The adsorption kinetics of cellulase and xylanase immobilized on magnetically separable, hierarchically ordered mesocellular mesoporous silica (M-HMMS) was investigated. The adsorption of cellulase on M-HMMS followed pseudo-secondorder kinetics while the xylanase adsorption followed the Avrami model. Intraparticle and film diffusion also affected this process. These results enable in-depth knowledge of the cellulase and xylanase adsorption mechanisms on M-HMMS for better future applications by improving the stability of the immobilization.

Cross-linked enzyme aggregate is a promising strategy among other enzyme immobilization technologies such as solid matrix linking and gel entrapping. Despite of having the advantage of being reused, cross-linked enzyme aggregate (CLEA) also offers greater stability during operation and storage. Preparation of CLEA involves two steps which are precipitation and cross-linking of the enzymes. The purpose of this study is to find the best precipitant for cross-linked enzyme aggregate of cellulase and xylanase. The tested precipitants were acetone, ammonium sulphate, dimethoxyethane (DME), n-propanol, polyethyleneglycol (PEG), and tert-butanol. The enzymes were precipitated and cross-linked using glutaraldehyde. The enzyme activities were determined through DNS method and the relative activities for resulted CLEA were compared. It was found that PEG was the best precipitant for CLEA-cellulase while DME, ammonium sulphate and tert-butanol contributed the highest activity retention for CLEA-cellulase-xylanase under cellulase and xylanase assay, and CLEA-xylanase, respectively.

Magnetically-separable enzyme system has been developed by adsorption, precipitation and cross-linking of enzymes in superparamagnetic hierarchically ordered mesoporous mesocellular silica (M-HMMS). The immobilization of xylanase within M-HMMS were compared between enzyme adsorption (EA), enzyme adsorption and cross-linking (EAC), and enzyme adsorption, precipitation and cross-linking (EAPC). EAPC includes higher enzyme activity immobilized within the matrix in comparison with the other methods. Furthermore, the immobilized enzyme is predicted to be prevented from leaching out of the matrix when exterior blow is being tested on the structure. Thus, the stability of the EAPC of this invention is anticipated to be maintained even after a long time passed since high enzyme activity compared with known method can be supported and immobilized within the matrix. Consequently, it is possible to improve performance of the enzymes by manipulating the preparation and operation condition.

No abstract

A novel greener MNC/PES membrane was developed through an electrospinning technique for lipase immobilization to catalyze the synthesis of ethyl valerate (EV). In this study, the covalent immobilization of Aspergillus oryzae lipase (AOL) onto an electrospun nanofibrous membrane consisting of magnetic nanocellulose (MNC) and polyethersulfone (PES) to produce EV was statistically optimized. Raman spectroscopy, Fourier-transform infrared spectroscopy: attenuated total reflection, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, thermal gravimetric analysis (TGA), and differential thermal gravimetric (DTG) of MNC/PES-AOL demonstrated that AOL was successfully immobilized onto the fibers. The Taguchi design-assisted immobilization of AOL onto MNC/PES fibers identified that 1.10 mg/mL protein loading, 4 mL reaction volume, 250 rpm stirring rate, and 50 °C were optimal to yield 72.09% of EV in 24 h. The thermal stability of MNC/PES-AOL was improved by ≈20% over the free AOL, with reusability for up to five consecutive esterification cycles while demonstrating an exceptional half-life of 120 h. Briefly, the electrospun MNC/PES fibers that immobilized AOL showed promising applicability in yielding relatively good EV levels. This study suggests that using MNC as fillers in a PES to improve AOL activity and durability for a longer catalytic process could be a viable option.