Effect of several factors on soluble lipase-mediated biodiesel preparation in the biphasic aqueous-oil systems

Abstract

Biodiesel is increasingly perceived as an important component of solutions to the important current issues of fossil fuel shortages and environmental pollution. Utilization of soluble lipase offers an alternative approach to lipase-catalyzed biodiesel production using immobilized enzyme or whole-cell catalysis. Soluble lipase NS81020, produced by submerged fermentation of genetically modified Aspergillus oryzae microorganism, was first proposed here as the catalyst of biodiesel preparation with oleic acid in the biphasic aqueous-oil systems. The effect factors such as enzyme concentration, water content, temperature, molar ratio of methanol to oil, stirring rate and pH of buffer solution on the esterification rate were investigated systematically. The reaction time could be shortened with the increasing of enzyme concentration as long as the maximum enzyme absorptive capacity on the interface in the biphasic aqueous-oil systems was not achieved. The optimal water content in the biphasic aqueous-oil systems was 10 wt% by oleic acid weight. The reaction rate was enhanced with the increasing molar ratio of methanol to oil, the increasing stirring rate or the decreasing temperature. Although soluble lipase NS81020 had lower activity at pH 10.55, hydroxyl ion conduced to restrain hydrolysis of methyl ester and facilitated the reaction toward the methyl ester formation.

Kinetic study on free lipase NS81006-catalyzed biodiesel production from soybean oil

“…6 and the simulated parameters for rate constant VEs and equilibrium constant K I are 90.7755 L/(mol.min) and 3.9087 respectively. Compared with other equilibrium constants shown in Table 2, the inhibitory constant of methanol are relative higher, which confirmed that the inhibitory effect of methanol existed in the reaction and this was consistent with many literatures [26][27][28].…”

“…4 was used to describe the esterification process of FFA. Meanwhile, it's also very important to incorporate the effect of methanol into the model since the presence of methanol in the reaction system may involve in the inactivation of enzyme [26,27]. Thereby, the inhibitory effect of methanol was also considered.…”

Combination of two lipases more efficiently catalyzes methanolysis of soybean oil for biodiesel production in aqueous medium

“…The result proved that alkaline pH was preferable for transesterification reaction. The same conclusion was also reported by Chen and Zhao separately [24,25]. The speculation was that hydroxyl ion depressed hydrolysis of FAMEs resulting in higher biodiesel conversion [24].…”

Current status and new developments of biodiesel production using fungal lipases

“…However, although free enzymes are significantly cheaper than immobilized lipases, in many cases they have poor operational stability and can only be used once, as they are inactivated [14]. There are a few reports available on soluble lipase-catalyzed biodiesel production [24,25], including the methanolysis of low cost crude soybean oil using Callera Trans L (lipase from T. lanuginosus) [26]. In order to prevent the addition of water to the reaction medium, the solution containing the free lipase can be freeze-dried.…”