Dataset Information

Degradation of Plastics under Anaerobic Conditions: A Short Review.

ABSTRACT: Plastic waste is an issue of global concern because of the environmental impact of its accumulation in waste management systems and ecosystems. Biodegradability was proposed as a solution to overcome this problem; however, most biodegradable plastics were designed to degrade under aerobic conditions, ideally fulfilled in a composting plant. These new plastics could arrive to anaerobic environments, purposely or frequently, because of their mismanagement at the end of their useful life. This review analyzes the behavior of biodegradable and conventional plastics under anaerobic conditions, specifically in anaerobic digestion systems and landfills. A review was performed in order to identify: (a) the environmental conditions found in anaerobic digestion processes and landfills, as well as the mechanisms for degradation in those environments; (b) the experimental methods used for the assessment of biodegradation in anaerobic conditions; and (c) the extent of the biodegradation process for different plastics. Results show a remarkable variability of the biodegradation rate depending on the type of plastic and experimental conditions, with clearly better performance in anaerobic digestion systems, where temperature, water content, and inoculum are strictly controlled. The majority of the studied plastics showed that thermophilic conditions increase degradation. It should not be assumed that plastics designed to be degraded aerobically will biodegrade under anaerobic conditions, and an exact match must be done between the specific plastics and the end of life options that they will face.

SUBMITTER: Quecholac-Pina X

PROVIDER: S-EPMC7023122 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Degradation of Plastics under Anaerobic Conditions: A Short Review.

Quecholac-Piña Xochitl X Hernández-Berriel María Del Consuelo MDC Mañón-Salas María Del Consuelo MDC Espinosa-Valdemar Rosa María RM Vázquez-Morillas Alethia A

Polymers 20200105 1

Plastic waste is an issue of global concern because of the environmental impact of its accumulation in waste management systems and ecosystems. Biodegradability was proposed as a solution to overcome this problem; however, most biodegradable plastics were designed to degrade under aerobic conditions, ideally fulfilled in a composting plant. These new plastics could arrive to anaerobic environments, purposely or frequently, because of their mismanagement at the end of their useful life. This revi ...[more]

PMID: 31948016

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Project description:Cell proliferation is achieved by numerous enzyme reactions. Temperature governs the activity of each enzyme, which overall determines the optimal growth temperature. Synthesizing useful chemicals and fuels utilizes only part of the metabolic pathways, especially the central metabolic pathways such as glycolysis and TCA cycle to metabolize glucose. However, the optimal temperature for the activity of the central metabolic pathways is inconclusive whether it is correlated with the optimal temperature for cell proliferation. Here, we found that Corynebacterium glutamicum wild type increased the metabolic activity to consume glucose under anaerobic (oxygen deprived) conditions at 42.5ºC, in which the cell hardly grows under aerobic conditions. Glucose consumption rate was increased by 24% at 42.5ºC compared to that at the optimal growth temperature of 30.0ºC. Transcriptional analysis showed that gapX gene encoding glycelaldehydre-3-phosphate dehydrogenase, glucokinase gene, and a gene involved in glucose uptake were upregulated at 42.5ºC. Production of fermentative lactate was increased by 69% than that at 30.0ºC, whereas succinate production was decreased by 13%. In addition to several glycolytic enzymes, the activity of pyruvate kinase was increased with increasing the temperature, whereas the activity of phosphoenolpyruvate carboxylase in anapleotic pathway leading to succinate synthesis was decreased. However, a metabolically engineered succinate over-producing strain, in which lactate production was shut off and pyruvate carboxylase encoding gene in another anapleotic pathway was overexpressed, produced 34% higher succinate at 42.5ºC than that at 30.0ºC with increased glucose consumption. This study provides the evidence that the optimal reaction temperature for production of fermentative products can be set beyond upper limit of growth temperature in C. glutamicum, and hence it could be applicable for producing various chemicals and fuels in C. glutamicum under anaerobic conditions and non-growing cell reactions in other microorganisms.

Project description:BackgroundAlgae encompass a wide array of photosynthetic organisms that are ubiquitously distributed in aquatic and terrestrial habitats. Algal species often bloom in aquatic ecosystems, providing a significant autochthonous carbon input to the deeper anoxic layers in stratified water bodies. In addition, various algal species have been touted as promising candidates for anaerobic biogas production from biomass. Surprisingly, in spite of its ecological and economic relevance, the microbial community involved in algal detritus turnover under anaerobic conditions remains largely unexplored.ResultsHere, we characterized the microbial communities mediating the degradation of Chlorella vulgaris (Chlorophyta), Chara sp. strain IWP1 (Charophyceae), and kelp Ascophyllum nodosum (phylum Phaeophyceae), using sediments from an anaerobic spring (Zodlteone spring, OK; ZDT), sludge from a secondary digester in a local wastewater treatment plant (Stillwater, OK; WWT), and deeper anoxic layers from a seasonally stratified lake (Grand Lake O' the Cherokees, OK; GL) as inoculum sources. Within all enrichments, the majority of algal biomass was metabolized within 13-16 weeks, and the process was accompanied by an increase in cell numbers and a decrease in community diversity. Community surveys based on the V4 region of the 16S rRNA gene identified different lineages belonging to the phyla Bacteroidetes, Proteobacteria (alpha, delta, gamma, and epsilon classes), Spirochaetes, and Firmicutes that were selectively abundant under various substrate and inoculum conditions. Within all kelp enrichments, the microbial communities structures at the conclusion of the experiment were highly similar regardless of the enrichment source, and were dominated by the genus Clostridium, or family Veillonellaceae within the Firmicutes. In all other enrichments the final microbial community was dependent on the inoculum source, rather than the type of algae utilized as substrate. Lineages enriched included the uncultured groups VadinBC27 and WCHB1-69 within the Bacteroidetes, genus Spirochaeta and the uncultured group SHA-4 within Spirochaetes, Ruminococcaceae, Lachnospiraceae, Yongiibacter, Geosporobacter, and Acidaminobacter within the Firmicutes, and genera Kluyvera, Pantoea, Edwardsiella and Aeromonas, and Buttiauxella within the Gamma-Proteobaceteria order Enterobacteriales.ConclusionsOur results represent the first systematic survey of microbial communities mediating turnover of algal biomass under anaerobic conditions, and highlights the diversity of lineages putatively involved in the degradation process.

Dataset Information

Degradation of Plastics under Anaerobic Conditions: A Short Review.

Publications

Degradation of Plastics under Anaerobic Conditions: A Short Review.

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