The Enzymatic Conversion of Brown Grease to Biodiesel in a Solvent-free Medium

Brown grease was used in this study on the conversion to biodiesel fatty acid methyl ester (FAME) by a two-stage reaction comprising esterification and transesterification using Novozym 435 in a solvent-free medium. The effects of methanol amounts and enzyme concentration on the first-stage reaction, and the operational stability of Novozym 435 in the two-stage reaction were investigated. The addition of biodiesel into the reaction system prior to two-stage reaction prevented the lipase from deactivation caused by excess amounts of methanol. Contents of >95 wt% FAME could be achieved even after 15 cycle reactions.