Microwave-assisted enzymatic synthesis of beef tallow biodiesel

Abstract

Optimal conditions for the microwave-assisted enzymatic synthesis of biodiesel have been developed by a full 2² factorial design leading to a set of seven runs with different combinations of molar ratio and temperature. The main goal was to reduce the reaction time preliminarily established by a process of conventional heating. Reactions yielding biodiesel, in which beef tallow and ethanol used as raw materials were catalyzed by lipase from Burkholderia cepacia immobilized on silica-PVA and microwave irradiations within the range of 8-15 W were performed to reach the reaction temperature. Under optimized conditions (1:6 molar ratio of beef tallow to ethanol molar ratio at 50°C) almost total conversion of the fatty acid presented in the original beef tallow was converted into ethyl esters in a reaction that required 8 h, i.e., a productivity of about 92 mg ethyl esters g⁻¹ h⁻¹. This represents an increase of sixfold for the process carried out under conventional heating. In general, the process promises low energy demand and higher biodiesel productivity. The microwave assistance speeds up the enzyme catalyzed reactions, decreases the destructive effects on the enzyme of the operational conditions such as, higher temperature, stability, and specificity to its substrate, and allows the entire reaction medium to be heated uniformly.

Selection of Lipases for the Synthesis of Biodiesel from Jatropha Oil and the Potential of Microwave Irradiation to Enhance the Reaction Rate

“…In the reaction medium, ethanol is a good microwave radiation absorption material [28], which would destroy the two-tier structure of the interface between ethanol and oil, making the functional groups much more highly reactive [56]. Microwave irradiation can also induce conformation changes in the lipase structure that facilitates the access of substrate molecules to the active sites and, consequently, the enzyme behaves slightly differently and may become more active [27]. …”

“…Moreover, experiments were also carried out to determine the feasibility of using nonconventional heating systems such as microwave irradiation. Microwave, a nonionizing radiation has been explored in recent years as an alternative heating system in many areas, including the enzymatic biodiesel synthesis [27–29]. Microwave heating involves directed absorption of energy by functional groups that bear ionic conductivity or a dipole rotational effect, and this energy is then released into the surrounding solution [28].…”

Use of ionic liquids as additives for the immobilization of lipase from Bacillus sp.

“…This procedure was repeated for 20 cycles. The biocatalyst half‐life time (t 1/2 ) was determined by applying the inverted linear decay model …”

Jatropha Oil Transesterification and Byproducts

“…However, the application of microwave radiation does not turn the use of catalysts obsolete. Catalysts under microwaves may be acidic, alkaline, or enzymatic, in homogeneous or heterogeneous media (Yuan et al 2009 ;Barnard et al 2007 ;Da Ros et al 2011 ;Liao and Chung 2011 ) . Besides a considerable reduction in reaction time, the use of microwaves brings about bene fi ts, such as reduced energy consumption and simpler process of bio diesel puri fi cation.…”