Effectiveness of polyethylene glycol and glutaraldehyde as enhancers for lipase-immobilized hybrid organic-inorganic nanoflowers

Abstract

The present study investigates the influence of polyethylene glycol (PEG) and glutaraldehyde (GA) on the synthesis and enzymatic activity of lipase hybrid nanoflowers. The effect of lipase concentration on hybrid nanoflower formation was first assessed, revealing that the optimum lipase concentration was 0.2 mg/mL. At this concentration, the encapsulation of lipase within the hybrid nanoflowers reached its maximum efficiency. Further, the effects of PEG and GA concentrations, as well as pH, on the enzymatic activity of the nanoflowers were evaluated. The results demonstrated that 2% (v/v) PEG and 3% (v/v) GA were the most effective concentrations, with the highest activity observed at pH 8. Comparative studies showed that GA-treated lipase hybrid nanoflowers exhibited a remarkable 160% increase in enzymatic activity over the free lipase, outperforming PEG in terms of catalytic performance. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopy analyses confirmed that both PEG and GA treatments altered the morphology and structural characteristics of the hybrid nanoflowers, with GA inducing more pronounced changes. Despite these morphological alterations, the enzymatic activity was significantly enhanced, particularly in the GA-treated hybrid nanoflowers. In conclusion, this study highlights the superior performance of glutaraldehyde as an enhancer for the production of highly active lipase hybrid nanoflowers, offering promising applications in biocatalysis and enzyme immobilization.

Keywords: Glutaraldehyde; Lipase hybrid nanoflowers; Polyethylene glycol.

Fig. 1

Mechanism of hybrid nanoflowers formation

Fig. 2

Assay mixture for oleic acid (a) and hybrid nanoflowers samples (b)

Fig. 3

Percentage activity recovery at different PEG concentrations (a), GA concentrations (b), and percentage activity recovery of PEG vs GA (c)

Fig. 4

Percentage activity recovery at 2% PEG (a), and at 3% GA (b) of different pH

Fig. 5

The blue precipitate formed at pH 4 (a), and other pH (b)

Fig. 6

Percentage activity recovery at different conditions

Fig. 7

SEM image for lipase hybrid nanoflowers without treatment (a, b), 2% PEG-treated lipase hybrid nanoflowers (c, d), and 3% GA-treated lipase hybrid nanoflowers (e, f)

Fig. 8

FTIR plot of lipase hybrid nanoflowers without treatment (a), PEG-treated lipase hybrid nanoflowers (b), and GA-treated lipase hybrid nanoflowers (c)

Fig. 9

Microscopic images of bioplastic at 40 $\times$ magnification (a, c) Before degradation (b, d) After degradation

Fig. 10

Degradation enhancement by a Untreated lipase hybrid nanoflowers (LHNF) b 2% PEG treated LHNF c 3% GA treated LHNF

Fig. 11

FTIR spectra of bioplastic a Before degradation b After degradation by untreated LHNF c After degradation by 2% PEG treated LHNF d After degradation by 3% GA treated LHNF