Degradation of polycarbonate by a polyester-degrading strain, Amycolatopsis sp. strain HT-6

Polymer-prodrug conjugates as candidates for degradable, long-acting implants, releasing the water-soluble nucleoside reverse-transcriptase inhibitor emtricitabine

Circulating, soluble polymer-drug conjugates have been utilised for many years to aid the delivery of sensitive, poorly-soluble or cytotoxic drugs, prolong circulation times or minimise side effects. Long-acting therapeutics are increasing in their healthcare importance, with intramuscular and subcutaneous administration of liquid formulations being most common. Degradable implants also offer opportunities and the use of polymer-prodrug conjugates as implant materials has not been widely reported in this context. Here, the potential for polymer-prodrug conjugates of the water soluble nucleoside reverse transciption inhibitor emtricitabine (FTC) is studied. A novel diol monomer scaffold, allowing variation of prodrug substitution, has been used to form polyesters and polycarbonates by step-growth polymerisation. Materials have been screened for physical properties that enable implant formation, studied for drug release to provide mechanistic insights, and tunable prolonged release of FTC has been demonstrated over a period of at least two weeks under relevant physiological conditions.

Biodegradation of bisphenol-A polycarbonate plastic by Pseudoxanthomonas sp. strain NyZ600

Bisphenol-A polycarbonate (PC) is a widely used engineering thermoplastic and its release has caused damage to the ecosystem. Microbial degradation of plastic represents a sustainable approach for PC reduction. In this study, a bacterial strain designated Pseudoxanthomonas sp. strain NyZ600 capable of degrading PC was isolated from activated sludge by using diphenyl carbonate as a surrogate substrate. Within a 30-day period of incubating with strain NyZ600, PC films were analyzed with atomic force microscopy, scanning electron microscope, water contact angle, X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, differential scan calorimeter and thermogravimetric analysis technique. The analyses results indicated that the treated PC films were bio-deteriorated and formed some "corrosion pits" on the PC film surface. In addition, strain NyZ600 performed broad depolymerization of PC indicated by the reduction of Mn from 23.55 to 16.75 kDa and Mw from 45.67 to 31.97 kDa and two degradation products bisphenol A and 4-cumylphenol (the two monomers of PC) were also found, which established that PC were biodegraded by strain NyZ600. Combing all above results, it is clear that the strain NyZ600 can degrade PC which provides a unique example for bacterial degradation of PC and a feasibility for the removal of PC waste.

Exploring biogeographic patterns of bacterioplankton communities across global estuaries

Estuaries provide an ideal niche to study structure and function of bacterioplankton communities owing to the presence of a multitude of environmental stressors. Bacterioplankton community structures from nine global estuaries were compared to understand their broad‐scale biogeographic patterns. Bacterioplankton community structure from four estuaries of Sundarbans, namely Mooriganga, Thakuran, Matla, and Harinbhanga, was elucidated using Illumina sequencing. Bacterioplankton communities from these estuaries were compared against available bacterioplankton sequence data from Columbia, Delaware, Jiulong, Pearl, and Hangzhou estuaries. All nine estuaries were dominated by Proteobacteria. Other abundant phyla included Bacteroidetes, Firmicutes, Acidobacteria, Actinobacteria, Cyanobacteria, Planctomycetes, and Verrucomicrobia. The abundant bacterial phyla showed a ubiquitous presence across the estuaries. At class level, the overwhelming abundance of Gammaproteobacteria in the estuaries of Sundarbans and Columbia estuary clearly stood out amidst high abundance of Alphaproteobacteria observed in the other estuaries. Abundant bacterial families including Rhodobacteriaceae, Shingomonadaceae, Acidobacteriaceae, Vibrionaceae, and Xanthomondaceae also showed ubiquitous presence in the studied estuaries. However, rare taxa including Chloroflexi, Tenericutes, Nitrospirae, and Deinococcus‐Thermus showed clear site‐specific distribution patterns. Such distribution patterns were also reinstated by nMDS ordination plots. Such clustering patterns could hint toward the potential role of environmental parameters and substrate specificity which could result in distinct bacterioplankton communities at specific sites. The ubiquitous presence of abundant bacterioplankton groups along with their strong correlation with surface water temperature and dissolved nutrient concentrations indicates the role of such environmental parameters in shaping bacterioplankton community structure in estuaries. Overall, studies on biogeographic patters of bacterioplankton communities can provide interesting insights into ecosystem functioning and health of global estuaries.

In vitro and in vivo degradation behavior of poly(trimethylene carbonate-co-d,l-lactic acid) copolymer

We present P(TMC-co-DLLA) copolymer with the molar ratio of TMC: DLLA = 15: 85 was used to systematic study of in vivo and in vitro degradation behaviors. Dense homogeneous copolymer specimens were prepared by compression molding method. The in vitro and in vivo degradation were, respectively, performed at simulative body condition and implanted into rat’s subcutaneous condition. Investigations were followed via physicochemical and histological analysis such as SEM, GPC, DSC, FTIR and H&E stain. The results demonstrate that copolymeric material can degrade in phosphate buffer solution (PBS) and in rat’s body, and the in vivo degradation rate is faster. Obvious decline of molecule weight and mass loss has been observed, which led to the attenuation of mechanical strength. Furthermore, apart from the hydrolysis, macrophagocytes took part in the phagocytosis in vivo, indicating that degradation rate could be regulated by the combinational mechanism. It is concluded that P(TMC-co-DLLA) copolymer is a promising candidate for tissue repair.

Ring-opening polymerization of ethylene carbonate: comprehensive structural elucidation by 1D & 2D-NMR techniques, and selectivity analysis

Meticulous structural elucidation and selectivity analysis of poly(ethylene ether carbonate) by multi-dimensional NMR.

Current biotechnological applications of the genus Amycolatopsis

Recently there has been increasing interest in possible biotechnological applications of the bacterial genus Amycolatopsis. This genus originally attracted attention for its antibiotic producing capabilities; although it is actually a multifaceted genus and a more diverse range of studies involving biotechnological processes have now been undertaken. Several works have demonstrated that the versatility shown by these bacteria is valuable in industrial applications. Here, we provide a condensed overview of the most important biotechnological applications such as bioremediation, biodegradation and bioconversion, as well as aspects that need to be explored further in order to gain a fuller insight into this genus, including its possible potential in the production of biofuel. Antibiotic production is not discussed since this is well covered by the latest edition of Bergey's Manual of Systematic Bacteriology. To our knowledge this is the first report highlighting the versatility and biotechnological potential of the genus Amycolatopsis.

Study of microbes having potentiality for biodegradation of plastics

Plastic is a broad name given to the different types of organic polymers having high molecular weight and is commonly derived from different petrochemicals. Plastics are generally not biodegradable or few are degradable but in a very slow rate. Day by day, the global demand of these polymers is sharply increasing; however, considering their abundance and potentiality in causing different environmental hazards, there is a great concern in the possible methods of degradation of plastics. Recently, there have been some debates at the world stage about the potential degradation procedures of these synthetic polymers and microbial degradation has emerged as one of the potential alternative ways of degradation of plastics. Alternatively, some scientists have also reported many adverse effects of these polymers in human health, and thus, there is an immediate need of a potential screening of some potential microbes to degrade these synthetic polymers. In this review, we have taken an attempt to accumulate all information regarding the chemical nature along with some potential microbes and their enzymatic nature of biodegradation of plastics along with some key factors that affect their biodegradability.

Facile fabrication of diblock methoxy poly(ethylene glycol)-poly(tetramethylene carbonate) and its self-assembled micelles as drug carriers

AB type diblock methoxy poly(ethylene glycol)-b-poly(tetramethylene carbonate) (mPEG-PTeMC) copolymers were designed for the first time and used as carriers for the sustained release of the hydrophobic drug ibuprofen. In this paper, we developed a facile ring-opening polymerization (ROP) method to prepare mPEG-PTeMC copolymers under the catalysis of Novozym-435 lipase. Attractively, the polymerization has been successfully performed at 30 degrees C, close to room temperature. The data show that the copolymer compositions agree well with the feed ratio of TeMC to mPEG, indicating the controllable feature of the polymerization. The copolymer structures were characterized by (1)H NMR, IR, SEC, and DSC measurements. mPEG-PTeMC exhibits no apparent in vitro cytotoxicity toward human embryonic kidney transformed 293T cells. Those amphiphilic copolymers can readily self-assemble into nanosized micelles (about 150 nm) in aqueous solution. Their critical micelle concentrations are in the range of (1.6-9.3) x 10(-7) mol/L, determined by fluorescence spectroscopy. The micelles present high stability in PBS solution, with no obvious change in micelle diameters over 5 days. Ibuprofen can be loaded effectively in mPEG-PTeMC micelles, and its sustained release behavior is observed. Transmission electron microscopy shows that the well-dispersed spherical micelles are around 25 nm in diameter, while the diameter is 30 nm after loading ibuprofen. The release rate increases when the chain length of the PTeMC block decreases. These properties show that the micelles self-assembled from mPEG-PTeMC copolymers would have great potential as carriers for the effective encapsulation as well as sustained release of hydrophobic drugs.

Biodegradability of plastics

Plastic is a broad name given to different polymers with high molecular weight, which can be degraded by various processes. However, considering their abundance in the environment and their specificity in attacking plastics, biodegradation of plastics by microorganisms and enzymes seems to be the most effective process. When plastics are used as substrates for microorganisms, evaluation of their biodegradability should not only be based on their chemical structure, but also on their physical properties (melting point, glass transition temperature, crystallinity, storage modulus etc.). In this review, microbial and enzymatic biodegradation of plastics and some factors that affect their biodegradability are discussed.

Biodegradable Polymers

Biodegradable materials are used in packaging, agriculture, medicine and other areas. In recent years there has been an increase in interest in biodegradable polymers. Two classes of biodegradable polymers can be distinguished: synthetic or natural polymers. There are polymers produced from feedstocks derived either from petroleum resources (non renewable resources) or from biological resources (renewable resources). In general natural polymers offer fewer advantages than synthetic polymers. The following review presents an overview of the different biodegradable polymers that are currently being used and their properties, as well as new developments in their synthesis and applications.

Diversity and abundance of Gram positive bacteria in a tidal flat ecosystem

Gram positive bacteria recently have been identified as important components of freshwater ecosystems and are also present in marine environments. However, their quantitative significance and possible role in the latter systems is still little studied, in particular in coastal regions. Therefore, we investigated the abundance and composition of Gram positive bacteria in the Wadden Sea, a tidal flat ecosystem in the German Bight of the North Sea. Applying fluorescence in situ hybridization we found that Actinobacteria constitute 4-7% of total bacteria in the Wadden Sea and slightly higher proportions in a freshwater drainage channel connected to the sea by a sluice. The application of denaturing gradient gel electrophoresis of 16S rRNA gene fragments after amplification by an Actinobacteria-specific primer set and subsequent sequencing showed that the composition of the actinobacterial community in the Wadden Sea was distinctly different from that in the freshwater system. A bacterial clone library of 111 clones yielded eight Gram positive phylotypes which are related closely to other marine phylotypes including the Marine Actinobacteria Clade but also to freshwater phylotypes. We applied dilution cultures, enriched with various biopolymers, Marine Broth and Fucus vesiculosus extracts, for isolating bacteria from the bulk water, suspended aggregates, the oxic surface and oxic/anoxic transition zone of the sediment. Fifty-three isolates affiliated to seven families of the order Actinomycetales and nine isolates to the family Bacillaceae. The salinity range (1-45 per thousand NaCl) and growth optimum of 14 strains from various families showed that all except one strain exhibited a rather broad range of sustained growth from 1 per thousand to >or= 20 per thousand NaCl and several strains exhibited an optimum of > 10 per thousand NaCl. The results indicate that the Gram positive bacterial community in the Wadden Sea is surprisingly diverse and consists mainly of indigenous species which appear to be well adapted to the environmental conditions of this coastal ecosystem.

Biodegradation of Aliphatic and Aromatic Polycarbonates

Polycarbonate is one of the most widely used engineering plastics because of its superior physical, chemical, and mechanical properties. Understanding the biodegradation of this polymer is of great importance to answer the increasing problems in waste management of this polymer. Aliphatic polycarbonates are known to biodegrade either through the action of pure enzymes or by bacterial whole cells. Very little information is available that deals with the biodegradation of aromatic polycarbonates. Biodegradation is governed by different factors that include polymer characteristics, type of organism, and nature of pretreatment. The polymer characteristics such as its mobility, tacticity, crystallinity, molecular weight, the type of functional groups and substituents present in its structure, and plasticizers or additives added to the polymer all play an important role in its degradation. The carbonate bond in aliphatic polycarbonates is facile and hence this polymer is easily biodegradable. On the other hand, bisphenol A polycarbonate contains benzene rings and quaternary carbon atoms which form bulky and stiff chains that enhance rigidity. Even though this polycarbonate is amorphous in nature because of considerable free volume, it is non-biodegradable since the carbonate bond is inaccessible to enzymes because of the presence of bulky phenyl groups on either side. In order to facilitate the biodegradation of polymers few pretreatment techniques which include photo-oxidation, gamma-irradiation, or use of chemicals have been tested. Addition of biosurfactants to improve the interaction between the polymer and the microorganisms, and blending with natural or synthetic polymers that degrade easily, can also enhance the biodegradation.

The genus Amycolatopsis: Indigenous plasmids, cloning vectors and gene transfer systems

The genus Amycolatopsis is a member of the phylogenetic group nocardioform actinomycetes. Most of the members of the genus Amycolatopsis are known to produce antibiotics. Additionally, members of this genus have been reported to metabolize aromatic compounds as the sole sources of carbon and energy. Development of genetic manipulation in Amycolatopsis has progressed slowly due to paucity of genetic tools and methods. The occurrence of indigenous plasmids in different species of Amycolatopsis is not very common. Till date, only three indigenous plasmids viz., pMEA100, pMEA300 and pA387 have been reported in Amycolatopsis species. Various vectors based on the indigenous plasmids, pMEA100, pMEA300 and pA387, have been constructed. These vectors have proved useful for molecular genetics studies of actinomycetes. Molecular genetic work with Amycolatopsis strains is not easy, since transformation methods have to be developed, or at least optimized, for each particular strain. Nonetheless, methods for efficient transformation (polyethyleneglycol (PEG) induced protoplast transformation, transformation by electroporation and direct transformation) have been developed and used successfully for the introduction of DNA into several Amycolatopsis species. The construction of plasmid cloning vectors and the development of gene transfer systems has opened up possibilities for studying the molecular genetics of these bacteria.

Biodegradability and biodegradation of poly(lactide)

Poly(lactide) (PLA) has been developed and made commercially available in recent years. One of the major tasks to be taken before the widespread application of PLA is the fundamental understanding of its biodegradation mechanisms. This paper provides a short overview on the biodegradability and biodegradation of PLA. Emphasis is focused mainly on microbial and enzymatic degradation. Most of the PLA-degrading microorganisms phylogenetically belong to the family of Pseudonocardiaceae and related genera such as Amycolatopsis, Lentzea, Kibdelosporangium, Streptoalloteichus, and Saccharothrix. Several proteinous materials such as silk fibroin, elastin, gelatin, and some peptides and amino acids were found to stimulate the production of enzymes from PLA-degrading microorganisms. In addition to proteinase K from Tritirachium album, subtilisin, a microbial serine protease and some mammalian serine proteases such as alpha-chymotrypsin, trypsin, and elastase could also degrade PLA.

Hydrolysis of polyesters by serine proteases

The substrate specificity of alpha-chymotrypsin and other serine proteases, trypsin, elastase, proteinase K and subtilisin, towards hydrolysis of various polyesters was examined using poly(L-lactide) (PLA), poly(beta-hydroxybutyrate) (PHB), poly(ethylene succinate) (PES), poly(ethylene adipate) (PEA), poly(butylene succinate) (PBS), poly(butylene succinate-co-adipate) (PBS/A), poly[oligo(tetramethylene succinate)-co-(tetramethylane carbonate)] (PBS/C), and poly(epsilon-caprolactone) (PCL). alpha-Chymotrypsin could degrade PLA and PEA with a lower activity on PBS/A. Proteinase K and subtilisin degraded almost all substrates other than PHB. Trypsin and elastase had similar substrate specificities to alpha-chymotrypsin.