title: Comparison of estimation capabilities of response surface methodology (RSM) with artificial neural network (ANN) in lipase-catalyzed synthesis of palm-based wax ester.
abstract: BACKGROUND
  Wax esters are important ingredients in cosmetics, pharmaceuticals, lubricants and other chemical industries due to their excellent wetting property. Since the naturally occurring wax esters are expensive and scarce, these esters can be produced by enzymatic alcoholysis of vegetable oils. In an enzymatic reaction, study on modeling and optimization of the reaction system to increase the efficiency of the process is very important. The classical method of optimization involves varying one parameter at a time that ignores the combined interactions between physicochemical parameters. RSM is one of the most popular techniques used for optimization of chemical and biochemical processes and ANNs are powerful and flexible tools that are well suited to modeling biochemical processes.
  
  
  RESULTS
  The coefficient of determination (R2) and absolute average deviation (AAD) values between the actual and estimated responses were determined as 1 and 0.002844 for ANN training set, 0.994122 and 1.289405 for ANN test set, and 0.999619 and 0.0256 for RSM training set respectively. The predicted optimum condition was: reaction time 7.38 h, temperature 53.9 degrees C, amount of enzyme 0.149 g, and substrate molar ratio 1:3.41. The actual experimental percentage yield was 84.6% at optimum condition, which compared well to the maximum predicted value by ANN (83.9%) and RSM (85.4%). The order of effective parameters on wax ester percentage yield were; respectively, time with 33.69%, temperature with 30.68%, amount of enzyme with 18.78% and substrate molar ratio with 16.85%, whereas R2 and AAD were determined as 0.99998696 and 1.377 for ANN, and 0.99991515 and 3.131 for RSM respectively.
  
  
  CONCLUSIONS
  Though both models provided good quality predictions in this study, yet the ANN showed a clear superiority over RSM for both data fitting and estimation capabilities.
authors.affiliation: Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia. mahiran@science.upm.edu.my
authors.forename: Mahiran
authors.initials: M
authors.lastname: Basri
authors.forename: Raja Noor Zaliha Raja Abd
authors.initials: RN
authors.lastname: Rahman
authors.forename: Afshin
authors.initials: A
authors.lastname: Ebrahimpour
authors.forename: Abu Bakar
authors.initials: AB
authors.lastname: Salleh
authors.forename: Erin Ryantin
authors.initials: ER
authors.lastname: Gunawan
authors.forename: Mohd Basyaruddin Abd
authors.initials: MB
authors.lastname: Rahman
mesh_terms: D000465:Algorithms; D002384:Catalysis; D004952:Esters / Q000138:chemical synthesis; D008049:Lipase / Q000378:metabolism*; D016571:Neural Networks, Computer; D000073878:Palm Oil; D010938:Plant Oils / Q000737:chemistry; D013696:Temperature; D014885:Waxes / Q000737:chemistry* / Q000378:metabolism
chemical_list: D004952:Esters; D010938:Plant Oils; D014885:Waxes; D000073878:Palm Oil; D008049:Lipase