Environmental assessment of biodegradable multilayer film derived from carbohydrate polymers

Multilayer films exhibit excellent properties for food packaging. However, existing products are not biodegradable. Conventional plastics, manufactured from fossil fuels, not only consume non-renewable and finite resources, but also impact heavily on waste disposal. For this reason, a new multilayer film has been developed in the Multibio Project for the production of food packaging. In this paper, the environmental impacts of the new biodegradable multilayer film—based on modified starch and polylactic acid (PLA)—and those of the conventional multilayer film—based on PP and PA6—are quantified in the categories of climate change, fossil fuel depletion, acidification and eutrophication. Conventional multilayer film has a 90% higher impact than the Multibio multilayer film. The main difference between the LCA presented and the cited literature is the inventory data obtained in the phase of polymer processing to obtain multilayer film, and the assessment of the disposal phase of the multilayer film wastes.     

Synthesis of a block copolymer of poly(3-hydroxybutyrate) and poly(ethylene glycol) and its application to biodegradable polymer blends

A block copolymer {P[(R,S)-HB-b-EG]} of atactic poly[(R,S)-3-hydroxybutyrate] {P[(R,S)-HB]} and poly(ethylene glycol) (PEG) was prepared by the ring-opening polymerization of -butyrolactone in the presence of a macroinitiator (PEG/ZnEt₂/H₂O) which had been produced by the reaction of ,-dihydroxy PEG ( _n=3000) with ZnEt₂/H₂O (1/0.6) catalyst. The block copolymer ( _n=10,500, _w/ _n=1.2) was an A-B-A triblock copolymer comprising atactic P[(R,S)-HB] (A) and PEG (B) segments. The miscibility, physical properties, and biodegradability of binary blends of microbial poly[(R)-3-hydroxybutyrate] {P[(R)-HB]} with the block copolymer P[(R,S)-HB-b-EG] has been studied. The glass-transition temperature (T _g) data showed that the P[(R)-HB]/P[(R,S)-HB-b-EG] blend was miscible in the amorphous state. The P[(R)-HB] film became flexible and tough by means of blending with P[(R,S)-HB-b-EG] block copolymer. The enzymatic degradation of blend films was carried out at 37°C and pH 7.4 in a 0.1M phosphate solution of an extracellular PHB depolymerase fromAlcaligenes faecalis. The enzymatic degradation took place solely on the surface of the blend films.     

Starch-Based Polymers in Extrusion Coating

The starch-based polymers exhibited shear thinning and elastic nature in rheological characterizations. Thin coatings with narrow neck-in could be produced at fairly high extrusion coating line speeds. Adhesion between the starch-based polymers and paperboard was typically weak. Water vapor barrier of starches was very poor. Soft starch grades had a good pinhole resistance and a good heat sealing performance. Brittle nature of starch caused cracking as the coated paperboards were creased.     

A user evaluation of biodegradable cutlery

This paper summarizes a study evaluating the acceptance and perceived performance of disposable cutlery made from starch-based biodegradable resins relative to nondegradable polystyrene cutlery. Two hundred forty-three sailors onboard three U.S. Navy vessels ate their lunch using either biodegradable cutlery made with resins manufactured by one of two commercial companies or polystyrene cutlery. The cutlery was rated on several sensory and performance dimensions as well as for overall acceptability. Results indicated that sailors rated both the biodegradable and the polystyrene utensils as easy to hold. There were also no differences in the perceived ease of using each of the spoons. However, compared to the polystyrene utensils, both types of biodegradable utensils were viewed as less sturdy, as having a less attractive color, and as being less acceptable overall. The biodegradable forks and knives were also rated as more difficult to use for piercing and cutting food than the polystyrene ones. In addition, several significant differences emerged between the two types of biodegradable cutlery. The results are discussed in terms of the need for continued consumer testing of products developed from biodegradable polymeric materials.     

Simulated marine respirometry of biodegradable polymers

Eleven microorganisms were isolated from several temperate marine locations in the northeast Altantic coast of the United States and one tropical location in the Pacific Ocean (Hawaii) for the purpose of developing a rapid and accurate method of screening biodegradable materials for their susceptibility to mineralization. The materials evaluated in this study included chemically modified starch, amylose and pullulan, poly(3-hydroxybutyrate-co-valerate), (PHB/V), cellulose acetate, and a modified lignin/styrene. Some of the soluble, unmodified, biologically produced substrates such as starch, pullulan, and amylose mineralized rapidly. In general, the synthetic, insoluble polymers and the chemically modified polymers, such as acetylated and chlorinated amylose and pullulan, mineralized more slowly, although the ultimate mineralization of some of the substituted polysaccharides equaled or exceeded that of the unmodified substrate. The insoluble bacterial polyester, PHB/V, degraded rapidly after a short induction period. Initial respiration rate data, in general, could not be used as a predictor of ultimate mineralization. It was found that the cumulative level of carbon dioxide evolved signifies the minimum extent of biodegradation of the substrate, and the oxygen consumed is a good indicator of the maximum extent of substrate degradation.Paper presented at the Biodegradable Materials and Packaging Conference, September 22–23, 1993, Natick, Massachusetts.     

Effects of biodegradable plastic components on metabolism of an estuarine benthos

We examined the metabolic response of an estuarine benthic community to additions of three materials being considered for use in manufacture of biodegradable substitutes for plastics. Diver-collected cores containing benthos were dosed with 59 g/m² of three test materials, cornstarch, a bacterial polyester (PHBV), and ethylene vinyl alcohol (EVOH), or left undisturbed as controls. Fluxes of dissolved nutrients (ammonia, nitrate + nitrite, phosphate, silica) and dissolved inorganic carbon (DIC) were similar in control cores and cores dosed with EVOH during a 1-month test period at 20°C. Fluxes in cores dosed with starch and PHBV differed significantly from controls but not from each other. After 2 weeks of incubation, production of DIC was higher in cores containing starch and PHBV, while efflux of ammonia, nitrate, and nitrite was reduced. After 4 weeks of incubation, production of DIC was similar among all treatments and controls, while efflux of ammonia was high in the starch- and PHBV-containing cores compared to controls and cores with EVOH. Fluxes of silica and phosphate were similar in all cores during the experiment. These results indicate that both starch and PHBV are carbon-rich substrates readily metabolized by the benthic community but that their presence significantly alters normal nutrient exchange patterns. This response is expected because of the high carbon-to-nitrogen ratio of starch and PHBV and indicates that impacts of these two materials would be similar. However, the high biological oxygen demand of such materials and resulting disturbance of normal nutrient regeneration patterns of the benthos (delayed ammonia efflux and potential stimulation of denitrification) must be considered in developing strategies for their disposal.Paper presented at the Biodegradable Materials and Packaging Conference, September 22–23, 1993, Natick, Massachusetts.     

Isolation and Identification of Microorganisms Able to Grow on the Polyester Amide BAK 1095

The polyester amide BAK 1095 is fully degraded by microorganisms. Bacteria that can grow on this polymer were isolated from various environments, such as freshwater, saltwater, arable land, woodland and compost. The mechanism of polymer degradation was examined using selected isolates. It was discovered that the bacteria selectively cleave the polymer at its ester bonds, releasing low-molecular water-soluble oligoamides. These can then be metabolised by other microorganisms [1, 2, 3]. The isolates were also tested for their ability to break down other ester-containing polymers such as Degranil W 50, a linear polyester urethane urea. Eight of the 12 strains examined were also able to break down this polymer.The isolated microorganisms predominantly belong to the genus Bacillus. Mesophilic, halophilic and thermophilic species were isolated. The studies show that polyester amide-degrading bacteria occur in numerous ecosystems and provide data on the microbial breakdown of random copolymers. Information was also obtained on the mechanism involved in the microbial breakdown of polyester amides.     

Influence of Fibers on the Mechanical Properties of Cassava Starch Foams

The utilization of renewable resources in packaging can provide solutions to ecological problems such as waste quantity. Agricultural resources are alternative raw materials, among which there is starch, a natural polysaccharide that can be used to form resistant foam under wet and warm conditions. The starch foam is obtained by thermo pressing process where cassava starch, water and additives are processed to form a rigid structure by swelling, gelatinization and network formation. Natural fibers can be used to improve the mechanical properties of starch foams. In this project was investigated the influence of the addition of fibers in the levels of 1, 2 and 3% of cassava (short fiber) and 1, 2 and 3% of wheat fiber (powered fiber) in the starch dough. The foams were characterized by physical methods of strength, flexibility, density and by Scanning Electron Microscopy (SEM). The increase in fibers quantity has resulted in foams with higher density and less flexibility, whatever the fiber type. Most fibers quantity did not improve the foam strength. Foam made with 1% of cassava fiber showed higher compression strength; by increasing the percentage quantity there was a decrease on the compression resistance. Foam made with wheat fiber presented a lower result in 2%. The fiber type had no statistical significance in strength, flexibility and density foam. Only the fiber quantity was significant. The results showed that both fibers presented limited dimensions to improve the reinforcement of the starch foams up to 1%.     

Dialdehyde starch and zein plastic: Mechanical properties and biodegradability

Dialdehyde starch (DAS) and zein, a hydrophobic corn protein, were investigated to produce biodegradable plastics with improved water resistance and mechanical properties. In the study, dialdehyde starch and zein ratio, plasticizers, and degree of starch oxidation were examined. Increased molding temperature and level of starch oxidation decreased water absorption of the plastic. Tensile strength and Young's modulus increased with starch oxidation. The biodegradation of starting materials and ground plastic specimens was studied in aerobic soil reactors maintained at 25°C for 180 days. Biodegradation of corn starch, zein, and dialdehyde starch for 180 days produced CO₂ equivalent to 64, 63, and 10% of theoretical carbon, respectively. Specimens of molded DAS and zein (3 : 1) plastic showed accelerated CO₂ evolution compared to DAS and other raw materials alone. By 180 days, specimens made with starch of low oxidation (1 and 5% oxidized) demonstrated a 60% biodegradation, and specimens with highly oxidized starch (90% oxidized) achieved 37% biodegradation.Paper presented at the Bio/Environmentally Degradable Polymer Society—Third National Meeting, June 6–8, 1994, Boston, Massachusetts.Journal Paper J-15927 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Project No. 3258.     

Comparison of the weight-loss degradability of various biodegradable plastics under laboratory composting conditions

Eight kinds of biodegradable plastics were compared for their degradability in controlled laboratory composting conditions. A thin film of each plastic was mixed into the composting material, and weight-loss degradability was calculated from the weight changes of the film during composting. It was found that weight-loss degradability strongly depended on the specific kind of biodegradable plastic; two were very high, four moderate, and the remaining two very slight. The most easily degradable plastic degraded by as much as 81.4% over 8 days of composting. By comparing the weight-loss degradability with ultimate degradability, which is defined as a molar ratio of carbon loss as CO₂ to the carbon contained in the biodegradable plastic, the order of the ease of degradation of the biodegradable plastics differed. Received: February 7, 2000 / Accepted April 14, 2000     

Rheological study of biodegradable blends of starch and polyvinyl alcohol

The rheological behavior of biodegradable blends of starch and poly(vinyl alcohol) (PVOH) was measured as a function of temperature, shear rate, and moisture content using a capillary rheometer. An excellent correlation was found with a rheological model which was used as a means to characterize the influence of starch/PVOH content as well as a qualification of the viscosity for simulation studies. This model consisted of a power law dependence on shear rate, an Arrhenius dependence on temperature, and an exponential dependence on moisture.Paper presented at the Biodegradable Materials and Packaging Conference, September 22–23, 1993, Natick, Massachusetts.Guest Editor: Dr. Randall Shogren, USDA.     

A test method to determine rapidly if polymers are biodegradable

Polycaprolactone and polycaprolactone/polyethylene blends were exposed to two consortia, one containing three fungi (Aspergillus niger, Gliocladium virens, andPenicillium funiculosum) and one five fungi (the three aforementioned plusAureobasidium pullulans andChaetomium globosum). Evidence of metabolization of the polymer by the five-fungus consortium was obtained from the greater oxygen consumption in the presence of polycaprolactone than in the absence of the polymer. Minor differences in the composition of the consortium result in major differences in the ability of the consortium to utilize the polymer as a carbon source.Certain commercial products are identified in order adequately to specify experimental procedures. In no case does such identification imply endorsement by the National Institute of Standards and Technology or that the material is necessarily the best available for the purpose.     

Processing and mechanical properties of biodegradable Poly(hydroxybutyrate-co-valerate)-starch compositions

Poly(hydroxybutyrate-co-valerate) (PHBV) is a completely biodegradable thermoplastic polyester produced by microbial fermentation. The current market price of PHBV is significantly higher than that of commodity plastics such as polyethylene and polystyrene. It is therefore desirable to develop low-cost PHBV based materials to improve market opportunities for PHBV. We have produced low-cost environmentally compatible materials by blending PHBV with granular starch and environmentally benign CaCO₃. Such materials can be used for specific applications where product biodegradability is a key factor and where certain mechanical properties can be compromised at the expense of lower cost. The inclusion of granular starch (25 wt%) and CaCO₃ (10 wt%) in a PHBV matrix (8% HV, 5% plasticizer) reduces the cost by approximately 40% and has a tensile strength of 16 MPa and flexural modulus of 2.0 Gpa, while the unfilled PHBV/plasticizer matrix has a tensile strength of 27 MPa and a flexural modulus of 1.6 GPa.Paper presented at the Bio/Environmentally Degradable Polymer Society—Third National Meeting, June 6–8, 1994, Boston, Massachusetts.The 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.     

Effects of Starch Moisture on Properties of Wheat Starch/Poly(Lactic Acid) Blend Containing Methylenediphenyl Diisocyanate

Methylenediphenyl diisocyanate was found to improve the interfacial interaction between poly(lactic acid)(PLA) and granular starch. The objective of this research was to study the effect of starch moisture content on the interfacial interaction of an equal-weight blend of wheat starch and PLA containing 0.5% methylenediphenyl diisocyanate by weight. Starch moisture (10% to 20%) had a negative effect on the interfacial binding between starch and PLA. The tensile strength and elongation of the blend both decreased as starch moisture content increased. At 20% moisture level, the starch granules embedded in the PLA matrix were observed to be swollen, resulting in poor strength properties and high water absorption by the blend.     

Toxicity screening of biodegradable polymers. II. Evaluation of cell culture test with medium extract

Cell culture testing with material extracts was applied to toxicity screening of some commercial degradable plastics: a plasticized cellulose acetate, an aliphatic polyester (Bionolle), polyhydroxybutyrate-co-hydroxyvalerate (Biopol), and polycaprolactone (TONE polymer). Cell culture medium with serum was used as extraction medium. Methods for the determination of morphology and viability of cells cultured in the extract were investigated. Phase-contrast light microscopy of cells, enhanced by neutral red staining, provides high-contrast images for qualitative evaluation of cell morphology and lysis. Compared to the determination of protein using the Bradford method and of neutral red uptake, the determination of dehydrogenase activity using 3-[4,5-dimethylthia-zol-2-yl]-2,5-diephenyl-tetrazolium bromide (MTT) is more sensitive and accurate. The relative MTT activity of cells cultured in fresh extracts indicate that TONE polymer (all shapes) and Bionolle (test bars and films) are comparable to materials currently used in the food industry (polyethylene terephthalate, atactic and isotactic polystyrene) with no toxic effects on cells.     

Toxicity screening of biodegradable polymers. I. Selection and evaluation of cell culture test methods

A screening test method for potential toxicity of biodegradable plastics on humans and the environment was selected and evaluated with samples of cellulose acetate, Bionolle, polyhydroxybutyrate-co-valerate (Biopol), and polycaprolactone (Tone polymer). Among the standardin vitro tests using animal cell cultures for the evaluation of biomedical materials, the test by direct contact and the test with extract were examined. Qualitative and quantitative determinations of the cell viability and morphology indicate that the test with extracts can be easily performed, providing reproducible and comparable results for all materials. Using the cell culture test with the extract of sterile samples, an estimation of the toxicity of a new polymeric material can be obtained within a few weeks.     

Biodegradation by Composting of Surface Modified Starch and PVA Blended Films

Several starch/PVA/glycerol polymer blends were prepared by a solution casting technique and examined for biodegradation by composting over 45 days. Within this time frame, the starch and glycerol components were fully degraded, leaving the PVA component essentially intact. The lowest PVA content film (20%) was selected as a polymer with enough PVA to impart important physical characteristics, but also enough starch to be considered biodegradable. The film characteristics were further improved by surface modification with chitosan. This modification did not interfere with the biodegradation of the starch component. Furthermore, there was slight evidence that PVA biodegradation had been initiated in composted, surface modified starch/PVA blends.     

Structure-biodegradation relationships of polymeric materials. 1. Effect of degree of oxidation on biodegradability of carbohydrate polymers

The biodegradability of oxidized starch and inulin has been studied in relation to the degree of periodate oxidation to dialdehyde derivatives, by measuring oxygen consumption and mineralization to carbon dioxide. A higher degree of oxidation of dialdehyde starch and dialdchyde inulin results in a lower rate at which the polymers are biodegraded. It is demonstrated that the biodegradation rate of dialdehyde inulin derivatives decreases more than that of equivalent starch derivatives. The differences in biodegradation behavior between dialdehyde starch and dialdehyde inulin, resulting from comparable modifications, are discussed in terms of conformational structure.     

Moisture Sorption Characteristics of Microbially Produced Polysaccharide and Polyvinyl Alcohol Blends

Moisture sorption characteristics of microbial polysaccharide (Ps.C101) from Pseudomonas caryophilli and polyvinyl alcohol (PVA) blends have been carried out at 27°C for water activity from 0.1 to 0.9. The sorption data was used to fit six different sorption isotherm models proposed in literature. The model constants were determined by linear fitting of the sorption equations. The ranges of applicability of water activity for isotherm models reported in this paper lie in between 0.1 and 0.4 for Brunaur–Emmet–Teller (BET) model (monolayer), and in between 0.2 and 0.9 for other models. The value of the coefficient of determination (R² = 0.97 ± 0.02) confirms the applicability of the equations studied.     

The influence of soil macroinvertebrates on primary biodegradation of starch-containing polyethylene films

The primary biodegradability of polyethylene (PE) films containing different percentages of cornstarch (0–50%) and other additives (prooxidant, oxidized polyethylene) was tested using four species of earthworms (Eisenia fetida, Lumbricus terrestris, Aporectodea trapezoides, Aporectodea tuberculata), three species of cockroaches (Periplaneta americana, Blaberus sp.,Blattella germanica), termites (Reticulotermes flavipes), sowbugs (Porcellio laevis), and crickets (Acheta domesticus). These studies were conducted to elucidate the potential role of soil macroinvertebrates in degrading starch/PE biodegradable plastics. The results of the macroinvertebrate bioassays indicate that crickets, cockroaches, and sowbugs consumed starch-containing PE films most readily. In addition, the degree to which the films were attacked and consumed was directly related to the starch content of the film. Films with oxidized polyethylene and those containing prooxidant (vegetable oil and a transition metal catalyst) were also consumed. None of the four species of earthworms tested or the termites showed any activity toward the starch/polyethylene films. These results have important implications for determining the fate of novel plastic formulations which claim to be biodegradable in natural environments. Studies such as these, coupled with studies on microbial degradation, will help provide the type of information needed to assess the environmental fate of biodegradable starch/PE plastics and fill the voids in the scientific database regarding this rapidly developing field.