Characterization of α-tocopherol as interacting agent in polyvinyl alcohol–starch blends

In this study, the interactions of α-tocopherol (α-TOH) in PVOH–starch blends were investigated. α-TOH is an interacting agent possesses a unique molecule of polar chroman “head” and non-polar phytyl “tail” which can improve surface interaction of PVOH and starch. It showed favorable results when blending PVOH–starch with α-TOH, where the highest tensile strengths were achieved at 60 wt.% PVOH–starch blend for 1 phr α-TOH and 50 wt.% for 3 phr α-TOH, respectively. This due to the formation of miscible PVOH–starch as resulted by the compatibilizing effect of α-TOH. Moreover, the enthalpy of melting (ΔH_m) of 60 wt.% PVOH–starch and 50 wt.% PVOH–starch added with 1 and 3 phr α-TOH respectively were higher than ΔH_m of the neat PVOH–starch blends. The thermogravimetry analysis also showed that α-TOH can be used as thermal stabilizer to reduce weight losses at elevated temperature. The surface morphologies of the compatible blends formed large portion of continuous phase where the starch granules interacted well with α-TOH by acting as compatilizer to reduce surface energy of starch for embedment into PVOH matrix.     

Physicochemical Properties of Biodegradable Polyvinyl Alcohol–Agar Films from the Red Algae <Emphasis Type="Italic">Hydropuntia cornea</Emphasis>

Agar obtained from the red alga Hydropuntia cornea was blended with polyvinyl alcohol (PVOH) in order to produce biodegradable films. In this study, we compare the properties of biopolymeric films formulated with agars extracted from H. cornea collected at different seasons (rainy and dry) in the Gulf of Mexico coast and PVOH as synthetic matrix. The films were prepared at different agar contents (0%, 25%, 50%, 75%, and 100%) and their optical, mechanical, thermal, and morphological properties analyzed. The tensile strength of PVOH–agar films increased when agar content was augmented. The formulation with 50% agar from rainy season (RS) had a significant higher tensile strength when compared to those from dry season (DS; p < 0.05). Tensile modulus also displayed an increasing trend and likewise, for 50% and 75% agar blends from RS showed higher values than those from DS (p < 0.05). In contrast, elongation at break decreased as the agar content increased, independently of the season. Environmental scanning electron microscopy images of PVOH–agar 75% biofilms from RS showed a homogeneous structure with good interfacial adhesion between the two components. The changes evidenced in the FTIR spectrum of this blend suggest that hydrogen bonding is taking place between the agar ether linkages (C-O-C) and the hydroxyl groups (OH) of the PVOH. Based on the above mentioned results, blends of PVOH and 75% agar from H. cornea collected in rainy season showed good properties for applications in the biodegradable packaging industry.     

The enzymatic hydrolysis of starch-based PVOH and polyol plasticised blends

Thermoplastic starch (TPS) materials present several advantages to the plastic industry and when blended with other materials they can exhibit improved mechanical and moisture sensitivity properties compared to pure TPS materials. However, the biodegradability of these blends, through such processes as enzymatic degradation, needs to be characterised to ensure the beneficial properties of TPS are not compromised. The aims of the study were to investigate the effect of varying polyvinyl alcohol (PVOH) content and polyol type within the TPS blends on the rate and extent of starch enzymatic hydrolysis using enzymes α-amylase and amyloglucosidase. The results of this study have revealed that TPS:PVOH blends with a PVOH content at 50 wt% exhibited a significantly reduced rate and extent of starch hydrolysis. The results suggest that this may have been attributed to interactions between starch and PVOH that further prevented enzymatic attack on the remaining starch phases within the blend. The extent of starch hydrolysis was not significantly affected by polyol type, however, the rate of starch hydrolysis from the maltitol blend was significantly reduced compared to sorbitol and glycerol substrates.     

The anaerobic degradability of thermoplastic starch: polyvinyl alcohol blends: potential biodegradable food packaging materials

A systematic study on the anaerobic degradability of a series of starch:polyvinyl alcohol (TPS:PVOH) blends was performed to determine their fate upon disposal in either anaerobic digesters or bioreactor landfills. The aims of the study were to measure the rate and extent of solubilisation of the plastics. The extent of substrate solubilisation on a COD basis reached 60% for a 90:10 (w/w) blend of TPS:PVOH, 40% for 75:25, 30% for 50:50 and 15% for PVOH only. The rate of substrate solubilisation was most rapid for the 90:10 blend (0.041 h(-1)) and decreased with the amount of starch in the blend in the following order 0.034 h(-1)(75:25); 0.023 h(-1)(50:50). The total solids that remained after 900 h were 10 wt.% (90:10); 23 wt.% (75:25); 55 wt.% (50:50); 90 wt.% (0:100). Starch containing substrates produced a higher concentration of volatile fatty acids (VFAs) and biogas, compared to the 0:100 substrate. The major outcome was that PVOH inhibited the degradation of the starch from the blend.     

Thermal Characterization and Phase Behavior of a Ready-to-Eat Breakfast Cereal Formulation and its Starchy Components

Gelatinization in excess of water and melting transition for different moisture contents of a ready-to-eat cereal formulation (RTE blend) and its major components, (i.e., oat flour, rice flour, and an oat–rice flour blend) were studied by differential scanning calorimetry (DSC) and rapid visco-analyzer (RVA). The highest swelling power was exhibited by the rice flour and the lowest by the RTE blend. Two endothermic peaks under excess of water were exhibited by all materials, at 53–75 °C and 80–102 °C, and they were associated to gelatinization and cereal protein denaturation, respectively. A third peak appearing in all materials except in rice flour, at higher temperatures (102–116 °C), was attributed to the melting of the amylose–lipid complexes. The effect of water in the melting of the flours and blends was well described by the Flory–Huggins equation and its parameters agreed well with those reported in the literature for starchy products. A theoretical value of the polymer–diluent (starch–water) interaction factor for starch of 0.36 was calculated from a combined model of Hildebrand empirical approach to solubility and the Flory–Huggins theory, and reasonably compared with the interaction parameter (χ) obtained for the materials considered in this work. State diagrams for the oat–rice flour blend and for the RTE blend going through an extrusion process were finally obtained.     

Crystallization behavior and environmental biodegradability of the blend films of poly(3-hydroxybutyric acid) with chitin and chitosan

Crystallization behavior and environmental biodegradability were investigated for the films of bacterial poly(3-hydroxybutyric acid) (PHB) blends with chitin and chitosan. The blend films showed X-ray diffractive peaks that arose from the PHB crystalline component. It was suggested that the lamellar thickness of the PHB crystalline component in the blends was large enough to show detectable X-ray diffractive peaks, but this was too small to show observable melting endotherm in the DSC thermogram and the crystalline band absorption in the FT-IR spectrum. In the PHB/chitin and PHB/chitosan blends, thermal transition temperatures of PHB amorphous region observed by dynamic mechanical thermal analysis were almost the same as that of neat PHB. Both the PHB/chitin and the PHB/chitosan blend films biodegraded in an environmental medium. Several blend films showed faster biodegradation than the pure-state component polymers.     

Effects of varying sex pheromone component ratios on the zigzagging flight movements of the oriental fruit moth,Grapholita molesta

As the ratio of (E)-8-dodecenyl acetate (E8–12Ac) to (Z)-8-dodecenyl acetate (Z8–12Ac) increased past optimal low levels in the pheromone blend, fewer males were able to fly 2.5 m upwind to the source. The tracks of males that flew in plumes of such high-(E)off-blends were slower and narrower than those of males flying to lower-(E)blends. The tracks were narrower, first of all, because as the proportion of E8–12Ac increased, the males steered more into the wind. More of their thrust was directed upwind and therefore their groundspeed to either side of the windline was reduced. In addition, males also reduced their airspeeds to high-(E)blends, which contributed to the decreased groundspeeds and narrower tracks. No significant changes in the frequency of counterturning were found in response to increasing proportions of E8–12Ac. The inability to continue upwind flight in a plume of an off ratio was indicated by in-flight arrestment in the plume. Arrestment resulted from changes in the course angles steered by the males and the airspeeds flown.     

Influence of fiber on the phase transformations in the starch-water system

High-sensitivity, temperature-controlled DSC measurements at a low heating rate and creation of differential DSC traces scaled with respect to the reference material (completely dehydrated starch or completely dehydrated fiber, or their respective blends) permitted investigation of the influence of fiber on phase transformations in the wheat-starch-water system in the course of thermal gelatinization. Thermal effects associated with water interactions over the temperature range from 283 to 384 K under atmospheric pressure were determined. These thermal effects and previous structural studies permit us to make the following observations: (1) The main endothermic transition associated with melting of the crystalline part of the starch granule followed by a helix-coil transition in amylopectin occurs over the temperature range 319-333 K independent of the water and fiber contents. Adding fiber causes that transition to disappear both in the native blends and in water suspensions at low water contents. After adding more water and heating, recrystallization is observed and the transition reappears. (2) The fiber content has practically no influence on the slow exothermic transformation, which follows melting and helix-coil transition in amylopectin, proving that the slow transformation has a specific chemical character. In this reaction, the free ends of the unwound helices of amylopectin reassociate with parts of amylopectin molecules other than their original helix duplex partner, forming physical junctions and creating more general amorphous hydrogen bonded associations. (3) The high-temperature transition and small, but reproducible, distortions on the peaks of the main endothermic transition for water contents near 70-80 wt % are associated with smectic and nematic transitions, respectively. These are significantly influenced by the fiber content; higher fiber content causes an almost complete disappearance of these transitions. (4) The slow exothermic effect appearing almost from the very beginning of the heating in the starch-water system, associated with softening and uptake of water in the amorphous growth rings of the starch granule, is significantly hindered by added fiber.     

Preparation of poly(ε-caprolactone)/poly(trimethylene carbonate) blend nanofibers by electrospinning

Poly(ε-caprolactone) (PCL)/poly(trimethylene carbonate) (PTMC) blend nanofibers have been prepared for the first time using an electrospinning process. The mixed dichloromethane (DCM) and N,N-dimethylformamide (DMF) (75/25, v/v) was found to be the most suitable solvent for electrospinning. Various blends of PCL/PTMC solutions were investigated for the formation of nano-scale fibers and it was found that the average diameter of the fibers was reduced and the morphology became finer when PTMC content was increased. FT-IR and DSC analysis indicated that the molecular interactions between PCL and PTMC were weak and they were phase-separated in the fibers. Due to the biocompatible properties of PCL and PTMC, the spun nanofibers developed here could have applications in the biomedical field.     

Division frequency of pea protoplasts in relation to starch accumulation

Division frequency of alginate-embedded pea (Pisum sativum var. Belman) protoplasts derived from embryonic shoot tips was studied quantitatively by image analysis in relation to starch accumulation and protoplast size. Protoplast divisions were observed from day 4 on and the number of protoplasts undergoing division increased in a stepwise manner to 70% the following days. The starch content increased rapidly during the first 3 days of culture prior to the onset of division and resulted a 4.2-fold increase in the intracellular starch area and a 3.0-fold increase (from 27% to 80%) in the number of protoplasts containing starch. Subsequent periods with rapid increases the number of dividing protoplasts were preceded by further starch accumulation. Dividing protoplasts were 33–60% smaller and contained 8–42% less starch than non-dividing protoplasts. However, calculations showed that, in the dividing protoplasts, the relative area covered by starch was 6–12% higher than in non-dividing protoplasts. These data suggest that starch accumulation precedes division of pea protoplasts.     

Direct fermentation of gelatinized sago starch to acetone–butanol–ethanol by Clostridium acetobutylicum

Direct fermentation of gelatinized sago starch into solvent (acetone–butanol–ethanol) by Clostridium acetobutylicum P262 was studied using a 250 ml Schott bottle anaerobic fermentation system. Total solvent production from fermentation using 30 g sago starch/l (11.03g/l) was comparable to fermentation using corn starch and about 2-fold higher than fermentation using potato or tapioca starch. At the range of sago starch concentration investigated (10–80 g/l), the highest total solvent production (18.82 g/l) was obtained at 50 g/l. The use of a mixture of organic and inorganic nitrogen source (yeast extract + NH₄NO₃) enhanced growth of C. acetobutylicum, starch hydrolysis and solvent production (24.47 g/l) compared to the use of yeast extract alone. This gave the yield based on sugar consumed of 0.45 g/g. Result from this study also showed that the individual concentrations of nitrogen and carbon influenced solvent production to a greater extent than did carbon to nitrogen (C/N) ratio.     

Diversity in amylopectin structure, thermal and pasting properties of starches from wheat varieties/lines

Structural, thermal and pasting diversity of starches from Indian and exotic lines of wheat was studied. Majority of the starches showed amylose content ranging between 22% and 28%. Endotherm temperatures (T_o, T_p and T_c) of the starches showed a range between 56–57, 60 –61 and 65.5–66.5 °C, respectively. Exotherms with T_p between 87.0 and 88.2 °C were observed during cooling of heated starches, indicating the presence of amylose–lipid complexes. Exotherm temperatures were negatively correlated to swelling power. Amylopectin unit chains with different degree of polymerization (DP) were observed to be associated with pasting temperature, setback and thermal (endothermic T_o, T_p, and T_c) parameters. Amylopectin unit chains of DP 13–24 showed positive relationship with endothermic T_o, T_p and T_c. Pasting temperature showed positive correlation with short chains (DP 6–12) while negative correlation with medium chain (DP 13–24) amylopectins. Setback was positively correlated to DP 16–18 and negatively to DSC amylose–lipid parameters.     

Microstructural imaging and characterization of the mechanical, chemical, thermal, and swelling properties of starch-chitosan blend films

Chitosan has wide range of applications as a biomaterial, but barriers still exist to its broader use due to its physical and chemical limitations. The present study evaluated the properties of the polymeric blend films obtained from chitosan and potato starch by the casting/solvent evaporation method. The swelling properties of the different films studied as a function of pH showed that the sorption ability of the blend films increased with the increasing content of starch. Fourier transform infrared (FTIR) analyses confirmed that interactions were present between the hydroxyl groups of starch and the amino groups of chitosan in the blend films while the x-ray diffraction (XRD) studies revealed the films to exhibit an amorphous character. Thermogravimetric analyses showed that in the blend films, the thermal stability increased with the increasing starch content and the stability of starch and chitosan powders reduced when they were converted to film. The differential scanning calorimetry (DSC) studies revealed an endotherm corresponding to water evaporation around 100 degrees C in all the films and an exotherm, corresponding to the decomposition in the chitosan and blend films. Scanning electron microscopy (SEM) observations indicated that the blend films were less homogenous and atomic force microscopy (AFM) studies revealed the chitosan films to be smooth and homogenous, while the starch films revealed characteristic granular pattern. The blend films exhibited an intermediate character with a slight microphase separation. The starch-chitosan blend films exhibited a higher flexibility and incorporation of potato starch into chitosan films improved the percentage elongation.     

Production of an amylase-degrading raw starch by Gibberella pulicaris

An endophytic fungus, Gibberella pulicaris, produced an amylase which degraded raw starches from cereals and other crops including raw potato, sago, tapioca, corn, wheat and rice starch. In each case, glucose was the main product. Among the raw starches used, raw potato starch gave the highest enzyme activity (85 units mg^–1 protein) and raw wheat starch the lowest (49 units mg^–1 protein). The highest amylase production (260 units mg^–1 protein) was achieved when the concentration of raw potato starch was increased to 60 g l^–1. Optimum hydrolysis was at 40°C and pH 5.5.     

Modeling of water sorption isotherms of chitosan blends

The blends obtained on the basis of biodegradable chitosan were investigated taking into consideration possible miscibility of their components due to the presence of hydrogen bonds leading to formation of complexes. However, the components of chitosan blends with hydroxypropyl cellulose, poly(ethylene oxide), poly(vinyl alcohol) and starch show good miscibility only on a domain scale of micron or less size.The Authors proposed the formula which considers the dependence of moisture content on the weight fraction of the blend components and taking into account the observed lack of additivity resulting from the presence of some molecular interactions (the parameter ð) of functional groups in the presence of water.Modelling of water sorption isotherms of polymer blends using the parameter ð leads to good correlations with the experimental results simultaneously indicating that the greatest deviation from the moisture additivity occurs in case of high water activity (water humidity).     

Discrimination of Aspergillus isolates at the species and strain level by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry fingerprinting

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI–TOF MS) was used to generate highly reproducible mass spectral fingerprints for 12 species of fungi of the genus Aspergillus and 5 different strains of Aspergillus flavus. Prior to MALDI–TOF MS analysis, the fungi were subjected to three 1-min bead beating cycles in an acetonitrile/trifluoroacetic acid solvent. The mass spectra contain abundant peaks in the range of 5 to 20 kDa and may be used to discriminate between species unambiguously. A discriminant analysis using all peaks from the MALDI–TOF MS data yielded error rates for classification of 0 and 18.75% for resubstitution and cross-validation methods, respectively. If a subset of 28 significant peaks is chosen, resubstitution and cross-validation error rates are 0%. Discriminant analysis of the MALDI–TOF MS data for 5 strains of A. flavus using all peaks yielded error rates for classification of 0 and 5% for resubstitution and cross-validation methods, respectively. These data indicate that MALDI–TOF MS data may be used for unambiguous identification of members of the genus Aspergillus at both the species and strain levels.     

Supercritical carbon dioxide (scCO2) induced gelatinization of potato starch

The degree of gelatinization (DG) of potato starch after treatment with scCO₂ was investigated. A broad range of experimental conditions were applied, including variations in temperature (50–90 °C), pressure (0.1–25 MPa), and the starch water content (16.2–40% wt/wt). Changes in the DG were observed by in situ FT-IR measurements, DSC and confirmed by the XRD analysis. The DG increases at higher temperatures and pressures. A maximum DG of about 14% was achieved at the highest pressure (25 MPa) and temperature in the range (90 °C). A series of experiments under N₂ pressure confirms that scCO₂ plays a special role in the gelatinization process.     

Wood biodeterioration control potential of Acalypha hispida leaf phenolic extract in combination with Trichoderma viride culture filtrate

The phenolic extract of Acalypha leaves inhibited growth of Gloeophyllum sepiarium and Pleurotus sp. (test wood-rot fungi) in potato dextrose agar, starch agar, starch glucose agar, carboxyl methyl cellulose agar and carboxyl methyl cellulose glucose agar. Fungicidal or fungistatic concentration of the extract (10–14 mg/ml) depended on the medium. However a lower concentration of the extract (8–10 mg/ml) in combination with Trichoderma viride culture filtrate caused a similar inhibitory pattern. Degradation of obeche (Triplochiton scleroxylon), mahogany (Khaya ivorensis) and walnut (Lovoa trichilioides) by the test fungi was limited or prevented by extract treatment of 8–10 mg/g wood. A similar inhibitory effect again occurred when a combination of T. viride filtrate and lower extract concentration (6–8 mg extract per gram of wood) was used. On-going wood decay was limited or halted by a combined treatment involving 8–12 mg extract per gram of wood depending on the fungal residence period. Treated stakes exposed to 6 months of tropical wet season retained resistance to fungal attack including soft rot. The phenolic extract of A. hispida may prove useful in an integrated chemical and biological approach to wood treatment.     

Geographical variation in female sex pheromones of the rice leaffolder moth, Cnaphalocrocis medinalis: identification of pheromone components in Japan

Sex pheromone components of the Japanese rice leaffolder moth, Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae) were identified from ovipositor extracts of virgin females as (Z)-11-octadecenal, (Z)-13-octadecenal, (Z)-11-octadecen-1-ol and (Z)-13-octadecen-1-ol at a ratio of 11:100:24:36 by GC-EAD, GC, GC-MS. The total amount was estimated to be ca.0.9 ng/female. Field bioassays in Kagoshima, Japan, showed that the two aldehydes are essential for male attraction and the alcohols may have a synergistic effect on the aldehydes. A rubber septum containing 0.9 mg of the four components at the natural ratio was shown to be an effective lure for monitoring this pest in Japan. The above four components are quite different from the sex pheromone components reported previously for the same species of either Philippine or Indian origin; components were shown to be (Z)-11-hexadecenyl acetate and (Z)-13-octadecenyl acetate at a ratio of 98:2 in the Philippine blend and 1:10 in the Indian blend. Furthermore, in the field tests in Japan, neither the Philippine blend nor the Indian blend showed any attractive activity, while the Japanese blend attracted significant numbers of male moths. These results suggest that there are remarkable geographical variations in the sex pheromone composition of this species or there are several distinct species using different sex pheromone blends.     

Adsorption-elution purification of chimeric <Emphasis Type="Italic">Bacillus stearothermophilus</Emphasis> leucine aminopeptidase II with raw-starch-binding activity

Summary A chimericBacillus stearothermophilus leucine aminopeptidase II (LAPsbd) has been constructed by introducing the raw-starch-binding domain of Bacillus sp. strain TS-23 α-amylase into the enzyme. LAPsbd was adsorbed onto raw starch and the adsorbed enzyme could be eluted from the adsorbent by soluble starch in 20 mM Tris–HCl buffer (pH 8.0). The adsorption of LAPsbd onto raw starch was affected by raw starch concentration, pH, and temperature, while the temperature and incubation time had no obvious effects on the elution of adsorbed enzyme. The molecular weight of purified enzyme was estimated to be 61 kDa. About 84% of LAPsbd in the cell free extract was recovered through one adsorption–elution cycle with a purification of 20-fold. The high quantity and purity of the recovered enzyme coupled with the easy performance make the adsorption–elution procedure suitable for industrial applications.