Purification and characterization of peroxidase from zucchini ( Cucurbita pepo L.)

Effects of zucchini polysaccharide on pasting, rheology, structural properties and in vitro digestibility of potato starch

Zucchini polysaccharide (ZP) has a unique molecular structure and a variety of biological activities. This study aimed to evaluate the effects of ZP (1, 2, 3, 4 and 5 %, w/w) on the properties of potato starch (PS), including pasting, rheological, thermodynamic, freeze-thaw stability, micro-structure, and in vitro digestibility of the ZP-PS binary system. The results showed that the appearance of ZP significantly reduced the peak, breakdown, final and setback viscosity and prolonged the pasting temperature of PS, whereas increased the trough viscosity. The tests of rheological showed that ZP had a damaging effect on PS gels. Meanwhile, the results of thermodynamic and Fourier transform infrared exhibited that the presence of ZP significantly retarded the retrogradation of PS, especially at a higher levels. The observation of the microstructure exhibited that ZP significantly altered the microscopic network structure of the PS gels, and ZP reduced the formation of the gel structure. Besides, ZP postponed the retrogradation process of PS gels. Moreover, ZP weakened the freeze-thaw stability of the PS gel. Furthermore, ZP also can decrease the digestibility and estimated glycemic index (eGI) value of PS from 86.04 % and 70.89 to 77.67 % and 65.22, respectively. Simultaneously, the addition of ZP reduced the rapidly digestible starch content (from 25.09 % to 16.59 %) and increased the slowly digestible starch (from 24.99 % to 26.77 %) and resistant starch content (from 49.92 % to 56.64 %). These results have certain guiding significance for the application of ZP in starch functional food.

A novel peroxidase from runner bean (Phaseolus coccineus L.): Enhanced affinity purification, characterization, and dye decolorization activity

In this study, a novel runner bean peroxidase (RBP) was purified and characterized. Affinity-based purification was performed with newly synthesized disubstituted 4-aminobenzohydrazides. In the purification results, 253-fold was achieved with a yield of 56.2%. Furthermore, molecular weight and enzyme purity were checked with the SDS-PAGE and observed a single band at 31.2 kDa. Optimum conditions were determined as temperature = 50°C, ionic strength = 0.2 M, and pH 7.0. Enzyme exhibited 31.2% of residual activity in the presence of 20% DMSO. Additionally, the redox-mediated decolorization effect of the enzyme was examined for Reactive Blue 19 and Acid Blue 25 dyes. As a result of 1-hr incubation, the enzyme removal activity of Reactive Blue 19 and Acid Blue 25 dyes was calculated as 47% and 57%, respectively. PRACTICAL APPLICATIONS: Peroxidases (PODs) ability to catalyze various redox reactions for many substrates makes them significant enzymes in industrial sectors. In our current report, a single-step strategy was developed and followed as an alternative to multi-step methods commonly used for the purification of PODs. During this process, high yield was achieved and the separation time was shortened. Also, the purification of RBP that can potentially supplant PODs used in the industrial applications was carried out for the first time. In addition, substrate specificity, catalytic behavior in water-miscible organic solvents, and dye bleaching activity of this enzyme have been determined to evaluate the utilization capacity in various processes.

Enzymatic characterization and validation of gene expression of phosphoglucomutase from Cordyceps militaris

The purification and characterization of PGM (Phosphoglucomutase) from Cordyceps militaris (C. militaris) was investigated. PGM was purified using a combination of ultrafiltration, salting-out and ion exchange chromatography resulting in 4.23-fold enhancement of activity with a recovery of 20.01%. Molecular mass was 50.01 kDa by SDS-PAGE. The optimal activity was achieved at pH 7.5 and 30 °C with NADPH as substrate. The results showed that SDS, DTT Li⁺, Cu²⁺, Na⁺, Mn²⁺ and Al³⁺ were effective PGM inhibitors; whereas glycerol, Zn²⁺, Mg²⁺, Ca²⁺, Fe²⁺ and Fe³⁺ could enhance the activity of PGM, and the K_m and V_max values were 11.62 mmol/L and 416.67 U/mL, respectively. At the same time, qRT-PCR was used to test the changes of mRNA transcription level of PGM gene encoding under two fermentation conditions: basic medium and optimized medium. The relative quantitative results of PGM target genes resulting in 2.60-fold enhancement than the control group.

Encapsulation of HRP Enzyme onto a Magnetic Fe3O4 Np–PMMA Film via Casting with Sustainable Biocatalytic Activity

Horseradish peroxidase (HRP) enzyme was effectively encapsulated onto an Fe3O4 nanoparticle–polymethyl methacrylate (PMMA) film via the casting method. The HRP was immobilized on the 0.5% Fe3O4Np–PMMA film and characterized by Fourier transform infrared spectroscopy and field emission scanning electron microscopy. Moreover, the reusability, thermal stability, optimum pH, optimum temperature, the influence of metal ions, and the effects of detergent and organic solvent were investigated. After optimizing the immobilization conditions, the highest efficiency of the immobilized enzyme was 88.4% using 0.5% Fe3O4Np–PMMA. The reusability of the immobilized HRP activity was 78.5% of its initial activity after being repeatedly used for 10 cycles. When comparing the free and immobilized forms of the HRP enzyme, changes in the optimum temperature and optimum pH from 30 to 40 °C and 7.0 to 7.5, respectively, were observed. The Km and Vmax for the immobilized HRP were estimated to be 41 mM, 0.89 U/mL for guaiacol and 5.84 mM, 0.66 U/mL for H2O2, respectively. The high stability of the immobilized HRP enzyme was obtained using metal ions, a high urea concentration, isopropanol, and Triton X-100. In conclusion, the applicability of immobilized HRP involves the removal of phenol in the presence of hydrogen peroxide, therefore, it could be a potential catalyst for the removal of wastewater aromatic pollutants.