Carbohydrates are monomers or polymers of ..
Which of the factors below weaken the hypothesis of abiotic synthesis of organic monomers ..
19/01/2018 · Fatimah Alshehrei
Biodegradable plastics are materials designed to degrade under environmental conditions or in municipal and industrial biological waste treatment facilities, and thus open the way for new waste management strategies . Some strains of Microorganisms can produce Polyhydroxy Alkonates (PHA), a bio plastic that is safe, has no toxic effects and can be easily biodegraded . This study focuses on the role of microorganisms in the biodegradation of synthetic and natural plastics polymers, and describes the biodegradation pathways.
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Tokiwa and Jarerat (2003) investigated the distribution and phylogenetic affiliation of polymer-degraders among actinomycetes obtained from culture collections. PHB-degraders were widely distributed among the families of Pseudonocardiaceae and the related genera micromonosporaceae, Thermonosporaceae, Streptosporangiaceae and Streptomycetaceae . Finally, Tansengco and Tokiwa (1998) investigated the biodegradability of spp. TT96, Thermotolerant ST-01 and strain MG respectively, against the PHAS .
Biodegradation of Synthetic and Natural Plastic by Microorganisms
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Plastic disposal is one of the greatest problems facing the environment today, as vast amounts of synthetic plastic remain non degradable. A number of microorganisms have the ability to degrade different types of plastic under suitable conditions, but due to the hardness of these polymers and their non-solubility in water, biological decomposition is a slow process. Natural plastics are made from plant and animal sources, or produced by a range of microorganisms, must be introduced. Some bacterial strains can produce and store bioplastics using carbon sources under suitable fermentation conditions. Such biomaterials are called polyhydroxyalkanoates (PHA) or biological polyester. They are safe, have no toxic by-products and can be degraded easily by microorganisms.
2. Tyler: When looking at life on Earth and the abiotic synthesis of polymers they are three stages to consider. The first step is the abiotic synthesis of small organic molecules in the origin of life, which then leads us to the abiotic synthesis of polymers. Enzymes catalyze in a cell that then join monomers that build polymers, which there are concerns into whether or not this could have happened. One of the key steps in the origin of life is the isolation of a collection of organic molecules within a membrane enclosed compartment, which is called formation of protocells. Once this happens we move to self replicating RNA, which when RNA is added to a RNA monomer new RNA molecules complementary to parts of the starting RNA sometimes assemble then monomers would adhire to clay particles and this is where the use of RNA world came into context. (Reece, Taylor, Simon, & Dickey, 2012).
Journal of Applied & Environmental Microbiology
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Microorganisms are able attach to a polymer’s surface, as long as the latter is hydrophilic. Once the organism is attached to the surface, it is able to grow using the polymer as its carbon source. In the primary degradation stage, the extracellular enzymes secreted by the organism cause the main chain to cleave, leading to the formation of low-molecular weight fragments, like oligomers, dimers or monomers. These low molecular weight compounds are further used by the microbes as carbon and energy sources. Small oligomers may also diffuse into the organism and get assimilated in its internal environment. These reaction pathways are illustrated in .
Anaerobic and aerobic biodegradation mechanism pathways are given in . Extracellular and intracellular depolymerize enzymes are actively involved in biological degradation of polymers. During degradation, microbial exoenzymes break down complex polymers, yielding short chains or smaller molecules like oligomers, dimers and monomers. These molecules are small enough to be water-soluble, and can pass through the semi-permeable outer bacterial membranes to be used as carbon and energy sources. This initial process of breaking down polymers is called depolymerization; and when the end products are inorganic species (e.g., CO2, H2O, or CH4), the degradation is called mineralization .
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Macromolecules and Their Monomeric Subunits
Primary Productivity & Dissolved Oxygen Lab - …
LabBench Activity Dissolved Oxygen and Aquatic Primary Productivity
Biological degradation of plastics: A comprehensive …
by Theresa Knapp Holtzclaw
The Thiol-Michael Addition Click Reaction: A Powerful …
The key attribute of the thiol-Michael addition reaction that makes it a prized tool in materials science is its modular “click” nature, which allows for the implementation of this highly efficient, “green” reaction in applications that vary from small molecule synthesis to in situ polymer modifications in biological systems to the surface functionalization of material coatings. Over the past few decades, interest in the thiol-Michael addition reaction has increased dramatically, as is evidenced by the number of studies that have been dedicated to elucidating different aspects of the reaction that range from an in-depth analysis aimed at understanding the mechanistic pathways of the reaction to synthetic studies that have examined modifying molecular structures with the aim of yielding highly efficient thiol-Michael reaction monomers. This review examines the reaction mechanisms, the substrates and catalysts used in the reaction, and the subsequent implementation of the thiol-Michael reaction in materials science over the years, with particular emphasis on the recent developments in the arena over the past decade.
There are plenty of ideas, but few clear facts
Synthetic Plastics are classified according to the characteristics of the reactions by which they are formed. If all atoms in the monomers are incorporated into a polymer, the polymer is called an ; if some monomer atoms are released into small molecules, such as water, the polymer is called a . Most addition polymers are made from monomers containing a double bond between carbon atoms. Such monomers are called , and most commercial addition polymers are . are made from monomers that have two different groups of atoms that can join together, such as ester or amide links. They include polymers like polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyurethane and polyethylene terephthalate, shown in .
Molecules | An Open Access Journal from MDPI
The chemical properties of plastics can be used as criteria for differentiating them into degradable and non-degradable polymers . Non-biodegradable plastics, usually known as synthetic plastics, are derived from petrochemicals. They have a lot of repetitions of small monomer units; make them a very high molecular weight.
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