title: Biodiesel Production from Citrillus colocynthis Oil Using Enzymatic Based Catalytic Reaction and Characterization Studies.
abstract: BACKGROUND
  Biodiesel is a green fuel consisting of long chain fatty acid monoalkyl esters, which can be blended with diesel or used alone which is usually produced from vegetable oils/fats by either lipasecatalyzed transesterification. In this investigation, an enzyme (Novozym 435) catalyzed process was optimized to prepare methyl esters from crude Citrullus colocynthis oil (CCO) by transesterification of CCO with methanol. However, as per our knowledge, lipase-catalyzed transesterification have not been used for biodiesel production from Citrullus colocynthis.
  
  
  OBJECTIVE
  The purpose of this work was to transesterify the CCO in the presence of Candida antarctica lipase as catalyst and methanol. Additionally, the physicochemical parameters/fuel properties of the Citrullus colocynthis methyl ester (CCME) were assessed and compared.
  
  
  METHODS
  Lipase-catalyzed reactions were carried out in three necked flask (50 mL) attached with reflux condenser and thermometer, immersed in oil bath at constant stirring speed (400 rpm). The reaction mixture was consisted of CCO and varying the calculated amount of methanol, tert-butyl alcohol, and Novozym 435. The experimental parameters reaction time, methanol/oil molar ratio, reaction temperature, tert-butanol content, Novozym 435 content and water content were optimized for the transesterification reaction. The CCME yield was measured using gas chromatograph. The fuel properties of the produced CCME were determined as per American Society for Testing and Materials (ASTM) and European (EN) biodiesel standard methods.
  
  
  RESULTS
  In this study, an enzymatic catalyst was employed to synthesize the CCME from CCO via transesterification. Several variables affecting the CCME yield were optimized as lipase quantity (4%), water content (0.5%), methanol/oil molar ratio (5:1), reaction temperature (43 °C), reaction medium composition (80% tertbutanol/ oil), and reaction time (3.7 h). A CCME yield of 97.8% was achieved using enzyme catalyzed transesterification of CCO under optimal conditions. The significant biodiesel fuel properties of CCME, i.e. cloud point (0.70 °C); cetane number (49.07); kinematic viscosity (2.27 mm2/s); flash point (143 °C); sulfur content (2 ppm) density (880 kg/m3) and acid value (0.076 mg KOH/g) were appraised. CCME also exhibited long-term storage stability (4.80 h) and all the biodiesel fuel properties were within the range of standards (ASTM D6751 and EN 14214).
  
  
  CONCLUSIONS
  The lipase-catalyzed transesterification produced better conversion than the base-catalyzed reaction. The fuel properties of CCME were within the limits of the ASTM D6751 and EN14214 standards. Furthermore, CCME showed good oxidative stability and a long shelf life due its high natural antioxidant content. CCME showed better fuel properties and long-term storage stability due to which it can be used as a potential alternative fuel.
authors.affiliation: Chemistry Department, College of Science, King Saud University, 1145 Riyadh, Saudi Arabia.|UR Physico-Chimie des Materiaux Solides, Chemistry Department, Science College, Tunis El Manar University, 2092 Tunis, Tunisia.
authors.forename: Imededdine Arbi
authors.initials: IA
authors.lastname: Nehdi
authors.affiliation: Chemistry Department, College of Science, King Saud University, 1145 Riyadh, Saudi Arabia.
authors.forename: Hassen Mohamed
authors.initials: HM
authors.lastname: Sbihi
authors.affiliation: Chemical Engineering Department, College of Engineering, King Saud University, 1145 Riyadh, Saudi Arabia.
authors.forename: Lahssen El
authors.initials: LE
authors.lastname: Blidi
authors.affiliation: Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
authors.forename: Umer
authors.initials: U
authors.lastname: Rashid
authors.affiliation: Department of Food Technology, Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
authors.forename: Chin Ping
authors.initials: CP
authors.lastname: Tan
authors.affiliation: Chemistry Department, College of Science, King Saud University, 1145 Riyadh, Saudi Arabia.
authors.forename: Saud Ibrahim
authors.initials: SI
authors.lastname: Al-Resayes
mesh_terms: D056804:Biofuels; D002384:Catalysis; D065986:Citrullus colocynthis / Q000737:chemistry*; D004800:Enzymes, Immobilized; D004951:Esterification; D004952:Esters / Q000737:chemistry; D005227:Fatty Acids / Q000737:chemistry; D005656:Fungal Proteins; D008049:Lipase / Q000737:chemistry*; D010084:Oxidation-Reduction; D010938:Plant Oils / Q000737:chemistry*
chemical_list: D056804:Biofuels; D004800:Enzymes, Immobilized; D004952:Esters; D005227:Fatty Acids; D005656:Fungal Proteins; D010938:Plant Oils; C093667:Novozyme 435; D008049:Lipase
keywords: Citrillus colocyhnthis oil; biodiesel; enzyme catalyst; methyl esters; oxidative stability; transesterification.