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  • 1
    Electronic Resource
    Electronic Resource
    Biodegradation of starch-poly(β-hydroxybutyrate-co-valerate) composites in municipal activated sludge (1995)
    Springer
    Journal of polymers and the environment 3 (1995), S. 205-213 
    Details
    ISSN: 1572-8900
    Keywords: Starch ; poly(β′-hydroxybutyrate-co-β-hydroxyvalerate) ; poly(hydroxyalkanoates) ; plastic ; blends ; composite ; biodegradation ; activated sludge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Injection-molded composites were prepared by blending PHBV5 with native cornstarch (30% and 50%) and with cornstarch precoated with PEO as a binding agent. These composites were evaluated for their biodegradability in municipal activated sludge by measuring changes in their physical and chemical properties over a period of 35 days. All composites lost weight, ranging from 45 to 78% within 35 days. Interestingly, the extent and rate of weight loss were quite similar in PHBV composites with no starch, with 30% starch, and with 50% starch. Weight loss was slowest in PHBV blends prepared with PEO-coated starch. For all samples, the weight loss was accompanied by a rapid deterioration in tensile strength and percentage elongation. The deterioration of these mechanical properties exhibited a relative rate of PHBV〉starch-PHBV〉PEO-coated starch-PHBV. Changes in starch/PHBV composition after biodegradation were quantified by FTIR spectroscopy. Increasing the starch content resulted in more extensive starch degradation, while the PHBV content in the blends became less susceptible to hydrolytic enzymes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02068675
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  • 2
    Electronic Resource
    Electronic Resource
    Accessibility of starch to enzymatic degradation in injection-molded starch-plastic composites (1995)
    Springer
    Journal of polymers and the environment 3 (1995), S. 107-113 
    Details
    ISSN: 1572-8900
    Keywords: Starch degradation ; starch-plastic ; composite ; starch hydrolysis ; amylase(s)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Most of the starch in starch-polyethylene-co-acrylic acid (EAA)-polyethylene (PE) composites prepared by injection molding was not accessible to starch-hydrolyzing enzymes. Even when these composites were treated with enzyme in the presence of Triton X-100 for 96 h, little starch hydrolysis was observed. However, when the starch-plastic material was pulverized, both the extent and the rate of starch hydrolysis increased dramatically, with about 70% hydrolysis of the starch within 18 h. Reactions carried out for up to 96 h showed that, while the enzyme was active, the reaction reached a plateau, achieving a total of 80% starch hydrolysis. Fourier transform infrared (FTIR) spectroscopy revealed that only starch, and not EAA or PE, was affected by enzyme in pulverized samples. Results indicated that while 80% of the starch in these composites was transiently inaccessible, perhaps due to EAA and PE forming an impermeable barrier to the enzyme, the other 20% remained inaccessible to enzymes. Also, the rate of starch digestion as determined by solubilized reducing sugar correlated with the particle size of the pulverized material, suggesting that a large available surface area is critical for rapid starch degradation in such composites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02067486
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  • 3
    Electronic Resource
    Electronic Resource
    Starch-based extruded plastic films and evaluation of their biodegradable properties (1996)
    Springer
    Biodegradation 7 (1996), S. 231-237 
    Details
    ISSN: 1572-9729
    Keywords: biodegradable plastic ; extrusion ; films ; starch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Plastic formulations containing up to 40% starch were prepared and blown into thin films using extrusion methods. Extruded films were evaluated for their biodegradability by exposing them to a consortium of starch degrading bacteria in the laboratory for 45 days and in the ‘La Silla’ river located in Monterrey, N.L. Mexico for up to 60 days. Biodegradability was assessed by measuring changes in weight loss and chemical composition of the films using Fourier transform infrared (FTIR) spectroscopy. While little or no degradation was apparent in control films made up of 100% low density polyethylene (LDPE) or 100% poly-(ethylene-co-acrylic acid) (EAA), most of the starch was depleted in starch-containing films exposed in the river. Starch degradation in films exposed to amylolytic bacteria in the laboratory was relatively slower. Also, increasing the amount of EAA from 25% to 50% substantially reduced starch depletion in these films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00058182
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  • 4
    Electronic Resource
    Electronic Resource
    Biodegradation of Injection Molded Starch-Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) Blends in a Natural Compost Environment (1998)
    Springer
    Journal of polymers and the environment 6 (1998), S. 91-98 
    Details
    ISSN: 1572-8900
    Keywords: Starch ; PHBV ; PHA ; plastic ; blends ; biodegradation ; soil ; compost
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Injection molded specimens were prepared by blending poly (hydroxybutyrate-co-valerate) (PHBV) with cornstarch. Blended formulations incorporated 30% or 50% starch in the presence or absence of poly-(ethylene oxide) (PEO), which enhances the adherence of starch granules to PHBV. These formulations were evaluated for their biodegradability in natural compost by measuring changes in physical and chemical properties over a period of 125 days. The degradation of plastic material, as evidenced by weight loss and deterioration in tensile properties, correlated with the amount of starch present in the blends (neat PHBV 〈 30% starch 〈 50% starch). Incorporation of PEO into starch-PHBV blends had little or no effect on the rate of weight loss. Starch in blends degraded faster than PHBV and it accelerated PHBV degradation. Also, PHBV did not retard starch degradation. After 125 days of exposure to compost, neat PHBV lost 7% of its weight (0.056% weight loss/day), while the PHBV component of a 50% starch blend lost 41% of its weight (0.328% weight loss/day). PHB and PHV moieties within the copolymer degraded at similar rates, regardless of the presence of starch, as determined by 1H-NMR spectroscopy. GPC analyses revealed that, while the number average molecular weight (Mn) of PHBV in all exposed samples decreased, there was no significant difference in this decrease between neat PHBV as opposed to PHBV blended with starch. SEM showed homogeneously distributed starch granules embedded in a PHBV matrix, typical of a filler material. Starch granules were rapidly depleted during exposure to compost, increasing the surface area of the PHBV matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022806222158
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  • 5
    Electronic Resource
    Electronic Resource
    Polymer compatibility and biodegradation of starch-poly(ethylene-co-acrylic acid)-polyethylene blendsThe mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 44 (1992), S. 1971-1978 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: X-ray diffraction, CP/MAS C-13 NMR, DSC, FTIR and fluorescence microscopy have been used to study the structure, compatibility, and morphology of films made from starch, poly(ethylene-co-acrylic acid) (EAA), and polyethylene (PE) before and after exposure to a mixture of highly amylolytic bacteria. The components of starch, amylose and amylopectin, interact with EAA via the formation of V-type inclusion complexes and hydrogen bonds. PE appears to be immiscible with the starch-EAA complex, with each forming sheetlike domains. The amylopectin in the films is susceptible to digestion by the bacterial consortium while the crystalline EAA-amylose complex is resistant. Digestion begins at the film surface and then proceeds inwards with sheetlike areas of starch removed. The good compatibility between starch and EAA as well as migration of EAA to the film surface explains the resistance of such films to digestion by conventional amylases.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070441112
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  • 6
    Electronic Resource
    Electronic Resource
    Hydrophilic foams containing corn products for horticultural useThe mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned. (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 51 (1994), S. 1311-1317 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polyurethane foams containing equal amounts of commercial unmodified cornstarch and a polyisocyanate-terminated polyether exhibit properties suitable for horticultural applications. The use of cornstarch in the foam formulation increased the volume by one-fourth as compared to the foam without cornstarch. This volume increase represents an economic advantage of 20% savings based on material cost. When cornstarch or corn flour is added to the foam formulation, the foams are more resistant to compressive force. Upon wetting and draining, the foams prepared with no auxiliary blowing agent and containing corn products exhibit higher volumes than do the unfilled foams. Radish seeds planted inside 25 mm cubes of foams began to sprout after 1 day. Early developmental growth for the plants was similar in the control and cornstarch-filled foams. Spectroscopic analyses of the starch-containing foams revealed that 60-70% of the cornstarch was metabolized within 4-5 weeks by a microbial consortium. Control polyurethane foams were not affected by the microorganisms tested. © 1994 John Wiley & Sons, Inc.This article is a U.S. Government work and, as such, is in the public domain in the United States of America.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070510718
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  • 7
    Electronic Resource
    Electronic Resource
    Complexes of starch polysaccharides and poly(ethylene co-acrylic acid): Structure and stability in solution (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 1701-1709 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Chiroptical methods have been used to study the conformation and interactions of amylose and amylopectin with poly(ethylene co-acrylic acid) (EAA) in aqueous solution. These studies, along with X-ray diffraction and solid-state NMR data, show that amylose and EAA, as well as amylopectin and EAA, form helical V-type inclusion complexes when mixed in aqueous suspension. This structure apparently accounts for the partial compatibility observed in films containing starch and EAA. About 2/3 by weight of EAA does not interact with amylose and probably represents the ethylene-rich central core of the EAA micelle. EAA/amylose complexes in 10 mM NaOH were stable to temperatures 〉 90°C, whereas EAA/amylopectin complexes in the same solvent were largely disrupted at this temperature. Urea, at a concentration of 8 M, further destabilized both EAA/amylopectin and EAA/amylose complexes. Solutions with an alkaline pH (〉 9.5) dispersed EAA optimally and allowed maximum complexing with amylose. At pH values 〉 13, the EAA/amylose complexes were weaker, most likely due to electrostatic repulsion between ionized hydroxyl groups of amylose and carboxyl groups of EAA.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070420625
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  • 8
    Electronic Resource
    Electronic Resource
    Complexes of starch polysaccharides and poly(ethylene co-acrylic acid): Structural characterization in the solid state (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 2279-2286 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The structural characterization of model complexes of amylose (AM) and amylopectin (AP) with poly(ethylene-co-acrylic acid) (EAA) was undertaken in order to better understand the interactions that occur between the polysaccharides and EAA in starch-EAA-polyethylene films. X-ray diffraction and CP/MAS 13C-NMR studies showed that precipitates from solution mixtures of AM and EAA form crystalline, helical V -type inclusion complexes. The proportion of AM forming the V -type complex in the EAA/AM blends, estimated from shifts in the C1 resonance of AM, increased with increasing EAA/AM ratio, reaching a value of about 80% at EAA/AM = 0.5 (w/w). Similar measurements for EAA/AP complexes showed 〈 10% V structure. Approximately 80% of the AM and 4% of the AP in these blends was resistant to amylase digestion, in good agreement with their V -structure contents as determined above. Resonances at 184 and 181 ppm were observed for the carboxyl carbon of EAA in the EAA/AM and EAA/AP complexes. The resonance at 181 ppm, which was not observed in pure EAA, probably reflects greater shielding of the carboxyl inside the polysaccharide helix as well as changes in hydrogen bonding. The intensity of this peak was 2-3 times larger for the EAA/AM than for the EAA/AP complexes. FTIR experiments suggest that most (〉 50%) of the EAA carboxyl groups were hydrogen bonded to polysaccharide hydroxyl groups in both AM and AP complexes when EAA/polysaccharide 〈 1.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070420819
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  • 9
    Electronic Resource
    Electronic Resource
    Isolation and characterization of an alkaline protease from the marine shipworm bacterium (1992)
    Springer
    Current microbiology 24 (1992), S. 111-117 
    Details
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Bacterial isolates from the gland of Deshayes of the marine shipworm (Psiloteredo healdi) produced extracellular protease activity when cultured with 1% cellulose. A protease with a relative molecular mass of 36,000 daltons as determined by SDS-PAGE and a pI of 8.6 was isolated from the medium and purified to electrophoretic homogeneity. No carbohydrate appeared to be associated with the protein. The enzyme was activated and stabilized by relatively high salt concentrations (〉0.2M). Below 0.1M salt, significant protein aggregation occurred, as well as autohydrolysis of the protease, both of which resulted in the loss of activity. The specific activity of the enzyme was 65,840 proteolytic units/mg with azocasein substrate of optimal temperature (42°C), pH (9.0), and salt concentration (0.20M NaCl). The activity was stable up to 40°C, from pH 3.0 to pH 11.9, and from 0.1M to 3.5M NaCl. These stabilities, as well as the protease's stability in the presence of chelators, oxidizing agents, and heavy metals, suggest the enzyme has potential for use in relatively low temperature (40°C) industrial applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01570907
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  • 10
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    Sodium-stimulated glutamate uptake in membrane vesicles of Escherichia coli: the role of ion gradients. (1977)
    National Academy of Sciences
    Details
    Publication Date: 1977-08-01
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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