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Lignocellulosic biomass has great potential as a low-cost source of fermentable sugar for the production of biofuels and high value organic acids. One potential biomass is oil palm empty fruit bunch, since it has high cellulose and hemicellulose content. However, its lignin content can hinder the access of cellulose and hemicellulose during the hydrolysis process. Therefore, an effective pretreatment for the delignification of lignocellulose biomass should be considered to reduce the lignin content. In this study, delignification of oil palm empty fruit bunch using peracetic acid and alkaline peroxide solution combined with the ultrasound method is investigated as a novel combination method of biomass pretreatment. The effect of pretreatment time was observed by using a peracetic acid solution for 1, 3, 5, 7 and 9 hours, followed by an alkaline peroxide solution for 4, 6, 8 and 10 hours. Based on the results, the best delignification was achieved by pretreatment using peracetic acid pretreatment for 3 hours, followed by alkaline peroxide pretreatment for 10 hours. Both pretreatments were assisted by the ultrasound method. The results show hemicellulose, cellulose and lignin content of 14.13%, 77.27% and 8.6% respectively. The lignin content was reduced by 68.73% and the cellulose content increased by 121.85%, relative to the untreated EFB. This result was considered as the best pretreatment, since the pretreatment time was shorter and high cellulose content together with low lignin content was achieved, which will improve the hydrolysis process.

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Adsorption-crosslinking is one of the immobilization methods to improve the reusability of lipase. It requires amino groups to reduce cross-link immobilization risk so that lipase–support interaction increases and the immobilization is attainable. Also, the amino group on the support is expected to increase lipase performance. This study aimed to analyze the effect of amino group addition on immobilized Aspergillus niger lipase by the adsorption-crosslinking using MP-64 macroporous anion resin and XAD-7HP macroporous nonionic resin that has been treated with chitosan. The chitosan-coated resin was characterized by Fourier transform infrared spectrometry (FTIR) and scanning electron microscope (SEM). Lipase immobilization was carried out by adding 10 ml lipase solution containing 0.75 g resins and shaken at 25°C for 150 rpm. Adsorption was achieved for 4 h, followed by cross-linking separately (adding 0.5% (v/v) glutaraldehyde and re-reacting for 20 min). Lipase activity was measured with the titrimetric of olive oil emulsion; mixed with Aspergillus niger lipase, emulsion, and a buffer solution (pH 6.5, ionic strength of 0.7); and incubated for 30 min at 37°C. The effect of amino-functional groups was investigated based on lipase loading and lipase activity. The best lipase loading and lipase activity of 83.79% and 29.41 U/g support were achieved in the adsorption-crosslinking using MP-64 resin coated with chitosan. After four cycles, biodiesel synthesis was maintained at 70.61% of the initial yield. These results indicated that chitosan as an affordable and readily available source of amino groups could be used to modify support for Aspergillus niger lipase immobilization.

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Cholesterol oxidase, a bio-catalyst that can catabolize cholesterol, has proven applications in medicine. Here, a support material was used to enhance the characteristics of the enzyme. Magnetite (Fe3O4) is widely used as an enzyme support; however, the interaction between the enzyme and the support should be capped with another material, such as chitosan biopolymerbased material. In this study, chitosan-magnetite materials were synthesized by mixing both compounds and activating with glutaraldehyde. The materials were then characterized by Fourier Transform Infrared (FTIR) Spectroscopy. The enzyme kinetic parameters were studied by following the cholesterol oxidation reaction using high-performance liquid chromatography (HPLC) and comparing the results between the free and the immobilized enzyme. The substrate concentration was 2.5 mg/mL. The effect of enzyme concentration was tested using different concentrations of enzyme (0.5, 1, and 2 mg/mL) to determine the best operating conditions. The best conditions for the oxidation reaction were immobilized enzyme at a 2 mg/mL concentration. Enzyme immobilization significantly decreased the optimum substrate concentration to 0.1 mg/mL.

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