In vitro degradation of starch/PVA films and biocompatibility evaluation

A series of starch/PVA (SP) films with the thickness of 0.05–0.1 mm were cast by solvent method. The swelling and degradation behaviors in simulated blood fluid (SBF) and simulated saliva fluid (SSF) within 30 days were investigated. In vitro biocompatibility was also evaluated. Research purpose of this work was to supply basic data for SP films' potential application in guide tissue regeneration (GTR) technology. It took 10–20 min for different samples to reach to their maximum water absorption and 30 min to lever off. The weight loss of all samples decreased rapidly in the first day in both of SBF or SSF, and then it changed slightly in SSF but decreased step by step in SBF. The mechanical properties of the wet SP films were satisfied with the requirement of GTR membrane. No matter in SBF or SSF, although the mechanical properties decreased rapidly in the first day, they changed slightly after that. Cytotoxicity and L929 fibroblasts attachment test proved that the SP film possesses excellent cell affinity. Hemolysis ratios of all samples were less than 5%. All results demonstrated that SP film is a promising candidate in GTR treatment. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of the oxidation and acetylation of banana starch on the mechanical and water barrier properties of modified starch and modified starch/chitosan blend films

Banana starch was oxidized at three different levels and afterwards acetylated. The double‐modified starch was used for film preparation with the addition of chitosan. The physical, mechanical, and barrier properties were tested. The oxidation level increased the moisture content of the film, but the acetylation and the addition of chitosan decreased this characteristic. The oxidation level increased the whiteness of the film, but the second modification (acetylation) and the addition of chitosan to the blend did not affect this parameter. The solubility increased with the temperature and the oxidation level but decreased with the storage time of the film. The oxidation increased and the acetylation reduced the solubility with respect to the native starch film. The dual modification produced a solubility value less than that of its oxidized counterpart, and the addition of chitosan produced the highest solubility value. The addition of chitosan increased the tensile strength of the film, and the effect was higher with the oxidation level and longest storage time. The addition of chitosan produced a higher elongation value than that of its double‐modified film, but at the longest storage time, this parameter decreased. The water vapor permeability increased with the oxidation level because of the hydrophilic character, but the acetylation reduced this parameter because the acetylation increased the hydrophobic character of the starch due to the ester group. Films prepared with the double‐modified banana starch and the addition of chitosan had some improved physical, mechanical, and barrier properties, and they may be used in specific applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

In vitro enzymatic degradation kinetics of polymeric blends of crosslinked starch and carboxymethyl cellulose

Hydrophilic blend matrices of crosslinked starch and carboxymethyl cellulose were synthesized and their susceptibilities to enzymatic degradation were assessed by taking α‐amylase as a model enzyme. The polymeric blends were characterized by FT‐IR spectroscopy, differential scanning calorimetry and scanning electron microscopy. The influence of the chemical compositions of the blends, and the pH values and temperatures of the α‐amylase solutions was investigated by studying the swelling and degradation kinetics of the blends. The impact of the concentrations of the enzyme solutions on the degradation profiles was also examined. The blends were found to exhibit a mixed type of degradation mechanism, ie both diffusion and surface erosion. Copyright © 2005 Society of Chemical Industry     

Synthesis,characterization, and enzymatic degradation of chitosan/PEG hydrogel films

Poly(ethyleneglycol) (PEG)/tartaric acid (TA)‐crosslinked chitosan hydrogel (CPT) films were prepared, and the formation of the PEG/TA‐crosslinked structure was confirmed by Fourier transformed infrared (FTIR), nuclear magnetic resonance (NMR), and scanning electron microscope (SEM) measurements. The thermal properties of the crosslinked films were also determined with thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) analysis. The swelling properties of the films were investigated at different temperature and pH values. It was found that the swelling ratio increased with the decrease of pH value of the surrounding buffer solutions, amount of PEG, and with the increase of temperature. Swelling behavior of the PEG/TA‐crosslinked chitosan hydrogel films depended on pH and reversible with the temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Tensile properties,degradation behavior,and water absorption of sago starch plastic films

Sago starch plastic films were prepared by a blending and casting method using various amounts of additives. The additives were glycerol (GLY), polyethylene glycol (PEG), and glutaraldehyde (GLU). Results indicated that the films had an optimum tensile strength of about 2.6 MPa and an optimum elongation at break of 74%. Meanwhile, a GLU content of five parts by weight gave the best tensile properties. Elongation at break of the films increased while tensile strength decreased upon increasing the level of plasticizer (GLY and PEG). The addition of plasticizer also increased the water absorption and soil burial degradation rate. However, the addition of GLU gave opposite results. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Synthesis,characterization, and enzymatic degradation of starch-grafted poly(methyl methacrylate) copolymer films

Graft copolymerization of methyl methacrylate (MMA) onto the corn starch (CS) backbone was carried out in an aqueous medium using ceric ammonium nitrate as an initiator under nitrogen atmosphere. The weight ratio of CS/MMA varied with their composition, as 7/3, 6/4, 5/5, 4/6, and 3/7 were used in this study of the graft efficiency and graft percentage (GP); thus, five different GP CS-g-PMMA copolymers were obtained. The molecular weight of CS-g-PMMA copolymers were measured by using gel permeation chromatography. The structure of CS and CS-g-PMMA copolymer were confirmed by infrared spectra. CS and CS-g-PMMA copolymers were characterized by thermal gravimetric analysis, differential scanning calorimetry, and scanning electron microscopy (SEM). Horowitz-Metzger and Broido methods were applied to investigate the thermal decomposition kinetics of CS-g-PMMA copolymers. The effect of GP on the activation energy of decomposition, crystallization behavior, and morphology was investigated. In addition, the biodegradability of CS-g-PMMA films were also studied by α-amylase treatment with different times. The weight loss of CS-g-PMMA films after α-amylase treatment were calculated. Finally, the morphology of CS-g-PMMA films before and after α-amylase treatment were observed by SEM photograph. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Thermally induced crystallization and enzymatic degradation studies of poly (L‐lactic acid) films

Poly(L ‐lactic acid) (PLLA) films with different crystallinities were prepared by solvent casting and subsequently annealed at various temperatures (T_a) (80–110°C). The effects of crystallinity on enzymatic degradation of PLLA films were examined in the presence of proteinase K at 37°C by means of weight loss, DSC, FTIR spectroscopy, and optical microscopy. DSC and the absorbance ratio of 921 and 956 cm^?1 (A₉₂₁/A₉₅₆) were used to evaluate crystallinity changes during thermally induced crystallization and enzymatic hydrolysis. The highest percentage of weight loss was observed for the film with the lowest initial crystallinity and the lowest percentage of weight loss was observed for the film with highest crystallinity. FTIR investigation of degraded films showed a band at 922 cm^?1 and no band at 908 cm^?1 suggested that all degraded samples form α crystals. The rate of degradation was found to depend on the initial crystallinity of PLLA film and shown that enzymatic degradation kinetics followed first‐order kinetics for a given enzyme concentration. DSC crystallinity and IR absorbance ratio, A₉₂₁/A₉₅₆ ratio, showed no significant changes with degradation time for annealed PLLA films whereas as‐cast PLLA film showed an increase in crystallinity with degradation; this revealed that degradation takes place predominantly in the free amorphous region of annealed PLLA films without changing long range and short range order © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

水解酶法回收木薯黄浆废水中的淀粉

以胰蛋白酶作为水解酶,采用水酶法从木薯黄浆废水中回收淀粉。通过调节酶加量、温度、时间、pH等因素,得到木薯淀粉的最佳回收条件:加酶量0.05 g/L,酶解时间3 h,酶解温度35℃,酶解pH值为8.5。在最佳条件下得到沉淀物质量为10.85 g/L,沉淀物中淀粉含量为80.4 g/100 g,粗淀粉质量为8.72 g/L。     

A kinetic model for enzymatic wheat starch saccharification

A kinetic model describing the enzymatic saccharification of wheat starch by a mixture of α‐amylase and amyloglucosidase has been developed. The model describes the influence of pH, glucose inhibition and starch and enzyme concentration. The results of experimental saccharification under different physical conditions, eg pH and temperature, were used to determine the parameters in the model. The dominant enzyme in the mixture was amyloglucosidase and the maximum rate of saccharification due to this enzyme was found to be optimal at pH 5, and increased Five‐Fold when the temperature was increased from 30 to 55 °C. Saccharification due to the action of amyloglucosidase was inhibited by the glucose produced and simulation showed that the maximum rate of saccharification decreased by 58% at a starch concentration of 140 g dm⁻³ compared with a starch concentration much less than 110 g dm⁻³ where the effect of glucose inhibition was negligible. © 2000 Society of Chemical Industry     

Synthesis and enzymatic degradation of regular network aliphatic polyesters

Regular network aliphatic polyesters were prepared from glycerol (Yg) and a series of various length aliphatic dicarboxylic acids (HOOC-(CH2)_n−2-COOOH, n = 4–10, 12 and 14). Prepolymers prepared by melt polycondensation were cast from dimethylformamide solution and post-polymerized at 230°C for various times to form a network. The resultant films were transparent, flexible and insoluble in organic solvents. The degree of reaction (D_R) estimated from the infrared absorbance of -OH and >CH₂ or >CH groups increased with increasing post-polymerization time and length of methylene chain. The heat distortion temperature also increased with increasing post-polymerization time and was 55, 28, 15, 6, 0, −1, −5, 4 and 32°C for Yg4, Yg5, Yg6, Yg7, Yg8, Yg9, Yg10, Yg12 and Yg14 post-polymerized for 4 h, respectively. Wide angle X-ray scattering patterns showed a distinct single diffraction peak, suggesting some ordered structure due to the establishment of a regular network. Density, water absorption and weight loss by alkali hydrolysis decreased with increasing methylene chain length. The enzymatic degradation was estimated by weight loss of the network films in a buffer solution of lipase at 37°C. The films of Yg4, Yg5, Yg6 and Yg7 showed no weight loss, but the weight loss increased greatly for Yg8, Yg9 and Yg10, and then decreased abruptly for Yg12 and Yg14. This suggests that the enzymatic degradation is affected by network structure, which allows the lipase to penetrate, and by the concentration of the enzymatically degradable ester linkage.     

Effect of enzymatic treatment of different starch sources on the in vitro rate and extent of starch digestion

Gelatinized wheat, potato and waxy maize starches were treated enzymatically in order to increase the degree of branching of the amylopectin fraction and thereby change the starch degradation profile towards a higher proportion of slowly digestible starch (SDS). The materials were characterized by single-pulse (1)H HR-MAS NMR spectroscopy and in vitro digestion profile according to the Englyst procedure. Using various concentrations and incubation times with branching enzyme (EC 2.4.1.18) without or with additional treatment with the hydrolytic enzymes; β-amylase (EC 3.2.1.2), α-glucosidase (EC 3.2.1.20), or amyloglucosidase (EC 3.2.1.3) the proportion of α-(1-6) linkages was increased by up to a factor of 4.1, 5 and 5.8 in waxy maize, wheat and potato starches, respectively. The proportion of SDS was significantly increased when using hydrolytic enzymes after treatment with branching enzyme but it was only for waxy maize that the proportion of α-(1-6) bonds and the in vitro digestion profile was significantly correlated.     

Mechanical and microstructural properties of pectin/starch films

Films were made from blends of high methoxy pectin and high amylose starch gelatinized in a microwave oven in the presence and absence of glycerol at times ranging from 10 to 105 s. Three thermodynamic transitions were observed when storage modulus, loss modulus, and loss tangent were plotted against temperature. All three transitions gave minima when the transition temperature was plotted against time of gelatinization. Overall, there were only modest changes in these moduli over the range of gelatinization times studied, with little difference between films made with the starch gelatinized in either the presence or absence of glycerol. Starch granules were found to disappear at gelatinization times between 20 and 30 s, although much smaller starch particles seemed to recur at gelatinization times of 75 s and above. The minima found in the transition temperature and modulus plots were believed to result from a minimum in the amount of intermolecular interactions between the starch molecules. © 1995 John Wiley & Sons, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

The degradation of high impact polystyrene with and without starch in concentrated activated sludge

Disposal of plastic solid waste is primarily accomplished by landfilling, degradation, and recycling. Degradation is highly justified in some applications. In this work, high impact polystyrene blended with starch (16–32% weight) in a “V” mixer is degraded in concentrated activated sludge for 12 weeks. Samples of 0.75 mm thickness were obtained in ribbon geometry by single screw extrusion. Mechanical degradation was determined by stress-strain tests. Gel permeation chromatography measurements established changes towards lower polymer molecular weights. Scanning electron microscopy examination showed the presence of microorganisms in the polymer samples, as well as changes in polymer morphology in areas near holes produced in samples. Results demonstrate the utility of concentrated activated sludge in polymer degradation and the effectiveness of starch inclusion as a filler to accelerate the structural molecular changes.     

Synthesis and enzymatic degradation of high molecular weight aliphatic polyesters

The aliphatic polyesters with high molecular weight have been prepared according to two methods. First is the synthesis of the polyesters by polycondensation of dimethyl succinate (DMS) with 1,4‐butanediol (BD) using various metal alkoxides as a catalyst. Among the metal alkoxides used, titanium tetraisopropoxide [Ti(OiPr)₄] gave the best results (highest molecular weight and yield). Thus, we have prepared aliphatic polyesters using a variety combinations of diesters [MeOOC—(CH₂)_x—COOMe, x = 2–8] with BD by the catalysis of Ti(OiPr)₄. The polyesters with high number‐average molecular weight (M_n > 35,000), except dimethyl adipate (DMA, x = 4)/BD polyester (M_n = 26,900), were obtained in high yield. The melting temperatures (T_m) of polyesters were relatively low (43.4–66.8°C) except that (115.6°C) of the DMS/BD polyester. Second is the synthesis of high molecular weight polyesters by chain extension reaction of lower molecular weight (M_n = 15,900–26,000) polyesters using hexamethylene diisocyanate (HDI) as a chain extender. The M_n values of chain‐extended polyesters consequently increased more than two times (M_n = 34,700–56,000). The thermal properties of polyesters hardly changed before and after chain extension. Enzymatic degradations of the polyesters were performed using three different enzymes (cholesterol esterase, lipase B, and Rhizopus delemar lipase) before chain extension. The enzymatic degradability varied depending on both thermal properties of polyesters [melting temperature and heat of fusion (crystallinity)] and the substrate specificity of enzymes, but it was the following order: cholesterol esterase > lipase B > R. delemar lipase. The ¹H‐NMR spectrum of water‐soluble degraded products of the polyester indicated that the polyester was degraded into a condensation product of diol with diester in a monomer form. The enzymatic degradation of chain extended polyesters was slightly smaller than that before chain extension, but proceeded steadily. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 340–347, 2001     

Formation of hydrophilic starch coatings on polyethylene films

Thin starch coatings were deposited onto polyethylene (PE) film surfaces when PE films were immersed in 1% jet cooked starch solutions and the hot solutions were allowed to cool. Normal cornstarch, waxy cornstarch, high amylose cornstarch, and solvent‐extracted normal cornstarch (to remove native lipid) were used in these experiments. Amounts of adsorbed starch varied from about 0.03–0.05 mg per cm² of PE, and these starch coatings imparted hydrophilic properties to film surfaces, as evidenced by contact angle measurements. Although starch could be removed by gently rubbing water‐wet PE surfaces, air‐dried coatings were more firmly attached, and did not separate from the PE surface when films were bent or flexed. SEM images of starch‐coated film surfaces showed that starch was deposited as particles less than 1 μm in diameter, and also as aggregates of these submicron particles. Despite the fact that some starch samples contained only very small amounts of amylose and native lipid, surface‐deposited starch in all experiments contained 90–100% amylose; and exhibited the same V_h X‐ray diffraction pattern, indicative of helical inclusion complex formation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1781–1788, 2002; DOI 10.1002/app.10589     

Reduction-oxidation photocycle dynamics of flavins in starch films

The blue-light photo-reduction (conversion of oxidized flavin quinone via flavin semiquinone to fully reduced flavin hydroquinone) and dark re-oxidation of the flavins riboflavin and lumiflavin in starch (α-amylose) films was studied by absorption and luminescence spectroscopy. Blue-light photo-excitation caused an absorption, fluorescence, and phosphorescence decrease which recovered in the dark. The photo-reduction dark-oxidation cycle could be repeated. The efficiency of photo-reduction decreased with exposed excitation energy, and the speed of re-oxidation in the dark slowed down with time after excitation. The absorption did not fully recover. The fluorescence efficiency after a long time of storage in the dark increased beyond the initial flavin quinone fluorescence efficiency. Flavin photo-excitation is thought to cause starch-flavin restructuring (static fluorescence quenching center formation), enabling enhanced photo-induced starch to flavin electron transfer with subsequent flavin reduction and starch oxidation. In the dark, after light switch-off, thermal reversion of flavin reduction and starch oxidation occurred.     

New evidences of accelerating degradation of polyethylene by starch

An investigation into the effects of starch on both, UV photo‐oxidative degradation and biodegradation, of HDPE was focused on the interface between HDPE and starch using Synchrotron‐FTIR microscope (SFTIR‐M) and scanning electronic microscope (SEM). Carbonyl group detection by FTIR was conducted to evaluate the effect of degradation following exposure to UV photo‐oxidative degradation. The results showed that the concentration of carbonyl groups on the interface were higher, suggesting the role of starch in accelerating the UV photo‐oxidative degradation of HDPE. The interface between HDPE and starch was further observed under SEM to study the morphological changes after UV photo‐oxidative degradation and biodegradation. Micro‐cracking was observed on the interface between starch and HDPE after UV photo‐oxidative degradation. Tensile testing after UV exposure showed that the variation rate of elongation was higher for the samples containing starch. Starch, an easily biodegradable material, can also act as initial source of nutrients for micro‐organisms (bacteria, fungi, and algae) in the blend materials thus enhancing their biodegradability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2282–2287, 2013     

Effect of acetylation and oxidation on some properties of breadfruit (Artocarpus altilis) seed starch

Starch extracted from seeds of Artocarpus altilis (Breadfruit) was chemically modified by acetylation and oxidation, and its functional properties were evaluated and compared with these of native starch. Analysis of the chemical composition showed that moisture content was higher for modified starches. Ash, protein, crude fiber and amylose contents were reduced by the modifications, but did not alter the native starch granules' irregularity, oval shape and smooth surface. Acetylation produced changes in water absorption, swelling power and soluble solids, these values were higher for acetylated starch, while values for native and oxidized starches were similar. Both modifications reduced pasting temperature; oxidation reduced maximum peak viscosity but it was increased by acetylation. Hot paste viscosity was reduced by both modifications, whereas cold paste viscosity was lower in the oxidized starch and higher in the acetylated starch. Breakdown was increased by acetylation and reduced with oxidation. Setback value was reduced after acetylation, indicating it could minimize retrogradation of the starch.     

Morphological,barrier, and mechanical properties of cassava starch films reinforced with cellulose and starch nanoparticles

A comparative performance study of cellulose and starch nanoparticles on plasticized starch reinforcement has been presented. Starch nanoparticles were obtained by ultrasound and acid hydrolysis, and cellulose nanoparticles were extracted by acid hydrolysis from microcrystalline cellulose and sisal fibers. The nanoparticles were characterized according to the zeta potential, the particle-size distribution, transmission electron microscopy, X-ray diffraction, and thermogravimetric analysis. The influence of the addition of these nanoparticles to starch films on the morphology, water vapor permeability (WVP), and mechanical properties of the nanocomposites films were investigated. The cellulose nanoparticles exhibited higher electrical stability than those originating from starch. Acid hydrolysis produced starch nanoparticles with higher crystallinity than ultrasound. All the nanoparticles significantly reduced the WVP. The cellulose nanoparticles significantly increased the tensile strength of the starch films; however, they reduced the flexibility of the nanocomposites. The results of this work support the application of starch and cellulose nanostructures for the development of reinforced biodegradable materials. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47001.