The Synthesis of Polyethersulfone (PES) Derivatives for the Immobilization of Lipase Enzyme

• Main Author: RAHMAHWATI (NIM : 10512036), NURLAELA
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/29803
• Institution: Institut Teknologi Bandung

<p align="justify">One of the crucial problems in Indonesian and the world is problem of energy caused by the energy production which is lower than the energy consumption. Therefore, since then it began the development of the alternative renewable energy. Because of the high availability of vegetable oil sources in Indonesia, therefore the development of biodiesel production as an alternative renewable energy is a versatile prospect. Biodiesel is a mixture of alkyl esters with long chain fatty acids produced by transesterification reaction between oil and alcohol. The use of enzymes as biocatalysts in this reaction has limitations in its reusability; therefore the reusability of enzymes can be improved by the enzymes immobilization process onto the appropriate solid support. One of solid support that potential for the enzymes immobilization process is polyethersulfone (PES). However, modifications of PES have to be performed to increase the hydrofilicity of the polymer. Polyethersulfone has been synthesized utilizing microwave-assisted reaction method (400 W, 170 oC, 60 minutes). The synthesized PES was confirmed by the appearance of characteristic peak in its FTIR spectrum corresponded to C-O-C vibration at wavenumber of 1235.8 cm-1. Relative molecular weight of the synthesized PES was found to be 1.3x106 Da (by microwave method) and 1.89x107 Da (by reflux method) based on the Ostwald viscometry method determination. The sulfonation of PES was conducted utilizing reflux method by reacting PES with the mixtures of H2SO4 (0 oC, +- 1 hour) : ClSO3H (82 oC, 30 minutes) in ratio of 2:1 (v/v). The results of the analysis of FTIR and 1H NMR spectra, as well as the determination of the degree of sulfonation using acid-base titration showed the conversion of sulfonation reaction was low because of the difficulty in substituting sulfone groups to the aromatic rings of PES. Nitration reaction was performed by refluxing PES and the mixtures of H2SO4 (0 oC, +- 30 minutes) and HNO3 (25 oC, 4 hours). The nitration product of PES (PES-NO2) was confirmed by the appearance of characteristic peak of -NO2 vibration in its FTIR spectrum at wavenumber of 1537 cm-1. The -NO2 groups of the synthesized PES-NO2 was subsequently reduced to be PES-NH2 using SnCl2.2H2O as reductor by reflux method (60 oC, +- 3 hours). The structure of PES-NH2 was confirmed by the appearance of characteristic peak of -NH2 vibration in its FTIR spectrum at wavenumber of 3358 cm-1. Candida Antarctica lipase was successfully immobilized onto the synthesized PES and its derivatives, which were confirmed by analyzing its FTIR spectra and by its activity tests in hydrolyzing p-nitrophenol palmitate into p-nitrophenol. The supernatant activity test results showed that the percent conversion of p-nitrophenol palmitate to become p-nitrophenol were 20.6% (free enzyme), 18.9% (supernatant of PES-enzyme), 5.4% (supernatant of PES-SO2Cl-enzyme), 3.7% (supernatant of PES-NH2-enzyme). The decrease in the supernatant enzyme activity showed that the enzyme has been successfully immobilized, however the absence of amide groups vibration in FTIR spectra showed only the physical adsorption of enzyme onto the synthesized polymers.<p align="justify">