Narrow Results

We have studied the distribution and bioelimination of the organophosphorus pesticide parathion in a native microcosm consisting of water, sediment, bivalves and aquatic plants. A common apparent clearance constant for biotic and abiotic components was suggested from the analysis of parathion accumulation and degradation.

In this work we developed a global model explaining the toxicokinetics of a lipophilic compound and particurlarly the common steady state degradation in an aquatic microcosm, using a set of linear differential equations. We simulated the distribution and degradation of the compound in the microcosm, and fitted single-compartment equation models to data, estimating the apparent sorption and elimination constants. We verified the existence of a common apparent degradation constant for all the compartments. We infer from the mathematical expressions and corroborate from the simulated data that the apparent degradation constant is equal to the sum of the metabolization rates at each biotic compartment multiplied by the compound mass ratios established at steady state between the biotic and the abiotic compartments.

Product kinetics simulation showed that steady state might also be achieved in the different compartments, with the same apparent constant as that obtained for toxicant clearance. As a practical result, the total radioactivity in water would serve to calculate the global clearance constant in a simple experimental way if a radiotracer is used. Physical and chemical degradation and chemical loss due to volatilization and CO₂ diffusion were analyzed in the microcosm model. The assessments of the cases where these factors affect the clearance process as well as the implications emerged are discussed.

The degradation control of implants has now become a most critical factor for investigation. The rapid degradation or uncontrolled degradation of metals causes allergic reaction and implants failure. The biocompatibility and biodegradability of biometals are essential properties for the development of bioimplants. The biodegradation is the chemical reaction of implants metal with the surrounding body fluids. The gradual dilution of metal oxide with the body fluid is considered as a degradation. Magnesium, zinc, and iron metals are biodegradable metals. The biodegradability of as-cast metals is not capable of fulfilling the need of patients, therefore, degradation of implants is required to be in control. Many more research articles have been published on improvement of corrosion resistive implant surface by coating, passivation oxide layer, plasma spraying, electropolishing, blasting, chemical etching, laser treatment, heat treatment, severe plastic deformation (SPD), alloying, and development of surface composites. This paper critically reviewed the surface modification and surface composite fabrication techniques to improve the biodegradability, biocompatibility, and strength of implants.

Starch/PVA biocomposite films reinforced with cellulose nanofibrils were prepared by solution casting method incorporating glycerol as a plasticizer. These biocomposite films along with unreinforced films were subjected to biodegradation in an aerobic compost pit. The extents of biodegradation of these films were studied in terms of persentage weight loss. The corresponding changes in the structures and properties of these biocomposites were investigated using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) study and Differential Scanning Calorimetry (DSC). The presence of fillers influenced the arrangement of the starch and PVA molecules in the film compared to that in the unreinforced film. A significant difference was observed in the nature of biodegradation of unreinforced and the reinforced films. The glass transition temperature, as observed from DSC, showed a decreasing trend, while the melting temperature showed an increasing trend after biodegradation. SEM micrographs revealed that the starch portions were consumed at a faster rate compared to polyvinyl alcohol, which was confirmed from XRD graphs also.

In this paper, a model with time delay describing biodegradation of Microcystins (MCs) is investigated. Firstly, the stability of the positive equilibrium and the existence of Hopf bifurcations are obtained. Furthermore, an explicit algorithm for determining the direction and the stability of the bifurcating periodic solutions is derived by using the normal form theory and center manifold argument. Finally, some numerical simulations are carried out to illustrate the applications of the results.

Bioartificial biodegradable materials were prepared mixing chitosan (CHI) and poly(vinyl alcohol) (PVA), then manufactured as films, and finally cross-linked with glutaraldehyde (GTA), both in the absence and in the presence of the edible hexa-alcohol sorbitol (SOR), as a plasticizer. The release of the components into water was tested by high performance liquid chromatography (HPLC); no release of CHI and scarce release of PVA were found. The water uptake was tested by measuring the swelling of the materials, after incubating them for 20 h in an atmosphere saturated with water vapor at 37°C. The swelling percentage increases with increasing CHI content in the blends, although it is the less hydrophilic polymer. This behavior was attributed to the difficulty of water to diffuse through the crystalline PVA structure, which is partially altered in the blends. The addition of SOR enhances the water sorption, as expected. The biodegradability of the materials was tested using the specific enzyme chitosanase, and was found to depend on the blend composition, as well as to be enhanced by the addition of SOR. The initial degradation rates were calculated; the maximum rates were found when the CHI to PVA ratio was 80:20 for all systems. The results of the enzymatic degradation generally agree with those of the swelling. The cross-linked blends were also tested as drug-delivery systems. The drugs chosen were the vitamin L-ascorbic acid (AsA) and the anti-cancer drug paclitaxel (PTX). The effective diffusion coefficients, Deff, were evaluated for the release of both the drugs from each material. Those of AsA are greater, of many powers of ten, than those of PTX, owing mainly to the hydrophilic nature of the first drug and to the hydrophobic of the second one. In conclusion, these materials seem available for biomedical use.

The human environment is at high risk of contamination by the extensive use of non-degradable resources as well as exhaustion of naturally available resources. To combat the environmental and energy issues, recent developments in nanotechnology have open gateways for the sustainable development of eco-friendly, biodegradable, and renewable polymeric materials. Nanocellulose, possessing unique features such as fibrous structure, high mechanical strength, large surface area, low visual scattering, low-cost, renewability, non-toxicity, biocompatibility, and easy availability, serves as an ideal material for diverse environmental applications. In addition, its unique three-dimensional fibril arrangement allows the impregnation of variety of nanosize materials to enable the development of nanocomposites in the form of hydrogels, aerogels, and films, papers, or membranes. Such substrates serve as templates for inorganic nanoparticles and polymers, or a combination of both. Such unique features make nanocellulose-based materials more efficient, robust, stable, reliable, and environmentally-friendly, thus enabling it to find potential applications in the development of antimicrobial filters and devices for removal of heavy metals, in water treatment and wastewaters purification, in the development of pollutant sensors, as well as in potential applications in catalysis and renewable energy. This chapter provides a comprehensive picture of the recent developments in nanocellulose-based materials to address various issues associated with environment and renewable energy.

Pharmaceutical pollution is a universal hazardous issue that affects humans and ecosystems through the release of active pharmaceutical ingredients (APIs). One of their major sources is antibiotics. These compounds survive classical treatment processes, which trigger the development of antibiotic-resistant bacterial strains in aquatic systems. Sulfamethoxazole is a widely used antibiotic that faces a change in the resistance patterns of the various bacterial strains that are sensitive to it. Since biodegradation is one of the main methods for pharmaceutical degradation, it requires the identification of the microbial strains that biodegrade various antibiotics to enable feasible upscale applications. In the work presented in this chapter, Chlorella vulgaris and Monoraphidium conortum were tested separately to degrade 3g/100 ml of sulfamethoxazole. A kinetic study was conducted to separately measure the degradation of the antibiotic by both strains. The results revealed that sulfamethoxazole increased the growth of Chlorella vulgaris and promoted its ability to produce both types of chlorophyll a and b, achieving maximum production of chlorophyll a of 0.135 mg/L and chlorophyll b of 0.095 mg/L at the 25^th day of growth while reaching only 0.1 mg/L of chlorophyll a and 0.034 mg/L of chlorophyll b in the control group. This was unlike the growth of Monoraphidium conortum that was inhibited by sulfamethoxazole achieving 0.09 mg/L of chlorophyll a and 0.079 of chlorophyll b in comparison to 0.094 mg/L of chlorophyll a and 0.12 of chlorophyll b in the control group. On the other hand, Chlorella vulgaris had a higher capacity to degrade sulfamethoxazole, reaching 0.024 mg/L of sulfamethoxazole after 20 days of introducing it to the algal culture, while Monoraphidium conortum degraded the antibiotic to 0.036 mg/L. These results suggest the supremacy of Chlorella vulgaris in the degradation of sulfamethoxazole while maintaining boosted growth behavior. A system of cell-immobilization support was designed and 3D-printed using micro texture to employ these systems in wastewater treatment from pilot to urban scales.

The microbial strains used for decontamination of different origin wastewater should not only be highly active to one of the contaminants but they should also be resistant enough to the remainder. Their resistance can be ensured by the degradation activity of the strains used towards most of the waste products present in the wastewater. Trichosporon cutaneum R57 is known as an effective biodegradant able to utilize and thus remove a number of toxic aromatic compounds from the environment. The present paper deals with processes of degradation and utilization of monohydroxyl derivatives of phenol (resorcinol, catechol and hydroquinone), as well as some of the most toxic aromatic pollutants of the environment like 2,6 - dinitrophenol, α-methylstyrene and acetophenone. The basic kinetic parameters for the biodegradation of the listed above compounds are reported. The highest initial concentrations which could be degraded by the investigated strain were as follow: resorcinol – 1.6 g/l; catechol – 1.3 g/l; hydroquinone – 1.2 g/l; 2,6-dinitrophenol – 0.7 g/l; α-methylstyrene and acetophenone – 0.5 g/l. The inhibition coefficients were calculated according to the Haldane-kinetics. The results obtained certainly proved the ability of strain T. cutaneum R57 to degrade wide range toxic contaminants present in industrial production wastewaters.

The aim of this work was to obtain a microbial consortium from the effluent of cassava flour production and to investigate its potential for biological treatment of this effluent. Experiments were carried out in a bioreactor with the effluent in the presence of ammonium sulfate at 28 - 30 oC, 1 vvm and 200 rpm. Three pulses of the effluent were weekly added to the bioreactor after seven days of cultivation. The nutrient concentrations of the effluent stimulated the growth of the autochthon microorganisms. The maximum growth of bacteria in the microbial consortium reached 108 CFU/mL at the stationary growth phase. Maximum activity of amylases, cellulases, lipases and proteases were detected after seven days of cultivation. The biodegradation of organic material by the microbial consortium was confirmed by the reduction of the chemical oxygen demand (80 %) and cyanide (28 %) during the biological treatment of the effluent. The microbial consortium obtained from the effluent from cassava flour production has potential on the biodegradation of the industrial effluent.

Biodegradation experiment was carried out to evaluate the effects supplementation of microbial consortium and bulking agents in biodegradation of crude oil in soil. The soil with indigenous microbes was spiked with crude oil at 50,000 ppm and a cocktail of microbial consortium at ratio 1:1:1:1 (v/w) which consist of Pseudomonas sp. UKMP 14-T, Acinetobactersp. UKMP 12-T and two fungi isolates Trichodermasp. (TriUKMP-1M and TriUKMP-2M). Bulking agents (sugarcane baggasse (SB) and empty fruit bunch (EFB) from oil palm) at 15% and 20% (w/w), respectively were added and mixed thoroughly. The pH and moisture content of the soil was maintained at 6.5 and 40% VWC, respectively. The degradation of crude oil from the soil was analyzed using gas chromatography-flame ionization detector (GC-FID) and the growth of bacteria was estimated using spread plate method. The result showed that biodegradation of crude oil by microbial consortium with addition of SB produced 100% Total Petroleum Hydrocarbon (TPH) degradation as compared to 91% with EFB after 30 days incubation. The control plot which contains only indigenous microbes showed 62% degradation at the same period of incubation. The results indicate that the types of the bulking agent may influence the intake of the nutrient source by microbial consortia hence influenced the percentage of the TPH degradation.

Sixteen strains of filamentous fungi were isolated from soil samples collected from Livingston Island, Antarctica. The isolates’ taxonomic identifications were performed based on morpho-dimensional parameters following the most suitable identification keys for the different genera. The affiliation of the investigated strains was established to the particular genera. The obtained fungal isolates were members mostly to the genera Penicillium, Aspergillus and Cladosporium. All strains were studied for their ability to adapt to aromatics containing media. Most of the investigated strains demonstrated good tolerance to the presence of 0.5 g/l phenol in the culture medium. More than that the investigations showed that strains were able to grow in a culture medium containing phenol in concentrations varying form 0.1 to 0.7 g/l as a single source of carbon and energy. The experiments carried out with hydroxyl-, methyl- and nitro- phenol derivatives revealed the capability of some of the strains to grow and utilize various of these aromatic compounds. The strains Aspergillus sp. AL1, Aspergillus sp. AL8, Aspergillus AL9, Aspergillus sp. AL15, Penicillium sp. AL5 and Penicillium AL11 were able to grow and utilize as a sole carbon sources 0.3 g/l of each examined aromatic compound. There were not found strains able to utilize any of the tested nitrophenols. The representatives of Cladosporium as well as strain Lecanicillium sp. AL12 did not show any capability to degrade phenol derivatives.

The intensive use of glyphosate [N-(phosphonomethyl) – glycine] to control weeds in agricultural areas all over the world requires special attention due to its toxicity to non-target organisms. The use of microorganisms in the degradation and detoxification of glyphosate polluted sites in the environment is an efficient tool and bioremediation is a very useful option to conventional cleanup methods. The objective of this study was to isolate the best bacterial strain with the ability of degrading high concentrations of glyphosate, a common herbicide used in the world. Then, the ability of the isolate to degrade glyphosate under varying nutrient was evaluated. The glyphosate utilization of the bacterium was screened using mineral medium containing glyphosate as sole C, N, P or C, N, P and glyphosate along additional C, N, P sources. Of all isolated bacteria, Pseudomonas (aeruginosa) showed the ability to utilize glyphosate efficiently and was therefore used for further biodegradation studies. The glyphosate biodegradation by Pseudomonas (aeroginosa) showed significant differences among 5 nutrient medium. The comparative effects of glyphosate on the growth of the isolates showed that there was significant (P < 0.05) growth in the medium containing glyphosate as an additional source of C/N/P). No inhibition of growth was observed at higher concentrations. But the percentage of degradation in the above medium (58.9%) was significantly (P <0.05) less than media containing glyphosate as sole sources of P (90.4%) or N (71.3%) and the medium containing glyphosate as source of P, N and C (72.8%). According to the results revealed that the bacterium exhibited a high capacity to efficiently degrade glyphosate as phosphorus source. It was also observed that it could degrade 21.25 g/lit glyphosate after 96 h incubation completely. It can be concluded that application of such isolated bacteria with the potential of degrading pesticides from contaminated site, can be used to remediate soil contaminated with pesticide.

Growth in biofilms is a general ability of microbial populations which are historically used in wastewater treatment. The basic aim of biofilm formation is the fixation of microorganisms at a given place as a means of stabilizing living conditions. In a biofilm environment, organisms are protected against negative environmental influences. Compared to dispersion growth, biofilms offer many advantages that allow their use in specific biological treatment of industrial wastewater. The crucial advantage is the increase in the residence time of biomass in biofilm reactors allowing concentrations of slow-growing microorganisms and the diffusion barrier of the biofilm which reduces the effects of toxicants and suboptimal physico-chemical conditions. The development of the biofilm depends on many factors, from the surface properties to the supply of nutrients and hydrodynamic forces in the bioreactor. The objective of many research projects in the field of wastewater treatment is to technologically improve the biomass carrier. The final requirements are excellent colonization, high cleaning efficiency given the maximum specific surface area, optimal density and ease of production. Based on these crucial parameters the Technical University of Liberec has begun the development of a new type of carrier which is based on the use of polymeric nanofiber materials. This has resulted in a yarn which consists of a carrier fiber with a layer of nanofibers (the diameter of the nanofibers is in the order of hundreds of nanometers). The clear advantages of nanotechnology are a high protected specific surface area which promotes the microbial population during initial adhesion to the surface of the carrier and also during future development, protection of the population from surrounding adverse effects, promoting the supply of nutrients and supporting the compactness of the biofilm. The aim of the article is to highlight the possibilities and potential of biofilms with the presence of a composite nanofiber carrier.

The effect was studied of several yeast strains of the genera Saccharomyces, Pichia, and Kluyveromyces on the persistence of four pesticides (pyraclostrobin, dimethoate, oxamyl, and pymetrozine) in brine during the fermentation process of vegetable products. The growth of yeast strains in a synthetic brine in the presence of the pesticides was recorded with a Bioscreen C kinetic growth reader and compared with their growth in a control brine without pesticides. After incubation for 7 days with the yeast strains, the concentration of pesticides in the synthetic brine was determined. Prior to this pesticide assay, the brines were centrifuged to removing the yeast pellets. The pesticides were determined in both yeast-free brine and yeast pellets and compared with the control consisting of sterile brine with pesticides. A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method was used to extract the pesticides, which were assayed by LC-MS. The effect of the yeasts on the concentration of the four pesticides in synthetic brine depended on the yeast strain, and was clearest on pymetrozine and pyraclostrobin.