Towards one-pot consolidated bioprocessing of cellulose to biodiesel: lipase-catalyzed transesterification at cellulose-coated oil-in-water emulsions as micro-reactors

BACKGROUND There is an urgent need for renewable energy sources as alternatives for fossil fuels. A promising alternative is biodiesel. This study is part of an overall objective to convert cellulose from pretreated biomass directly to biodiesel, using cellulose-coated emulsion particles as micro-reactors for a cascade of biochemical reactions in a 'one-pot' consolidated process. RESULTS This study presents a 'proof-of-concept' for the crucial step in this process: the ability of lipase integrated within oil-in-water emulsion particles encapsulated by natural cellulose to catalyze transesterification of encapsulated oil with ethanol dissolved in an aqueous medium. We develop and examine such integrated microparticles for generation of fatty acid ethanol ester (FAEE) by lipase-catalyzed transesterification of castor oil at the particle core-shell interface with aqueous ethanol. The activity of lipase-catalyzed transesterification was studied using NMR quantification of FAEE while various conditions such as oil-to-ethanol molar ratio, lipase concentration and temperature were examined. The highest conversion was obtained for an oil-to-ethanol molar ratio of 1:30 with lipase concentration of 6.42 x 10(-3) wt% at 40 degrees C. CONCLUSIONS It is expected that the results of this study, together with ongoing experiments of ethanol production by integration of cellulose-coated emulsion particles with yeasts and cellulolytic enzymes, as well as further optimization, will provide the complete transformation of cellulose to biodiesel by enzymatic hydrolysis, yeast fermentation and lipase-catalyzed transesterification, in a single emulsion-based consolidated bioprocess. (c) 2022 Society of Chemical Industry (SCI).