Assessment of the efficiency and stability of enzymatic membrane reaction utilizing lipase covalently immobilized on a functionalized hybrid membrane.

Enzyme immobilization in membrane bioreactors has been considered as a practical approach to enhance the stability, reusability, and efficiency of enzymes. In this particular study, a new type of hybrid membrane reactor was created through the phase inversion method, utilizing hybrid of graphene oxide nanosheets (GON) and polyether sulfone (PES) in order to covalently immobilize the Candida rugosa lipase (CRL). The surface of hybrid membrane was initially modified by (3-Aminopropyl) triethoxysilane (APTES), before the use of glutaraldehyde (GLU), as a linker, through the imine bonds. The resulted enzymatic hybrid membrane reactors (EHMRs) were then thoroughly analyzed by using field-emission scanning electron microscopy (FE-SEM), contact angle goniometry, surface free energy analysis, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, attenuated total reflection (ATR), and energy-dispersive X-ray (EDX) spectroscopy. The study also looked into the impact of factors such as initial CRL concentration, storage conditions, and immobilization time on the EHMR's performance and activity, which were subsequently optimized. The results demonstrated that the CRLs covalently immobilized on the EHMRs displayed enhanced pH and thermal stability compared to those physically immobilized or free. These covalently immobilized CRLs could maintain over 60% of their activity even after 6 reaction cycles spanning 50 days. EHMRs are valuable biocatalysts in developing various industrial, environmental, and analytical processes.

The immobilization of Candida rugosa lipase on the modified polyethersulfone with MOF nanoparticles as an excellent performance bioreactor membrane.

In this study, the modified nanocomposite membrane of polyethersulfone (PES) with NH2-MIL-101(Cr) as a metal-organic framework (MOF) is exploited for Candida rugosa lipase (CRL) immobilization. To that end, the various amounts of NH2-MIL-101(Cr) nanoparticles are blended into PES casting solution to fabricate ultrafiltration membrane via phase inversion technique. The incorporation efficiency of NH2-MIL-101(Cr) nanoparticles on the membrane morphology is investigated using various techniques, namely atomic force microscopy (AFM), X-ray diffraction (XRD), and contact angle goniometry. In terms of water pure flux and CRL immobilization efficiency, the best performance is observed for PES-NH2-MIL1% membrane. This bioactive membrane (CRL@GA@PES-NH2-MIL1%) displays an improvement in pH and thermal stability and separation performance that makes it a fruitful candidate for using in bioreactors. The examination of the wet- and dry-storage stability of CRL@GA@PES-NH2-MIL1% demonstrates the high stability for the wet bioactive membrane. The reusability inspection of CRL@GA@PES-NH2-MIL1% represents about 50% conservation of the residual activity after 12 sequential usage cycles.

The performance of immobilized Candida rugosa lipase on various surface modified graphene oxide nanosheets.

In this study, we have reported the synthesis of graphene oxide nanosheets (GON) and its functionalization with 2, 4, 6-trichloro-1, 3, 5-triazine (TCT) through two routes, (a) directly reaction of GON with TCT (GON-1), and (b) reaction of GON with pre-functionalized TCT with 3-aminopropyltriethoxysilane (APTS) (GON-2). Subsequently, GON, GON-1 and GON-2 have been used as supports for immobilization of Candida rugosa lipase (CRL). Several techniques such as XRD, SEM, EDS, UV-Vis, CHNS, FTIR and AFM were applied to characterize the nano-structures and success of synthesis, functionalization and CRL immobilization processes. The results corresponding to optimization of immobilization process revealed the following order for values of loading capacity, immobilization yield and leaching of CRL: GON > GON-1 > GON-2, while this order is reversed for, specific activity and recovery activity. The assessment of operational parameters represents the high storage stability and reasonable reusability for all the immobilized CRL while the pH and thermal stability of CRL@GON-2 are higher than two others. It seems the longer linker of GON-2 could more effectively prevent the unfavorable interaction between enzyme-enzyme and enzyme-product that consequently resulted the best catalytic performance, pH and thermal stability. The advantages of these supports make them suitable candidates for practical applications.