High-Performance and Fully Renewable Soy Protein Isolate-Based

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High-Performance and Fully Renewable Soy Protein Isolate-based Film from Microcrystalline Cellulose via Bio-Inspired Poly(Dopamine) Surface Modification Haijiao Kang, Xiangshuo Song, Zhong Wang, Wei Zhang, Shifeng Zhang, and Jianzhang Li ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.6b00917 • Publication Date (Web): 15 Jun 2016 Downloaded from http://pubs.acs.org on June 18, 2016

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ACS Sustainable Chemistry & Engineering

High-Performance and Fully Renewable Soy Protein Isolate-based Film from Microcrystalline Cellulose via Bio-Inspired Poly(Dopamine) Surface Modification Haijiao Kang,a,b Xiangshuo Song,a,b Zhong Wang,a,b Wei Zhang,a,b Shifeng Zhang,a,b* and Jianzhang Lia,b* a

MOE Key Laboratory of Wooden Material Science and Application, Beijing Forestry

University, No. 35 Tsinghua East Road, Haidian District, Beijing 100083, P. R. China; b

Beijing Key Laboratory of Wood Science and Engineering, Beijing Forestry

University, No. 35 Tsinghua East Road, Haidian District, Beijing 100083, P. R. China. * To whom correspondence should be addressed. E-mail: [email protected] (S. Zhang).

1

ACS Paragon Plus Environment


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Abstract: A novel and facile marine mussel-inspired surface modification approach for microcrystalline celluloses (MCC) and the enhanced interfacial adhesion with the soy protein isolate (SPI) matrix was demonstrated to develop renewable composite films. The

surface

composition

and

micromorphology

of

the

poly(dopamine)

(PDA)-modified MCC (PDMCC) were characterized by the X-ray photoelectron spectroscopy

(XPS),

attenuated

total

reﬂectance-Fourier

transform

infrared

spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The biomimetic adherent PDA layer was successfully coated onto the MCC surface via dopamine self-polymerization through the simply dip-coating method. As expected, the ad-layer of PDA between the PDMCC and peptide chains greatly enhanced the mechanical properties of the resultant films. Due to the favorable interfacial adhesion between PDMCC and SPI, as certified by solid state 13C Nuclear Magnetic Resonance (13C NMR) and atomic force microscopy (AFM), the tensile strength of the PDMCC/SPI film was improved by 82.3%, and its water absorption was reduced by 31.3% in comparison to the unmodified SPI film. Keywords: Soy protein isolate, poly(dopamine), microcrystalline cellulose, mussel-inspired surface modification, interfacial adhesion

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Introduction Bio-based polymers have garnered a great deal of research interest in recent years as a reaction to the overdependence on petroleum-based materials.1-3As amphiphilic biopolymers, proteins are considered ideal film materials due to their functional side chains.4 Soybean is a plant protein source with a wide range of potential applications.5 Soy protein isolate (SPI) based films were explored extensively to secure eco-friendly materials in several fields, such as packaging, drug delivery, and tissue regeneration.6-7 However, the fundamental hydrophilicity and strong molecular interactions of natural soy proteins limit their practical application. Many previous studies in SPI modification were attempted on physical treatment,8 chemical crosslinking,9 or block copolymerization.10 The blending of organic or inorganic materials such as fibers or TiO2 was a relatively effective approach in stiffness improvements.11-12 Among these, natural fillers from renewable resources showed a great potential for eco-enhancement to SPI composite materials and extending its industrial applications.5, 13 Microcrystalline cellulose (MCC) is a plant-based fiber and possesses high cellulose content and relatively high crystallinity.14 It was applied for both synthetic and natural matrices,15-17 such as high-density polyethylene (HDPE), and chitosan. However, the interfacial bonding between cellulose and matrix is mostly intra-/inter-molecular hydrogen bonding, which are partly less reactive.16-18 Both surface physical and chemical treatments (such as silane coupling, maleic anhydride grafts) are potential approaches to enhance the bi-phase interfacial adhesion.18-19 However, these approaches are complicated multi-step processing and/or could generate toxic side by-products.20

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Inspired by the marine mussel protein that can adhere very well to almost all substrates, Lee et al. developed a simple, versatile dip-coating method for surface functional modification.21 It was found that the mussel-secreted byssus protein tethered them to marine substrata and protected from mechanical stress.22-23 The coexistence of the catechol moiety of DOPA (3,4-dihydroxy-phenyl-alanine) and the primary amine group of lysine were crucial in byssus protein to adhere in an aqueous milieu.24,25 Thus, small molecules with cathchol-amine moieties, such as dopamine and norepinephrine, were explored in effort to mimic mussel adhesion.21, 26-27 For this manner of chemical modification, a thin layer of poly(dopamine) (PDA) was formed via dopamine self-polymerization, and the PDA layer extended to play as a versatile platform generating the secondary reactions both in activity and functionality.28-29 There

are

several

reports

on

fiber

surface

modification

via

dopamine

dip-coating,20,30-32 but none yet for natural MCC. Furthermore, there has been no report regarding PDA-coated MCC (PDMCC) for improving the interfacial adhesion to the SPI matrix. In this study, an eco-friendly cellulose/SPI composite film with active interface adhesion was prepared without necessitating toxic organic reagent during the modification. Firstly the MCC was dip-coated by dopamine, and then the PDA generated interactions with the SPI side chains via Michael addition or Schiff base reactions. 30 The interfacial adhesion between PDMCC and SPI was improved, which benefits the SPI based composites. The surface composition and microstructure of MCC, PDMCC, and the thermo stability, mechanical properties and water resistance of the resultant composite films were examined. Experimental

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Materials. SPI (95% protein) was provided by Yuwang Ecological Food Industry Co., Ltd. Microcrystalline cellulose (MCC, (C6H10O5)n) was acquired from Sinopharm Chemical Reagent Co., Ltd. The dopamine (97% purity) and tris(hydroxymethyl aminomethane) (Tris) were purchased from Tianjin Heowns Biochem Co., Ltd. Glycerol (99% purity), sodium dodecyl sulfate (SDS, analytical grade) and other chemical reagents were purchased from Beijing Chemical Reagents Co., Ltd. and used without further purification. Surface modification of MCC and film preparation. The MCC surface modification was facilitated simply by immersing the MCC into a dilute dopamine buffer solution. The immersion solution (1.0 g/L) was pre-prepared by dissolving dopamine in tris-HCl (10 mM, 500 mL) buffer solution with pH 8.5. Next, 1.0 g MCC was added and gently stirred at 30°C for 5 hours. The PDMCC was then purified through three cycles of pump-filtration and distilled water rinsing, and then freeze-dried to afford the dark brown powder. The SPI-based film was prepared via a two-step casting method.9 Firstly, the SPI (5 g), glycerol (2.5 g), and distilled water (95 g) were sequentially added into a 250 mL beaker and stirred for 30 min. The beaker content was adjusted with NaOH solution (10%, w/w) to pH 9.0 ± 0.1, and then heated in a water bath at 85°C for another 30 min. A certain amount of MCC or PDMCC (as listed in Table 1) was dispersed in the SPI solution with the aid of surfactant SDS (the weight ratio of SDS to MCC or PDMCC was 1:1) under a constant stir. Secondly, the aforementioned suspension was poured into a Teﬂon-coated plate after removing bubbles by ultrasound treatment, and then vacuum dried at 45°C. Films were stripped after 24 h drying and placed into a saturate-K2CO3-regulated (50 ± 2% relative humidity) desiccator for further use. 5



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Table 1 Experimental details and summary of the SPI-based films. Entry SPI MCC/SPI-1 MCC/SPI-2 MCC/SPI-3 PDMCC/SPI-1 PDMCC/SPI-2 PDMCC/SPI-3 a

SPI (g) 5.0 5.0 5.0 5.0 5.0 5.0 5.0

Glycerol (g) 2.5 2.5 2.5 2.5 2.5 2.5 2.5

Water (g) 95 95 95 95 95 95 95

MCC (g) 0.05(1 wt%)a 0.10(2 wt%) 0.15(3 wt%) -

PDMCC (g) 0.05(1 wt%) 0.10(2 wt%) 0.15(3 wt%)

The proportion of modifiers to the SPI solid content.

Characterization. The attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR, Nicolet 6700) was employed to characterize the chemical structural changes of the celluloses and films, in the wavelength range 650 to 4000 cm−1 and with 32 scans. The Solid state 13C Nuclear Magnetic Resonance (13C NMR, JEOL ECS 400 MHz) spectra was operated with 3.2 mm CP/MAS probe at a spinning of 15 000 Hz. The X-ray photoelectron spectroscopy (XPS, Thermo Fisher Scientific Co.) was carried out with monochromatic Al Kα radiation (1486.6 eV). The X-ray beam was a 200 mm-diameter beam raster over a 2 mm by 0.4 mm area on the specimens. Spectra were collected using pass energy of 50 eV and resolution of 0.1 eV. The Scanning electron microscopy (SEM, Hitachi S-3400N) was applied with an accelerating voltage of 5 kV to observe the surface morphology of the specimens. Atomic force microscopy (AFM, Bruker Multimode 8) was used to observe the surface morphology of SPI-based films. The topographic (height) and phase images were collected in the tapping mode using a monolithic Si tip with a resonance frequency between 250 to 300 kHz.

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The thermogravimetric analysis (TGA, Q50) with a temperature range from 40 to 600°C and a heating rate at 10°C·min-1 was applied under nitrogen atmosphere (100 mL·min-1). The mechanical properties of SPI-based films were determined with a tensile testing machine (DCP-KZ300) at a loading speed of 50 mm·min-1 and an initial gauge length of 50 mm. The stress-strain curves of the specimens (10 × 80 mm2) were obtained.33 Films’ thickness (five replicates) was measured with a digimatic micrometer. The tensile strength (TS) and elongation at break (EB) of each film were determined by a mean value of six replicates. The water barrier properties of the films were measured on the basis of weight variation; five specimens (20 × 20 mm2) for each film were tested. The moisture content (MC), total soluble matter (TSM), and water absorption (WA) of the specimens were calculated according to Eqs. S1-S3.9, 33 The surface hydrophilicity of the SPI-based films was investigated by water contact angles (WCA, OCA-20 Dataphysics Instruments GmbH). A sessile droplet (3 µL, measured by microsyringe) of distilled water was dropped onto the surface and the angles of both sides recorded at an interval of 0.1 s for 180 s. Results and Discussion Structural analysis of MCC, PDMCC, and cellulose/SPI composite films. The simple dip-coating approach in dopamine solution has been proven effective for fabricating adherent PDA layer on a wide range of materials.21 The catechol in dopamine was oxidized to benzoquinone and described as: the oxidation of dopamine to dopamine-quinone, its intramolecular cyclizaiton led to the oxidation of leucodopaminechrome,

5,6-dihydroxyindole

and

further

oxidation

to

5,6-indolequinone (Scheme 1).26 The PDA layer containing quinone and/or -NH/-OH 7



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groups could react with -SH/-NH2 groups via Michael addition or Schiff base reactions of the protein side chains as presented in Scheme 1.20, 23,29

Scheme 1. Proposed mechanism of PDA-coating via dopamine polymerization and chemical reactions of PDMCC and SPI. The surface modification of MCC was ascertained by comparing the XPS spectra of the MCC and PDMCC surfaces. Figure 1 shows the XPS wide scan and C 1s core-level spectra of the untreated MCC (Figure 1A) and PDMCC (Figure 1B). The wide scan spectra of MCC showed peak components of C 1s and O 1s ascribed to the C and O elements, while the N 1s peak arose in the PDMCC spectra corresponding to the N elements. The C 1s core-level spectrum of MCC was curved-fitted to three peak components containing the binding energy (BE) at 284.2 eV for C-C species, at 285.7 eV for C-O species, and at 286.9 eV for O-C=O species.20, 30 After the dopamine coating treatment, the C 1s core-level spectrum of PDMCC changed to four peak components and BE at 284.9 eV, which was likely attributable to the C-N species. In addition, the intensity of the C-C curve-fit spectrum in PDMCC increased compared to that of the MCC specimen. Taken together, these results demonstrated that the PDA layer was successfully coated onto the MCC surface.

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Figure 1. XPS wide-scan and C 1s core-level spectra of (A1-A2) untreated MCC and (B1-B2) PDMCC. The chemical structures of MCC and PDMCC were investigated by ATR-FTIR and showed in Figure 2A. For MCC, the characteristic peak assignments from 2000 to 1000 cm-1 included: asymmetric CH2 bending and wagging at 1428 and 1315 cm-1; C-CH2-C bending at 1160 cm-1; and C-O stretching vibration at 1058 and 1035 cm-1, in accordance with findings by Lee et al.34 The bands at 3332 and 2890 cm-1 were attributed to the stretching of -OH and C-H groups, respectively. After the oxidative dopamine self-polymerization, the characteristic peaks of MCC were relatively well-retained and new bands at 1596 and 1505 cm-1 appeared, indicating aromatic C=C stretching vibrations and some new characteristic peaks of C=N, N-H deformation vibration in the PDMCC.35 The broad overlapped band around 3332 cm-1 was attributed to catechol -OH/ N-H groups stretching of PDMCC which became thin and sharpened in comparison to that of MCC.36 These results were probably 9



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indicative of the polymerization of dopamine and the successfully coating on the MCC surface (Scheme 1). Figure 2B shows the ATR-FTIR spectra of the SPI-based films, as well the PDMCC powder. The amide bands at 1645, 1539, and 1237 cm-1 were referred to the amideⅠ(C=O stretching), amide Ⅱ(N-H bending), and amide Ⅲ (C-N and N-H stretching), respectively.33 The broad absorption band at 3280 cm-1 was attributed to the O-H and N-H bending vibrations,9, 18 and the peak at 2937 cm-1 was assigned to the stretching vibrations of methylene groups.33 The broad absorption peak at 1596 cm-1 in PDMCC disappeared in PDMCC/SPI films, partly demonstrating the physical/chemical combinations between PDA and SPI chains.

Figure 2. ATR-FTIR spectra of the (A) MCC and PDMCC monomers; (B) SPI-based films: (a) SPI, (b) MCC/SPI, (c) PDMCC/SPI-1, (d) PDMCC/SPI-2, (e) PDMCC/SPI-3 films and (f) PDMCC monomer. Furthermore, the

13

C NMR spectra were applied to further detect the reactions

between PDMCC and SPI matrix (Figure 3). Noticeable peaks of the cellulose carbon atoms (C1-C6) were between 60 and 110 ppm in the PDMCC spectrum.14 The peak at 103.5 ppm, 85.4 ppm, and 67.8 ppm, were due to the ordered cellulose C1, C4 and C6 carbons, respectively. Besides, the peaks between 110-156 ppm were referred to different aromatic carbons of the PDA layer.28 The major peaks of SPI spectrum were consistent with the report of Ma et al.10 The chemical shifts in 155-170 ppm of 10


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carbonyl; 115-130 ppm of aromatic carbon; 45-65 ppm of α-carbon; 25-45 ppm of β-carbon and methylene and methyl groups in 15-25 ppm were also observed as shown in Figure 3. Compared to the unmodified SPI film, the characteristic peaks of PDMCC/SPI film were well-retained and only weak peak at 103.5 ppm of C1 atom in PDMCC could be seen, probably due to the small proportion of PDMCC to SPI (2 wt%). Broader and more intense peaks at 163.1 and 124.9 ppm were observed in the PDMCC/SPI film compared with the unmodified SPI films, demonstrating the physical/chemical combination of PDMCC to SPI matrix. Corresponding to the findings of insert SEM images (fracture surface morphologies of MCC/SPI and PDMCC/SPI films) in Figure 3: differ from the broad interspace between MCC and SPI matrix (Figure 3A), the PDMCC was more tightly surrounded by the SPI matrix, confirming the favorable bi-phase interfacial adhesion in PDMCC/SPI films.

Figure 3. Solid-state

13

C NMR spectra of PDMCC powder, SPI film and

PDMCC/SPI film; Insert SEM images of fracture surface of (A) MCC/SPI film and (B) PDMCC/SPI film. Thermal performance of MCC, PDMCC, and cellulose/SPI films. The thermal properties of MCC, PDMCC and the cellulose/SPI films were examined by TGA.

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(Figure 4) The thermo-degradation data are listed in Table S1. Figure 4A shows the weight loss traces and derivative TG (DTG) curves of MCC and PDMCC powders, respectively. The main decomposition stage around 350°C was attributed to the degradation of carbonaceous matter in MCC. The temperature at maximum degradation rate (Tmax) in DTG curve of PDMCC was increased from 350.54°C to 352.99°C in MCC, and the subsequent weight loss of PDMCC slightly decreased, from 93.53% to 90.55%, (Table S1). Both these results indicated the deposition of the PDA layer onto the MCC surface.20 As shown in Figure 4B, the SPI-based films underwent three degradation stages: generally, 20°C to 130°C for dehydration reaction; 130°C to 270°C mainly for glycerol degradation; 270°C to 450°C for backbone peptides degradation.9, 33 The degradation peak of cellulose around 350°C disappeared in the cellulose/SPI films, and the weight losses (ML3) in the third stage slightly decreased in comparison with the control one (Table S1), demonstrating the favorable bi-phase combination.20 In the second stage, the cellulose/SPI films degraded faster and with greater weight loss compared to the control, which could explain the diminished toughness of the composite films by the reduced EB (Table 2). However, Tmax2 listed in Table S1 only shows a slight increase. Therefore, the addition of cellulose did not have much influence on the thermal stability of the SPI-based films.

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Figure 4. Thermogravimetric (TG) and derivative thermogravimetric (DTG) curves of (A) MCC before and after dopamine coating; (B) typical SPI, MCC/SPI, and PDMCC/SPI films. Micromorphology analysis of MCC, PDMCC, and cellulose/SPI films. The surface morphology of MCC before and after coating treatment was observed by SEM. The unmodified MCC showed an uneven surface with grooves and micropits, and with a diameter range about 10-50 µm in Figure 5A, C. After the dopamine coating treatment, the deposited PDA was spotted onto MCC and roughed the PDMCC surface (Figure 5B, D). Therefore, the dip-coating method successfully produced an adherent PDA layer onto the MCC surface, which could act as versatile active binding sites to chemically combine with SPI chains.21

Figure 5. SEM images of (A,C) untreated MCC powder; (B,D) PDA-coated PDMCC powder. The surface nano-topographies of the SPI, MCC/SPI, and PDMCC/SPI films were examined by AFM. The unsmooth surface of SPI film shown in Figure 6A was 13



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probably resulted from the massive nonpolar, polar, and charged amino acids, and the peptide chains self-aggregation during the drying process, and similar findings were reported by Jensen et al.37 After the integration with MCC or PDMCC, the surface needlepoints of the unmodified SPI film were shaved away, (Figure 6B-C) probably resulted from the polar/charged moieties in SPI physically/chemically combined with celluloses, corresponding to the ATR-FTIR and

13

C NMR analysis results. The

cellulose/SPI films retained rough surfaces and the root-mean-square roughness (Rq) (across a 10.0 × 10.0 µm2 area) of the SPI, SPI/MCC, and SPI/PDMCC films were 33.1 ± 4.24 nm, 101 ± 2.54 nm, and 72.5 ± 4.75 nm, respectively. The Rq of cellulose/SPI films were much higher than that of the unmodified SPI film, mostly due to the incompatibility between MCC and SPI chains. However, the PDMCC was relatively more compatible to the peptide chains, as its Rq was lower than that of the MCC/SPI film. This was attributed to the rough PDMCC surface and the better interfacial adhesion between PDMCC and SPI matrix.31,38

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Figure 6. AFM height images and 3D topography of (A1-2) unmodified SPI film, (B1-2) MCC/SPI film, and (C1-2) PDMCC/SPI film. Mechanical properties and water resistance of cellulose/SPI composite films. Generally, cellulose fibrils can reinforce the synthetic/natural matrices due to the resultant high crystallinity and high aspect ratio. 11,15 However, the mutual hydrogen bonding is somewhat inferior to chemical bonds and leads to the weak phase interfacial adhesion.16, 18 The dopamine-coating modification for MCC could expose versatile active binding sites to the -SH/-NH2 groups of the SPI chains, and converted MCC to a more potent reinforcement to the SPI films.20-21 The TS and EB of the SPI-based films are listed in Table 2. After celluloses were incorporated, TS of the MCC/SPI-2 and PDMCC/SPI-2 films increased to 5.2 MPa and 6.2 MPa, counting the increases of 52.9% and 82.3%, respectively, compared to the unmodified film. However, excessive cellulose addition lowered TS, probably due

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to the bulk aggregation of celluloses which induced stress concentration, and caused films’ mechanical breakage.16 Obviously, TS of the PDMCC/SPI films were higher than that of the MCC/SPI films at the same cellulose addition, due to the rough and active PDMCC surfaces physically/chemically combining to the SPI matrix. EB of both MCC/SPI and PDMCC/SPI films decreased because of the heterogeneous combination of celluloses with the SPI matrix, which partly disabled the composite films interfacial stress transferring, and caused to self-stiffen. The thickness of cellulose/SPI films ranged from 0.296 nm to 0.369 mm, as shown in Table 2. Table 2. Mechanical properties (TS, EB) and thicknesses of SPI-based films. Entry

Thickness (mm)

Tensile strength (MPa)

Elongation at break (%)

SPI MCC/SPI-1 MCC/SPI-2 MCC/SPI-3 PDMCC/SPI-1 PDMCC/SPI-2 PDMCC/SPI-3 Increment (%) b

0.365 (0.030)a 0.329 (0.006) 0.296 (0.016) 0.369 (0.014) 0.341 (0.015) 0.330 (0.017) 0.302 (0.094) -

3.4 (0.20) 4.9 (0.27) 5.2 (0.26) 4.5 (0.31) 5.2 (0.19) 6.2 (0.23) 5.1 (0.31) 82.3

132 (0.09) 98 (0.06) 68 (0.12) 110 (0.17) 83 (0.13) 67 (0.18) 93 (0.07) -49.2

a

Mean (standard deviation). Increment calculated from the mechanical properties of PDMCC/SPI-2 film compared to SPI film.

b

The effects of MCC or PDMCC addition on the water resistance (moisture, WA, TSM) and the surface hydrophilicity (WCA) of cellulose/SPI films were tested and showed in Table S2. Both WA and TSM decreased when 1wt% or 2wt% MCC or PDMCC incorporated. Compared to the control, the WA and TSM of the PDMCC/SPI-2 film were decreased by 31.3% and 21.5%, respectively. The WCA values increased cooperating with PDMCC. The active interfacial adhesion in PDMCC/SPI composite films might promote the SPI chains crosslinking and form denser polymeric network, and thus resisted the water molecules permeation. 16


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Conclusions A fully renewable, plant-derived, and nature-inspired composite film with enhanced mechanical properties and water resistance was developed from SPI and surface-modified MCC using the dopamine dip-coating method in this study. The superficial active groups on the MCC surface through dopamine self-oxidative polymerization were confirmed by the XPS, ATR-FTIR, and TGA analysis. The exposed quinone/-NH/-OH groups on the PDA layer apparently generated secondary reactions to the SPI matrix, which increased the interfacial adhesion between celluloses and SPI chains. The mechanical properties and water resistance of the PDMCC/SPI films were enhanced due to the highly crystallized MCC and the elevated active interface via PDA physical/chemical bonding. The TS of PDMCC/SPI films increased from 3.4 MPa to 6.2 MPa, and the WA and TSM decreased by 31.3% and 21.5%, respectively, compared to the unmodified one. Validated by the laboratory experiments, this research proposed a facile method for chemically combining high-performance celluloses with natural protein matrices, which brought hope to accelerate the development of green and renewable composite materials.

Supporting Information The equations S1-S3 of the moisture content (MC), total soluble matter (TSM), and water absorption (WA) calculation, the thermo-degradation data of MCC, PDMCC monomers, and SPI-based films in Table S1, and the Moisture, WA, TSM, and WCA of SPI-based films in Table S2 are listed in the Supporting Information file.

Corresponding Author Shifeng Zhang, E-mail: [email protected], Tel: 86 (+10) 62336072; Jianzhang Li, E-mail: [email protected] (Z. Li). 17



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Acknowledgment This work is partially supported by the National Forestry Public Welfare Industry Major Projects of Scientific Research (201504502), and the Fundamental Research Central Funds for the Universities (BLYJ201624).

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For Table of Contents use only High-performance and Fully Renewable Soy Protein Isolate-based Film from Microcrystalline Cellulose via Bio-Inspired Poly(Dopamine) Surface Modification Haijiao Kang, Xiangshuo Song, Zhong Wang, Wei Zhang, Shifeng Zhang,* and Jianzhang Li*

A mussel-inspired surface modification of micro-cellulose to reinforce the biodegradable soy protein isolate films is developed to response the sustainable pursuits.

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High-Performance and Fully Renewable Soy Protein Isolate-Based

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