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1.
Zhan-Yong Wang Fan Li Zi-Qi Guo Yan Wang Shan Chen 《Journal of Polymers and the Environment》2011,19(4):827-833
A gene encoding a poly(l-lactic acid) (PLA) depolymerase from Pseudomonas sp. strain DS04-T was cloned and overexpressed in Escherichia coli. The recombinant PLA depolymerase with a molecular weight of 19.2 kDa was purified to homogeneity. The optimum pH and temperature
of the PLA depolymerase are 8.5 and 60 °C, respectively. K+, Ca2+ and Ni2+ enhance the enzyme activity, while Na+, Zn2+, Mg2+, Cu2+, Fe2+, Mn2+ and Co2+ inhibit it. The inhibition of different chemicals on the PLA depolymerase activity were examined, in which EDTA was found
to have a significantly inhibitory effect. The main degradation product of the depolymerase is identified as lactic acid monomer
by mass spectrometric analysis. Physicochemical properties, substrate specificity and sequence analysis indicated that PME
is a new type of PLA depolymerase. 相似文献
2.
Rachana Bhatt K. C. Patel Ujjval Trivedi 《Journal of Polymers and the Environment》2010,18(2):141-147
An extracellular poly(3-hydroxybutyrate) (PHB) depolymerase produced by a thermotolerant fungal soil isolate, Aspergillus fumigatus 202, was purified and characterized. Maximum PHB depolymerase production was obtained at the end of 48 h with initial medium
pH 7.0 and 45 °C in Bushnell Haas Minerals medium containing PHB as sole source of carbon. The PHB depolymerase was purified
using size exclusion chromatography to a fold purification of 20.62 and 61.62% yield. SDS-PAGE and isoelectric focusing revealed
the molecular weight and pI of the purified enzyme as 63,744 Da and 4.2, respectively. N-terminal amino acid sequence of purified
enzyme was HAXDAYLVK. This non-glycosylated enzyme was most active at pH 9.0 and 45 °C. Purified enzyme was inactivated by
N-bromosuccinimide and dithiothreitol suggesting the involvement of tryptophan residues and disulfide bonds at its active
site. Nonionic detergents like Tween 20, Tween 80 and Triton X-100 inhibited the enzyme activity. Ions like Ca+2 and Mg+2 (5 mM) increased the enzyme activity 1.5 times. Fe+2 effectively inhibited the enzyme activity to 88% whereas Hg+2 completely inhibited the enzyme. 相似文献
3.
Ivan S. Ristić Ljiljana Tanasić Ljubiša B. Nikolić Suzana M. Cakić Olivera Z. Ilić Radmila Ž. Radičević Jaroslava K. Budinski-Simendić 《Journal of Polymers and the Environment》2011,19(2):419-430
Different synthesis methods were applied to determine optimal conditions for polymerization of (3S)-cis-3,6-dimethyl-1,4-dioxane-2,5-dione (l-lactide), in order to obtain poly(l-lactide) (PLLA). Bulk polymerizations (in vacuum sealed vessel, high pressure reactor and in microwave field) were performed
with tin(II) 2-ethylhexanoate as the initiator. Synthesis in the vacuum sealed vessel was carried out at the temperature of
150 °C. To reduce the reaction time second polymerization process was carried out in the high pressure reactor at 100 °C and
at the pressure of 138 kPa. The third type of rapid synthesis was done in the microwave reactor at 100 °C, using frequency
of 2.45 GHz and power of 150 W at the temperature of 100 °C. The temperature in this method was controlled via infrared system
for in-bulk measuring. The solution polymerization (with trifluoromethanesulfonic acid as initiator) was possible even at
the temperature of 40 °C, yielding PLLA with narrow molecular weight distribution in a very short period of time (less than
6 h). The obtained polymers had the number-average molecular weights ranging from 43,000 to 178,000 g mol−1 (polydispersity index ranging from 1 to 3) according to the gel permeation chromatography measurements. The polymer structure
was characterized by Fourier transform infrared and NMR spectroscopy. Thermal properties of the obtained polymers were investigated
using thermogravimetry and differential scanning calorimetry. 相似文献
4.
Masahiro Miura Atsushi Shimahata Toshio Nishikawa Masakazu Aoyama Kiyoshi Tada Junichi Horiuchi Masahiro Nakahara Chikara Sakai 《Journal of Material Cycles and Waste Management》2011,13(1):80-83
To prepare a substrate for microbial conversion of xylose into xylitol, the culm of Sasa senanensis was hydrolyzed with dilute sulfuric acid. When the reaction temperature was fixed at 121°C, an optimum yield of xylose was
obtained by treatment with 2% sulfuric acid for 1 h. An increase in the sulfuric acid concentration or a prolonged reaction
time resulted in a decrease in the xylose yield. A fermentable substrate with a relatively high xylose concentration (36.7
g l−1) was obtained by hydrolysis with 2% sulfuric acid with a liquid-to-solid ratio of 5 g g−1. During hydrolysis at elevated temperatures, certain undesired byproducts were also generated, such as degradation products
of solubilized sugars and lignin, which are potential inhibitors of microbial metabolism. These compounds were, however, successfully
removed from the hydrolysate by treatment with activated char. 相似文献
5.
Huandong Yang Zhichao Wu Dujuan He Huabin Zhou Hailong Yang 《Journal of Polymers and the Environment》2017,25(4):1033-1043
The enzyme assisted extraction conditions of polysaccharide from Cordyceps militaris mycelia were firstly investigated by kinetics analysis and the optimal operating was found to be: extraction temperature 40 °C; solid-solvent ratio 1:20; extraction pH 4.0; cellulase concentration 2.0%. The polysaccharide extraction yield was 5.99% under these optimized conditions. Furthermore, a fundamental investigation of the biosorption of Pb2+ from aqueous solution by the C. militaris polysaccharide was performed under batch conditions. The suitable pH (5.0), polysaccharide concentration (0.20 g L?1), initial Pb2+ concentration (300 mg L?1) and contact time (40 min) were outlined to enhance Pb2+ biosorption from aqueous medium. The Langmuir isotherm model and pseudo first order kinetic model fitted well to the data of Pb2+ biosorption, suggesting the biosorption of Pb2+ onto C. militaris polysaccharide was monolayer biosorption and physical adsorption might be the rate-limiting step that controlled the adsorption process. FTIR analysis showed that the main functional groups of C. militaris polysaccharide involved in adsorption process were carbonyl, carboxyl, and hydroxyl groups. 相似文献
6.
You-Wei Cui Hong-Yu Zhang Si-Yuan Ji Zhi-Wu Wang 《Journal of Polymers and the Environment》2017,25(2):277-285
Haloferax mediterranei is an extremely halophilic archaeon that is able to synthesize polyhydroxyalkanoate (PHA) in high salt environment with low sterility demand. In this study, a mathematical model was validated and calibrated for describing the kinetic behavior of H. mediterranei at 15, 20, 25, and 35 °C in synthetic molasses wastewater. Results showed that the production of PHA by H. mediterranei, ranging from 390 to 620 mg h?1 L?1, was strongly dependent on the temperature. The specific growth rate (µ max), specific substrate utilization rate (q max), and specific decay rate (k d) of H. mediterranei increased with temperature following Arrhenius equation prediction. The estimated activation energy was 58.31, 25.59, and 22.38 kJ mol?1 for the process of cell growth, substrate utilization, and cell decay of H. mediterranei, respectively. The high temperature triggered the increased PHA storage even without nitrogen limitation. Thus, working at high temperatures seems a good strategy for improving the PHA productivity of H. mediterranei. 相似文献
7.
Lobna Daoud Houda Hmani Manel Ben Ali Mouna Jlidi Mamdouh Ben Ali 《Journal of Polymers and the Environment》2018,26(1):23-32
Over a hundred of halophilic/halotolerant microorganisms were screened for alkaline protease production. The bacterium showing the highest enzyme production was characterized and identified as Bacillus halodurans US193 on the basis of 16S rRNA gene analysis. It was alkalophilic, thermophilic and halotolerant since it grew optimally at pH 9.7 and 50?°C with tolerance of up to 125 g NaCl l?1. The alkaline protease was purified 4.9 times with about 40186.1 U/mg as specific activity. It exhibited optimal activity at pH 10, 70?°C and 0.25 M NaCl with perfect stability at wide ranges of pH (6–12), temperatures (30–60?°C) and NaCl concentrations (0–2 M). The serine alkaline protease maintained high stability in the presence of Cu2+, Mg2+, Ba2+ and Ca2+ ions, various organic solvents [50% (v/v)] and ionic and non ionic detergent additives. In addition, it was more compatible with various commercialized detergents than other reported detergent proteases, and was very efficient in blood stain removal. These findings let B. halodurans US193 alkaline protease be an ideal candidate for many industrial processes at harsh conditions, especially as a bio-additive in detergent industry. 相似文献
8.
To develop a high performance environment friendly material, highly branched polyester/clay nanocomposites have been prepared
from Mesua ferrea Linn seed oil-based polyester resin and hydrophilic bentonite nanoclay. The prepared nanocomposites were characterized by
Fourier transform infra-red spectroscopy, X-ray diffractometer, scanning electron microscope, transmission electron microscope
and rheological studies. Partial exfoliation of clay layers by the polymer chains with good interfacial interactions was observed
in the nanocomposites. The formation of delaminated nanocomposites was manifested through the enhancement of tensile strength,
scratch hardness, chemical resistance, impact resistance, thermostability, etc. The results show enhancement of three times
in tensile strength and 18 °C in thermostability by inclusion of 5 wt% nanoclay as compared to the pristine polymer. By the
influence of 5 wt% nanoclay four times enhancement in elongation at break as compared to the pristine polymer was noticed.
Thus these nanocomposites have the potential to be used in many advanced applications. 相似文献
9.
Tara Sankar Pathak Jung-Ho Yun Se-Jong Lee Dae-Jin Baek Ki-Jung Paeng 《Journal of Polymers and the Environment》2010,18(1):45-56
Alginates, extracted from algae are linear unbranched polymers containing β-(1→4)-linked d-mannuronic acid (M) and α-(1→4)-linked l-guluronic acid (G) residues. The conversion of alginic acid into the metal alginate is confirmed using FTIR spectroscopy.
Asymmetric and symmetric stretching of free carboxyl group present in metal alginate occurs almost at the same position in
various solvent compositions. Total intrusion volume of metal alginate prepared in propanol (0.0742 mL/g) is greater compared
to those in ethanol (0.0648 mL/g) and methanol (0.0393 mL/g) as solvent. Surface morphology as well as porosity and pore size
distribution of metal alginate are greatly influenced by solvent. It can be seen from thermal analysis results that calcium
alginate prepared using different solvent compositions started decomposing at 100 °C, but rapid degradation started around
200 °C. The results showed a stepwise weight loss during thermal sweep, indicating different types of reactions during degradation.
First and second step of rapid degradation was situated around 200–300 and 300–550 °C, respectively; whereas the final step
is situated around 550–650 °C. The trend of degradation was similar for all the solvents, although the amount of final residue
varied from one solvent to another. At the same time, lower thermal stability was also observed with higher heating rates.
Additionally, a kinetic analysis was performed to fit with TGA data, where the entire degradation process has been considered
as three consecutive first order reactions. 相似文献
10.
Yueqin Yu Lingxiu Liu Yanyan Kong Erchi Zhang Yanping Liu 《Journal of Polymers and the Environment》2011,19(4):926-934
A high-swelling superabsorbent was synthesized with biodegradable N-maleyl chitosan as cross-linker, acrylic acid (AA) and acrylamide (AM) as the monomers, ammonium peroxodisulfate–sodium bisulfite
(NaHSO3) as redox initiation system, by means of aqueous solution polymerization. The best reaction condition was based on the orthogonal
experiment design. The optimal conditions on distilled water absorbency and on 0.9 wt% NaCl solution absorbency were monomer
concentration 20 wt%, mole ratio of AA to (AA + AM) 60%, the neutralization degree of AA 40%, cross-linker concentration 2%
and monomer concentration 25 wt%, mole ratio of AA to (AA + AM) 60%, neutralization degree of AA 50% and cross-linker concentration
1%, respectively. Factors influencing the water absorbency of superabsorbent also were investigated, by single factor experiment
method. The absorbency of superabsorbents in distilled water and 0.9 wt% NaCl solution increased and then decreased with the
increasing of monomer concentration, mole ratio of AA to (AA + AM) and degree of neutralization of AA. With the increasing
of cross-linker concentration, the absorbency in distilled water increased and then decreased, but it decreased all the time
in 0.9 wt% NaCl solution. In enzymatic degradation tests, the weight loss of superabsorbent was related to the content of
cross-linker. 相似文献
11.
Leila Asadollahi Hossein Salehizadeh Ning Yan 《Journal of Polymers and the Environment》2016,24(2):119-128
In this research, a biosurfactant-producing bacterium with capability of asphaltene degradation was isolated from oil-contaminated soil samples, and identified as Bacillus cereus. This strain produced an effective biosurfactant in the presence of molasses and the surface tension was reduced to the level of 36.4 mN/m after 48 h under optimum conditions. The optimum values of carbon-to-nitrogen ratio (C:N), pH, and temperature for biosurfactant production were determined as 30:1, 7.3 and 29 °C, respectively, using response surface methodology. The maximum emulsification activity in the culture broth was 53 % after 48 h using kerosene at 25 °C. The goodness of fit of four growth kinetic models including Tessier, Contois, Logistic and Westerhoff was compared for the bacterial growth and molasses utilization of B. cereus in 5-L batch bioreactor during 120 h. Conducted kinetic study showed that biosurfactant production had a good fit with the Contois growth kinetic model (R2 = 0.962) and the maximum specific growth rate (µ max ), saturation constant (K s ) and the yield of biomass per substrate (Y x/s ) were determined to be 0.145 h?1, 1.83 g/L and 0.428 g/g, respectively. The asphaltene biodegradation in flask was evaluated by FTIR analysis and quantified by a spectrophotometer. This bacterium was able to degrade up to 40 % of asphaltene as a sole carbon and energy source after 60 days at 28 °C. The resulting surface tension of 30.2 mN/m with the critical micelle concentration of 23.4 mg/L indicated good efficiency of the biosurfactant. 相似文献
12.
Poly-β-hydroxybuyrate (PHB) is a carbon—energy storage material which is accumulated as intracellular granule in variety of
microorganism under nutrient starved conditions. Solid PHB is a biodegradable thermoplastic polymer and is utilizable in various
ways similar to many conventional plastics. Ralstonia eutropha (Alcaligenes sp.), a gram negative bacteria accumulates PHB as insoluble granules inside the cells when nutrients other than carbon are
limited. In this report effort has been made to analyze PHB granule synthesis inside Alcaligenes sp. NCIM 5085 by transmission electron microscopy and qualitative estimation of PHB was carried out by fourier transform
infrared spectroscopy which provide better precision compared to other conventional techniques previously applied for PHB
determination. Maximum PHB concentration of 2.20 ± 0.40 g/L and cell biomass of 3.42 ± 0.20 g/L was obtained after 48.0 h
of fermentation. Leudking-Piret equation deduced mixed growth associated product formation which varies from earlier reports. 相似文献
13.
Xiaoping Hu Satoshi Osaki Miki Hayashi Mureo Kaku Susumu Katuen Hiroshi Kobayashi Fusako Kawai 《Journal of Polymers and the Environment》2008,16(2):103-108
We intended to find thermophilic degraders of terephthalate-containing Biomax® films. Films in mesh bags were buried in composts (inside temperature: approximately 55–60 °C), resulting in the degradation of them in 2 weeks. Fluorescent microscopy of films recovered from composts showed that microorganisms gradually covered the surface of a film during composting. DGGE analysis of microorganisms on the composted film indicated the presence of Bacillus species as main species (approximately 80% of microbial flora) and actinomycetes (approximately 10–20%) as the second major flora. Isolation of Biomax®-utilizing bacteria was focused on these two genera: two actinomycetes and one Bacillus species were isolated as pure best degraders from the composted polymer films, which were fragmented into small pieces. All the strains were thermophilic and identified, based on their 16S rDNA analyses. Degradation of polymer films was confirmed by (1) accelerated fragmentation of films in composts, compared with a control (no inoculum) and resultant decrease in molecular weights, (2) growth in a powdered Biomax® medium, compared with a control without powdered Biomax®, and (3) production of terephthalate in a powdered Biomax® medium. In this way, we concluded that these bacteria were useful for degradation of thermostable Biomax® products. 相似文献
14.
Rushdya R. A. Hassan Maisa M. A. Mansour 《Journal of Polymers and the Environment》2018,26(7):2698-2707
The current study is interested in evaluating the decay of cotton, Whatman and chemical pulp caused by Trichoderma harzianum and Paecilomyces variotii. The structural changes of the paper were evaluated by Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM). The SEM results show differences in hyphae colonization and paper decay patterns between studied species under the current study; P. variotii caused an eroded structure in the cotton (cavity forming), whereas the initial T. harzianum colonization produced rupture and erosion (soft-rot decay type II) for the three types of paper ,the gaps were elongated with sharp pointed ends, which consisted either of individual cavities or in chains. Moreover, FTIR results confirmed that there a relationship could be observed between fungal decay and crystalline cellulose content because the intensity of peaks at 1335 and 1111 cm?1 significantly decreased due to the fungal decay. Furthermore, the intensity of O–H stretching absorption slightly decreased, and this may be attributed to hydrolysis of cellulose molecules. 相似文献
15.
Anupan Youngpreda Titiporn Panyachanakul Vichien Kitpreechavanich Sarote Sirisansaneeyakul Sunit Suksamrarn Shinji Tokuyama Sukhumaporn Krajangsang 《Journal of Polymers and the Environment》2017,25(4):1131-1139
Poly(dl-lactic acid) or PLA is a biodegradable polymer. It has received much attention since it plays an important role in resolving the global warming problem. The protease produced by Actinomadura keratinilytica strain T16-1 was previously reported as having PLA depolymerase potential and being applicable to PLA biodegradation, which was used in this work. Therefore, this research demonstrates the important basic knowledge on the biological degradation process by the crude PLA-degrading enzyme from strain T16-1. Its re-polymerization was evaluated. The optimization of PLA degradation by statistical methods based on central composite design was determined. Approximately 6700 mg/l PLA powder was degraded by the crude enzyme under optimized conditions: an initial enzyme activity of 200 U/ml, incubated at 60 °C for 24 h released 6843 mg/l lactic acid with 82% conversion, which was similar to the commercial enzyme proteinase K (81%). The degradable products were re-polymerized repeatedly by using commercial lipase as a catalyst under a nitrogen atmosphere for 6 h. A PLA oligomer was achieved with a molecular weight of 378 Da (n = 5). This is the first report to demonstrate the high efficiency of the enzyme to degrade 100% of PLA powder and to show the biological recycling process of PLA, which is promising for the treatment and utilization of biodegradable plastic wastes in the future. 相似文献
16.
Channa argus, a type of snakehead fish native to China, is a popular food fish in certain Asian countries but is a known destructive invasive species in the US. In this study, the two collagens, i.e. acid-soluble collagen (ASC) and pepsin-solubilized collagen (PSC), were obtained from C. argus skin. The yield of ASC was 28.0% and that of PSC was 16.8% on the dry bases. The collagens were identified as the collagen of type I by SDS–PAGE patterns. The Tds were approximately 27.0?°C. Similar ultraviolet spectra of both collagens were observed. Fourier Transform infrared spectra indicated PSC structure had a little change due to the loss of terminal domains by pepsin digestion. The results of XRD proved that the two collagens retained their helical structures. The results suggest that the collagens isolated from C. argus can potentially be alternative sources of vertebrate collagens for use in the food and other industries. 相似文献
17.
Vinay K. Khatiwala Nilanshu Shekhar Saroj Aggarwal U. K. Mandal 《Journal of Polymers and the Environment》2008,16(1):61-67
The biodegradation behavior of PCL film with high molecular weight (80,000 Da) in presence of bacterium Alcaligenes faecalis and the analysis of degraded polymer film have been carried out. Thin Films of PCL were prepared by means of solution casting
method and the bacterial degradation behavior was carried in basal medium, in presence of bacteria with time variation after
UV treatment. It was observed that after UV treatment the degradation of polymer film was increased and the degradation rate
followed a three steps degradation mechanism. The degraded polymer film was analyzed by means of Differential Scanning Calorimeter
(DSC), Thermo Gravimetric Analyzer (TGA) and Fourier Transform Infrared Spectroscope (FTIR). DSC results revealed that at
the initial stages of the degradation up to 15–20 days, the bacterium preferentially degrades the amorphous parts of the polymer
film over the crystalline zone. Thermo gravimetric analysis highlighted the low temperature stability of degraded films with
extent of degradation. FTIR results showed the chain scission mechanism of the polymer chains and also supported the preferential
degradation of amorphous phase over crystalline phase in the initial stages of the degradation. 相似文献
18.
Jeong Huy Ko Yeon-Ho Kwak Kyung-Seun Yoo Jong-Ki Jeon Sung Hoon Park Young-Kwon Park 《Journal of Material Cycles and Waste Management》2011,13(3):173-179
Experiments were performed in order to investigate the possibility for the development of catalysts for low-temperature selective
catalytic reduction (SCR) using municipal waste char and RDF byproduct. Physical and chemical activations, using water, and
HCl and KOH, were employed to increase the catalytic activities. The characteristics of the activated catalysts were investigated
using N2 adsorption–desorption and FT-IR. The catalysts activated chemically using basic treatment showed higher NO
x
removal efficiencies than those activated physically or chemically using acidic treatment. The de-NO
x
performance of the activated catalysts was dependent on the chemical properties, such as oxygen functional groups as well
as physical properties, such as specific surface area and pore volume. In order to investigate the effect of MnO
x
, which has been reported to be efficient for the removal of NO
x
in low-temperature SCR processes, the chemically activated catalyst was impregnated with manganese. The Mn-impregnated catalyst
had the highest NO
x
conversion at all of the temperatures tested in this study. 相似文献
19.
H. Majdoub L. Picton D. Le Cerf S. Roudesli 《Journal of Polymers and the Environment》2010,18(4):451-458
Polysaccharides were isolated from nopals mucilage pulp and peel of Opuntia Ficus Indica (OFI) and Opuntia litoralis (OL) by aqueous extraction and purified by ultrafiltration. Studying the glycosyl residue composition, these polysaccharides
were assumed to be rhamnogalacturonan I (RG-I). The macromolecular features of these compounds have been characterized by
SEC/MALLS and by low shear viscosimetry. In the present work, we have undertaken a comparative study about different polysaccharides
resulting from OFI and OL growing in different area. This comparison is to see the influence of the geographical area in which
these two plants push on the mechanism of retention of water by the different polysaccharides extract. The polysaccharides
resulting from the nopal peels of the two plants are highly methylated (>70%), thus they are much more hydrophobic especially
for peels of OFI growing in the desert area than those resulting from pulps. Consequently, they probably prevent the evaporation
of water in nopals by increasing their water retention capacity. Prickly pear nopals of OFI and OL contain a significant amount
of water (>80%), carbohydrates (75% compared to the soluble matter), proteins (8% compared to the soluble matter) and salt
(17% compared to the soluble matter). Thus, they represent an important source of water and alimentation especially in the
arid and semi-arid areas. 相似文献
20.
Latif Aref Amir H. Navarchian Daniyal Dadkhah 《Journal of Polymers and the Environment》2017,25(3):628-639
Poly(acrylamide-co-maleic acid)/montmorillonite nanocomposites, were synthesized via in situ polymerization with different maleic acid and MMT content. The capability of the hydrogel for adsorption of crystal violet (CV) was investigated in aqueous solutions at different pH values and temperatures. The pseudo-second-order kinetics model could fit successfully the adsorption kinetic data. The effects of maleic acid to acrylamide molar ratio (MAR), weight percent of MMT (MMT%), the pH of medium and the solution temperature (T) on the CV adsorption capacity (q e ) of adsorbents were studied by Taguchi experimental design approach. The results indicated that increasing the MMT% leads to a greater q e . The q e value of adsorbents increased also with increasing both MAR and pH, while reduced when the temperature of medium increased. The relatively optimum conditions to achieve a maximum CV adsorption capacity for P(AAm/MA)/MMT adsorbents were found as: 0.06 for MAR and 5 % of MMT%, medium pH = 7 and T = 20 °C. 相似文献