Abstract
Palm fatty acid distillate (PFAD) is a residual fatty acids rich-stream obtained in the palm oil refining process. Its potential as raw material for butyl esters syntheses using immobilized lipases (Novozym 435® and Lipozyme RM IM®) in solvent-free system have been explored. A simplified tool for optimizing reaction parameters (Substrate-Enzyme Relation, SER) conciliates the masses of reagents and biocatalysts to obtain valuable insights into the shift of chemical equilibrium and the probability of deleterious effects on immobilized lipases. This mathematical relation had been studied when a single acid and alcohol are involved, but here SER is adopted when a mixture of similar chain-length acids is present in the reaction media. Experimental assays have revealed a range of reaction conditions of molar ratio and biocatalyst loadings equivalent to SER − 42 to − 12, that achieved maximum conversions higher than 90 % using biocatalysts loading lower than 2.0 % (wt/wt of PFAD mass) and less than 10 % of n-butanol stoichiometric excess. Similar SER trends were observed when comparing single reactants conversions results and a mixture of acids (C16–C18) and one alcohol involved, indicating the applicability of SER as optimization tool for enzymatic esterifications using a complex matrix.
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•Butyl esters syntheses may be optimized using a simplified method (SER).•High yields achieved using minimum stoichiometric excess and biocatalyst loading.•SER allows to find optimum condition with reduced number of assays.•SER trends in single reactants esterification are also observed in a mixture of acids.