Synergistic Effect and Mechanisms of Combining Ultrasound and Pectinase on Pectin Hydrolysis

Abstract

The current study aimed to investigate the synergistic effect of ultrasound and pectinase on pectin hydrolysis. Effects of ultrasound on the hydrolysis rate of pectin, enzymatic kinetics parameters and pectinase structures (determined by the DNS method, Michaelis-Menten equation, chemical reaction kinetics model, fluorescence spectroscopy and circular dichroism spectroscopy) were also studied in order to illuminate the mechanisms of the synergistic effect. The hydrolysis rate of pectin achieved maximum value with ultrasound treatment at 4.5 W mL −1 intensity and ultrasound time of 10 min, increasing by 32.59 % over the control. The optimum temperature for the hydrolysis reaction was 50°C and kept unchanged with ultrasound treatment. Besides, the value of V m a x increased whereas K m decreased in the sonoenzymolysis reaction compared with that in the routine enzymolysis reaction. Results indicated that under ultrasound irradiation, pectin was hydrolyzed at an elevated rate and the pectinase exhibited stronger affinity to the substrate. Fluorescence spectra revealed that ultrasound favorably decreased the amount of tryptophan on the pectinase surface; while the far-UV circular dichroism spectra showed an increased fraction of β-sheet and a reduced fraction of random coil in the secondary conformation. Changes in the pectinase structures contributed to the enhancement of pectinase activity and the consequent promotion of the hydrolysis process. Results of pectin degradation kinetics certified the synergistic effect of ultrasound and pectinase at the temperature range of 20-50°C, which were evidenced from the positive values of the synergistic coefficients.

Degradation kinetics and structural characteristics of pectin under simultaneous sonochemical-enzymatic functions

“…Then, it gradually increased to 50 kDa as the intensity further increased to 9 W mL -1 . Low-intensity ultrasound accelerated the enzymatic degradation process and achieved maximum effect at 4.5 W mL -1 , which was attributed to the increased pectinase activity with ultrasound treatment (Ma et al, 2016). As the of the sonoenzymolysis products became higher than that of the enzymolysis products, an antagonistic effect between ultrasound and pectinase was observed when the intensity exceeded 8.1 W mL -1 .…”

“…As the of the sonoenzymolysis products became higher than that of the enzymolysis products, an antagonistic effect between ultrasound and pectinase was observed when the intensity exceeded 8.1 W mL -1 . Excessive free radicals and strong shear forces generated from intense ultrasound conditions could disrupt enzyme conformations and inactivated pectinase (Ma et al, 2015;Ma et al, 2016), which leads to the reduction in the degradation extent. Chain length of polymers is closely linked to their functions (Cooke & Shi, 2006); thus, it is important to study the distributions of the degradation products.…”

“…Combination of ultrasound and enzymes has been observed to promote degradation of a series of polymers, such as dextran (Bashari et al, 2013), cellulose (Prajapat, Das & Gogate, 2016b;Szabo & Csiszar, 2013), guar gum (Prajapat et al, 2016a), xylan (Sun, Zhang, Xiao & Jin, 2015), pectin (Ma et al, 2016), etc. Our previous study (Ma et al, 2016) applied the combination of ultrasound and pectinase to pectin degradation.…”

Optimizing a sustainable ultrasound-assisted extraction method for the recovery of polyphenols from lemon by-products: comparison with hot water and organic solvent extractions

“…This difference could be due to the higher extraction temperatures applied in this study, as well as to the different physical parameters of the solvents that were employed. High extraction temperatures might lead to the weakening of cell walls by enhancing the activity of some enzymes [27], facilitating cell wall damage due to cavitation phenomena. Moreover, high temperatures can increase the number of cavitation bubbles facilitating greater cell wall disruption [23].…”

“…The recovery yields of TPC and rutin increased when the extraction temperature increased from 23 °C (ambient temperature) to 50 and 40 °C, respectively (P<0.05) ( Table 1). Higher extraction temperatures might lead to higher recovery yields of TPC and rutin by increasing their solubility and weakening cell wall structure by enhancing the activity of some enzymes [27].…”