Abstract
By using pig pancreatic lipase (EC 3.1.1.3 or PPL) as a biocatalyst, covalently immobilized on amorphous AlPO4 support, a new second generation biodiesel was obtained in the transesterification reaction of sunflower oil with ethanol. The resulting biofuel is composed of fatty acid ethyl esters and monoglycerides (FAEE/MG) blended in a 2:1 molar ratio. This novel product, which integrates glycerol as monoacylglycerols (MG) into the biofuels composition, has similar physicochemical properties as conventional biodiesel and also avoids the removal step of the by-product by washing of the biodiesel with water. Immobilization of PPL was achieved by covalent attachment of the ε-amino group of the lysine residues of PPL with the aldehyde groups of p-hydroxybenzaldehyde linked on a hybrid organic-inorganic functionalized AlPO4 surface. With this procedure, the PPL biocatalyst was strongly fixed to the inorganic support surface (94.3%). Nevertheless, the efficiency of the immobilized enzyme was relatively lower compared to that of the free PPL, but it showed a remarkable stability as well as a great capacity of reutilization (25 reuses) without a significant loss of its initial catalytic activity. Therefore, this enzymatic method allows the production of a biodiesel which integrates the glycerol, allows a more efficient fabrication method and minimizes the waste production as compared to the conventional alkali-catalyzed process.
Highlights
It is well known that transport is almost totally dependent on fossil resources, petroleum-based fuels such as gasoline, diesel, liquefied petroleum gas and compressed natural gas
Since the retention times of different derivatives of fatty acids are considered very closely related to the physico-chemical properties of these compounds, the great similarity of RT values obtained is a clear demonstration of the similarity among the rheological properties of different MG with their corresponding FAME or Fatty Acid Ethyl Esters (FAEE), which are crucial to allow its use as a fuel capable to substitute for petroleum products
The efficiency of pig pancreatic lipase (PPL) is remarkably reduced in the production of a conventional biodiesel
Summary
It is well known that transport is almost totally dependent on fossil resources, petroleum-based fuels such as gasoline, diesel, liquefied petroleum gas and compressed natural gas. Obtained through the 1,3-selective partial ethanolysis of the triglycerides with PPL, is a mixture of two parts of FAEE and one part of MG, that integrates the glycerol as a soluble derivative product (MG) in the diesel fuel, but unlike these methods, no specific reagent (such as dimethyl carbonate or methyl acetate) more expensive than methanol (or ethanol) are used This strategy is based on obtaining an incomplete alcoholysis by application of 1,3-selective lipases, so that the glycerol remains in the form of monoglyceride which avoids the production of glycerol as a by-product, reducing the environmental impact of the process. This amorphous material, tailored by a controlled sol-gel method that allows us to obtain a high surface area as well as a high number of surface -OH groups, is a very adequate support component for the covalent attachment of enzymes, according to the results obtained in the immobilization of lipases, phosphatase and GOD enzymes [48,49,50,51,52,53] as well as homogeneous organometallic complex [54,55]
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