Enhanced degradation of polyvinyl alcohol by Pycnoporus cinnabarinus after pretreatment with Fenton's reagent

Degradation of polyvinyl alcohol (PVA) was investigated by using a combination of chemical treatment with Fenton's reagent and biological degradation with the white rot fungus Pycnoporus cinnabarinus. Inclusion of the chemical pretreatment resulted in greater degradation of PVA than the degradation observed when biological degradation alone was used.     

Enhancement of Pyrroloquinoline Quinone Production and Polyvinyl Alcohol Degradation in Mixed Continuous Cultures of Pseudomonas putida VM15A and Pseudomonas sp. Strain VM15C with Mixed Carbon Sources

In a mixed continuous culture of Pseudomonas putida VM15A and Pseudomonas sp. strain VM15C with polyvinyl alcohol (PVA) as the sole source of carbon, growth of the PVA-degrading bacterium VM15C and, hence, PVA degradation were limited by the growth factor, pyrroloquinoline quinone, produced by VM15A. Feeding of a carbon source for VM15A, ethanol, with PVA enhanced pyrroloquinoline quinone production and caused increases in the VM15C population and PVA degradation in a mixed continuous culture. There was an optimum range for PVA degradation of the ethanol concentration, although pyrroloquinoline quinone concentrations in continuous mixed cultures increased with increasing ethanol concentration.     

Biodegradation of polyvinyl alcohol by a brown-rot fungus, Fomitopsis pinicola

A brown-rot fungus, Fomitopsis pinicola, degraded polyvinyl alcohol (PVA) in quartz sand but not in liquid culture. From gel permeation chromatography analysis, the high-molecular-weight fraction of PVA was decreased by the action of F. pinicola but the coloration of the culture filtrate with I₂ solution increased. The reason for the increase in coloration was assumed to be the increase in the low-molecular-weight fraction in degraded PVA. Diffuse reflectance infrared Fourier transform spectral analysis showed that spectral changes of the fungally degraded PVA were similar to those of PVA treated with Fenton’s reagent suggesting that PVA degradation by F. pinicola was via the Fenton reaction. F. pinicola can thus be used to degrade PVA in woody wastes.     

Localization of Polyvinyl Alcohol Oxidase Produced by a Bacterial Symbiont, Pseudomonas sp. Strain VM15C

An axenic culture of a polyvinyl alcohol (PVA)-degrading symbiont, Pseudomonas sp. strain VM15C, was established on PVA with a crude preparation of the growth factor (factor A) produced by the symbiotic partner Pseudomonas putida VM15A. An increase of factor A in the culture medium enhanced the cell-associated PVA oxidase activity as well as the growth rate, but decreased production of extracellular PVA oxidase. PVA oxidase in cells grown on PVA was present in the periplasmic space at a higher ratio than in cells grown on peptone. PVA degradation occurred rapidly with washed cells. PVA was also degraded by immobilized cells entrapped in agar gels.     

Mixed Continuous Cultures of Polyvinyl Alcohol-Utilizing Symbionts Pseudomonas putida VM15A and Pseudomonas sp. Strain VM15C

Stable mixed continuous cultures of Pseudomonas sp. strain VM15C and Pseudomonas putida VM15A, the former of which produced a polyvinyl alcohol (PVA)-degrading enzyme and the latter of which produced an essential growth factor for PVA utilization by strain VM15C, were established with PVA as the sole source of carbon and energy with chemostat cultivation. A high extent of PVA degradation was achieved at dilution rates of less than 0.030/h. The predominant strain in the cultures was the primary metabolizer of PVA, strain VM15C. The growth supporter, strain VM15A, existed as a minor population, although its population was maintained at an almost constant level throughout a dilution region in which the VM15C population decreased markedly as the dilution rate was raised. A crude growth factor which was prepared from a culture supernatant of strain VM15A and increased the specific growth rate of strain VM15C with PVA in an axenic batch culture was also effective for enhancing the VM15C population and PVA degradation in the mixed continuous culture at a high dilution rate (0.064/h). This indicated that the growth-limiting substrate for strain VM15C in the mixed continuous culture is the growth factor produced by strain VM15A.     

Biochemistry of microbial polyvinyl alcohol degradation

Effect of minor chemical structures such as 1,2-diol content, ethylene content, tacticity, a degree of polymerization, and a degree of saponification of the main chain on biodegradability of polyvinyl alcohol (PVA) is summarized. Most PVA-degraders are Gram-negative bacteria belonging to the Pseudomonads and Sphingomonads, but Gram-positive bacteria also have PVA-degrading abilities. Several examples show symbiotic degradation of PVA by different mechanisms. Penicillium sp. is the only reported eukaryotic degrader. A vinyl alcohol oligomer-utilizing fungus, Geotrichum fermentans WF9101, has also been reported. Lignolytic fungi have displayed non-specific degradation of PVA. Extensive published studies have established a two-step process for the biodegradation of PVA. Some bacteria excrete extracellular PVA oxidase to yield oxidized PVA, which is partly under spontaneous depolymerization and is further metabolized by the second step enzyme (hydrolase). On the other hand, PVA (whole and depolymerized to some extent) must be taken up into the periplasmic space of some Gram-negative bacteria, where PVA is oxidized by PVA dehydrogenase, coupled to a respiratory chain. The complete pva operon was identified in Sphingopyxis sp. 113P3. Anaerobic biodegradability of PVA has also been suggested.     

Some Characteristics of Pseudomonas 0–3 which Utilizes Polyvinyl Alcohol

Pseudomonas 0–3 strain which was isolated from soil can grow on polyvinyl alcohol (PVA) as a sole carbon source. When 0.5 per cent of PVA (500, 1500 or 2000) was employed as the carbon source in the culture medium, PVA was almost completely lost from the culture fluid after a week and the concentration of total organic carbon measured by a TOC analyzer decreased from the initial value of about 2700 ppm to 250~300 ppm after 7~10 days culture. This bacterium was found to produce and secrete an inducible enzyme which degrade PVA. The way by which this enzyme degrades PVA was examined and the results were obtained which suggested that PVA was broken down oxidatively in a way of endowise splitting. However, the mechanism of PVA degradation has not been clarified yet. The optimum pH and temperature for enzyme activity were examined and they were 7.5~8.5 and 35~45°C, respectively. Morphological and biological characteristics of this bacterium were examined and it was similar to a strain of Pseudomonas boreopolis.     

Cell surface structure enhancing uptake of polyvinyl alcohol (PVA) is induced by PVA in the PVA-utilizing <Emphasis Type="Italic">Sphingopyxis</Emphasis> sp. strain 113P3

Polyvinyl alcohol (PVA)-utilizing Sphingopyxis sp. 113P3 (reidentified from Sphingomonas sp. 113P3) removed almost 0.5% PVA from culture supernatants in 4 days. Faster degradation of 0.5% PVA was performed by the periplasmic fraction. The average molecular size of PVA in the culture supernatant or cell-bound PVA was gradually shifted higher, suggesting that lower molecular size molecules are degraded faster. Depolymerized products were found in neither the culture supernatant nor the cell-bound fraction; however they were recovered from the periplasmic fraction. As extracellular or cell-associated PVA oxidase activity was almost undetectable in strain 113P3, degradation of PVA must be performed by periplasmic PVA dehydrogenase after uptake into the periplasm. Following the consumption of PVA, a dent appeared on the cell surface on day 2 and increased in size and depth for 4 days and was maintained for 8 days. Ultrastructural change on the cell surface was only observed in PVA medium, but not in nutrient broth (NB), suggesting that the change is induced by PVA. Fluorescein-4-isothiocyanate-labeled PVA was bound more to cells grown in PVA than to cells grown in NB. No binding was found with PVA-grown cells treated with formaldehyde. Thus, a dent on the cell surface seems to be related to the uptake of PVA.     

Glass transition behavior of the vitrification solutions containing propanediol, dimethyl sulfoxide and polyvinyl alcohol

Knowledge of the glass transition behavior of vitrification solutions is important for research and planning of the cryopreservation of biological materials by vitrification. This brief communication shows the analysis for the glass transition and glass stability of the multi-component vitrification solutions containing propanediol (PE), dimethyl sulfoxide (Me₂SO) and polyvinyl alcohol (PVA) by using differential scanning calorimetry (DSC) during the cooling and subsequent warming between 25 and −150 °C. The glass formation of the solutions was enhanced by introduction of PVA. Partial glass formed during cooling and the fractions of free water in the partial glass matrix increased with the increasing of PVA concentration, which caused slight decline of glass transition temperature, T_g. Exothermic peaks of devitrification were delayed and broadened, which may result from the inhibition of ice nucleation or recrystallization of PVA.     

Partially Disordered Structure in Intravirus Coat Protein of Potyvirus Potato Virus A

Potyviruses represent the most biologically successful group of plant viruses, but to our knowledge, this work is the first detailed study of physicochemical characteristics of potyvirus virions. We measured the UV absorption, far and near UV circular dichroism spectra, intrinsic fluorescence spectra, and differential scanning calorimetry (DSC) melting curves of intact particles of a potato virus A (PVA). PVA virions proved to have a peculiar combination of physicochemical properties. The intravirus coat protein (CP) subunits were shown to contain an unusually high fraction of disordered structures, whereas PVA virions had an almost normal thermal stability. Upon heating from 20°C to 55°C, the fraction of disordered structures in the intravirus CP further increased, while PVA virions remained intact at up to 55°C, after which their disruption (and DSC melting) started. We suggest that the structure of PVA virions below 55°C is stabilized by interactions between the remaining structured segments of intravirus CP. It is not improbable that the biological efficiency of PVA relies on the disordered structure of intravirus CP.     

Pseudomonas fluorescens lipase immobilization on polysiloxane–polyvinyl alcohol composite chemically modified with epichlorohydrin

The technique based on sol–gel approach was used to generate silica matrices derivatives by hydrolysis of silane compounds. The present work evaluates a hybrid matrix obtained with tetraethoxysilane (TEOS) and polyvinyl alcohol (PVA) on the immobilization yield of lipase from Pseudomonas fluorescens. The resulting polysiloxane–polyvinyl alcohol (POS–PVA) matrix combines the property of PVA as a suitable polymer to retain proteins with an excellent optical, thermal and chemical stability of the host silicon oxide matrix. Aiming to render adequate functional groups to the covalent binding with the enzyme the POS–PVA matrix was chemically modified using epichlorohydrin. The results were compared with immobilized derivative on POS–PVA activated with glutaraldehyde. Immobilization yield based on the recovered lipase activity depended on the activating agent and the highest efficiency (32%) was attained when lipase was immobilized on POS–PVA activated with epichlorohydrin, which, probably, provided more linkage points for the covalent bind of the enzyme on the support. This was confirmed by determining the morphological properties using different techniques as X-ray diffraction and scanning electron microscopy (SEM). Comparative studies were carried out to attain optimal activities for free lipase and immobilized systems. For this purpose, a central composite experimental design with different combinations of pH and temperature was performed. Enzymatic hydrolysis with the immobilized enzyme in the framework of the Michaelis–Menten mechanism was also reported. Under optimum conditions, the immobilized derivative on POS–PVA activated with epichlorohydrin showed to have more affinity for the substrate in the hydrolysis of olive oil, with a Michaelis–Menten constant value (K_m) of 293 mM, compared to the value of 401 mM obtained for the immobilized lipase on support activated with glutaraldehyde. Data generated by DSC showed that both immobilized derivatives have similar thermal stabilities.     

Biological degradation of PVA/CH blends in terrestrial and aquatic conditions

A new material, the water soluble blend of poly-vinyl alcohol and collagen hydrolysate (PVA/CH) was developed in Slovakia. Results from a recent biodegradation study including three blend variants differing in the collagen content are presented. Two different biodegradation tests, one in compost environment, the other at aquatic conditions and additional compost analysis after degradation of the polymer have been done. Degradation rates were determined for both test systems and the carbon conversion rates were calculated by drawing up a carbon balance out of the aquatic test. The results proofed positive influence of collagen hydrolysate on degradation but also show a relatively low biological degradability of PVA under the applied test conditions. At least, no negative influence on the compost composition was detected.     

Biodegradation of a polyvinyl alcohol-starch blend plastic film

Attempts were made to elucidate the degradation mechanism of a polyvinyl alcohol (PVA)-starch blend plastic. A part of the starch fraction of this plastic was dissolved into an aqueous phase in a control test. Treatment with a PVA-degrading bacterium or enzyme gave a maximal weight loss of approximately 70% and film breakage occurred. Since this plastic contains 40% PVA, it is apparent that not only the PVA fraction but also a considerable portion of the starch fraction was lost from the film by treatment with the PVA-degrading enzyme. As the PVA-degrading bacterium and enzyme used here showed no starch-degrading activity, loss of the starch fraction seems to depend on its dissolution with degradation of the PVA fraction. These experimental results indicated that the degradation of the PVA fraction is an important requisite for complete degradation or decomposition of this plastic film.     

Screening of microorganisms able to degrade low-rank coal in aerobic conditions: Potential coal biosolubilization mediators from coal to biochemicals

Coal is one of the major sources of energy, fuel, and other related chemicals. The processes to utilize coal for energy, fuel and other chemicals such as coal combustion, liquefaction, carbonization, and gasification pose a great threat to the environment by emitting toxic particles and CO₂ to the atmosphere. Thus, biological beneficiation of coal can be a good strategy to utilize coal with environmental sustainability. Here, we report the screening of microorganisms able to degrade or depolymerize coal. These host strains are potential candidates for the development of biological treatment process of coal. A total of 45 microbial strains were isolated from sludge enriched with coal and were identified based on 16S rRNA sequencing. Four strains of three genera, Cupriavidus sp., Pseudomonas sp., and Alcaligenes sp., were further characterized for their abilities to degrade coal. The degree of coal degradation was analyzed by measuring the increase in absorbance at 450 nm by UV spectroscopy. These microorganisms were also able to increase the pH of the culture media as a response to the acidic nature of coal. Laccase-like activity was also found in these strains when tested for RBBR dye degradation. Since biological degradation of coal through the use of microorganisms is a good alternative to chemical combustion of coal, microbial strains isolated in this study can be potential biological catalysts for coal conversion into valuable chemicals.     

Mechanical and water barrier properties of starch/PVA composite films by adding nano-sized poly(methyl methacrylate-co-acrylamide) particles

The aim of this work is to prepare starch/PVA composite films added nano-sized poly(methyl methacrylate-co-acrylamide) (PMMA-co-AAm) particles and to investigate the mechanical properties, water barrier properties, and soil burial degradation for the films. Composite films were prepared by using corn starch, polyvinyl alcohol (PVA), nano-sized PMMA-co-AAm particles, and additives, i.e., glycerol (GL), xylitol (XL), and citric acid (CA). Nano-sized PMMA-co-AAm particles were synthesized by emulsion polymerization. The results of the evaluation of properties for prepared films indicated that compared with films without PMMA-co-AAm particles, the mechanical properties and water resistance were improved up to 70-400% by the addition of nano-sized PMMA-co-AAm. In addition, the results of the soil burial biodegradation revealed that films added PMMA-co-AAm particles were degraded by about 45-65% after 165 days.     

Paracoccus denitrificans SD1 mediated augmentation with indigenous mixed cultures for enhanced removal of N,N-dimethylformamide from industrial effluents

Bioaugmentation is an effective treatment method to reduce recalcitrant pollutants from polluted sites. Dimethylformamide (DMF) is a very common toxic organic solvent among the effluents of textile and pharma industries. DMF was degraded by pre-adapted Paracoccus denitrificans SD1 with indigenous mixed cultures in both bioaugmentation and non-bioaugmentation conditions. In free cell condition, augmentation was not much significant due to competition among the bacterial cells and direct exposure of cells to toxic level of DMF. To enhance the degradation of DMF, cells were entrapped in PVA–alginate matrix individually and collectively for bioaugmentation experiments. Bioaugmentation is successful when immobilized P. denitrificans SD1 is introduced higher inoculum volume with indigenous cultures in continuous packed bed reactor system. This treatment has succeeded in removing 91.3% of 3% (v/v) DMF from the industrial effluent. This investigation advocates that bioaugmentation enhances the DMF removal efficiency by about 20% when compared to individual degradation by P. denitrificans SD1.     

Biodegradation of polyvinyl alcohol by a mixed microbial culture

A mixed culture capable of degrading 1 g l⁻¹ polyvinyl alcohol (PVA) completely was screened from sludge samples at Pacific Textile Factory, Wuxi, China. This mixed culture had stronger capability of degrading PVA with low polymerization and high saponification than degrading PVA with high polymerization and low saponification. Inorganic nitrogen source was more suitable for the mixed culture to grow and degrade PVA than organic nitrogen source. Microorganisms and relative abundance of this mixed culture were explored by terminal restriction fragment length polymorphism (T-RFLP). Small PVA molecules were detected in cell extracts of the mixed culture. This indicated that PVA degradation in the mixed culture was in fact a combined action of extracellular and intracellular enzymes. Two strains producing extracellular PVA-degrading enzyme were isolated from the mixed culture. They could individually degrade PVA1799 with polymerization of 1700 from initial average molecular weight 112,981 to 98,827 Da and 84,803 Da, respectively. However, only small amount of PVA124 in polymerization of 400 could be degraded by these two strains.     

Symbiotic Utilization of Polyvinyl Alcohol by Mixed Cultures

Polyvinyl alcohol (PVA)-utilizing cultures were obtained from various sources. They were mixed cultures even after cyclical transfer to liquid and plate media with PVA as a sole source of carbon. Component bacteria were isolated from the several mixed cultures, and it was shown that PVA was utilized symbiotically by two bacterial members which could not utilize PVA in each respective pure culture. From a mixed culture, strains VM15, VM15A (Pseudomonas putida) and VM15C (Pseudomonas sp.) were isolated as members essential for PVA utilization. VM15C was the predominant strain in the mixed-culture population and produced PVA-degrading enzyme. The culture supernatant of VM15A enabled VM15C to grow on PVA. VM15A was presumed to supply VM15C with a unique growth stimulant which was distinct from usual growth factors.     

Pyrroloquinoline Quinone-Dependent Cytochrome Reduction in Polyvinyl Alcohol-Degrading Pseudomonas sp. Strain VM15C

A polyvinyl alcohol (PVA) oxidase-deficient mutant of Pseudomonas sp. strain VM15C, strain ND1, was shown to possess PVA dehydrogenase, in which pyrroloquinoline quinone (PQQ) functions as a coenzyme. The mutant grew on PVA and required PQQ for utilization of PVA as an essential growth factor. Incubation of the membrane fraction of the mutant with PVA caused cytochrome reduction of the fraction. Furthermore, it was found that in spite of the presence of PVA oxidase, the membrane fraction of strain VM15C grown on glucose without PQQ required PQQ for cytochrome reduction during incubation with PVA. The results provide evidence that PVA dehydrogenase couples with the electron transport chain of PVA-degrading bacteria but that PVA oxidase does not.     

Production of Polyvinyl Alcohol Oxidase by a Symbiotic Mixed Culture

Production of polyvinly alcohol (PVA) oxidase by Pseudomonas sp. strain VM15C, a PVA degrader of a symbiotic PVA-utilizing mixed culture, was examined in various cultures. Despite the absence of PVA in the culture in nutrient broth, VM15C showed approximately the same productivity of PVA oxidase activity as that in the culture with PVA as the sole carbon source, whereas the productivity in the culture with glucose was lower than that of either the nutrient broth or the PVA culture. PVA oxidase activity produced in the nutrient broth culture was predominantly present in the cells, and most of the activity appeared to be in the cytoplasm. In contrast, in the culture with PVA as the sole carbon source, the activity was present in the culture fluid in a larger ratio than in the nutrient broth culture. Thus, production of PVA oxidase activity by this strain was constitutive and repressible, although localization of the produced activity was changed by growth conditions.