Increased Biodegradation Rates Research Articles

Novel Biocomposite of Starch and Flax Fiber Modified with Tannic Acid with Biocidal Properties.

The purpose of this paper was to develop novel biocomposites with biocidal properties in microorganisms, with enhanced mechanical strength and hydrophobicity as well as with increased biodegradation rates. The main idea and the novelty of this work was to use cross-linking compounds and, at the same time, biocidal compounds-natural compounds of plant origin with biocidal properties. The authors assumed that the modification of flax fiber by natural plant compound will reduce the hydrophilicity of novel biocompositie. Biopolymer based on thermoplastic starch reinforced with flax fibres modified with tannic acid (TA) was prepared by extrusion and injection molding processes. The effects of TA modification on the mechanical and structural properties of biocomposites were analyzed through DMA, tensile tests, DSC, and TG. The biocidal and wettability properties of the biocomposites were investigated. The article also discusses the outcomes of research conducted on the structural characteristics and rates of the biodegradation of biocomposites.

Evaluation of the Mechanical and Biocidal Properties of Lapacho from Tabebuia Plant as a Biocomposite Material.

The aim of this article is to discuss in detail the physicochemical properties of polylactide (PLA) reinforced by cortex fibers, which may cause bacterial mortality and increased biodegradation rates. PLA biocomposites containing cortex Lapacho fibers from Tabebuia (1–10 wt%) were prepared by extrusion and injection moulding processes. The effects of Lapacho on the mechanical and biocidal properties of the biocomposites were studied using tensile and impact tests, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), thermogravimetry (TG), and the method of evaluating the antibacterial activity of antibacterial treated according to the standard ISO 22196:2011. It also presented the effects of Lapacho on the structural properties and biodegradation rates of biocomposites. This research study provides very important results complementing the current state of knowledge about the biocidal properties of Lapacho from Tabebuia plants and about cortex-reinforced biocomposites.

Comparing the European Union System for the Evaluation of Substances (EUSES) environmental exposure calculations with monitoring data for alkyl sulphate surfactants

BackgroundThe European surfactant and detergent industry initiated a project to conduct an EUSES-based environmental exposure assessment for the total volume of alkyl sulfate (AS) surfactants, and to verify if the EUSES assessment leads to a realistic prediction of the environmental exposure or to an over- respectively under-estimation of the environmental concentrations of the surfactants. Verification of the EUSES environmental concentration prediction (Clocaleffluent) was carried out by benchmarking them against environmental monitoring data. Recently published data from the United States of America adjusted to the European Union (EU) frame conditions were used for the assessment, as for the EU only historical data from the mid-1990s are available. In addition to the standard (default) EUSES assessment, a higher tier assessment using substance-specific properties, particularly increased biodegradation rates (192 per day instead of the default of 24 per day for WWTP), was conducted.ResultsA figure of 178,400 tonnes of AS was established as the total maximum volume (2016) handled annually in Europe. This total volume includes the volumes from all EU manufacturers and all registered AS > 100 t/a, as well as the amount of AS contained in EU REACH registered alkyl ether sulfates (AES). The total tonnage was split and assigned to the different uses as reported to ECHA in the C12 AS, Na (151-21-3) registration dossier in 2010. The EUSES calculation was limited to widespread (professional and consumer) uses, covering in total 97,889 t of AS homologues. The EUSES calculation gave a Clocaleffluent of 335 µg/L for the SimpleTreat “readily” biodegradation rate default and a Clocaleffluent of 44.6 µg/L for the AS-specific degradation rates. Recent US monitoring data showed a mean effluent concentration of 4.24 µg alkyl sulfates/L (∑ C12 + C14 + C16 homologues). Taking into account the different annual per capita AS use (including AS from AES) in the US (295 g) and the EU (348 g), the daily per capita water use (EU 200 L, US 408 L), and the WWTP efficiency in the EU and the US (comparable), an US to EU adjustment factor of 2.4 was established. Application of the adjustment factor to the US monitoring data resulted in a calculated EU mean effluent concentration = 10.18 µg alkyl sulfates/L (∑ C12, C14, C16 homologues). This value was used as an independent benchmark for the EUSES calculations.ConclusionsComparing the predicted Clocaleffluent = 335 µg alkyl sulfates/L (SimpleTreat default) and a Clocaleffluent = 44.6 µg Alkyl Sulfates/L (AS-specific degradation rates) with the 10.18 µg alkyl sulfates/L from the adjusted monitoring data it is evident, that the EUSES calculation overestimates the AS environmental exposure by factors of > 32 and > 4, respectively. Taking into consideration, that only widespread uses (covering only 50% of the total AS volume) were included in the EUSES calculation, the overestimation of the default exposure by a factor of 4 is still conservative, despite the fact, that eightfold higher, substance-specific biodegradation rates were used. In conclusion, using the 2010 C12-AS REACH dossier (CAS-No. 151-21-3) as an example, it has been shown, that EUSES model exposure calculations using default biodegradation rates significantly overestimate effluent concentrations.

Controlling the biodegradation rates of poly(globalide-co-ε-caprolactone) copolymers by post polymerization modification

Controlling the degradation rates of polymers is crucial for their application in tissue engineering or to achieve degradation of the polymers in the wastewater purification. As hydrophobic polyesters often exhibit very slow degradation rates, we report here increased biodegradation rates of poly(globalide-co-ε-caprolactone) copolymers (PGlCL) produced by enzymatic ring-opening copolymerization and post-functionalized with N-acetylcysteine by thiol-ene reaction. The degradation rates of the PGlCL and post-modified PGlCL-NAC films were determined by weight-loss experiments. The polymer films were immersed in phosphate-buffered saline (PBS) solution, and PBS containing lipase from Pseudomonas cepacia. The degree of functionalization affected the degradation behavior, and samples with a higher degree of functionalization presented higher weight loss. Finally, a degradation assay was performed in activated sludge, and PGlCL-NAC presented high degradability, having a degradation behavior similar to starch. Density Functional Theory (DFT) calculations were used to assess the changes in chemical properties and electronic charge distribution of PGlCL after its functionalization with NAC, helping to understand its influence in their degradability. The results obtained confirm the possibility to increase the degradation rates of copolyesters based on caprolactone and globalide by thiol-ene post-functionalization, being a promising alternative for applications in biomedicine or the packaging sector.

Controlling the dissolution of iron through the development of nanostructured Fe-Mg for biomedical applications

In the field of biodegradable metallic materials, rapid and non-uniform biodegradation, caused by uncontrolled corrosion rates, is a potential shortcoming. Among the prominent biodegradable materials, magnesium is an attractive choice, however, it is prone to rapid dissolution. In contrast, iron possesses a slow dissolution rate. To approach the middle ground, instead of making magnesium more corrosion-resistant, the less-explored approach of making iron less corrosion-resistant is employed here. In this study, iron, and magnesium, having contrasting corrosion rates, are combined via magnetron co-sputtering. The idea of combinatorial synthesis is employed to fabricate two model nanostructured Fe-Mg samples, i.e. CSFM-1 (Fe85Mg15), and CSFM-2 (Fe65Mg35), exhibiting a controlled and uniform degradation in phosphate-buffer saline solution. The structural characterization of the two samples demonstrates a substitutional solid solution of bcc-Fe—Mg in CSFM-1 and an amorphous short-range-ordered structure in the CSFM-2 sample. Electrochemical investigation shows increased corrosion rates for the two Fe-Mg samples in comparison to pure Fe, validated by relatively active corrosion potentials, higher corrosion current densities, faster anodic dissolution, and lower charge transfer resistances, governed by chemical composition and non-equilibrium nanostructures. Finally, nano-indentation testing of the two samples reveals relatively higher hardness and lower elastic moduli, a suitable combination for bio-implants. Statement of SignificanceThe use of Mg as a biodegradable in-vivo implant material is problematic because of its high dissolution rate and potential for hydrogen gas generation. This is the first time that the idea of combinatorial synthesis is employed to fabricate two model nanostructured Fe-Mg systems, i.e. CSFM-1 (Fe85Mg15), and CSFM-2 (Fe65Mg35), exhibiting a controlled and uniform degradation. The structural characterization of the two systems demonstrates a substitutional solid solution of bcc-Fe—Mg in CSFM-1 and an amorphous short-range-ordered structure in the CSFM-2 system. Electrochemical investigation shows increased biodegradation rates for the two Fe-Mg systems in comparison to pure Fe, validated by relatively active corrosion potentials, higher corrosion current densities, faster anodic dissolution, and lower charge transfer resistances, governed by chemical composition and non-equilibrium nanostructures.

Biochar amendment as a remediation strategy for surface soils impacted by crude oil

The impact of organic bulking agents on the biodegradation of petroleum hydrocarbons in crude oil impacted soils was evaluated in batch laboratory experiments. Crude oil impacted soils from three separate locations were amended with fertilizer and bulking agents consisting of biochars derived from walnut shells or ponderosa pine wood chips produced at 900 °C. The batch reactors were incubated at 25 °C and sampled at pre-determined intervals to measure changes in total petroleum hydrocarbons (TPH) over time. For the duration of the incubation, the soil moisture content was adjusted to 75% of the maximum water holding capacity (MWHC) and prior to each sampling event, the sample was manually stirred. Results show that the addition of fertilizer and bulking agents increased biodegradation rates of TPH. Soil samples amended with ponderosa pine wood biochar achieved the highest biodegradation rate, whereas the walnut shell biochar was inhibitory to TPH biodegradation. The beneficial impact of biochars on TPH biodegredation was more pronounced for a soil impacted with lighter hydrocarbons compared to a soil impacted with heavier hydrocarbons. This study demonstrates that some biochars, in combination with fertilizer, have the potential to be a low-technology and eco-friendly remediation strategy for crude oil impacted soils.

Influence of contaminant exposure on the development of aerobic ETBE biodegradation potential in microbial communities from a gasoline-impacted aquifer

Aerobic biodegradation of ethyl tert butyl ether (ETBE) in a gasoline-impacted aquifer was investigated in laboratory microcosms containing groundwater and aquifer material from ETBE-impacted and non-impacted locations amended with either ETBE, or ETBE plus methyl tert butyl ether (MTBE). As sole substrate, ETBE was biodegraded (maximum rate of 0.54 day−1) without a lag in ETBE-impacted microcosms but with a lag of up to 66 days in non-impacted microcosms (maximum rate of 0.38 day−1). As co-substrate, ETBE was biodegraded preferentially (maximum rate of 0.25 and 0.99 day−1 in non-impacted and impacted microcosms, respectively) before MTBE (maximum rate of 0.24 and 0.36 day−1 in non-impacted and impacted microcosms, respectively). Further addition of ETBE and MTBE reduced lags and increased biodegradation rates. ethB gene copy numbers increased significantly (>100 fold) after exposure to ETBE, while overall cell numbers remained constant, suggesting that ethB-containing microorganisms come to dominate the microbial communities. Deep sequencing of 16S rRNA genes identified members of the Comamonadaceae family that increased in relative abundance upon exposure to ETBE. This study demonstrates the potential for ETBE biodegradation within the unsaturated and saturated zone, and that ETBE biodegrading capability is rapidly developed and maintained within the aquifer microbial community over extended timescales.

Corrosion Behavior of Magnesium Based Foam Structure in Hank’s Solution

Metal foam is a new class of materials with promising applications and a unique combination of physical, chemical, and mechanical properties. The purpose of biodegradable implants is to support tissue regeneration and healing in a particular application by material degradation and implant replacement through the surrounding tissue. Magnesium alloys are expected to be degraded in the body and its corrosion products not deleterious to the surrounding tissue. In the present study, the foam metal was manufactured via powder metallurgy with a different variation of sintering temperature and TiH2 used as a foaming agent which are added to Mg-1Ca-3Zn alloy as much 3% wt TiH2. The sintering temperatures were 500, 550 and 600 °C with a constant holding time of 5 hours. It’s critical that the sintering temperature is carefully selected in consideration of their corrosion behavior. This paper reports the study of the behavior of the Mg-Ca-Zn alloy metal foam which evaluated by SEM, EDX, and electrochemical corrosion test in Hank’s solutions. After exposure, the SEM result of Mg-Ca-Zn-3TiH2 to Hank’s solution, a volcano-like structure is formed. The streams of H2 bubbles form at local sites on the Mg alloy surface where electrochemical reactions are taking place, leading to the particular structure with around shape and often with a hole in the center. The corresponding EDS result maps reveal enrichment of O, Ca, P and Mg as corrosion product. Potentiodynamic polarization experiments conducted at 37 °C and pH 7.4 indicated the increased biodegradation rates resulted from porous structure of foam samples. Corrosion rate in 500oC sintering temperature were 1.99 millimiles per year (mmpy) with corrosion current density (Icorr) 87.3.10-6 A/cm2, corrosion rate in 550 °C sintering temperature were 2,16 mmpy with Icorr 94.4.10-6 A/cm2 and rate in 600 °C sintering temperature were 2.41 mmpy with Icorr 105.10-6 A/cm2. The results showed that the increasing of sintering temperature could influence the corrosion resistance of Mg alloy.

Bioremediation of diesel-contaminated soil by heated and humidified biopile system in cold climates

Abstract Bioremediation is a proven and widely accepted technology for the remediation of soil contaminated with various mixtures of petroleum hydrocarbons (PHC) in temperate climates but its application in cold climates has received far less attention. Low ambient temperature is one of the main factors limiting microbial degradation of the organic contaminants in such locations. Heating the soil should therefore enhance bioremediation as laboratory studies have shown increased biodegradation rates in Arctic soils with increasing soil temperature. A biopile is one of the many bioremediation techniques to treat hydrocarbon-contaminated soil where the soil is piled over an air distribution system and aerated. The air distribution system can also be used to provide heat to the soil in order to optimize soil temperature when conditions are limiting. However, heating the soil by forced air may cause excessive drying of the soil which may inhibit microbial activity and promote volatilization of the contaminants rather than their biodegradation. During treatment of hydrocarbon contaminated soils in a biopile system, biodegradation is preferred over volatilization and should be optimized. Few field-scale studies have tested the use of heated biopile systems in cold climates. This paper examines the effect of humidifying the air for the treatment of PHC-contaminated soil by an aerated/heated biopile system. Three biopiles were constructed with soil freshly contaminated with diesel fuel (initial total petroleum hydrocarbon concentration, [TPH], ~ 11,000 mg/kg dry weight) and operated for 10 months in Kingston, ON, Canada. One biopile was heated with an aerating/heating system previously tested in the Arctic. A second biopile was also aerated and heated but received water by humidifying the air prior to entering the soil pile. A third biopile was passively aerated by pipes protruding from the soil pile. TPH, available nutrients content, and pH were monitored by periodic collection and analysis of soil samples. Volatilization of hydrocarbon compounds was measured by trapping them on activated charcoal. Temperature and moisture were monitored continuously with a datalogger. Hydrocarbon concentrations in soil and charcoal samples were measured by solvent extraction followed by gas chromatography flame ionization detection (GC/FID) analysis. Significant TPH reduction was observed in all systems. TPH reduction followed first-order kinetics for the first two-third of the treatment. The humidified system maintained optimal soil moisture content and produced significantly lower final TPH than the other two treatments (~ 300 mg/kg dry weight). Findings suggest that humidifying the air enhanced biodegradation and minimized volatilization. The removal of hydrocarbons of different carbon chain lengths was investigated by GC/FID analysis. Three hydrocarbon fractions were defined ( nC15) based on equivalent straight-chain alkane ranges. Results from this analysis showed that all fractions were removed during treatment, but the overall data suggest that biodegradation was dominant for the highest molecular weight fraction.

Crystallization and enzymatic degradation of novel poly(ε-caprolactone-co-propylene succinate) copolymers

A series of novel poly(ε-caprolactone-co-propylene succinate) P(CL-co-PSu) copolymers having low propylene succinate content and high molecular weight were synthesized following a combinatory scheme of ring opening and polycondensation reactions, in an attempt to obtain copolymers of sufficient performance and increased biodegradation rates. Enzymatic hydrolysis of the copolymers was studied in the presence of mixture of Rhizopus delemar and Pseudomonas cepacia lipases. Much higher hydrolysis rates, comparing to neat PCL, were proved by both mass loss measurements and scanning electron microscopy (SEM) observations of the degraded film surfaces. Thermodynamics of cocrystallization and wide-angle X-ray diffraction (WAXD) patterns were investigated to estimate the extent of comonomer cocrystallization. Results of the study showed that comonomer inclusion may hold, though the molar fraction of the comonomer in the PCL crystals is lower than in the bulk. This means that not only the observed decrease of the degree of crystallinity from about 48% for PCL to about 29% for the P(CL-co-PSu) 75/25 favours enzymatic hydrolysis, but also the enrichment of the amorphous phase in the fast degrading propylene succinate units plays its role. The non-isothermal crystallization rates of the copolymers, like the melting points, decreased substantially when the propylene succinate content exceeded 8 mol%. The activation energy of crystallization was calculated using the isoconversional method of Friedman, over the whole range of crystallization temperatures. An increase was found in the activation energy with increasing the comonomer content in the copolymers also proving the reduced symmetry along the copolymer chains due to the presence of comonomer units.

SHORELINE CLEANUP BY ACCELERATION OF CLAY-OIL FLOCCULATION PROCESSES

ABSTRACT During the cleanup operations following the Sea Empress oil spill, it was observed that the oil emulsion did not adhere strongly to the shoreline and that fine mineral particles present in the surf waters interacted with oil to form clay-oil floes. In an attempt to enhance clay-oil flocculation, Amroth beach was subjected to repeated “surf washing”: the oiled cobbles from the high water mark were moved down to the intertidal zone using an excavator at low tide. After 4 days of treatment, most of the oil emulsion was removed from the cobbles. We estimate that the majority of the oil was removed as clay-oil flocs and that the remainder was released from the cobbles as a broken surface slick. Microscopic and chemical analysis of samples of flocs and oiled sediments showed that energy imparted to the surf zone resulted in clay-oil flocculation, which increased biodegradation rates of the residual oil. Surf washing increased the availability of fine mineral particles, which (1) minimized the contact of oil directly with the substrate, thereby reducing the adhesion of oil to the shoreline, and (2) prevented the recoalescence of oil droplets, thereby promoting the dispersion of oil within the surf zone.

Effect of added heavy metal ions on biotransformation and biodegradation of 2-chlorophenol and 3-chlorobenzoate in anaerobic bacterial consortia

The effect of added Cd(II), Cu(II), Cr(VI), or Hg(II) at 0.01 to 100 ppm on metabolism in anaerobic bacterial consortia which degrade 2-chlorophenol (2CP), 3-chlorobenzoate (3CB), phenol, and benzoate was examined. Three effects were observed, including extended acclimation periods (0.1 to 2.0 ppm), reduced dechlorination or biodegradation rates (0.1 to 2.0 ppm), and failure to dechlorinate or biodegrade the target compound (0.5 to 5.0 ppm). 3CB biodegradation was most sensitive to Cd(II) and Cr(VI). Biodegradation of benzoate and phenol was most sensitive to Cu(II) and Hg(II), respectively. Adding Cr(VI) at 0.01 ppm increased biodegradation rates of phenol (177%) and benzoate (169%), while Cd(II) and Cu(II) at 0.01 ppm enhanced biodegradation rates of benzoate (185%) and 2CP (168%), respectively. Interestingly, with Hg(II) at 1.0 to 2.0 ppm, 2CP and 3CB were biodegraded 133 to 154% faster than controls after an extended acclimation period, suggesting adaptation to Hg(II). Metal ions were added at inhibitory, but sublethal, concentrations to investigate effects on metabolic intermediates and end products. Phenol accumulated to concentrations higher than those in controls only in the 2CP consortium with added Cu(II) at 1.2 ppm but was subsequently degraded. There was no effect on benzoate, and little effect on acetate intermediates was observed. In most cases, methane yields were reduced by 23 to 97%. Thus, dehalogenation, aromatic degradation, and methanogenesis in these anaerobic consortia showed differential sensitivities to the heavy metal ions added. These data indicate that the presence of heavy metals can affect the outcome of anaerobic bioremediation of aromatic pollutants. In addition, a potential exists to use combinations of anaerobic bacterial species to bioremediate sites contaminated with both heavy metals and aromatic pollutants.

Biodegradable and Tensile Properties of Cotton/Cellulose Acetate Nonwovens

A possible candidate as an environmentally friendly nonwoven fabric is one that can be formed from the thermal calendering of a cotton/cellulose acetate blend. Our results focus on biodegradable properties of the fibers as well as tensile properties of the fabric. Cotton, which is a comfortable, absorbent, biodegradable fiber, is the base fiber in the nonwovens. Cellulose acetate, which is a thermoplastic, hydrophilic, mod ified cellulosic fiber, is used for the binder fiber. We examine the biodegradability of cellulose acetate, cotton, and these fibers in the blend using an ASTM standard pro cedure in which the amount of CO 2 evolved from the decomposition of cellulose acetate and cotton fibers due to microbial activity is monitored. Increased biodegra dation rates in fiber blends are attributed to the synergistic effects of multi-enzyme systems. Opening, blending, carding, and thermal calendering processes are used to fabricate the nonwovens. Pretreatment with solvent vapors is introduced to modify the softening temperatures of the cellulose acetate and to lower the calendering tem peratures. The success of this procedure is demonstrated in enhanced tensile strength of the nonwoven. In addition, modifying tensile properties with solvent vapor pre treatment shows how enhanced strength can be obtained with lower calendering tem peratures.

Dibutylphthalate degradation in estuarine and freshwater sites

Biotic and abiotic degradation of di-n-butylphthalate (DBP) in water and sediment/water systems from six different sites was investigated under laboratory conditions. DBP disappearance was rapid in all microbially active systems and substantially reduced under sterile conditions. Adaptation of microbial populations to degrade DBP was indicated in six of nine evaluations conducted. The presence of sediment significantly increased biodegradation rates in five of the six sites.