Date of Award
Program or Major
Doctor of Philosophy
P T Vasudevan
Diminishing petroleum reserves and increasing environmental awareness has led to an urgent need to develop alternative fuels, such as biodiesel. However, the conventional method to produce biodiesel uses environmentally harmful chemical catalysts. A relatively new development in the production of biodiesel is through enzymatic trans/- esterification with a lipase catalyst. Despite several advantages, there are a few technical and economical obstacles that limit this process: (1) immiscibility of the hydrophilic methanol and hydrophobic triglyceride which results in the formation of an interface leading to mass transfer resistance, (2) insufficient availability of large quantities of inexpensive lipase suitable for catalysis, and (3) stripping of essential water from the active site by the strong polarity of methanol causing a reduction in enzyme activity after multiple reuses. Each obstacle is addressed by:
· Examining the effect of 15 organic solvents on activity of lipase from three sources, namely Candida antarctica, Pseudomonas cepacia, and Thermomyces lanuginosus, in the trans/-esterification of used vegetable oil with the goal of recommending the best solvent through solvent engineering. · Cloning and over-expressing recombinant lipase from T lanuginosus in tobacco for the enzymatic production of biodiesel in order to develop an abundant inexpensive biocatalyst. · Investigating the effects of reaction parameters on the trans/-esterification of used vegetable oil and their effects on enzymatic activity over consecutive reactions with a view to lowering costs.
The major findings are: (i) there appears to be a correlation between the solvent's hydrophobicity (log P) and biodiesel yield, (ii) the choice of lipase can have a considerable effect on the reaction kinetics and biodiesel yield, (iii) a thermophilic fungus lipase gene can be constitutively expressed in tobacco without adversely affecting plant growth or development, (iv) plants systems offer a promising platform for producing recombinant enzymes for biodiesel production, (v) the type of methanol addition does not appear to greatly affect the biodiesel yield when fresh enzyme is used, but does significantly affect the enzyme's activity during subsequent reuse, and (vi) optimization of reaction parameters such as methanol addition, reaction temperature, and solvent can minimize enzymatic deactivation and increase enzyme reusability without significantly affecting biodiesel yield.
Gagnon, Michael Dore, "Engineering lipases and solvents for trans/-esterification of used vegetable oils" (2013). Doctoral Dissertations. 731.