Selective chemical modification of soy protein for a tough and applicable plant protein-based material

Abstract

Soy protein, one of the most abundant plant proteins, has gained considerable attention and popularity in recent years due to its biocompatibility, biodegradability, and renewability. However, the poor mechanical properties and high moisture sensitivity of soy protein-based materials have limited their wider application in practical use. In the present study we have overcome these shortcomings by the use of an aqueous reagent, tetrakis(hydroxylmethyl) phosphonium chloride (THPC), to modify the amino groups of the lysine (Lys) and arginine (Arg) residues present in soy protein. Solid state 13 C cross polarization/magic-angle spinning nuclear magnetic resonance (CP/MAS NMR) and 31 P NMR spectroscopy have confirmed the success of the chemical reaction by replacement of the hydroxymethyl arm of THPC, both qualitatively and quantitatively. Fourier-transform infrared (FTIR) spectroscopy, rheological observations, transmission electron microscopy (TEM) and atomic force microscopy (AFM) have been used to confirm the changes in the coherent tertiary structure of soy protein after modification, increasing the interconnection between the molecular chains. Finally, we have been able to produce a modified soy protein film, which provides a good combination of tensile strength and extensibility under either dry (10 AE 2 MPa and 25 AE 3%) or wet (5 AE 1 MPa and 200 AE 20%) conditions. In addition the modified soy protein film has unexpectedly been found to exhibit antimicrobial properties, and this adds to the merits of the final product. We believe that the method described further broadens the application of natural soy protein-based materials, for example in antimicrobial packaging films.

Epichlorohydrin-Cross-linked Hydroxyethyl Cellulose/Soy Protein Isolate Composite Films as Biocompatible and Biodegradable Implants for Tissue Engineering

“…The 13 C NMR spectra of the original SPI, HEC and HEC/SPI-50 powders as well as EHSF-0, EHSF-30, EHSF-70, and EHSF-100 films are shown in Figure . The 13 C NMR spectrum of SPI powder displayed 5 major signals corresponding to carbonyl (168–183 ppm), aromatic (129–141 ppm), α-C (48–68 ppm), β-C (24–39 ppm), methylene, and methyl groups (16–24 ppm), which are far away from the backbone. − These signals shifted to (166–179 ppm), (126–133 ppm), (46–63 ppm), (19–35 ppm), and (12–17 ppm) in EHSF-100, respectively. The signal at 70–81 ppm for SPI powder lost its resolution greatly in EHSF-100, indicating that the SPI was cross-linked with ECH.…”

Marine Microalgae Biomolecules and Their Adhesion Capacity to Salmonella enterica sv. Typhimurium

“…Additionally, the HSQC spectrum ( Figure 4b (Figure 4), COSY ( Figure S1), and TOCSY ( Figure S2) spectra, presented in Table 4 are in agreement with previously reported resonances [38][39][40][41]. In accordance with the methylation analysis, the NMR data suggest the presence of a highly branched β- NMR spectrum (Figure 5c) showed signals corresponding to the carbonyl carbon of the main chain and carboxylic groups of the acidic amino acids side chain (180-165 ppm), aromatic amino acids (140-115 ppm),  and  carbons (65-45 ppm and 45-25 ppm, respectively), and methylene and methyl groups of the aliphatic side chains (2510 ppm) [47]. The 1 H NMR spectra of the other alkaline fractions, LA-s, GA-s, and GA-p (data not shown), presented the same characteristic protein resonances that were described for the LA-p fraction.…”

“…The 1 H NMR spectrum (Figure 5b) showed signals in the region of the backbone amide protons (10.0-7.0 ppm), aromatic and side-chain amide protons (8.0-6.0 ppm), α-proton (5.5-3.5 ppm), methine, methylene (3.5-1.0 ppm), and methyl protons (2.0-0 ppm) of the aliphatic side chains [46]. The 13 C NMR spectrum (Figure 5c) showed signals corresponding to the carbonyl carbon of the main chain and carboxylic groups of the acidic amino acids side chain (180-165 ppm), aromatic amino acids (140-115 ppm), α and β carbons (65-45 ppm and 45-25 ppm, respectively), and methylene and methyl groups of the aliphatic side chains (25−10 ppm) [47].…”

Fabrication of Composite Hydrogels Based on Soy Protein Isolate and their Controlled Globular Protein Delivery

“…Soy protein isolate (SPI), a protein with reproducible resource, good biocompatibility, and biodegrade ability, has a significant potential in the bioscience and biotechnology . A large number of biocompatible protein composite materials based on SPI was constructed by chemical grafting, blending, and self‐assembly .…”