…The studies has been mainly performed with commercial lipases (Novozym 435, Lipozyme RM IM) using methanol or ethanol as acyl acceptor, with conversions higher than 75 %, in solvent-free or in solvent media [239]. The production of FAMEs from waste grease using C. antarctica B lipase as biocatalyst in an ultrasound system, reached a yield of 98.2 % after 20 min reaction time [240]. The synthesis of biodiesel from sunflower using Lipozyme TL-addition, the reaction was favoured when the stoichiometric relation oil:methanol of 1:3 was used [241].…”