磁性纳米粒子负载木瓜蛋白酶的制备、表征及用于果汁澄清(英文)

The preparation,characterization,and application of silica-coated magnetic nanoparticles for papain immobilization is reported.Papain was covalently attached onto the(3-chloropropyl) trimethoxysilane-modified silica-coated magnetic nanoparticles. The enzyme-immobilized nanoparticles were characterized by Fourier transform infrared spectroscopy,X-ray powder diffraction,scanning electron microscopy,and vibrating sample magnetometry techniques.Response surface methodology combined with statistical analyses using Minitab were employed to evaluate optimum operating conditions to immobilize papain on the magnetic nanoparticles.The optimum conditions were: temperature = 27.3℃,pH of the enzyme solution = 7.1,concentration of papain = 3.3 mg/mL,and immobilization time = 10 h.Compared with the free papain,the immobilized papain displayed enhanced enzyme activity,better tolerance to variations in the medium pH and temperature,improved storage stability,and good reusability.Both the free and immobilized enzymes were effective for the clarification of pomegranate juice.

Fast-dissolving antioxidant nanofibers based on Spirulina protein concentrate and gelatin developed using needleless electrospinning

Spirulina is a microalga that is well-known for its high protein content and biological activities directly related to its antioxidant capacity.The objective of this study was to produce fast-dissolving antioxidant nanofibers based on Spirulina protein concentrate (SPC) and gelatin using needleless electrospinning technique.The effect of mixing ratios of SPC (10% w/w) and gelatin (20% w/w) on the viscosity,electrical conductivity and surface tension of electrospinning solutions as well as diameter and morphology of resulting nanofibers was investigated.Increasing the SPC level in the solution blends resulted in a decrease in apparent viscosity and electrical conductivity and an almost stable trend in surface tension (29.25–32.19 mN/m) that led to diminish of diameter of the nanofibers.Scanning electron microscopy images showed that SPC/gelatin ratio of 40:60 led to the production of uniform and bead-free nanofibers with a relatively smaller average diameter (208.7 ± 46.5 nm).Atomic force microscopy images indicated mesh-like,fibrillary,and bead-free structures.Fourier transform infrared spectroscopy verified the formation of composite nanofibers and intermolecular interactions between both proteins.X-ray diffraction and thermal analysis showed higher amorphous structure and stability of produced SPC/gelatin nanofibers in comparison to pure materials which was favorable for formation of stable fast-dissolving fibers.Results of DPPH and ABTS radical scavenging activities showed that the antioxidant activity of composite nanofibers significantly improved with increasing SPC mixing ratio (p < 0.05).The dissolution test demonstrated that SPC/gelatin nanofibers can be rapidly dissolved in aqueous medium within 2 s.Finally,the results indicated that the electrospun SPC/gelatin nanofibers could be potentially used for nutraceutical delivery in food and packaging applications under high humidity.