Date of this Version
Schwartz, Cory M. "Development and Utilization of a Pair of Sol-Gel Entrapped Lipases for Biodiesel Production from High Free Fatty Acid Oils." MS thesis. University of Nebraska-Lincoln, 2014.
Biodiesel, which consists of fatty acid alkyl esters, is one of the most widely adopted and successful renewable fuels. Traditional physiochemical biodiesel production methods require high cost refined feedstocks, and so alternative methods of catalysis and feedstocks have been explored. This research investigated the use of polysiloxane entrapped lipases to catalyze the production of biodiesel from low cost feedstocks.
In this work, lipase from Burkholderia cepacia (lipase PS) and lipase B from Candida antarctica (CalB) were separately entrapped using sol-gel chemistry. Optimal reaction conditions for the esterification of free fatty acids by immobilized CalB with methanol were determined. Immobilized CalB and lipase PS were then used separately and in combination on a variety of model and real substrates, to assess their suitability as catalysts for biodiesel production, with yields of 97.2 wt.% fatty acid methyl esters (FAME) from a 50% free fatty acid (FFA) model substrate after a 24 h reaction time and 94.5 wt.% FAME from yellow grease. The stability of the pair of lipases over multiple uses was then examined, and the lipases were found to retain over 95% of their activity over 10 cycles of 6 h reactions.
Experiments were conducted to compare the efficacy of the lipases when ethanol replaced methanol as the acyl acceptor for the esterification and transesterification reactions, as biodiesel from ethanol has superior fuel characteristics and lower environmental impact. Reactions utilizing ethanol showed similar results to methanol reactions, but with slower reaction rates. The toxicity of methanol and ethanol to each lipase’s activity was examined, and it was found that methanol caused a loss of over 90% of lipase activity to both the lipase PS and CalB when incubated for 6 h, while ethanol caused less than 50% activity loss in both cases.
Adviser: Hossein Noureddini