A study of biodegradation/γ-irradiation on the degradation of p-chloronitrobenzene

A microbial strain, Vagococcus sp. B32, was isolated and applied to degrade p-chloronitrobenzene (p-CNB) in aqueous solutions. Three degradation methods: biodegradation, direct γ-irradiation and ⁶⁰Co-γ pre-irradiation with biodegradation by B32 were carried out. The decrease of p-CNB and the net increase of Cl⁻ were investigated to evaluate the degradation efficiency. The preliminary results showed that the combined method of pre-irradiation with biodegradation of B32 was more effective than the two others.     

Enzyme-mediated biodegradation of heat treated commercial polyethylene by Staphylococcal species

Extruded low-density polyethylene (LDPE) films commonly available in the market as 20-micron thick carrier bags were autoclaved, overlaid on nutrient agar plates and inoculated with BP/SU1 strain of Staphylococcus epidermis. The nutrient agar plate showed growth of the organism within two to three days. The polymer film supporting the growth of the organism showed pore formation as recorded by SEM analysis. The growth of BP/SU1 is supported by the presence of shredded LDPE as its only carbon source in inorganic salt minimal nutrient medium. The organism survives even after three months of inoculation and this is accompanied by gradual breakdown of the size of the shredded plastic as seen by light scattering. The cell-free supernatant of the organism, grown with the help of shredded plastic shows the presence of the over expressed proteins with approximate molecular weight of about 55 kDa and 35 kDa, through SDS-PAGE analysis.     

Effect of sepiolite on the biodegradation of poly(lactic acid) and polycaprolactone

PLA and PCL nanocomposites prepared by adding 5 wt% of a sepiolite (SEPS9) were degraded in compost, leading to effective degradation for all samples.PLA and PLA/SEPS9 seem to be mainly degraded by a bulk mechanism, showing a significant level of polymer degradation, however the presence of SEPS9 particles partially delays the degradation probably due to a preventing effect of these particles on polymer chain mobility and/or PLA/enzymes miscibility. PCL and PCL/SEPS9 showed a preferential surface mechanism of degradation; and in contrast to PLA, sepiolite does not present a considerable barrier effect on the degradation of PCL.     

Atmospheric and soil degradation of aliphatic-aromatic polyester films

The degradation of an aliphatic-aromatic biodegradable polyester film was studied under conditions of solar exposure and soil burial in a tropical area. Film samples were evaluated for changes over 40 weeks by visual examination, scanning electronic microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, mechanical properties, molecular weight, gel content, and thermal properties. Photodegradation played a major role in the atmospheric degradation of the film, causing it to lose integrity and mechanical properties after week 8 due to main chain scission and crosslinking. SEM micrographs and FTIR spectra indicated that photodegradation started at the exposed side of the film and propagated through the polymer matrix after week 8. FTIR spectra also indicated that subsequent photooxidation processes took place. The reduction of molecular weight of the soil burial samples was much slower than that of the non-crosslinked portion of solar exposed film samples. The reduction of number average molecular weight of the non-crosslinked solar exposed samples followed a first order reaction, whereas the soil burial samples show a surface erosion biodegradation behavior. The relationship among total solar radiation, gel content and number average molecular weight indicated that an accumulated total solar radiation of 800 MJ/m², reached in approximately 7 weeks at the exposure site, is required for PBAT mulch film integrity loss.     

Dependence of fungal biodegradation of PEG/castor oil-based polyurethane elastomers on the hard-segment structure

In the context of protecting of the environment, this work studies the biodegradation of PEG-based polyurethane elastomer films in the presence of the soft rot fungus Chaetomium globosum, determined via the Petri-dish test. Using PEG with high-molecular weight (MW = 1500) as a chain extender led to polyurethane elastomers with lower physical crosslink density and higher swelling rates. The structural modifications in the hard-segment area (CO and N-H peaks) are considerable and were analyzed by FTIR spectroscopy. Biodegradation lowers the final mechanical properties, but increases yield points, especially in the case of polyurethane elastomers crosslinked with castor oil. Polyurethane elastomer samples showed visible degradation proved by the mechanical weakening of the films. Thus, breaking strains decrease from 670-1180% to 500-680% and tensile strengths decreased from 11.5-27.5 MPa to 4-11.5 MPa after 130 days of fungal biodegradation. The changes in the morphology of the polyurethane films surface were analyzed by SEM and have been found to exhibit increasing porous structure and fungal hyphae. The effects of the hard-segment composition of the polyurethane elastomers on the fungal biodegradation behaviour were investigated.     

Effect of environment on the degradation of starch and pro-oxidant blended polyolefins

The aim of this study was to understand the rate of degradation of commercial pro-oxidant blended and starch blended High Density Polyethylene (HDPE), pro-oxidant blended Low Density Polyethylene (LDPE), and starch blended polypropylene in three different environments, namely under direct sunlight, buried in soil and immersed in marine waters for a period of 150 days. The bio-fouling parameters were also monitored in the case of polymers deployed in sea water. Exposure to sunlight showed highest weight loss (>10%) and samples buried in soil showed the lowest (∼1%). Pro-oxidant blended HDPE showed higher weight loss when compared to starch blended (22.7 as against 11%). Scanning electron microscopy revealed surface deterioration and decrease in contact angle indicated reduction in surface hydrophobicity. Increase in the carbonyl and hydroxyl groups in the infra-red spectrum of the exposed samples suggested abiotic degradation. Starch blended PP exposed to sunlight showed the highest thermo gravimetric weight loss (63.8%) followed by the same polymer buried in soil (46.1%).     

固定化细菌去除苯甲酸类化合物的研究

用富集培养法，从工业废水中分离到能以苯甲酸类化合物为唯一碳源和能源而生长的细菌不动杆菌ＢＪ１和产碱杆菌ＳＢ１。用海藻酸钙共固定化的ＢＪ１和ＳＢ１菌株于３０℃培养７２ｈ以后，模拟工业废水中１ｇ／Ｌ的苯甲酸，邻羟基苯甲酸，间羟基苯甲酸，以羟基苯甲酸，邻苯二甲酸和苯乙酸的去除率分别为８９％，９８％，９７％，１００％，９０％和６１％。     

Bioremediation of Aged Petroleum Oil Contaminated Soil: From Laboratory Scale to Full Scale Application

Large quantity of aged petroleum oil contamination such as dehydrated oil sludge, generated in the disposal process of oil-containing sewage in Indonesia. This study aims to investigate the OSCS removal by mean of bioremediation technique. Results found that petrofilic consortia and biosurfactants addition increased the removal efficiency up to 46% and 85%, respectively. At full scale application, this technique succeed in removing of 46 g TPH per kg soil from 4 883 m³ of OSCS during 16 mo of treatment. These results suggest that petrofilic consortia and biosurfactants addition stimulate the biodegradation and overcome the limitation of OSCS degradation process.     

Biodegradable microspheres with poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) Enriched surface: Thermo-responsibility,biodegradation and drug release

Microspheres with thermo-responsible surface were fabricated by PCL-b-PEO-b-PNIPAM triblock copolymers. Thermo-responsible morphological changes of PCL-b-PEO-b-PNIPAM microspheres immersed in aqueous solution at temperatures above the LCST (e.g. 37 °C) were observed from porous surface structure to compact surface layer. Enzymatic degradation and in vitro drug release results showed that the thermo-responsible surface layer greatly influenced the degradation of microspheres as well as the drug release behavior from microspheres. With the copolymerization of PNIPAM block into PCL-b-PEO copolymers, the drug release could be well regulated by changing temperatures and microspheres composition, which revealed the great potentials of microspheres with thermo-responsible surface for controlled drug release.     

Biological effects of magnesium particles degradation on UMR-106 cell line: influence of fluoride treatments

Mg-based materials are promising for orthopedic, dental, and cardiovascular applications but their high degradation rate in vivo (release of Mg ions and debris particles) is cause of great concern. Protective treatments involving fluoride conversion coatings have been proposed in order to reduce corrosion rates. The aim of this study was to evaluate Mg debris biodegradation and its possible cytotoxic effects on osteoblastic cells in situ. Neutral Red dying and Acridine Orange staining techniques were used as endpoints to analyse the cytotoxic effects at 100-2000 μg/mL concentration range. Results showed a marked variation of Mg ion concentration in the culture medium after different exposure periods (1, 2, or 24h). Interestingly, the release rate of magnesium ions was dependent on the presence or absence fluoride treatment. Adverse effects induced by ≥1000 μg/mL MP doses and Mg ion concentrations higher than 480 μg/mL were observed on cells. Results showed significant differences between the concentration of Mg ions in the presence and absence of cells. This fact reveals a dynamic equilibrium mediated by Mg ion input and output in the cells that leads to the change in MP corrosion rates. Fluoride release from conversion coatings did not show cytotoxic effects.