Immobilized Burkholderia cepacia Lipase on pH-Responsive Pullulan Derivatives with Improved Enantioselectivity in Chiral Resolution

Abstract

Abstract:A kind of pH-responsive particle was synthesized using modified pullulan polysaccharide. The synthesized particle possessed a series of merits, such as good dispersity, chemical stability and variability of particle size, making it a suitable carrier for enzyme immobilization. Then, Burkholderia cepacia lipase (BCL), a promising biocatalyst in transesterification reaction, was immobilized on the synthesized particle. The highest catalytic activity and immobilization efficiency were achieved at pH 6.5 because the particle size was obviously enlarged and correspondingly the adsorption surface for BCL was significantly increased. The immobilization enzyme loading was further optimized, and the derivative lipase was applied in chiral resolution. Under the optimal reaction conditions, the immobilized BCL showed a very good performance and significantly shortened the reaction equilibrium time from 30 h of the free lipase to 2 h with a conversion rate of 50.0% and ee s at 99.2%. The immobilized lipase also exhibited good operational stability; after being used for 10 cycles, it still retained over 80% of its original activity. Moreover, it could keep more than 80% activity after storage for 20 days at room temperature in a dry environment. In addition, to learn the potential mechanism, the morphology of the particles and the immobilized lipase were both characterized with a scanning electron microscope and confocal laser scanning microscopy. It was found that the enlarged spherical surface of the particle in low pH values probably led to high immobilized efficiency, resulting in the improvement of enantioselectivity activity in chiral resolution.

Lipase Immobilized on a Novel Rigid–Flexible Dendrimer-Grafted Hierarchically Porous Magnetic Microspheres for Effective Resolution of (R,S)-1-Phenylethanol

“…The immobilization efficiency gradually declines from 76.8 to 70.3% with the rise of medium pH value, which may be due to the ability of EDC to activate the amino of PFMMs-G 3.0 being reduced over 6.0 of pH value, resulting in a lower PFL loading. 37 However, a significant increase in the activity recovery from 478 to 864% is observed as the pH value increases from 6.0 to 9.0, which can be attributable to the "pH memory" mechanism of lyophilized lipase, 38 which is in agreement with the previous report from Kajiwara et al 39 Then, a remarkable decline of the activity recovery takes place when pH value is beyond 9.0, revealing a lower stability of the immobilized enzyme under a higher pH value. Therefore, the optimum medium pH value is set at 9.0.…”

Recent Trends in Biomaterials for Immobilization of Lipases for Application in Non-Conventional Media

“…The immobilized lipase was applied in the resolution of (R,S)-1-phenylethanol in n-heptane, with a conversion to (R)-1-phenylethyl acetate of 50%, in 2 h at 45 °C, with an enantiomeric excess of the substrate of 99%. The immobilized lipase also had good operational stability; after being used for 10 cycles, it still retained over 80% of its original activity [120]. Natural materials that are generally classified as agro-industrial wastes have also been used to immobilize lipases.…”

“…Pullulan is a fungal polysaccharide consisting of maltotriose units (three glucose units linked by α-1,4 glycosidic bonds) connected by α-(1,6) glycosidic bonds. Xu et al [120] immobilized a lipase from Burkholderia cepacia by ionic adsorption onto spherical particles of pullulan acetate modified with succinic anhydride (Figure 21). The immobilized lipase was applied in the resolution of (R,S)-1-phenylethanol in n-heptane, with a conversion to (R)-1-phenylethyl acetate of 50%, in 2 h at 45 • C, with an enantiomeric excess of the substrate of 99%.…”

Fe, N, S-codoped carbon frameworks derived from nanocrystal superlattices towards enhanced oxygen reduction activity

“…Recently, iron, nitrogen and sulfur codoped carbon-based materials have gained increasing attention for its synergistic effect. For example, sulfur-doped Fe/N/C nanosheets [13], porous Fe–N–S/C catalyst [14] and Fe 1–x S/Fe 3 O 4 /N, S-doped porous carbon [15] have been designed and studied. The unique nature of S enables the modification of the electronic structure of iron and nitrogen codoped carbon materials, which leads to the boost of the ORR reactivity [16–18].…”