Abstract: Starch is a natural, renewable, biodegradable polysaccharide produced by many plants as a storage polymer. It usually has two major components and appears as a mixture of two glucosidic macromolecules very different in structure and properties: largely linear amylose of molecular weight between one thousand and one million, consisting of R-(1f4)-linked D-glucose, and amylopectin, having the same backbone as amylose but with a myriad of R-(1f6)-linked branch points. The most commercially important starch comes from corn, wheat, rice, potatoes, tapioca, and peas. Native starch occurs in the form of discrete and partially crystalline microscopic granules that are held together by an extended micellar network of associated molecules. Starch has received considerable attention during the past two decades as a biodegradable thermoplastic polymer and as a biodegradable particulate filler. Indeed, products from agricultural sources, such as starch, offer an attractive and cheap alternative in developing degradable materials. Starch is not truly thermoplastic as most synthetic polymers. However, it can be melted and made to flow at high temperatures under pressure and shear. If the mechanical shear becomes too high, then starch will degrade to form products with low molecular weight. Addition of water or other plasticizers enables starch to flow under milder conditions and reduces degradation considerably. However, the thermomechanical stability is strongly reduced by the addition of plasticizers. By itself, starch is a poor choice as a replacement for any plastic. It is mostly water soluble, difficult to process, and brittle. In principle, some of the properties of starch can be significantly improved by blending it with synthetic polymers. Physical incorporation of granular starch or starch derivatives as a functional additive and filler into synthetic polymers during processing has been largely used since the first announcements of using starch in combination with synthetic polymer either as starch gel blends with ethylene acrylic acid copolymers by Westhoff et al.1 or as particulate starch dispersions in polyolefins by Griffin.2 More recently, increasing interest in developing new and inexpensive biodegradable materials has led to a substantive amount of research in polymer blends containing starch.3-8 However, the mechanical properties of films are generally reduced by incorporation of starch. Like most of the polymers, starch is immiscible with most of the synthetic polymers at the molecular level. Grafting of synthetic polymers on starch is known to improve some of its properties, but although the grafting of starch with synthetic polymers has been known for 30 years, very few processes have led to full-scale commercialization. Another way of using starch in the material field is the processing of starch microcrystals, which can be obtained as an aqueous suspension. This filler brings a great reinforcing effect to a polymeric matrix, as shown previously.9 In this work, an attempt was made to improve the thermomechanical properties and to decrease the water sensitivity of starch-based systems, preserving the biodegradability of the material. An alternative way to palliate these restrictions is the use of cellulose as a natural and biodegradable filler. Natural cellulose fibers are gaining attention as a reinforcing phase in thermoplastic matrixes. Its low density, a highly reduced wear of the processing machinery, and a relatively reactive surface may be mentioned as attractive properties, together with their abundance and low price. In addition, the recycling by combustion of cellulose composites is easier in comparison with inorganic filler systems. Nevertheless, such fibers are used only to a limited extent in industrial practice, which may be explained by difficulties in achieving acceptable dispersion levels. Cellulose fibers are constituted of long threadlike bundles, called microfibrils, of cellulose molecules stabilized laterally by hydrogen bonds between hydroxyl groups of adjacent molecules. Cellulose microfibrils can also be found as intertwined microfibrils in parenchyma cell wall, in particular from potato pulp. They can be extracted from this biomass by a chemical treatment, leading to purified cellulose, followed by a mechanical treatment in order to obtain a homogeneous suspension due to the individualization of the microfibrils. This suspension has been used afterward to process composite materials with a high level of dispersion, by mixing with an aqueous suspension of gelatinized starch as matrix. Potato pulp was purified according to the treatment displayed in Figure 1. After the removal of starch granules, the remaining pulp is traditionally pressed and dried to be marketed as cattle feed. This byproduct was provided, as pellets, by Avebe Co. (Haussimont, France). The pellets were hydrated into water and ground in a Waring blender apparatus for 10 min. The potato slurry was then poured on a 0.25 mm sieve and washed with water, to remove most of the remaining starch granules. The alkali extraction with sodium hydroxide (NaOH) solution allowed the solubilization of pectins, residual starch, and hemicelluloses, which were then removed by filtration and finally rinsed with distilled water. The resulting insoluble residue was bleached with a sodium chlorite (NaClO2) solution, as already described for sugar beet.10,11 At this stage, the different cell walls are individualized, as shown in Figure 2A, but the microfibrils are still associated within the cell wall. To extract and individualize the microfibrils from the cell walls, a mechanical treatment is required. The insoluble bleached cellulosic pulp was suspended in distilled water (2 wt %) and disintegrated for 15 min in a Waring blender. The suspension was then homogenized by 15 passes through a Manton-Gaulin laboratory homogenizer, described elsewhere by Dufresne et * To whom correspondence should be addressed (e-mail: dufresne@cermav.cnrs.fr). 2693 Macromolecules 1998, 31, 2693-2696

Abstract: Introduction Background Biodegradation as a Treatment Alternative Combined Technologies Current Treatment Technologies On-Site or Ex Situ Processes In Situ Processes Biodegradation/Mineralization/Biotransformation/Bioaccumulation of Petroleum Constituents and Associated Heavy Metals Chemical Composition of Fuel Oils Organic Compounds Heavy Metals Intermediate Metabolites and End Products of Biodegradation Factors Affecting Biodegradation in Soil-Water Systems Chemical and Physical Factors Biological Factors Soil/Environmental Factors Optimization of Bioremediation Variation of Soil Factors Biological Enhancement Contaminant Alteration Volatile Organic Compounds (VOCs) in Petroleum Products Emissions Produced from Soil Contamination Parameters Affecting Volatilization Control of VOC Emissions Monitoring Bioremediation Microbial Counts Other Monitoring Methods Rate of Biodegradation Differing Biotic and Abiotic Processes Treatment Trains Limitations of Soil Treatment Systems Remediation Guidelines Combined Technologies Examples of the Use of Treatment Trains List of Tables List of Illustrations References Index

Abstract: Reversible sorption of phenolic acids by soils may provide some protection to phenolic acids from microbial degradation. In the absence of microbes, reversible sorption 35 days after addition of 0.5–3 μmol/g of ferulic acid or p-coumaric acid was 8–14% in Cecil Ap horizon and 31–38% in Cecil Bt, horizon soil materials. The reversibly sorbed/solution ratios (r/s) for ferulic acid or p-coumaric acid ranged from 0.12 to 0.25 in Ap and 0.65 to 0.85 in Bt horizon soil materials. When microbes were introduced, the r/s ratio for both the Ap and Bt horizon soil materials increased over time up to 5 and 2, respectively, thereby indicating a more rapid utilization of solution phenolic acids over reversibly sorbed phenolic acids. The increase in r/s ratio and the overall microbial utilization of ferulic acid and/or p-coumaric acid were much more rapid in Ap than in Bt horizon soil materials. Reversible sorption, however, provided protection of phenolic acids from microbial utilization for only very short periods of time. Differential soil fixation, microbial production of benzoic acids (e.g., vanillic acid and p-hydroxybenzoic acid) from cinnamic acids (e.g., ferulic acid and p-coumaric acid, respectively), and the subsequent differential utilization of cinnamic and benzoic acids by soil microbes indicated that these processes can substantially influence the magnitude and duration of the phytoxicity of individual phenolic acids.

Abstract: Polylactic acid (PLA) polymer film was degraded in abiotic and biotic environments to understand the role of microbes in the degradation process of lactic acid based polymers. The degradation studies were conducted in a well-characterized biotic system, an abiotic system, a sterile aqueous system, and a desiccated environment maintained at 40, 50, and 60 degrees C. The combination of experiments in different environments isolated the distinct effect of microbes, water, and temperature on the morphological changes in the polymer during degradation. Due to lack of availability of radiolabeled PLA, various analytical techniques were applied to observe changes in the rate and/or mechanism of degradation. CO2 evolved, weight loss, and molecular weights were measured to evaluate the extent of degradation. X-ray diffraction and differential scanning calorimetry techniques monitored the morphological changes in the polymer. FTIR was used as a semiquantitative tool to gather information about the chemistry of the degradative process. Neither of the above analytical techniques indicated any difference in the rate or mechanism of degradation attributable to the presence of microorganisms. The extent of degradation increased at higher process temperatures. FTIR data were evaluated for significant statistical difference by t-test hypothesis. The results confirmed hydrolysis of ester linkage as the primary mechanism of degradation of PLA. On the basis of these data, a probable path of PLA degradation has been suggested.

Abstract: Random aliphatic-aromatic copolyesters synthesized from 1,4-butanediol, adipic acid, and terephthalic acid (BTA) have excellent thermal and mechanical properties and are biodegradable by mixed cultures (e.g., in compost). Over 20 BTA-degrading strains were isolated by using compost as a microbial source. Among these microorganisms, thermophilic actinomycetes obviously play an outstanding role and appear to dominate the initial degradation step. Two actinomycete strains exhibited about 20-fold higher BTA degradation rates than usually observed in a common compost test. These isolates were identified as Thermomonospora fusca strains. They appeared to be particularly suitable for establishment of rapid degradation tests and were used in comparative studies on the biodegradation of various polyesters.

Abstract: Although many polycyclic aromatic hydrocarbons (PAHs) are known to be biodegraded under aerobic conditions, most contaminated sediments are anaerobic. With recent results demonstrating that some bicyclics and PAHs can be degraded without oxygen, information on specific biodegradation rates and electron acceptor stoichiometry is lacking. A fluidized bed reactor (FBR) enrichment approach was used to enrich for bacteria from creosote-contaminated marine sediments with nitrate or sulfate as the sole potential terminal electron acceptors and with naphthalene, biphenyl, dibenzofuran, and phenanthrene as the sole source of carbon and energy. Influent and effluent analysis showed removal of naphthalene, biphenyl, and phenanthrene in the FBRs but not dibenzofuran after 100−200 days. Batch incubations of FBR cells, using strict anaerobic techniques, confirmed the transformation of naphthalene, biphenyl, and phenanthrene with stoichiometric removal of nitrate by the nitrate FBR enrichment. Similarly, phenanthrene, b...

Abstract: Biodegradable terephthalate polymers are described comprising the recurring monomeric units shown in formula (I): wherein R is a divalent organic moiety; R' is an aliphatic, aromatic or heterocyclic residue; x is ≥ 1; and n is 0-5,000, wherein the biodegradable polymer is biocompatible before and upon biodegradation. Processes for preparing the polymers, compositions containing the polymers and biologically active substances, articles useful for implantation or injection into the body fabricated from the compositions, and methods for controllably releasing biologically active substances using the polymers, are also described.

Abstract: Anaerobic degradation of eight commercially available biodegradable polymers was compared in two anaerobic tests using digestion sludge, according to ISO 11734 and ASTM D.5210-91. Cotton, polyhydroxybutyrate/hydroxyvalerate copolymer (PHB/PHV), starch blend, thermoplastic cellulose acetate, and cellulose acetate fibers proved to be anaerobically degradable, but only a low extent of degradation was found for polylactide, polyvinylalcohol, and polycaprolactone. Both test methods gave the same overall results, but with the ISO medium, longer lag phases and greater ranges of variation in the results were observed. These effects are presumably due to low concentrations of carbon dioxide in the ISO medium. Carbon dioxide has been demonstrated to be essential for the growth of various anaerobic bacteria, notably homoacetogenic and methanogenic bacteria.

Abstract: Recent work has shown that a fraction of a contaminant solubilized in the micellar phase of some nonionic surfactants is directly available for biodegradation, meaning that the contaminant can be transferred directly from the core of the micelle to cell without having to transfer to the water phase first. This study extends the understanding of the bioavailability of the micellar phase for a single compound to a multicomponent system of contaminants. Biodegradation experiments were conducted with binary and ternary mixtures of naphthalene, phenanthrene, and pyrene in the presence of a nonionic surfactant, Triton X-100. A mixed bacterial culture, isolated and enriched from a PAH-contaminated soil at the Wurstsmith Air Force Base, MI, was used for the biodegradation experiments. In the absence of the surfactant and at surfactant concentrations below cmc, the multisubstrate Monod kinetics adequately simulated the biodegradation kinetics of the binary and ternary mixtures. In the multicomponent systems, as in...

Abstract: Mixtures of 2,4- and 2,6-dinitrotoluene are produced in large quantities as precursors of polyurethane foams and the explosive 2,4,6-trinitrotoluene (TNT). The two isomers are widely distributed in contaminated groundwater and soil. Bacteria capable of growing with the individual isomers as the sole source of carbon, nitrogen, and energy have been isolated previously. However, attempts to degrade 2,4- and 2,6-DNT simultaneously have failed. We tested the hypothesis that a mixed culture could degrade an isomeric DNT mixture if the bacteria were grown in an aerobic biofilm at low substrate concentrations. Such conditions were achieved with a fluidized-bed biofilm reactor (FBBR). The reactor was fed aqueous solutions containing 2,4- (40 mg L-1) and 2,6-DNT (10 mg L-1). The feed flow rate was gradually increased to yield surface loading rates of 36−600 mg of DNT m-2 d-1. Removal efficiencies higher than 98% for 2,4-DNT and 94% for 2,6-DNT were achieved at all loading rates. The nitrogen released from DNT was ...

Abstract: Conclusive evidence of methyl tert-butyl ether (MTBE) biotransformation and complete mineralization under aerobic conditions in environmental samples and enrichment cultures is reviewed, in addition to increasing evidence of MTBE biotransformation under anaerobic conditions. The metabolic pathway of MTBE appears to have two key intermediates, tert-butyl alcohol (TBA) and 2-hydroxy isobutyric acid (HIBA). The first enzyme in MTBE biodegradation has been identified as either a cytochrome P450 or a nonhemic monooxygenase in different isolates. Mixed and pure cultures of microorganisms have utilized MTBE as a sole carbon and energy source. Cometabolism of MTBE with n-alkanes at rates of 3.9 to 52 nmol/min/mg protein has been documented. The presence of co-contaminants such as BTEX has either not affected or seemed to limit MTBE biodegradation. Some studies of MTBE natural attenuation have attributed mass loss to biodegradation, while others have attributed mass loss to dilution and dispersion. Recent advances...

Abstract: We conducted a laboratory study at 10 °C on the biological decontamination of the waste water from a garage and car-wash that was contaminated with anionic surfactants (57 mg l−1) and fuel oil (184 mg hydrocarbons l−1). The indigenous microorganisms degraded both contaminants efficiently after biostimu- lation by an inorganic nutrient supply. After 7 days at 10 °C, the residual contaminations were 11 mg anionic surfactants l−1 and 26 mg hydrocarbons l−1. After 35 days, only the anionic surfactants had been further reduced to 3 mg l−1. Bioaugmentation of the unfertilized waste water with a cold-adapted inoculum, able to degrade both hydrocarbons (diesel oil) and anionic surfactants (sodium dodecyl sulphate), resulted in a significant increase of the hydrocarbon biodegradation during the first 3 days of decontamination, whereas biodegradation of anionic surfactants was inhibited during the first 21 days following inoculation. Bioaugmentation of the nutrient-amended waste water was without any effect.

Abstract: The biodegradation of polycaprolactone incubated in sea water for several weeks was investigated. For comparison, the hydrolytic degradation in a buffered salt solution was also examined. The weight, tensile strength and morphological changes were recorded during the period of biodegradation.

Abstract: The possibility of enhancing the intrinsic ex-situ bioremediation of a chronically polychlorinated biphenyl-contaminated soil by using cyclodextrins was studied in this work. The soil, contaminated with a large array of polychlorinated biphenyls and deriving from a dump site where it has been stored for about 10 years, was found to contain indigenous cultivable aerobic bacteria capable of utilising biphenyl and chlorobenzoic acids. The soil was amended with inorganic nutrients and biphenyl, saturated with water, and treated in aerobic batch slurry- and fixed-phase reactors. Hydroxypropyl-beta-cyclodextrin and gamma-cyclodextrin, added to both reactor systems at the concentration of 10 g/L at the 39th and 100th days of treatment, were found to generally enhance the depletion rate and extent of the soil polychlorobiphenyls. Despite some abiotic losses could have affected the depletion data, experimental evidence, such as the production of metabolites tentatively characterized as chlorobenzoic acids and chloride ion accumulation in the reactors, indicated that cyclodextrins significantly enhanced the biological degradation of the soil polychlorobiphenyls. This result has been ascribed to the capability of cyclodextrins of enhancing the availability of polychlorobiphenyls in the hydrophilic soil environment populated by immobilised and suspended indigenous soil microorganisms. Both cyclodextrins were metabolised by the indigenous soil microorganisms at the concentration at which they were used. Therefore, cyclodextrins, both for their capability of enhancing the biodegradation of soil polychlorobiphenyls and for their biodegradability, can have the potential of being successfully used in the bioremediation of chronically polychlorinated biphenyl-contaminated soils. Copyright 1998 John Wiley & Sons, Inc.

Abstract: utilizes cyanide as the sole source of carbon and nitrogen. Agar, alginate, and carrageenan were screened as the encapsulating matrices for P. putida. Alginate-immobilized cells of P. putida degraded sodium cyanide (NaCN) more efficiently than non-immobilized cells or cells immobilized in agar or carrageenan. The end products of biodegradation of cyanide were identified as ammonia (NH3) and carbon dioxide (CO2). These products changed the medium pH. In bioreactors, the rate of cyanide degradation increased with an increase in the rate of aeration. Maximum utilization of cyanide was observed at 200 ml min−1 of aeration. Immobilized cells of P. putida degraded cyanides, cyanates and thiocyanates to NH3 and CO2. Use of Na[14C]-CN showed that 70% of carbon of Na[14C]-CN was converted into 14CO2 and only 10% was associated with the cell biomass. The substrate-dependent kinetics indicated that the K m and V max values of P. putida for the substrate, NaCN were 14 mM and 29 nmol of oxygen consumed mg protein−1 min−1 respectively.

Abstract: The contamination of soils and sediments by petroleum is a matter of international concern because of the toxicity and refractory character of the aromatic components in the absence of oxygen1. Gaseous oxygen can be injected into the anaerobic zone of a contaminated environment2 to stimulate biodegradation, but this is costly and inefficient. Other more soluble electron acceptors, such as nitrate or sulphate, can be used instead, but oxidation is slow and hydrocarbon degradation is incomplete3. Here we describe how chlorite dismutation by perchlorate-reducing bacteria can be used as an alternative source of oxygen for degrading contaminants. This dismutation of chlorite into molecular oxygen and chloride is an intermediate step in the microbial reduction of perchlorate or chlorate4.

Abstract: A model system comprising microbial degradation of naphthalene in the presence of cadmium has been developed to evaluate metal toxicity associated with polyaromatic hydrocarbon biodegradation and its reduction by the use of unmodified and surfactant-modified clays in comparison with a commercially available chelating resin (Chelex 100; Bio-Rad). The toxicity of cadmium associated with naphthalene biodegradation was shown to be reduced significantly by using the modified-clay complex and Chelex resin, while unmodified clay has no significant impact on this reduction. The degree of metal toxicity reduction can be quantitatively related to the metal adsorption characteristics of these adsorbents, such as adsorption capacity and selectivity.

Abstract: Five microorganisms, three bacteria and two yeasts, capable of degrading Tapis light crude oil were isolated from oil-contaminated soil in Bangkok, Thailand. Soil enrichment culture was done by inoculating the soil in mineral salt medium with 0.5% v/v Tapis crude oil as the sole carbon source. Crude oil biodegradation was measured by gas chromatography method. Five strains of pure microorganisms with petroleum degrading ability were isolated: three were bacteria and the other two were yeasts. Candida tropicalis strains 7Y and 15Y were identified as efficient oil degraders. Strain 15Y was more efficient, it was able to reduce 87.3% of the total petroleum or 99.6% of n-alkanes within the 7-day incubation period at room temperature of 25 +/- 2 degrees C.

Abstract: Carvone, the principal component of spearmint oil, induces biodegradation of polychlorinated biphenyls (PCB) by Arthrobacter sp. strain B1B. This study investigated the effectiveness of the repeated application of carvone-induced bacteria for bioremediation of Aroclor-1242-contaminated soil. Control treatments compared a single inoculation of carvone-induced cells, repeated applications of noninduced cells, and repeated applications of cell-free carvone/fructose medium. The results showed that repeated application of carvone-induced bacteria was the most effective treatment for mineralizing PCB, resulting in 27 ± 6% degradation of Aroclor 1242 after 9 weeks; whereas a single application of cells resulted in no significant degradation. Addition of cell-free, carvone/fructose medium resulted in 10% degradation of PCB, which suggests that this treatment stimulated biodegradation of PCB by the indigenous microflora. The di- and trichlorobiphenyls were the most readily degraded congeners. More highly chlorinated congeners, which had been previously shown to be degraded in liquid culture, were not substantially degraded in soil, indicating that low bioavailability may have limited their degradation. With the development of new technology, which permits automated in situ fermentation and delivery of degrader microorganisms, the repeated application of carvone-induced bacteria may facilitate bioremediation of PCB-contaminated soils.