ABSTRACT
With the escalation of plastic bans and restrictions, bio-based plastics, represented by polylactic acid (PLA), have become a major alternative to traditional plastics in the current market and are unanimously regarded as having potential for development. However, there are still several misconceptions about bio-based plastics, whose complete degradation requires specific composting conditions. Bio-based plastics might be slow to degrade when it is released into the natural environment. They might also be harmful to humans, biodiversity and ecosystem function as traditional petroleum-based plastics do. In recent years, with the increasing production capacity and market size of PLA plastics in China, there is an urgent need to investigate and further strengthen the management of the life cycle of PLA and other bio-based plastics. In particular, the in-situ biodegradability and recycling of hard-to-recycle bio-based plastics in the ecological environment should be focused. This review introduces the characteristics, synthesis and commercialization of PLA plastics, summarizes the current research progress of microbial and enzymatic degradation of PLA plastics, and discusses their biodegradation mechanisms. Moreover, two bio-disposal methods against PLA plastic waste, including microbial in-situ treatment and enzymatic closed-loop recycling, are proposed. At last, the prospects and trends for the development of PLA plastics are presented.
Subject(s)
Humans , Ecosystem , Biodegradable Plastics , Polyesters , Biodegradation, EnvironmentalABSTRACT
With the continuously increasing demands of plastic products in the current society, the challenge of disposing plastic waste is constantly increasing, leading to the urgent need of mitigating plastic pollution. As a consequence, much attention has been paid to biodegradable plastics due to their degradability in a bio-active environment under certain conditions. Biodegradable plastics herald vast development potentials and considerable market prospects. The degradation of numerous types of biodegradable plastics will be affected by many factors. A thorough understanding of degradation mechanisms as well as functional microbial strains and enzymes is the key to comprehensive utilization and efficient treatment and disposal of biodegradable plastics. The article summarized the types, properties, advantages and disadvantages, and main applications of common biodegradable plastics. The degradation mechanisms, functional microbial strains and enzymes, as well as the degradation degree and duration under different environmental conditions, were also summarized. This review may help better understand the degradation of biodegradable plastics wastes.
Subject(s)
Biodegradable Plastics , Biodegradation, EnvironmentalABSTRACT
Polycyclic aromatic hydrocarbons (PAHs) are a class of persistent pollutants that are widely distributed in the environment. Due to their stable structure and poor degradability, PAHs exhibit carcinogenic, teratogenic, and mutagenic toxicity to the ecological environment and organisms, thus increasing attentions have been paid to their removals and remediation. Green, safe and economical technologies are widely used in the bioremediation of PAHs-contaminated soil. This article summarizes the present status of PAHs pollution in soil of China from the aspects of origin, migration, fate, and pollution level. Meanwhile, the types of microorganisms and plants capable of degrading PAHs, as well as the underlying mechanisms, are summarized. The features of three major bioremediation technologies, i.e., microbial remediation, phytoremediation, and joint remediation, are compared. Analysis of the interaction mechanisms between plants and microorganisms, selection and cultivation of stress-resistant strains and plants, as well as safety and efficacy evaluation of practical applications, are expected to become future directions in this field.
Subject(s)
Biodegradation, Environmental , Polycyclic Aromatic Hydrocarbons/toxicity , Soil , Soil Microbiology , Soil PollutantsABSTRACT
Plastics are widely used in daily life. Due to poor management and disposal, about 80% of plastic wastes were buried in landfills and eventually became land and ocean waste, causing serious environmental pollution. Recycling plastics is a desirable approach, but not applicable for most of the plastic waste. Microbial degradation offers an environmentally friendly way to degrade the plastic wastes, and this review summarizes the potential microbes, enzymes, and the underpinning mechanisms for degrading six most commonly used plastics including polyethylene terephthalate, polyethylene, polyvinyl chloride, polypropylene, polystyrene and polyurethane. The challenges and future perspectives on microbial degradation of plastics were proposed.
Subject(s)
Biodegradation, Environmental , Plastics , Polyurethanes , RecyclingABSTRACT
Objective::To study the degradation of salvianolate lyophilized injection (SLI) and establish a stability-indicating analysis method. Method::UPLC-Q-TOF-MS/MS was used to conduct a qualitative study on the main components of SLI, and a stability-indicating analysis method was established for simultaneous determination of the original components of SLI and its degradation products. The stability of SLI were systematically assessed under physicochemical conditions of high temperature, oxidation, metal ions. Result::Totally 13 main active ingredients in SLI were identified, and a semi-quantitative analysis was performed. Under the conditions of high temperature, oxidation, light, trivalent ion and divalent ion, 6, 4, 3, 4 and 1 new degradation products were added respectively. The established stability-indicating analysis method can simultaneously determine the degradation products of the main components and their active components in SLI, with a good separation effect. Conclusion::According to the degradation mechanism of the main ingredients in SLI, macromolecular polyphenol acid compounds are degraded into small molecular compounds, such as tanshinol and protocatechu aldehyde by a series of reactions, like benzofuran open-loop, hydrolysis of ester bond and removal of DSS. The stability-indicating analysis method can be used for the stability quality control of traditional Chinese medicine Salvianolate Lyophilized Injection (SLI).
ABSTRACT
Anthraquinone dyes, which contain anthraquinone chromophore groups, are the second largest class of dyes after azo dyes and are used extensively in textile industries. The majority of these dyes are resistant to degradation because of their complex and stable structures; consequently, a large number of anthraquinone dyes find their way into the environment causing serious pollution. At present, the microbiological approach to treating printing and dyeing wastewater is considered to be an economical and feasible method, and reports regarding the bacterial degradation of anthraquinone dyes are increasing. This paper reviews the classification and structures of anthraquinone dyes, summarizes the types of degradative bacteria, and explores the possible mechanisms and influencing factors of bacterial anthraquinone dye degradation. Present research progress and existing problems are further discussed. Finally, future research directions and key points are presented.
Subject(s)
Adsorption , Anthraquinones , Chemistry , Classification , Metabolism , Bacteria , Metabolism , Biodegradation, Environmental , Coloring Agents , Chemistry , Classification , Metabolism , Hydrogen-Ion Concentration , TemperatureABSTRACT
Anthraquinone dyes, which contain anthraquinone chromophore groups, are the second largest class of dyes after azo dyes and are used extensively in textile industries. The majority of these dyes are resistant to degradation because of their complex and stable structures; consequently, a large number of anthraquinone dyes find their way into the environment causing serious pollution. At present, the microbiological approach to treating printing and dyeing wastewater is considered to be an economical and feasible method, and reports regarding the bacterial degradation of anthraquinone dyes are increasing. This paper reviews the classification and structures of anthraquinone dyes, summarizes the types of degradative bacteria, and explores the possible mechanisms and influencing factors of bacterial anthraquinone dye degradation. Present research progress and existing problems are further discussed. Finally, future research directions and key points are presented.
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Chlorinated aliphatic hydrocarbons (CAHs) with characteristics of high toxicity, biological accumulation and recalcitrance to degradation as well as carcinogenicity, teratogenesis and mutagenicity, are seriously harmful to human health and ecological environment. CAHs degradation depends on biotic and abiotic responses that exist diversified interactive effects, so it is important to clarify the mechanism of CAHs degradation via biotic and abiotic mutual promoting to significantly enhance the CAHs-contaminated site restoration. In this work, a series of pathways for CAHs degradation was first introduced and summarized as three means on reductive dechlorination, aerobic cometabolism and direct oxidation, and biotic and abiotic typical factors affecting CAHs degradation were concluded from these. Then, mechanisms of induced degradation and synergistic degradation were indicated from the perspective of mutual promoting degradation both with biotic and abiotic responses, and furthermore, the application and technical limitations of CAHs degradation enhanced via biotic and abiotic mutual promoting were reviewed and analyzed. Finally, the development of CAHs degradation technology in future was prospected.
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OBJECTIVE:To establish a method for the separation and detection of related substances in baicalein,identify its structure and preliminarily explore the degradation mechanism. METHODS:HPLC was adopted to detect the baicalein,related impurities and forced destruction of degradation products in synthesis process:the column was ES Industries? FluoroSep-RP Phenyl with mobile phase of 0.3%formic acid-methanol-acetonitrile(gradient elution)at a flow rate of 1.0 mL/min,the detection wavelength was 275 nm,the column temperature was 10℃,and the injection volume was 10μL. LC-MS/MS was conducted to identify the related substances and conjecture degradation mechanism:the column was ES Industries? FluoroSep-RP Phenyl with mobile phase of 0.3%formic acid- methanol (gradient elution)at a flow rate of 1.0 mL/min,the detection wavelength was 275 nm,column temperature was 10℃,and the injection volume was 10μL;ion source was electrospray ion source,positive and negative ions,nebulizer pressure was 55 psi and the drying gas flow was 11 L/min,drying gas temperature was 350℃,capillary voltage was 4.0 kV,detection modes were full-scan first-order MS and selective ion full-scan second-order MS,scan ranges were m/z 100-1000 (first-order MS) and 50-500(second-order MS),ionization voltage was 80-135 eV,and the collision energy was 10-30 eV. RESULTS:The linear range of baicalein was 2.4-480μg/mL(r=0.9999);RSDs of precision,stability and reproducibility tests were lower than 2.0%;the limit of quantitation was 7.2 ng,the limit of detection was 2.4 ng. Baicalein was well separated with related substance and 3 major degradation products,the related substance was chemical synthesis precursor wood butterfly;the degradation products were 6,7-quinone derivatives and 7,8-quinone derivatives,which were isomers;oxidative degradation products were benzoic acid phenyl ester derivatives. CONCLUSIONS:The main mechanisms of alkali degradation and oxidative degradation of baicalein include pyran, reciprocal rearrangement and oxidation reaction;the established method is specific and sensitive,and can be used for the detection of related substances in baicalein.
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We isolated and enriched mixed microorganisms SWA1 from landfill cover soils supplemented with trichloroethylene (TCE). The microbial mixture could degrade TCE effectively under aerobic conditions. Then, we investigated the effect of copper ion (0 to 15 μmol/L) on TCE biodegradation. Results show that the maximum TCE degradation speed was 29.60 nmol/min with 95.75% degradation when copper ion was at 0.03 μmol/L. In addition, genes encoding key enzymes during biodegradation were analyzed by Real-time quantitative reverse transcription PCR (RT-qPCR). The relative expression abundance of pmoA gene (4.22E-03) and mmoX gene (9.30E-06) was the highest when copper ion was at 0.03 μmol/L. Finally, we also used MiSeq pyrosequencing to investigate the diversity of microbial community. Methylocystaceae that can co-metabolic degrade TCE were the dominant microorganisms; other microorganisms with the function of direct oxidation of TCE were also included in SWA1 and the microbial diversity decreased significantly along with increasing of copper ion concentration. Based on the above results, variation of copper ion concentration affected the composition of SWA1 and degradation mechanism of TCE. The degradation mechanism of TCE included co-metabolism degradation of methanotrophs and oxidation metabolism directly at copper ion of 0.03 μmol/L. When copper ion at 5 μmol/L (biodegradation was 84.75%), the degradation mechanism of TCE included direct-degradation and co-metabolism degradation of methanotrophs and microorganisms containing phenol hydroxylase. Therefore, biodegradation of TCE by microorganisms was a complicated process, the degradation mechanism included co-metabolism degradation of methanotrophs and bio-oxidation of non-methanotrophs.
Subject(s)
Biodegradation, Environmental , Copper , Chemistry , Methylocystaceae , Metabolism , Oxidation-Reduction , Soil Microbiology , Trichloroethylene , MetabolismABSTRACT
OBJECTIVE: A phenomenon was found that the content of simvastatin decreased after simvastatin tables was strored for a longtime. But few studies focused on drug quality affected by coating. This article designed a series of experiments to explore this phenomenon. METHODS: Acceleration tests were carried out to study the effect of ingredients of coating and solvent on the stability of simvastatin. Furthermore these degradated impurities were isolated and identified. According to the structure of these impurities, mechanism of reactions was speculated. RESULTS: This study revealed that simvastatin seems like to generate simvastatin acid, dehydrated simvastatin, and simvastatin acid esters in contaction with water, ethanol and aluminum oxide, thus water, ethanol and aluminum oxide might be main reasons for degradation of simvastatin tablets. CONCLUSION: The impact of the coating material and coating solvents should be considered carefully during the screening of simvastatin coating materials.