title: Production of biodiesel from vegetable oil and microalgae by fatty acid extraction and enzymatic esterification.
abstract: The aim of this work was to obtain biodiesel (methyl esters) from the saponifiable lipids (SLs) fraction of the microalga Nannochloropsis gaditana, whose biomass dry weight contains 12.1 wt% of these lipids. SLs were extracted from the microalga as free fatty acids (FFAs) for subsequent transformation to methyl esters (biodiesel) by enzymatic esterification. Extraction as FFAs rather than as SLs allows them to be obtained with higher purity. Microalgal FFAs were obtained by direct saponification of lipids in the biomass and subsequent extraction-purification with hexane. Esterification of FFAs with methanol was catalysed by lipase Novozym 435 from Candida antarctica. Stability studies of this lipase in the operational conditions showed that the esterification degree (ED) attained with the same batch of lipase remained constant over six reaction cycles (36 h total reaction time). The optimal conditions attained for 4 g of FFAs were 25°C, 200 rpm, methanol/FFA molar ratio of 1.5:1, Novozym 435/FFA ratio of 0.025:1 w/w and 4 h reaction time. In these conditions the ED attained was 92.6%, producing a biodiesel with 83 wt% purity from microalgal FFAs. Several experimental scales were tested (from 4 to 40 g FFAs), and in all cases similar EDs were obtained.
authors.affiliation: Area of Chemical Engineering, University of Almería, 04120, Almería, Spain. Electronic address: clb450@ual.es.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Castillo López
authors.affiliation: Area of Chemical Engineering, University of Almería, 04120, Almería, Spain. Electronic address: lesteban@ual.es.
authors.forename: Luis
authors.initials: L
authors.lastname: Esteban Cerdán
authors.affiliation: Area of Chemical Engineering, University of Almería, 04120, Almería, Spain. Electronic address: arobles@ual.es.
authors.forename: Alfonso
authors.initials: A
authors.lastname: Robles Medina
authors.affiliation: Area of Chemical Engineering, University of Almería, 04120, Almería, Spain. Electronic address: nle877@ual.es.
authors.forename: Elvira
authors.initials: E
authors.lastname: Navarro López
authors.affiliation: Area of Chemical Engineering, University of Almería, 04120, Almería, Spain. Electronic address: mvl200@ual.es.
authors.forename: Lorena
authors.initials: L
authors.lastname: Martín Valverde
authors.affiliation: Area of Chemical Engineering, University of Almería, 04120, Almería, Spain. Electronic address: estrella@ual.es.
authors.forename: Estrella
authors.initials: E
authors.lastname: Hita Peña
authors.affiliation: Area of Chemical Engineering, University of Almería, 04120, Almería, Spain. Electronic address: pagonza@ual.es.
authors.forename: Pedro A
authors.initials: PA
authors.lastname: González Moreno
authors.affiliation: Area of Chemical Engineering, University of Almería, 04120, Almería, Spain. Electronic address: emolina@ual.es.
authors.forename: Emilio
authors.initials: E
authors.lastname: Molina Grima
mesh_terms: D055162:Biocatalysis; D056804:Biofuels / Q000032:analysis / Q000600:supply & distribution*; D018533:Biomass; D002175:Candida / Q000201:enzymology; D002384:Catalysis; D004795:Enzyme Stability; D004800:Enzymes, Immobilized; D004951:Esterification; D004952:Esters / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000302:isolation & purification* / Q000378:metabolism*; D005656:Fungal Proteins; D006586:Hexanes / Q000737:chemistry; D008049:Lipase / Q000378:metabolism*; D050356:Lipid Metabolism; D000432:Methanol / Q000737:chemistry; D058086:Microalgae / Q000737:chemistry / Q000378:metabolism*; D010938:Plant Oils / Q000737:chemistry / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors
chemical_list: D056804:Biofuels; D004800:Enzymes, Immobilized; D004952:Esters; D005230:Fatty Acids, Nonesterified; D005656:Fungal Proteins; D006586:Hexanes; D010938:Plant Oils; C026385:n-hexane; C093667:Novozyme 435; D008049:Lipase; D000432:Methanol
keywords: Biodiesel; Free fatty acid; Lipase; Microalga; Nannochloropsis gaditana; Novozym 435; Used vegetable oil