Abstract: Poly(vinyl alcohol) (PVA) is a water soluble synthetic polymer, with a backbone composed only of carbon atoms and is biodegradable under both aerobic and anaerobic conditions. This polymer can be prepared by the hydrolysis of polyvinylacetate and is one of the most important synthetic polymers used in commercial, industrial, medical and nutraceutical applications. The environmental issues caused by PVA industrial practice have increased globally. Several methods have been used to treat PVA industrial discharge including in particular physicochemical methods such as electrocoagulation. Nowadays, use of bioremediation for PVA release, which has caused serious pollution problems in the natural environment, has attracted much interest. The bioremediation ability of microorganisms and their PVA degrading enzymes, especially PVA oxidases/hydrolases, has long been perceived. These enzymes as well as symbiotic microorganisms could be an effective means for biodegradation of PVA.

Abstract: Polyhydroxybutyrates (PHBs) are macromolecules synthesized by bacteria. They are inclusion bodies accumulated as reserve materials when the bacteria grow under different stress conditions. Because of their fast degradability under natural environmental conditions, PHBs are selected as alternatives for production of biodegradable plastics. The aim of this work was to isolate potential PHB producing bacteria, evaluate PHB production using agro-residues as carbon sources. Among fifty bacterial strains isolated from different localities, ten PHB accumulating strains were selected and compared for their ability to accumulate PHB granules inside their cells. Isolate Arba Minch Waste Water (AWW) identified as Bacillus spp was found to be the best producer. The optimum pH, temperature, and incubation period for best PHB production by the isolate were 7, 37 °C, and 48 h respectively at 150 rpm. PHB production was best with glucose as carbon source and peptone as nitrogen source. The strain was able to accumulate 55.6, 51.6, 37.4 and 25% PHB when pretreated sugar cane bagasse, corn cob, teff straw (Eragrostis tef) and banana peel were used as carbon sources respectively. Fourier transform-infrared authentication results of the extracted and purified PHB identified its functional units as C–H, CH2, C=O and C–O groups. UV–Vis spectrophotometric analysis and biodegradability test confirmed the similarity of the extract with standard PHB and its suitability for bioplastic production. The isolated Bacillus sp can be used for feasible production of PHB using agro-residues especially sugarcane bagasse which can reduce the production cost in addition to reducing the disposal problem of these substrates. The yield of PHB can further be boosted by optimization of production parameters as substrates.

Abstract: A variety of renewable starting materials, such as sugars and polysaccharides, vegetable oils, lignin, pine resin derivatives, and proteins, have so far been investigated for the preparation of bio-based polymers. Among the various sources of bio-based feedstock, vegetable oils are one of the most widely used starting materials in the polymer industry due to their easy availability, low toxicity, and relative low cost. Another bio-based plastic of great interest is poly(lactic acid) (PLA), widely used in multiple commercial applications nowadays. There is an intrinsic expectation that bio-based polymers are also biodegradable, but in reality there is no guarantee that polymers prepared from biorenewable feedstock exhibit significant or relevant biodegradability. Biodegradability studies are therefore crucial in order to assess the long-term environmental impact of such materials. This review presents a brief overview of the different classes of bio-based polymers, with a strong focus on vegetable oil-derived resins and PLA. An entire section is dedicated to a discussion of the literature addressing the biodegradability of bio-based polymers.

Abstract: Polyurethane (PU) is widely used in many aspects of modern life because of its versatility and resistance. However, PU waste disposal generates large problems, since it is slowly degraded, there are limited recycling processes, and its destruction may generate toxic compounds. In this work, we isolated fungal strains able to grow in mineral medium with a polyester PU (PS-PU; Impranil DLN) or a polyether PU (PE-PU; Poly Lack) varnish as the only carbon source. Of the eight best Impranil-degrading strains, the six best degraders belonged to the Cladosporium cladosporioides complex, including the species C. pseudocladosporioides, C. tenuissimum, C. asperulatum, and C. montecillanum, and the two others were identified as Aspergillus fumigatus and Penicilliumchrysogenum. The best Impranil degrader, C. pseudocladosporioides strain T1.PL.1, degraded up to 87% after 14 days of incubation. Fourier transform infrared (FTIR) spectroscopy analysis of Impranil degradation by this strain showed a loss of carbonyl groups (1,729 cm −1 ) and N—H bonds (1,540 and 1,261 cm −1 ), and gas chromatography-mass spectrometry (GC-MS) analysis showed a decrease in ester compounds and increase in alcohols and hexane diisocyanate, indicating the hydrolysis of ester and urethane bonds. Extracellular esterase and low urease, but not protease activities were detected at 7 and 14 days of culture in Impranil. The best eight Impranil-degrading fungi were also able to degrade solid foams of the highly recalcitrant PE-PU type to different extents, with the highest levels generating up to 65% of dry-weight losses not previously reported. Scanning electron microscopy (SEM) analysis of fungus-treated foams showed melted and thinner cell wall structures than the non-fungus-treated ones, demonstrating fungal biodegradative action on PE-PU. IMPORTANCE Polyurethane waste disposal has become a serious problem. In this work, fungal strains able to efficiently degrade different types of polyurethanes are reported, and their biodegradative activity was studied by different experimental approaches. Varnish biodegradation analyses showed that fungi were able to break down the polymer in some of their precursors, offering the possibility that they may be recovered and used for new polyurethane synthesis. Also, the levels of degradation of solid polyether polyurethane foams reported in this work have never been observed previously. Isolation of efficient polyurethane-degrading microorganisms and delving into the mechanisms they used to degrade the polymer provide the basis for the development of biotechnological processes for polyurethane biodegradation and recycling.

Abstract: The intrinsic biodegradability of hydrocarbons and the distribution of proficient degrading microorganisms in the environment are very crucial for the implementation of bioremediation practices. Among others, one of the most favorable methods that can enhance the effectiveness of bioremediation of hydrocarbon-contaminated environment is the application of biosurfactant producing microbes. In the present study, the biodegradation capacities of native bacterial consortia towards total petroleum hydrocarbons (TPH) with special emphasis to poly aromatic hydrocarbons (PAHs) were determined. The purpose of the study was to isolate TPH degrading bacterial strains from various petroleum contaminated soil of Assam, India and develop a robust bacterial consortium for bioremediation of crude oil of this native land. From a total of 23 bacterial isolates obtained from three different hydrocarbons contaminated samples 5 isolates, namely KS2, PG1, PG5, R1 and R2 were selected as efficient crude oil degraders with respect to their growth on crude oil enriched samples. Isolates KS2, PG1 and R2 are biosurfactant producers and PG5, R1 are non-producers. Fourteen different consortia were designed involving both biosurfactant producing and non-producing isolates. Consortium 10, which comprises two Bacillus strains namely, Bacillus pumilus KS2 and Bacillus cereus R2 (identified by 16s rRNA sequencing) has shown the best result in the desired degradation of crude oil. The consortium showed degradation up to 84.15% of total petroleum hydrocarbon (TPH) after five weeks of incubation, as revealed from gravimetric analysis. FTIR (Fourier transform infrared) and GCMS (Gas chromatography-mass spectrometer) analyses were correlated with gravimetric data which reveals that the consortium has removed a wide range of petroleum hydrocarbons in comparison with abiotic control including different aliphatic and aromatic hydrocarbons.

Abstract: Petroleum polymers contribute to non-degradable waste materials and it would therefore be desirable to produce ecofriendly degradable materials. Biodegradation of polyhydroxybutyrate (PHB) in the presence of oligomer hydrolase and PHB depolymerase gave 3-hydroxybutyric acid which could be oxidized to acetyl acetate. Several bacteria and fungi can degrade PHB in the soil. Biodegradation of PHB showed a significant decrease in the molecular weight (Mw), number-average molecular weight (Mn) and the dispersity (Mw/Mn) for all the film formulations. Nanofibers of PHB and its composites showed faster degradation compared to other films and displayed complete degradation after 3 weeks. The SEM micrographs showed various surface morphology changes including alterations in appearance of pores, cavity, grooves, incisions, slots and pointers. Such changes were due to the growth of microorganisms that secreted PHB depolymerase enzyme which lead to the biopolymer films degradation. However, PHB nanofibers and its composites films in the presence of TiO2 demonstrated more surface changes with rupture of most nanofibers in which there was a drop in fibres diameter. The degradation of biopolymers help to overcome some of the pollution problems associated with the use of petroleum polymers. PHB nanofiber and its TiO2 composite were degraded faster compared to other PHB film types due to their three dimensional and high surface area structures. The presence of TiO2 nanoparticles in the composite films slowdown the degradation process compared to PHB films. Additionally, the PHB and its composite films that were prepared from UV treated PHB films led to acceleration of the degradation.

Abstract: Soils contaminated with hazardous chemicals worldwide are awaiting remediation activities; bioremediation is often considered as a cost-effective remediation approach. Potential bioapproaches are biostimulation, e.g. by addition of nutrients, fertiliser and organic substrates, and bioaugmentation by addition of compound-degrading microbes or of organic amendments containing active microorganisms, e.g. activated sludge or compost. In most contaminated soils, the abundance of the intrinsic metabolic potential is too low to be improved by biostimulation alone, since the physical and chemical conditions in these soils are not conducive to biodegradation. In the last few decades, compost or farmyard manure addition as well as composting with various organic supplements have been found to be very efficient for soil bioremediation. In the present minireview, we provide an overview of the composting and compost addition approaches as 'stimulants' of natural attenuation. Laboratory degradation experiments are often biased either by not considering the abiotic factors or by focusing solely on the elimination of the chemicals without taking the biotic factors and processes into account. Therefore, we first systemise the concepts of composting and compost addition, then summarise the relevant physical, chemical and biotic factors and mechanisms for improved contaminant degradation triggered by compost addition. These factors and mechanisms are of particular interest, since they are more relevant and easier to determine than the composition of the degrading community, which is also addressed in this review. Due to the mostly empirical knowledge and the nonstandardised biowaste or compost materials, the field use of these approaches is highly challenging, but also promising. Based on the huge metabolic diversity of microorganisms developing during the composting processes, a highly complex metabolic diversity is established as a 'metabolic memory' within developing and mature compost materials. Compost addition can thus be considered as a 'super-bioaugmentation' with a complex natural mixture of degrading microorganisms, combined with a 'biostimulation' by nutrient containing readily to hardly degradable organic substrates. It also improves the abiotic soil conditions, thus enhancing microbial activity in general. Finally, this minireview also aims at guiding potential users towards full exploitation of the potentials of this approach.

Abstract: Secretion of organic acids is an important mechanism for phosphate solubilizing bacteria (PSB) to dissolve insoluble phosphorus in soil. However, the composition of organic acids produced by PSB in the presence of different phosphorus compounds is poorly known, and little is known about the ability of PSB to degrade pollutants in sediment. In this study, we isolated a strain Pseudomonas sp. PSB12 from the sediment of the Qihe River. PSB12 had maximum phosphate solubilization index (SI) of 3.86 on Pikovskaya's agar medium. The phosphate solubilizing activity was associated with the release of organic acids produced from glucose, while the composition of organic acids produced by PSB12 was dependent on the phosphorus forms. When initial soluble phosphorus was insufficient (in MP1 and MP2 media), gluconic acid was the predominant organic acid. In contrast, formic acid, butyrate, and propanedioic acid were the main organic acids produced when only soluble phosphorus (MP3) was supplied. RT-PCR indicate...

Abstract: Biodegradable plastics are mostly applied in packaging materials (eg shopping bags), waste collection bags, catering products, and agricultural applications In this last case, degradation takes place directly in soil where biodegradable plastic products are intentionally left after use (eg mulch films for weeds control) Due to the growing volumes of biodegradable polymers and plastics, interest in their environmental safety is increasing and more research is carried out Some attempt has been made to apply biotests, used in other sectors of environmental sciences, in the assessment of biodegradable plastics safety In this work, the quality of soils after biodegradation of the bioplastics Mater-Bi has been assessed with a large array of biotests based on model organisms representative of the different trophic levels in the food chains of the edaphic and aquatic ecosystems Mater-Bi was degraded under controlled conditions for 6 months at a 1% concentration The selected organisms included bacteria and protozoa (V fischeri and D discoideum, respectively), the green alga P subcapitata, plants (the monocotyledon S saccharatum and the dicotyledon L sativum), and invertebrates animals (D magna, a freshwater crustacean, and the Oligochaeta earthworm E andrei), using both acute and chronic endpoints The results of the applied ecotoxicological tests showed that the Mater-Bi materials tested at very high doses did not affect the soil quality Soil exposed to Mater-Bi has no noxious effects on edaphic organisms; in particular, mono and dicotyledon plants results, indicate that Mater-Bi plastic products are innocuous for agricultural uses The use of more sensitive chronic endpoints allows to exclude possible effects at population level This is the first time that such a comprehensive approach is applied to the assessment of possible ecotoxicity effects induced by biodegradable plastics in soil and represents a possible starting point for improved standardized testing schemes

Abstract: One of the utmost man-made problems faced today has been the ever-increasing plastic waste filling the world. It accounts for an estimated 20–30% (by volume) of municipal solid waste in landfill sites worldwide. Research on plastic biodegradation has been steadily growing over the past four decades. Several fungi have been identified that produce enzymes capable of plastic degradation in various laboratory conditions. This paper presents a study that determined the ability of fungi to degrade low molecular weight polyvinyl chloride (PVC) by the enzyme laccase. We have isolated a fungal species, Cochliobolus sp., from plastic dumped soils and they were cultured on Czapek Dox Agar slants at 30°C. The effectiveness of this fungal species on the degradation of commercial low molecular weight polyvinyl chloride (PVC) was studied under laboratory conditions. Significant differences were observed from the FTIR, GC-MS, and SEM results in between control and Cochliobolus sp. treated PVC.

Abstract: . Biodegradable and sustainable feedstocks are increasingly replacing petroleum-based materials commonly used for single- or multi-use packaging applications. A study was conducted to evaluate the potential of an innovative biocomposite material patented by Ecovative Design LLC (Green Island, N.Y.) for use in commercial products and packaging. The biocomposite material utilizes the fungus mycelium as a matrix to bind cellulosic plant fibers. The test samples were manufactured with different fiber-fungal strain combinations, using cotton ginning waste and hemp pith as core material and fiber fabric on the surface. The physico-mechanical properties of the biocomposites were evaluated to develop a thorough understanding of the material which may lead to future applications. The properties evaluated included specific gravity, surface hardness, water absorption, coefficient of linear thermal expansion, and resistance to tension and compression stress. The density profile results indicated that the material is extremely light, buoyant, and highly hydrophilic. Surface hardness test showed that the material has a soft outer surface with high elasticity. The tensile and compression properties showed the material can be used in targeted packaging applications where lightweight, resiliency, and biodegradability are desirable.

Abstract: This study investigated the impacts of individual chlorinated solvents and their mixtures on aerobic 1,4-dioxane biodegradation by Pseudonocardia dioxanivorans CB1190. The established association of these co-occurring compounds suggests important considerations for their respective biodegradation processes. Our kinetics and mechanistic studies demonstrated that individual solvents inhibited biodegradation of 1,4-dioxane in the following order: 1,1-dichloroethene (1,1-DCE) > cis-1,2-diochloroethene (cDCE) > trichloroethene (TCE) > 1,1,1-trichloroethane (TCA). The presence of 5 mg L(-1) 1,1-DCE completely inhibited 1,4-dioxane biodegradation. Subsequently, we determined that 1,1-DCE was the strongest inhibitor of 1,4-dioxane biodegradation by bacterial pure cultures exposed to chlorinated solvent mixtures as well as in environmental samples collected from a site contaminated with chlorinated solvents and 1,4-dioxane. Inhibition of 1,4-dioxane biodegradation rates by chlorinated solvents was attributed to delayed ATP production and down-regulation of both 1,4-dioxane monooxygenase (dxmB) and aldehyde dehydrogenase (aldH) genes. Moreover, increasing concentrations of 1,1-DCE and cis-1,2-DCE to 50 mg L(-1) respectively increased 5.0-fold and 3.5-fold the expression of the uspA gene encoding a universal stress protein. In situ natural attenuation or enhanced biodegradation of 1,4-dioxane is being considered for contaminated groundwater and industrial wastewater, so these results will have implications for selecting 1,4-dioxane bioremediation strategies at sites where chlorinated solvents are present as co-contaminants.

Abstract: Poly(lactic acid), PLA, is a polyester that can be produced from lactic acid derived from renewable resources. This polymer offers attracting uses in packaging industry due to its biodegradability and high tensile strength. However, PLA is quite brittle, which limits its applications. To overcome this drawback, PLA was plasticized with epoxy-type plasticizer derived from a fatty acid, octyl epoxy stearate (OES) at different loadings (1, 3, 5, 10, 15, and 20 phr). The addition of OES decreases the glass transition temperature and provides a remarkable increase in elongation at break and impact-absorbed energy. Plasticizer saturation occurs at relatively low concentrations of about 5 phr OES; higher concentration leads to phase separation as observed by field emission scanning electron microscopy (FESEM). Optimum balanced mechanical properties are obtained at relatively low concentrations of OES (5 phr), thus indicating the usefulness of this material as environmentally friendly plasticizer for PLA industrial formulations.