The enzyme phosphoketolase ( EC 4.1.2.9 ) catalyzes the chemical reactions
67-593: Phosphoketolase is considered a promiscuous enzyme because it was demonstrated to use 3 different sugar phosphates as substrates. In a recent genetic study, more than 150 putative phosphoketolase genes exhibiting varying catalytic properties were found in 650 analyzed bacterial genomes. This enzyme belongs to the family of lyases , specifically the aldehyde-lyases, which cleave carbon-carbon bonds. It participates in 3 metabolic pathways : pentose phosphate pathway , methane metabolism , and carbon fixation . It employs one cofactor , thiamin diphosphate . Phosphoketolase
134-409: A high catalytic rate towards a particular substrate to produce a particular product, but also to avoid the production of toxic or unnecessary products. For example, if a tRNA synthesis loaded an incorrect amino acid onto a tRNA, the resulting peptide would have unexpectedly altered properties, consequently to enhance fidelity several additional domains are present. Similar in reaction to tRNA synthesis,
201-412: A larger mechanistic elasticity (reaction types) and broader specificities. The liberal drift threshold (caused by the low selective pressure due to the small population size) allows the fitness gain endowed by one of the products to maintain the other activities even though they may be physiologically useless. In biocatalysis , many reactions are sought that are absent in nature. To do this, enzymes with
268-402: A man-made chemical. Enzymes are evolved to catalyze a particular reaction on a particular substrate with high catalytic efficiency ( k cat /K M , cf . Michaelis–Menten kinetics ). However, in addition to this main activity, they possess other activities that are generally several orders of magnitude lower, and that are not a result of evolutionary selection and therefore do not partake in
335-467: A patchwork fashion (hence its name, the patchwork model ). This primordial catalytic versatility was later lost in favour of highly catalytic specialised orthologous enzymes. As a consequence, many central-metabolic enzymes have structural homologues that diverged before the last universal common ancestor . Promiscuity is not only a first trait, but also a very widespread property in modern genomes. A series of experiments have been conducted to assess
402-506: A pseudomonad muconate lactonizing enzyme II, allowing them to promiscuously catalyse the activity of O-succinylbenzoate synthase ( menC ). Conversely, promiscuity can be decreased as was the case of γ-humulene synthase (a sesquiterpene synthase) from Abies grandis that is known to produce 52 different sesquiterpenes from farnesyl diphosphate upon several mutations. Studies on enzymes with broad-specificity—not promiscuous, but conceptually close—such as mammalian trypsin and chymotrypsin, and
469-577: A restrictive regulation, therefore increasing the reaction rate ( v ) of the promiscuous activity of the enzyme making its effects more pronounced physiologically ("gene dosage effect"). On the other, enzymes may evolve an increased secondary activity with little loss to the primary activity ("robustness") with little adaptive conflict (§ Robustness and plasticity below ). A study of four distinct hydrolases (human serum paraoxonase (PON1), pseudomonads phosphotriesterase (PTE), Protein tyrosine phosphatase(PTP) and human carbonic anhydrase II (CAII)) has shown
536-447: A reusable technique that strengthens through further use by limiting the migration space of these cells to target specific areas and not fully consume their cleansing abilities. Despite encouraging results, Actinobacteria has only been used in controlled lab settings and will need further development in finding the cost effectiveness and scalability of use. Bioremediation can be used to mineralize organic pollutants, to partially transform
603-405: A small promiscuous activity towards the required reaction are identified and evolved via directed evolution or rational design . An example of a commonly evolved enzyme is ω-transaminase which can replace a ketone with a chiral amine and consequently libraries of different homologues are commercially available for rapid biomining ( eg. Codexis ). Another example is the possibility of using
670-494: A wide variety of hydrocarbons, including components of gasoline, kerosene, diesel, and jet fuel. Under ideal aerobic conditions, the biodegradation rates of the low- to moderate-weight aliphatic , alicyclic , and aromatic compounds can be very high. As molecular weight of the compound increases, the resistance to biodegradation increases simultaneously. This results in higher contaminated volatile compounds due to their high molecular weight and an increased difficulty to remove from
737-417: Is Lindane which was a commonly used insecticide in the 20th century. Long time exposure poses a serious threat to humans and the surrounding ecosystem. Lindane reduces the potential of beneficial bacteria in the soil such as nitrogen fixation cyanobacteria. As well as causing central nervous system issues in smaller mammals such as seizures, dizziness, and even death. What makes it so harmful to these organisms
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#1732855852806804-514: Is a promiscuous activity as the enzyme catalyses an inactivating reaction towards a novel substrate it did not evolve to catalyse. This could be because of the demonstration that there are only a small number of distinct ligand binding pockets in proteins. Mammalian xenobiotic metabolism , on the other hand, was evolved to have a broad specificity to oxidise, bind and eliminate foreign lipophilic compounds which may be toxic, such as plant alkaloids, so their ability to detoxify anthropogenic xenobiotics
871-445: Is a similar approach used to treat wastes including wastewater, industrial waste and solid waste. The end goal of bioremediation is to remove harmful compounds to improve soil and water quality. Bioventing is a process that increases the oxygen or air flow into the unsaturated zone of the soil, this in turn increases the rate of natural in situ degradation of the targeted hydrocarbon contaminant. Bioventing, an aerobic bioremediation,
938-483: Is a very effective modern technique for restoring natural systems by removing toxins from the environment. Of the many ways to deal with pesticide contamination, bioremediation promises to be more effective. Many sites around the world are contaminated with agrichemicals. These agrichemicals often resist biodegradation, by design. Harming all manners of organic life with long term health issues such as cancer, rashes, blindness, paralysis, and mental illness. An example
1005-429: Is actually a result of a compromise between fidelity and evolvability. For example, for restriction endonucleases incorrect activity ( star activity ) is often lethal for the organism, but a small amount allows new functions to evolve against new pathogens. Plants produce a large number of secondary metabolites thanks to enzymes that, unlike those involved in primary metabolism, are less catalytically efficient but have
1072-466: Is also underway to develop methods to remove metals from water by enhancing the sorption of the metal to cell walls. This approach has been evaluated for treatment of cadmium, chromium, and lead. Genetically modified bacteria has also been explored for use in sequestration of Arsenic. Phytoextraction processes concentrate contaminants in the biomass for subsequent removal. Metal extractions can in principle be performed in situ or ex situ where in situ
1139-636: Is an alternative to bioremediation. While organic pollutants are susceptible to biodegradation , heavy metals cannot be degraded, but rather oxidized or reduced. Typical bioremediations involves oxidations. Oxidations enhance the water-solubility of organic compounds and their susceptibility to further degradation by further oxidation and hydrolysis. Ultimately biodegradation converts hydrocarbons to carbon dioxide and water. For heavy metals, bioremediation offers few solutions. Metal-containing pollutant can be removed, at least partially, with varying bioremediation techniques. The main challenge to bioremediations
1206-504: Is an extension of this. Bioremediation Bioremediation broadly refers to any process wherein a biological system (typically bacteria, microalgae, fungi in mycoremediation , and plants in phytoremediation ), living or dead, is employed for removing environmental pollutants from air, water, soil, flue gasses, industrial effluents etc., in natural or artificial settings. The natural ability of organisms to adsorb, accumulate, and degrade common and emerging pollutants has attracted
1273-414: Is bioventing, which is inexpensive to bioremediate contaminated sites, however, this process is extensive and can take a few years to decontaminate a site. > Another major drawback is finding the right species to perform bioremediation. In order to prevent the introduction and spreading of an invasive species to the ecosystem, an indigenous species is needed. As well as a species plentiful enough to clean
1340-422: Is how quickly distributed it gets through the brain and fatty tissues. While Lindane has been mostly limited to specific use, it is still produced and used around the world. Actinobacteria has been a promising candidate in situ technique specifically for removing pesticides. When certain strains of Actinobacteria have been grouped together, their efficiency in degrading pesticides has enhanced. As well as being
1407-689: Is less cost there is also less of an ability to determine the scale and spread of the pollutant. The pollutant ultimately determines which bioremediation method to use. The depth and spread of the pollutantare other important factors. Heavy metals are introduced into the environment by both anthropogenic activities and natural factors. Anthropogenic activities include industrial emissions, electronic waste, and mining. Natural factors include mineral weathering, soil erosion, and forest fires. Heavy metals including cadmium, chromium, lead and uranium are unlike organic compounds and cannot be biodegraded. However, bioremediation processes can potentially be used to minimize
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#17328558528061474-482: Is not only a compromise between stability and catalytic efficiency, but also for specificity and evolvability, the latter two dictating whether an enzyme is a generalist (highly evolvable due to large promiscuity, but low main activity) or a specialist (high main activity, poorly evolvable due to low promiscuity). Examples of these are enzymes for primary and secondary metabolism in plants (§ Plant secondary metabolism below ). Other factors can come into play, for example
1541-495: Is preferred since it is less expensive to excavate the substrate. Bioremediation is not specific to metals. In 2010 there was a massive oil spill in the Gulf of Mexico . Populations of bacteria and archaea were used to rejuvenate the coast after the oil spill. These microorganisms over time have developed metabolic networks that can utilize hydrocarbons such as oil and petroleum as a source of carbon and energy. Microbial bioremediation
1608-810: Is rate: the processes are slow. Bioremediation techniques can be classified as (i) in situ techniques, which treat polluted sites directly, vs (ii) ex situ techniques which are applied to excavated materials. In both these approaches, additional nutrients, vitamins, minerals, and pH buffers are added to enhance the growth and metabolism of the microorganisms. In some cases, specialized microbial cultures are added ( biostimulation ). Some examples of bioremediation related technologies are phytoremediation , bioventing , bioattenuation, biosparging , composting (biopiles and windrows), and landfarming . Other remediation techniques include thermal desorption , vitrification , air stripping , bioleaching , rhizofiltration , and soil washing. Biological treatment, bioremediation,
1675-435: Is required to be excavated to above ground. While it is an ex situ technique, it can also be considered an in situ technique as Landfarming can be performed at the site of contamination. Ex situ techniques are often more expensive because of excavation and transportation costs to the treatment facility, while i n situ techniques are performed at the site of contamination so they only have installation costs. While there
1742-405: Is the inference and synthesis of a gene from the ancestral form of a group of genes, which has had a recent revival thanks to improved inference techniques and low-cost artificial gene synthesis, resulting in several ancestral enzymes—dubbed "stemzymes" by some —to be studied. Evidence gained from reconstructed enzyme suggests that the order of the events where the novel activity is improved and
1809-432: Is the low bioavailability. Altering the pH and temperature of the contaminated soil is a resolution to increase bioavailability which, in turn, increased degradation of harmful compounds. The compound acrylonitrile is commonly produced in industrial setting but adversely contaminates soils. Microorganisms containing nitrile hydratases (NHase) degraded harmful acrylonitrile compounds into non-polluting substances. Since
1876-423: Is the most common form of oxidative bioremediation process where oxygen is provided as the electron acceptor for oxidation of petroleum , polyaromatic hydrocarbons (PAHs), phenols , and other reduced pollutants. Oxygen is generally the preferred electron acceptor because of the higher energy yield and because oxygen is required for some enzyme systems to initiate the degradation process. Microorganisms can degrade
1943-411: The alkaline phosphatase superfamily, which catalyse hydrolytic reaction on the sulfate, phosphonate, monophosphate, diphosphate or triphosphate ester bond of several compounds. Despite the separation the homologues have a varying degree of reciprocal promiscuity: the differences in promiscuity are due to mechanisms involved, particularly the intermediate required. Enzymes are generally in a state that
2010-488: The action of microbial consortium . Within the consortium, the product of one species could be the substrate for another species. Anaerobic bioremediation can in principle be employed to treat a range of oxidized contaminants including chlorinated ethylenes ( PCE , TCE , DCE , VC) , chlorinated ethanes ( TCA , DCA ), chloromethanes ( CT , CF ), chlorinated cyclic hydrocarbons, various energetics (e.g., perchlorate , RDX , TNT ), and nitrate . This process involves
2077-1157: The addition of an electron donor to: 1) deplete background electron acceptors including oxygen, nitrate, oxidized iron and manganese and sulfate; and 2) stimulate the biological and/or chemical reduction of the oxidized pollutants. The choice of substrate and the method of injection depend on the contaminant type and distribution in the aquifer, hydrogeology, and remediation objectives. Substrate can be added using conventional well installations, by direct-push technology, or by excavation and backfill such as permeable reactive barriers (PRB) or biowalls. Slow-release products composed of edible oils or solid substrates tend to stay in place for an extended treatment period. Soluble substrates or soluble fermentation products of slow-release substrates can potentially migrate via advection and diffusion, providing broader but shorter-lived treatment zones. The added organic substrates are first fermented to hydrogen (H 2 ) and volatile fatty acids (VFAs). The VFAs, including acetate, lactate, propionate and butyrate, provide carbon and energy for bacterial metabolism. During bioattenuation, biodegradation occurs naturally with
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2144-897: The addition of nutrients or bacteria. The indigenous microbes present will determine the metabolic activity and act as a natural attenuation. While there is no anthropogenic involvement in bioattenuation, the contaminated site must still be monitored. Biosparging is the process of groundwater remediation as oxygen, and possible nutrients, is injected. When oxygen is injected, indigenous bacteria are stimulated to increase rate of degradation. However, biosparging focuses on saturated contaminated zones, specifically related to ground water remediation. UNICEF, power producers, bulk water suppliers, and local governments are early adopters of low cost bioremediation, such as aerobic bacteria tablets which are simply dropped into water. Biopiles, similar to bioventing, are used to remove petroleum pollutants by introducing aerobic hydrocarbons to contaminated soils. However,
2211-446: The arylesterase activity. This means firstly that a specialist enzyme (monofunctional) when evolved goes through a generalist stage (multifunctional), before becoming a specialist again—presumably after gene duplication according to the IAD model—and secondly that promiscuous activities are more plastic than the main activity. The most recent and most clear cut example of enzyme evolution is
2278-435: The bifunctional isopropylmalate isomerase/homoaconitase from Pyrococcus horikoshii have revealed that active site loop mobility contributes substantially to the catalytic elasticity of the enzyme. A promiscuous activity is a non-native activity the enzyme did not evolve to do, but arises due to an accommodating conformation of the active site. However, the main activity of the enzyme is a result not only of selection towards
2345-643: The distribution of promiscuous enzyme activities in E. coli . In E. coli 21 out of 104 single-gene knockouts tested (from the Keio collection ) could be rescued by overexpressing a noncognate E. coli protein (using a pooled set of plasmids of the ASKA collection ). The mechanisms by which the noncognate ORF could rescue the knockout can be grouped into eight categories: isozyme overexpression (homologues), substrate ambiguity, transport ambiguity (scavenging), catalytic promiscuity, metabolic flux maintenance (including overexpression of
2412-486: The environment due to the potential of horizontal gene transfer. Genetically modified organisms are classified and controlled under the Toxic Substances Control Act of 1976 under United States Environmental Protection Agency . Measures have been created to address these concerns. Organisms can be modified such that they can only survive and grow under specific sets of environmental conditions. In addition,
2479-522: The environment. Most bioremediation processes involve oxidation-reduction reactions where either an electron acceptor (commonly oxygen) is added to stimulate oxidation of a reduced pollutant (e.g. hydrocarbons) or an electron donor (commonly an organic substrate) is added to reduce oxidized pollutants (nitrate, perchlorate , oxidized metals, chlorinated solvents, explosives and propellants). In both these approaches, additional nutrients, vitamins, minerals, and pH buffers may be added to optimize conditions for
2546-448: The experience with harmful contaminants are limited, laboratory practices are required to evaluate effectiveness, treatment designs, and estimate treatment times. Bioremediation processes may take several months to several years depending on the size of the contaminated area. The use of genetic engineering to create organisms specifically designed for bioremediation is under preliminary research. Two category of genes can be inserted in
2613-423: The extracted groundwater is treated, oxygenated, amended with nutrients and re-injected. However, the amount of oxygen that can be provided by this method is limited by the low solubility of oxygen in water (8 to 10 mg/L for water in equilibrium with air at typical temperatures). Greater amounts of oxygen can be provided by contacting the water with pure oxygen or addition of hydrogen peroxide (H 2 O 2 ) to
2680-480: The first subunit of tyrocidine synthetase ( tyrA ) from Bacillus brevis adenylates a molecule of phenylalanine in order to use the adenyl moiety as a handle to produce tyrocidine , a cyclic non-ribosomal peptide . When the specificity of enzyme was probed, it was found that it was highly selective against natural amino acids that were not phenylalanine, but was much more tolerant towards unnatural amino acids. Specifically, most amino acids were not catalysed, whereas
2747-516: The gene is duplication is not clear cut, unlike what the theoretical models of gene evolution suggest. One study showed that the ancestral gene of the immune defence protease family in mammals had a broader specificity and a higher catalytic efficiency than the contemporary family of paralogues, whereas another study showed that the ancestral steroid receptor of vertebrates was an oestrogen receptor with slight substrate ambiguity for other hormones—indicating that these probably were not synthesised at
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2814-436: The glycerophosphodiesterase ( gpdQ ) from Enterobacter aerogenes shows different values for its promiscuous activities depending on the two metal ions it binds, which is dictated by ion availability. In some cases promiscuity can be increased by relaxing the specificity of the active site by enlarging it with a single mutation as was the case of a D297G mutant of the E. coli L-Ala-D/L-Glu epimerase ( ycjG ) and E323G mutant of
2881-494: The large component of a synthase in the absence of the amine transferase subunit), pathway bypass, regulatory effects and unknown mechanisms. Similarly, overexpressing the ORF collection allowed E. coli to gain over an order of magnitude in resistance in 86 out 237 toxic environment. Homologues are sometimes known to display promiscuity towards each other's main reactions. This crosswise promiscuity has been most studied with members of
2948-531: The last common ancestor of the paralogues was mainly active on maltose-like substrates with only trace activity for isomaltose-like sugars, despite leading to a lineage of iso-maltose glucosidases and a lineage that further split into maltose glucosidases and iso-maltose glucosidases. Antithetically, the ancestor before the latter split had a more pronounced isomaltose-like glucosidase activity. Roy Jensen in 1976 theorised that primordial enzymes had to be highly promiscuous in order for metabolic networks to assemble in
3015-497: The main activity and are under neutral selection. Despite ordinarily being physiologically irrelevant, under new selective pressures, these activities may confer a fitness benefit therefore prompting the evolution of the formerly promiscuous activity to become the new main activity. An example of this is the atrazine chlorohydrolase ( atzA encoded) from Pseudomonas sp. ADP evolved from melamine deaminase ( triA encoded), which has very small promiscuous activity toward atrazine,
3082-411: The main activity is "robust" towards change, whereas the promiscuous activities are weak and more "plastic". Specifically, selecting for an activity that is not the main activity (via directed evolution ), does not initially diminish the main activity (hence its robustness), but greatly affects the non-selected activities (hence their plasticity). The phosphotriesterase (PTE) from Pseudomonas diminuta
3149-418: The microorganism Dehalococcoides can further reduce DCE and VC to the non-toxic product ethene. The molecular pathways for bioremediation are of considerable interest. In addition, knowing these pathways will help develop new technologies that can deal with sites that have uneven distributions of a mixture of contaminants. Biodegradation requires microbial population with the metabolic capacity to degrade
3216-434: The microorganisms. In some cases, specialized microbial cultures are added ( bioaugmentation ) to further enhance biodegradation. Approaches for oxygen addition below the water table include recirculating aerated water through the treatment zone, addition of pure oxygen or peroxides, and air sparging . Recirculation systems typically consist of a combination of injection wells or galleries and one or more recovery wells where
3283-599: The mobility of these material in the subsurface, lowering the potential for human and environmental exposure. Heavy metals from these factors are predominantly present in water sources due to runoff where it is uptake by marine fauna and flora. Hexavalent chromium (Cr[VI]) and uranium (U[VI]) can be reduced to less mobile and/or less toxic forms (e.g., Cr[III], U[IV]). Similarly, reduction of sulfate to sulfide (sulfidogenesis) can be used to immobilize certain metals (e.g., zinc , cadmium ). The mobility of certain metals including chromium (Cr) and uranium (U) varies depending on
3350-418: The next most catalysed native amino acid was the structurally similar tyrosine, but at a thousandth as much as phenylalanine, whereas several unnatural amino acids where catalysed better than tyrosine, namely D-phenylalanine, β-cyclohexyl-L-alanine, 4-amino-L-phenylalanine and L-norleucine. One peculiar case of selected secondary activity are polymerases and restriction endonucleases, where incorrect activity
3417-513: The organism: degradative genes, which encode proteins required for the degradation of pollutants, and reporter genes, which encode proteins able to monitor pollution levels. Numerous members of Pseudomonas have been modified with the lux gene for the detection of the polyaromatic hydrocarbon naphthalene. A field test for the release of the modified organism has been successful on a moderately large scale. There are concerns surrounding release and containment of genetically modified organisms into
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#17328558528063484-410: The oxidation state of the material. Microorganisms can be used to lower the toxicity and mobility of chromium by reducing hexavalent chromium, Cr(VI) to trivalent Cr(III). Reduction of the more mobile U(VI) species affords the less mobile U(IV) derivatives. Microorganisms are used in this process because the reduction rate of these metals is often slow in the absence of microbial interactions Research
3551-537: The physiology of the organism. This phenomenon allows new functions to be gained as the promiscuous activity could confer a fitness benefit under a new selective pressure leading to its duplication and selection as a new main activity. Several theoretical models exist to predict the order of duplication and specialisation events, but the actual process is more intertwined and fuzzy (§ Reconstructed enzymes below ). On one hand, gene amplification results in an increase in enzyme concentration, and potentially freedom from
3618-415: The pollutant. The biological processes used by these microbes are highly specific, therefore, many environmental factors must be taken into account and regulated as well. It can be difficult to extrapolate the results from the small-scale test studies into big field operations. In many cases, bioremediation takes more time than other alternatives such as land filling and incineration . Another example
3685-468: The pollutants, or alter their mobility. Heavy metals and radionuclides generally cannot be biodegraded, but can be bio-transformed to less mobile forms. In some cases, microbes do not fully mineralize the pollutant, potentially producing a more toxic compound. For example, under anaerobic conditions, the reductive dehalogenation of TCE may produce dichloroethylene (DCE) and vinyl chloride (VC), which are suspected or known carcinogens . However,
3752-407: The process of bioremediation. Landfarming , or land treatment, is a method commonly used for sludge spills. This method disperses contaminated soil and aerates the soil by cyclically rotating. This process is an above land application and contaminated soils are required to be shallow in order for microbial activity to be stimulated. However, if the contamination is deeper than 5 feet, then the soil
3819-488: The promiscuous activities of cysteine synthase ( cysM ) towards nucleophiles to produce non-proteinogenic amino acids . Similarity between enzymatic reactions ( EC ) can be calculated by using bond changes, reaction centres or substructure metrics ( EC-BLAST Archived 2019-05-30 at the Wayback Machine ). Whereas promiscuity is mainly studied in terms of standard enzyme kinetics, drug binding and subsequent reaction
3886-567: The rise of bioremediating enzymes in the past 60 years. Due to the very low number of amino acid changes, these provide an excellent model to investigate enzyme evolution in nature. However, using extant enzymes to determine how the family of enzymes evolved has the drawback that the newly evolved enzyme is compared to paralogues without knowing the true identity of the ancestor before the two genes diverged. This issue can be resolved thanks to ancestral reconstruction. First proposed in 1963 by Linus Pauling and Emile Zuckerkandl, ancestral reconstruction
3953-425: The soil is excavated and piled with an aeration system. This aeration system enhances microbial activity by introducing oxygen under positive pressure or removes oxygen under negative pressure. Windrow systems are similar to compost techniques where soil is periodically turned in order to enhance aeration. This periodic turning also allows contaminants present in the soil to be uniformly distributed which accelerates
4020-437: The soil. Bioremediation can be carried out by bacteria that are naturally present. In biostimulation, the population of these helpful bacteria can be increased by adding nutrients. Bacteria can in principle be used to degrade hydrocarbons. Specific to marine oil spills, nitrogen and phosphorus have been key nutrients in biodegradation. The bioremediation of hydrocarbons suffers from low rates. Bioremediation can involve
4087-424: The time. This variability in ancestral specificity has not only been observed between different genes, but also within the same gene family. In light of the large number of paralogous fungal α-glucosidase genes with a number of specific maltose-like (maltose, turanose, maltotriose, maltulose and sucrose) and isomaltose-like (isomaltose and palatinose) substrates, a study reconstructed all key ancestors and found that
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#17328558528064154-494: The tracking of modified organisms can be made easier with the insertion of bioluminescence genes for visual identification. Genetically modified organisms have been created to treat oil spills and break down certain plastics (PET). Additive manufacturing technologies such as bioprinting offer distinctive benefits that can be leveraged in bioremediation to develop structures with characteristics tailored to biological systems and environmental cleanup needs, and even though
4221-503: The use of biological resources in treatment of contaminated environment. In comparison to conventional physicochemical treatment methods bioremediation may offer advantages as it aims to be sustainable, eco-friendly, cheap, and scalable. Most bioremediation is inadvertent, involving native organisms. Research on bioremediation is heavily focused on stimulating the process by inoculation of a polluted site with organisms or supplying nutrients to promote their growth. Environmental remediation
4288-439: The water. In some cases, slurries of solid calcium or magnesium peroxide are injected under pressure through soil borings. These solid peroxides react with water releasing H 2 O 2 which then decomposes releasing oxygen. Air sparging involves the injection of air under pressure below the water table. The air injection pressure must be great enough to overcome the hydrostatic pressure of the water and resistance to air flow through
4355-414: The whole site without exhausting the population. Finally the species should be resilient enough to withstand the environmental conditions. These specific criteria may make it difficult to perform bioremediation on a contaminated site. In agricultural industries, the use of pesticides is a top factor in direct soil contamination and runoff water contamination. The limitation or remediation of pesticides
4422-405: Was evolved to become an arylesterase (P–O to C–O hydrolase) in eighteen rounds gaining a 10 shift in specificity (ratio of K M ), however most of the change occurred in the initial rounds, where the unselected vestigial PTE activity was retained and the evolved arylesterase activity grew, while in the latter rounds there was a little trade-off for the loss of the vestigial PTE activity in favour of
4489-645: Was previously used for biotechnological purposes as it enables the construction of synthetic pathways that allow complete carbon conservation without the generation of reducing power . This EC 4.1 enzyme -related article is a stub . You can help Misplaced Pages by expanding it . Promiscuous activities Enzyme promiscuity is the ability of an enzyme to catalyze an unexpected side reaction in addition to its main reaction. Although enzymes are remarkably specific catalysts, they can often perform side reactions in addition to their main, native catalytic activity. These wild activities are usually slow relative to
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