what can be added to nh3 and nh4 to render it inert

AMMONIA Assimilation AND AMINO ACID BIOSYNTHESIS

P.J. LEA , in Techniques in Bioproductivity and Photosynthesis (Second Edition), 1985

Publisher Summary

This chapter discusses ammonia assimilation and amino acid biosynthesis. Ammonia is toxic to all living things; if the internal concentration within a plant cell rises to a higher place 1.0 mM, all photosynthetic reactions within the chloroplast are switched off. It is therefore essential that the ammonia is alloyed rapidly and efficiently and is carried out by the enzyme glutamine synthetase. The enzyme has a very loftier affinity for ammonia and tin can remove the compound from solution at levels equally low as ane.0 μM. In the leaf, the majority of glutamine synthetase is nowadays in the chloroplast but a second different form is too nowadays in the cytoplasm. The ammonia is initially assimilated into the amide position. The enzyme glutamate synthase carries out the transfer of the amide nitrogen to ii-oxoglutarate to yield glutamate. The enzyme requires reducing power, which is either supplied as reduced ferredoxin or nicotinamide adenine dinucleotide hydride. Thus a two-step reaction carries out the process of ammonia assimilation, which is known as the glutamate synthase cycle. This ammonia is immediately reassimilated by the glutamate synthase cycle at a rate in C ₃ plants that may be 10 times higher than that of nitrate reduction. In C₄ plants where photorespiration rates are lower, the requirements for ammonia reassimilation are less.

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Amino Acid Synthesis☆

50. Reitzer , in Reference Module in Biomedical Sciences, 2014

Ammonia Assimilation and Metabolism of Glutamate and Glutamine

The syntheses of glutamine and glutamate are the master mechanisms for ammonia assimilation. Glutamine synthetase (GS) is the merely enzyme that synthesizes glutamine, but two enzymes synthesize glutamate–glutamate dehydrogenase (GDH) and glutamate synthase, which aminate α-ketoglutarate with ammonia and glutamine, respectively ( Effigy 2 ). Either GS or GDH can be the major ammonia assimilatory enzyme ( Figure ii ). Their K_m south for ammonia are about 0.ane and ii   mM, respectively. GDH-dependent ammonia assimilation does not consume free energy, but GS-dependent assimilation does. GS is the master enzyme of ammonia assimilation when either the ammonia concentration is depression, or free energy is not limiting ( Figure 2(a) ). GS also metabolically traps ammonia, which is important during nitrogen-limited growth, when ammonia can leak through the membrane. Whenever GS is the master road of ammonia absorption, glutamate synthase synthesizes glutamate ( Figure ii(a) ). Cells without either GS or glutamate synthase neglect to utilize nigh organic nitrogen sources. GDH assimilates ammonia when energy is limiting ( Figure 2(b) ). Mutants lacking GDH abound less well in carbon-limited medium.

Figure 2. Glutamine and glutamate synthesis, ammonia assimilation, and their control. (a) The reactions with energy backlog. (b) The reactions during energy-limited growth. (c) The regulatory proteins that control GS adenylyiation, GS synthesis, and the Ntr response: solid symbols, nitrogen limitation; open up symbols, nitrogen excess. α-Ketoglutarate antagonizes the actions of P_II in nitrogen excess conditions.

Glutamate and glutamine are not only the main products of ammonia assimilation, simply they are also the nitrogen donors for the synthesis of essentially all nitrogen-containing compounds. Glutamate provides approximately 72% of the cell'southward nitrogen, generally via reversible transaminations, while glutamine provides approximately 28% of the nitrogen for synthesis of histidine, tryptophan, asparagine, purines, pyrimidines, amino sugars, and p-aminobenzoate. In free energy-rich media, glutamine's amide besides provides the nitrogen for glutamate synthesis.

Glutamate also contributes to other functions. Glutamate is the precursor for proline, arginine, and the polyamine putrescine. Glutamate decarboxylation is required for resistance to extreme acid (pH   ≤   2). The decarboxylation consumes a proton, and the product, γ-aminobutyrate, is exported by an exchange reaction, which brings in another molecule of glutamate. Glutamate is an osmotically regulated anion. Its concentration varies in parallel with K⁺. This covariation has at least one known part: K⁺ accumulation increases the internal pH, which glutamate counterbalances past lowering the pH.

Both glutamate and glutamine can exist used as sole nitrogen sources but are non good carbon sources for E. coli. Even though glutamine is the signal of nitrogen sufficiency (described below), glutamine equally a nitrogen source limits growth and induces the Ntr response. Glutamate synthase may be the most important glutamine catabolic enzyme, although several enzymes with glutaminase activeness take also been detected. Eastward. coli does not possess a catabolic GDH. Instead, glutamate might be degraded past transamination-dependent transfer of the nitrogen to aspartate, and aspartate degradation to fumarate and ammonia.

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Nitrogen Bicycle, Biological

Elisabeth A. Holland , Antje Yard. Weitz , in Encyclopedia of Physical Science and Technology (3rd Edition), 2003

III.C Ammonia Assimilation and Plant Nitrogen Uptake

Autotroph organisms assimilate inorganic nitrate (NO_iii ⁻) ions into their body substances subsequently conversion of NO₃ ⁻ into ammonium. The combined process of nitrate reduction and ammonia assimilation is referred to equally the assimilatory nitrate reduction. Immoblization of nitrogen into organic N reduces the probability of nitrogen loss from the ecosystem.

Inorganic nitrogen (NO₂ ⁻ and NO₃ ⁻) molecules may enter the biological N cycle through plant uptake via roots or leaves. Plants assimilate inorganic nitrate dissolved in soil pore h2o or jump exchangeably to soil particles with the h2o sucked through the root tissue into the plant internal transport flow. Stomata dynamics control the transpiration flow and, thus indirectly, the root nutrient uptake. Agronomists use the NO₃ ⁻ concentration of the establish sap flow to evaluate the plant nitrogen supply. Stomata conductivity controls the uptake of gaseous nitrogen (NO₂) from the atmosphere into leaves through passive diffusive ship. Atmospheric NO₂ together with carbon dioxide (CO₂) diffuses through the stomata opening. Inside the leaf, NO₂ dissolves into the intercellular water of the stomata tissue and gets transformed to NO₂ ⁻ or NO_iii ⁻. In constitute cells, inorganic nitrogen may be assimilated into the biological nitrogen cycle through direct incorporation into organic compounds or after reduction by the enzyme nitrate reductase. Isotope studies suggest that assimilated atmospheric nitrogen may be allocated in any growing office of the institute. Direct uptake of nitrogen deposited from the atmosphere onto above-ground plant surfaces (cuticula, bawl) is of pocket-size importance for the nitrogen supply of plants.

Until recently, it was thought that all N taken up by plants was taken upwards as a mineral form (NH₄ ⁺ and NO₃ ⁻) through their roots or every bit a gas through leaves and stomata (NH₃, NO, NO_two, or HNO₃). In that location is an accumulating body of evidence to propose that plant roots are capable of taking upward relatively simply amino acids direct, thus bypassing N mineralization (Näsholm et al., 1999; Schimel and Chapin, 1996). This pathway is particularly important for boreal and tundra plants. Plant associations with mycorrhizal fungi may too play an inportant role in the nitrogen nutrition of plants through increasing surface area available for absorption and the production of proteases.

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Agricultural and Related Biotechnologies

R.R. Pathak , ... N. Raghuram , in Comprehensive Biotechnology (Second Edition), 2011

4.16.4.3 Manipulating Genes of N Assimilation

Several attempts at transgenic manipulation of the enzymes of primary and secondary assimilation have been fabricated as described in Table 1 . Primary nitrate assimilation involves NR, NiR, plastidic GS (GS2), and Fd-GOGAT, while cytosolic GS (GS1) and NADH-GOGAT are a office of secondary ammonia assimilation and remobilization. NR is considered as a rate-limiting step in nitrate metabolism. In that location have been reports of overexpression of two genes nia1 and nia2 for NR in Arabidopsis, tobacco, murphy, and lettuce, without whatever specific comeback in NUE. Similarly, little improvement in phenotype and NiR activity levels were observed when nii factor was overexpressed in tobacco and Arabidopsis under CaMV 35S promoter, though in that location was an increase in the NiR transcript level. Overexpression of GS2 has as well been reported in rice and tobacco, but no pregnant comeback in terms of NUE was observed. Though, transgenic tobacco plants overexpressing GS showing improved capacity for photorespiration and an increased tolerance to drought while transgenic rice plants showed only better growth rate. The potential of transgenic plants with overexpressed Fd-GOGAT gene has not been tested yet, although barley mutants with reduced Fd-GOGAT revealed changes in various nitrogenous metabolites, decreased leaf protein, rubisco activity, and nitrate contents.

The genes of secondary ammonia absorption take also been overexpressed in a diverseness of crops for developing transgenic with enhanced NUE. GS1 has emerged as a potential candidate from among all the genes that have been tested so far. Overexpression of GS1 factor has been tried in several plants such as wheat, tobacco, and maize have resulted in college grain yield and biomass with improved N content. Transgenic overexpression and antisense technology has been employed to modulate the expression of NADH-GOGAT gene in rice and alfalfa plants. Though the genes of secondary ammonia assimilation appear to be good candidates for improving NUE in short run, the results may vary with crop to crop variation.

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Examples of Pathway Manipulations: Metabolic Engineering science in Exercise

Gregory N. Stephanopoulos , ... Jens Nielsen , in Metabolic Engineering, 1998

half-dozen.4.1. ALTERATION OF NITROGEN METABOLISM

An early success of metabolic engineering was the alteration of the nitrogen assimilation pathway of the methylotrophic bacterium Methylophilus methylotrophus to enhance the yield of single-cell protein (scp). M. methylotrophus was the industrial pick for the production of scp from methanol due to its high carbon conversion efficiency, methanol tolerance, and nutritional profile. However, the ammonia absorption pathway of this organism has a major drawback: it utilizes the glutamine synthase (GS) and glutamate synthase system (GOGAT) that requires mol of ATP for every mole of ammonia transported into the prison cell (encounter Section ii.4.ane). In contrast, the respective e. coli nitrogen absorption pathway uses glutamate dehydrogenase (GDH), which requires no ATP consumption (Fig. 6.18). G. methylotrophus probably uses the energetically suboptimal pathway for ammonia assimilation because it evolved in an environs of depression ammonia concentrations, every bit GS has a much higher affinity for ammonia than GDH. The glutamate dehydrogenase gene (gdh) of due east. coli cloned on a shuttle vector was shown to complement gs mutants of M. methylotrophus (Windass et al., 1980). As a result, the engineered organism exhibited college methanol conversion into cellular carbon, presumably because ammonia utilization is more energy-efficient via GDH than via the coupled GS/GOGAT pathway. The efficiency of carbon conversion was increased by four-seven%.

Figure 6.xviii. Pathways of bacterial ammonia assimilation.

This work, which was one of the first industrial applications of metabolic engineering, illustrated that the properties of organisms that evolved to maximize the chances for survival in their natural habitat are non necessarily optimal in the artificial environment of a large-scale bioreactor.

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Media for industrial fermentations

Peter F. Stanbury , ... Stephen J. Hall , in Principles of Fermentation Engineering (Tertiary Edition), 2017

Nitrogen sources

Examples of commonly used nitrogen sources

Most industrially used microorganisms can utilize inorganic or organic sources of nitrogen. Inorganic nitrogen may be supplied every bit ammonia gas, ammonium salts, or nitrates (Hutner, 1972). Ammonia has been used for pH control and as the major nitrogen source in a defined medium for the commercial production of human serum albumin by Saccharomyces cerivisiae (Collins, 1990). Ammonium salts such as ammonium sulfate will usually produce acid weather as the ammonium ion is utilized and the gratis acid will exist liberated. On the other hand nitrates will normally cause an alkali metal drift as they are metabolized. Ammonium nitrate will beginning crusade an acrid drift equally the ammonium ion is utilized, and nitrate assimilation is repressed. When the ammonium ion has been exhausted, at that place is an alkaline drift as the nitrate is used equally an alternative nitrogen source (Morton & MacMillan, 1954). One exception to this blueprint is the metabolism of Gibberella fujikuroi (Infringe et al., 1961, 1964 ). In the presence of nitrate the assimilation of ammonia is inhibited at pH 2.eight–3.0. Nitrate assimilation continues until the pH has increased enough to allow the ammonia assimilation mechanism to restart.

Organic nitrogen may exist supplied equally amino acid, protein or urea, or in a complex media as yeast excerpt. In many instances growth will be faster with a supply of organic nitrogen, and a few microorganisms take an absolute requirement for amino acids. Information technology might be thought that the main industrial need for pure amino acids would be in the deliberate addition to amino acrid requiring mutants used in amino acid production. Notwithstanding, amino acids are more commonly added every bit complex organic nitrogen sources, which are nonhomogeneous, cheaper, and readily bachelor. In lysine production, methionine and threonine are obtained from soybean hydrolysate since it would exist likewise expensive to utilise the pure amino acids (Nakayama, 1972a).

Other proteinaceous nitrogen compounds serving as sources of amino acids include corn-steep liquor (come across also carbon sources), soya meal, peanut meal, cotton fiber-seed meal (Pharmamedia, Table 4.viii; and Proflo), Distillers' solubles meal, and yeast extract. Analysis of many of these products which include amino acids, vitamins, and minerals are given by Miller and Churchill (1986) and Atkinson and Mavituna (1991a). In storage these products may be afflicted by wet, temperature changes, and ageing.

Table iv.viii. The Limerick of Pharmamedia (Traders Protein, Southern Cotton Oil Company, Division of Archer Dariels Midland Co.)

Component	Quantity
Total solids	99%
Carbohydrate	24.one%
Reducing sugars	1.2%
Nonreducing sugars	1.ii%
Poly peptide	57%
Amino nitrogen	4.7%
Components of amino nitrogen
Lysine	4.5%
Leucine	6.1%
Isoleucine	3.iii%
Threonine	3.3%
Valine	4.vi%
Phenylalanine	5.9%
Tryptophan	1.0%
Methionine	1.v%
Cystine	1.5%
Aspartic acid	nine.seven%
Serine	four.6%
Proline	3.9%
Glycine	3.8%
Alanine	3.9%
Tyrosine	three.4%
Histidine	iii.0%
Arginine	12.3%
Mineral components
Calcium	two,530 ppm
Chloride	685 ppm
Phosphorus	13,100 ppm
Atomic number 26	94 ppm
Sulphate	18,000 ppm
Magnesium	seven,360 ppm
Potassium	17,200 ppm
Fatty	4.five%
Vitamins
Ascorbic acrid	32.0 mg kg–1
Thiamine	4.0 mg kg–1
Riboflavin	four.8 mg kg–1
Niacin	83.3 mg kg–i
Pantothenic acrid	12.4 mg kg–1
Choline	3,270 mg kg–ane
Pyidoxine	16.four mg kg–1
Biotin	one.v mg kg–i
Folic acid	1.6 mg kg–1
Inositol	10,800 mg kg–1

Chemically defined amino acid media devoid of protein are necessary in the production of certain vaccines when they are intended for human employ.

Factors influencing the choice of nitrogen source

Control mechanisms exist past which nitrate reductase, an enzyme involved in the conversion of nitrate to ammonium ion, is repressed in the presence of ammonia (Brown, MacDonald, & Meers, 1974). For this reason ammonia or the ammonium ion is the preferred nitrogen source. In fungi that have been investigated, the ammonium ion represses uptake of amino acids by general and specific amino acid permeases (Whitaker, 1976). In Aspergillus nidulans, ammonia too regulates the product of alkaline metal and neutral proteases (Cohen, 1973). Therefore, in mixtures of nitrogen sources, private nitrogen components may influence metabolic regulation then that there is preferential absorption of one component until its concentration has diminished.

Information technology has been shown that antibody production by many microorganisms is influenced past the type and concentration of the nitrogen source in the civilisation medium (Aharonowitz, 1980). Antibiotic production may be inhibited by a quickly utilized nitrogen source ( $\text{N}{\text{H}}_4^{+},\text{N}{\text{O}}_{\mathrm{three}}^{-},$ and certain amino acids). The antibiotic production only begins to increase in the culture broth after most of the nitrogen source has been consumed.

In shake flask media experiments, salts of weak acids (eg, ammonium succinate) may be used to serve equally a nitrogen source and eradicate the source of a potent acid pH change due to chloride or sulfate ions which would be present if ammonium chloride or sulfate were used as the nitrogen source. This procedure makes it possible to employ lower concentrations of phosphate to buffer the medium. Loftier phosphate concentrations inhibit product of many secondary metabolites (see section: Minerals).

The utilise of circuitous nitrogen sources for antibody production has been a common practice. They are idea to help create physiological conditions in the trophophase, which favor antibiotic product in the idiophase (Martin & McDaniel, 1977). For case, in the production of polyene antibiotics, soybean meal has been considered a good nitrogen source because of the balance of nutrients, the low phosphorus content, and tiresome hydrolysis. It has been suggested that this gradual breakup prevents the aggregating of ammonium ions and repressive amino acids. These are probably some of the reasons for the selection of ideal nitrogen sources for some secondary metabolites (Table 4.ix).

Table 4.ix. Best Nitrogen Sources for Some Secondary Metabolites

Product	Primary Nitrogen Source(southward)	References
Penicillin	Corn-steep liquor	Moyer and Coghill (1946)
Bacitracin	Peanut granules	Inskeep, Benett, Dudley, and Shepard (1951)
Riboflavin	Pancreatic digest of gelatine	Malzahn, Phillips, and Hanson (1959)
Novobiocin	Distillers' solubles	Hoeksema and Smith (1961)
Rifomycin	Pharmamedia	Sensi and Thiemann (1967)
	Soybean meal, (NH4)2So4
Gibberellins	Ammonium common salt and natural plant nitrogen source	Jefferys (1970)
Butirosin	Dried beef blood or haemoglobin with (NH4)iiSO4	Claridge, Bush, Defuria, and Price (1974)
Polyenes	Soybean meal	Martin and McDaniel (1977)

In gibberellin production the nitrogen source has been shown to accept an influence on directing the production of different gibberellins and the relative proportions of each type (Jefferys, 1970).

Other predetermined aspects of the process can too influence the option of nitrogen source. Rhodes (1963) has shown that the optimum concentration of available nitrogen for griseofulvin production showed some variation depending on the form of inoculum and the type of fermenter being used. Evidently these factors must be borne in mind in the interpretation of results in media-development programs.

Some of the complex nitrogenous material may not exist utilized by a microorganism and create problems in downstream processing and effluent treatment. This tin be an important factor in the final pick of substrate.

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Omics Approaches for Designing Biofuel Producing Cocultures for Enhanced Microbial Conversion of Lignocellulosic Substrates

David B. Levin , ... Richard Sparling , in Directly Microbial Conversion of Biomass to Advanced Biofuels, 2015

Nutrient Complementation in Cellulolytic Cocultures

No naturally occurring organism identified to date is capable of effective depolymerization of lignocelluloses and complete utilization of derived soluble oligomers or monomers, which is the central theme of CBP. Still, robust co-beingness of microbial consortia are abundant in nature, which achieve more than challenging tasks through mutually beneficial interactions between dissimilar species such as substitution of growth factor or metabolites. ⁶¹ Therefore, co-culturing strategies are existence adopted in which complementary or synergistic phenotypes in singled-out organisms tin improve the conversion of lignocellulose into biofuels and/or value-added products. ^{11,16,62–65}

In silico analyses of amino acrid synthesis pathways in known cellulose and biofuel-producing Firmicutes using the Integrated Microbial Genomics (IMG) database ^66,67 accept been done for 27 mesophiles, 19 thermophiles, and four hyperthermophiles (Table 3 ) to identify the potential for metabolite complementarity for strains in coculture. Among these, glutamine and glutamate are the firsthand products of ammonia assimilation and essential nitrogen donors for the synthesis of other intermediates. Amino acids are not only protein precursors, simply likewise precursors for numerous other crucial compounds, such every bit polyamines, Due south-adenosylmethionine, pantothenic acid, and nucleotides. ⁶⁸ Very fiddling information is bachelor in the literature for the pathways of amino acrid metabolism and their regulation. The availability of genome sequences has the potential to increase our knowledge of amino acid synthesis in bacteria and facilitate development of cost-reduced minimal media.

Table 3. Cellulolytic and noncellulolytic mesophilic, thermophilic, and hyperthermophilic Firmicutes

Genome Status	Genome Name	Temperature Optimum	Metabolism
Permanent draft	Clostridium alkalicellulosi Z-7026, DSM 17461	35 °C	Cellulose degrader
Draft	Clostridium termitidis CT1112, DSM 5398	37 °C	Cellulose degrader
Finished	Clostridium phytofermentans ISDg	37 °C	Cellulose degrader, ethanol product, acetate producer
Finished	Clostridium cellulolyticum H10	35 °C	Cellulose degrader
Draft	Clostridium cellulovorans 743B, ATCC 35296	37 °C	Cellulose degrader
Draft	Clostridium papyrosolvens DSM 2782	25 °C	Cellulose degrader, xylan degrader
Finished	Clostridium saccharolyticum WM1, DSM 2544	37 °C	Cellulose degrader, ethanol product
Typhoon	Clostridium carboxidivorans P7, DSM 15243	37–forty °C	Solvent producer, acetogenic
Finished	Clostridium ljungdahlii PETC, DSM 13528	37 °C	Ethanol product, acetogen
Finished	Clostridiales sp. SM4/1	forty °C	Cellulose degrader
Finished	Clostridiales sp. SSC/two	40 °C	Cellulose degrader
Finished	Clostridiales sp. SS3/four	xl °C	Cellulose degrader
Typhoon	Clostridium sp. URNW	37 °C	Cellobiose-degrading, hydrogen production, acetate producer
Finished	Butyrivibrio fibrisolvens 16/4	37 °C	Cellulose degrader
Finished	Ruminococcus sp. 18P13	40 °C	Cellulose degrader
Finished	Ruminococcus sp. SR1/5	twoscore °C	Cellulose degrader
Finished	Ruminococcus albus 7	40 °C	Cellulose degrader
Draft	Ruminococcus albus 8	xl °C	Cellulose degrader
Finished	Ruminococcus torques L2-14	forty °C	Cellulose degrader
Finished	Ruminococcus obeum A2-162	twoscore °C	Cellulose degrader
Finished	Ruminococcus bromii L2-63	40 °C	Cellulose degrader, ethanol product
Draft	Ruminococcus flavefaciens FD-ane	37 °C	Cellulose degrader
Finished	Eubacterium siraeum V10Sc8a	40 °C	Cellulose degrader
Permanent draft	Eubacterium cellulosolvens vi	forty °C	Cellulose degrader
Draft	Marvinbryantia formatexigens I-52, DSM 14469	37 °C	Cellulose degrader
Permanent Draft	Cohnella panacarvi Gsoil 349, DSM 18696	thirty °C	Xylan degrader
Finished	Bacillus pumilus SAFR-032	37 °C	Biomass degrader
Draft	Clostridium stercorarium BW, DSM 8532	65 °C	Cellulose and xylan degrader
Finished	Clostridium thermocellum ATCC 27405	sixty °C	Cellulose degrader, ethanogenic
Typhoon	C. thermocellum DSM 2360	threescore °C	Cellulose degrader, ethanol product, ethanogenic
Finished	C. thermocellum LQ8, DSM 1313	sixty °C	Cellulose degrader, ethanogenic, ethanol production
Finished	Clostridium clariflavum EBR 45, DSM 19732	55 °C	Cellulose degrader
Draft	Thermoanaerobacter ethanolicus JW 200	60 °C	Xylose consumer, ethanol production
Finished	Thermoanaerobacter pseudethanolicus 39E, ATCC 33223	65 °C	Sugars fermentor, iron reducer, ethanol product
Draft	Thermoanaerobacter thermohydrosulfuricus WC1	60 °C	Xylan degrader
Finished	Thermoanaerobacter brockii finnii Ako-1, DSM 3389	65 °C	Saccharolytic
Finished	Thermoanaerobacter italicus Ab9, DSM 9252	seventy °C	Saccharolytic
Finished	Thermoanaerobacterium xylanolyticum 60-11	60 °C	Saccharolytic
Finished	Thermoanaerobacter sp. X514	60 °C	Solvent producer
Finished	Thermoanaerobacterium thermosaccharolyticum DSM 571	60 °C	Cellulose degrader
Finished	Thermoanaerobacterium saccharolyticum JW/SL-YS485, DSM 8691	xxx–66 °C	Xylan degrader
Finished	Caldicellulosiruptor lactoaceticus 6A, DSM 9545	68–75 °C	Cellulose degrader, biomass degrader, nitrogen producer
Finished	Caldicellulosiruptor bescii Z-1320, DSM 6725	75 °C	Cellulose degrader
Draft	Caldicellulosiruptor lactoaceticus 6A, DSM 9545	68–75 °C	Cellulose degrader, biomass degrader, nitrogen producer
Finished	Caldicellulosiruptor kronotskyensis 2002	70 °C	Cellulose degrader, biomass degrader, nitrogen producer
Finished	Caldicellulosiruptor saccharolyticus DSM 8903	65 °C	Cellulose degrader, biomass degrader, nitrogen producer
Finished	Caldicellulosiruptor kristjanssonii 177R1B, DSM 12137	78 °C	Cellulose degrader, nitrogen producer, biomass degrader
Finished	Caldicellulosiruptor hydrothermalis 108	79 °C	Cellulose degrader, biomass degrader, nitrogen producer
Finished	Caldicellulosiruptor obsidiansis OB47	79 °C	Cellulose degrader, biomass degrader, nitrogen producer
Finished	Caldicellulosiruptor owensensis OL	79 °C	Cellulose degrader, biomass degrader, nitrogen producer

About of the selected Firmicutes associated with lignocellulose fermentation are auxotroph for l-lysine except C. cellulolyticum H10, C. thermocellum ATCC 27405, C. thermocellum DSM 2360, and Caldicellulosiruptor saccharolyticus DSM 8903. All listed mesophilic and thermophilic Firmicutes are prototrophic for l-glutamate and fifty-glutamine and auxotrophic for glycine. In the case of l-histidine, only Bacillus pumilus SAFR-032 is prototrophic. Analysis showed the presence of 50-proline metabolism in very few organisms, such as C. phytofermentans ISDg, C. cellulolyticum H10, Cohnella panacarvi Gsoil 349, B. pumilus SAFR-032, C. thermocellum ATCC 27405, T. pseudethanolicus 39E, and Thermoanaerobacter sp. X514, are prototrophic whereas Clostridiales sp. SS3/4 and Ruminococcus sp. 18P13 are auxotrophic. Most mesophilic, thermophilic, and hyperthermophilic bacteria are auxotrophic for l-alanine, 50-aspartate, fifty-phenylalanine, l-tyrosine, l-tryptophan, 50-arginine, l-asparagine, fifty-cystein, l-isoleucine, l-leucine, fifty-serine, fifty-threonine, and l-valine (Table 4). However, caution has to be taken when looking at such analyses because they can occasionally exist misleading. For example, C. thermocellum has been shown to abound in amino-acid-free minimal media ^12,69 despite genomic analyses to the contrary. Metabolic interactions and cross-feeding of growth nutrients between some biofuel producing cocultures that utilized lignocellulose-derived substrates are briefly discussed below.

Table iv. In silico analyses of amino acrid synthesis of mesophilic, thermophilic, and hyperthermophilic Firmicutes from IMG/ER

Genome Proper noun	Lys	Glu	Ala	Asp	Phe	Tyr	Trp	His	Gly	Arg	Asn	Cys	Gln	Ile	Leu	Pro	Ser	Thr	Val
Mesophiles
C. alkalicellulosi Z-7026, DSM 17461	–	P	–	–	A	A	A	A	–	A	P	–	P	A	A	–	A	A	A
C. termitidis CT1112, DSM 5398	–	P	P	A	A	A	A	A	A	A	P	–	P	A	A	–	A	A	A
C. phytofermentans ISDg	–	P	P	P	A	A	A	A	A	P	P	P	P	P	P	P	A	–	P
C. cellulolyticum H10	P	P	P	P	A	A	P	A	A	P	P	–	P	A	A	P	A	A	P
C. cellulovorans 743B, ATCC 35296	A	P	P	P	A	A	A	A	A	–	P	–	–	A	A	–	–	–	A
C. papyrosolvens DSM 2782	–	P	P	A	A	A	A	A	A	–	P	–	–	A	A	–	A	A	P
C. saccharolyticum WM1, DSM 2544	–	P	–	P	A	A	A	A	A	–	P	P	–	–	A	–	A	A	–
Clostridiales sp. SSC/2	–	P	P	A	A	A	A	A	A	A	P	–	–	A	A	–	A	A	A
Clostridiales sp. SM4/1	A	P	A	A	A	A	A	A	A	A	P	A	–	A	A	–	A	A	A
Clostridiales sp. SS3/four	–	P	–	A	A	A	A	A	A	A	P	–	–	A	A	A	–	A	A
Clostridium sp. URNW	A	P	–	–	A	A	A	A	A	A	P	–	–	A	A	–	–	–	A
Butyrivibrio fibrisolvens 16/4	–	–	A	P	A	A	A	A	A	A	–	–	P	–	A	–	–	A	–
Ruminococcus sp. 18P13	–	P	A	A	A	A	A	A	A	–	–	A	P	A	A	A	A	A	A
Ruminococcus sp. SR1/v	A	P	–	A	A	A	A	A	A	A	P	–	–	A	A	–	–	A	A
R. albus seven	–	P	A	A	A	A	A	A	A	–	P	P	P	A	A	–	–	–	A
R. albus 8	–	P	A	A	A	A	A	A	A	–	P	P	P	A	A	–	–	–	A
R. torques L2-14	–	P	–	A	A	A	A	A	A	A	P	–	–	A	A	–	–	A	A
R. obeum A2-162	–	P	–	–	A	A	A	A	A	A	P	–	–	A	A	–	–	A	A
R. bromii L2-63	A	P	–	A	A	A	A	A	A	A	A	–	P	A	A	–	A	A	A
R. flavefaciens FD-1	A	P	A	A	A	A	A	A	A	–	P	P	P	P	A	–	–	A	P
E. siraeum V10Sc8a	A	–	A	–	A	A	A	A	A	A	–	–	–	A	A	–	A	A	A
E. cellulosolvens 6	–	P	P	A	A	A	A	A	A	A	P	–	–	A	A	–	–	A	A
Chiliad. formatexigens I-52, DSM 14469	–	P	–	P	A	A	A	A	A	–	P	–	–	–	A	–	A	A	–
C. carboxidivorans P7, DSM 15243	A	P	P	–	A	A	A	A	A	A	P	–	–	A	A	–	–	–	A
C. ljungdahlii PETC, DSM 13528	–	P	–	–	A	A	A	A	A	A	P	–	–	A	A	–	A	–	A
C. panacarvi Gsoil 349, DSM 18696	–	P	–	P	A	A	A	A	A	A	–	–	–	A	A	P	A	–	A
B. pumilus SAFR-032	A	P	P	P	P	P	P	P	A	P	P	P	P	P	P	P	A	P	P
Thermophiles and hyperthermophiles
T.ethanolicus JW 200	A	P	–	–	A	A	A	A	A	A	P	–	–	A	A	–	A	–	A
C. thermocellum ATCC 27405	P	P	P	P	A	A	P	A	A	P	P	P	P	–	P	P	A	A	P
C. thermocellum DSM 2360	P	P	P	A	A	A	A	A	A	P	P	P	P	A	A	–	A	A	P
C. thermocellum LQ8, DSM 1313	–	P	P	A	A	A	A	A	A	–	P	P	P	A	A	–	A	A	A
C. clariflavum EBR 45, DSM 19732	–	P	–	A	A	A	A	A	–	–	P	–	–	A	A	–	A	–	A
C. stercorarium BW, DSM 8532	–	P	P	P	A	A	A	A	–	–	P	–	P	A	A	–	A	A	A
T. pseudethanolicus 39E, ATCC 33223	A	P	P	P	P	P	P	A	A	P	P	–	P	–	P	P	A	P	P
T. thermohydrosulfuricus WC1	A	P	–	–	A	A	A	A	A	A	P	–	–	A	A	–	A	–	A
T. saccharolyticum JW/SL-YS485, DSM 8691	A	P	P	–	A	A	A	A	A	A	P	–	–	A	A	–	A	–	A
T. brockii finnii Ako-1, DSM 3389	A	P	–	–	A	A	A	A	A	A	P	–	–	A	A	–	A	–	A
T. italicus Ab9, DSM 9252	A	P	–	A	A	A	A	A	–	A	P	–	–	A	A	–	A	–	A
T. xylanolyticum Threescore-eleven	A	P	–	–	A	A	A	A	A	A	P	–	–	A	A	–	A	–	A
Thermoanaerobacter sp. X514	A	P	P	P	P	P	P	A	A	P	P	–	P	–	P	P	A	P	P
T. thermosaccharolyticum DSM 571	A	P	–	A	A	A	A	A	A	A	P	–	–	A	A	–	A	–	A
C. lactoaceticus 6A, DSM 9545	A	P	–	A	A	A	A	A	–	A	P	–	P	A	A	–	A	–	A
C. bescii Z-1320, DSM 6725	–	P	–	A	A	A	A	A	A	A	P	–	P	–	P	–	A	–	P
C. lactoaceticus 6A, DSM 9545	A	P	–	A	A	A	A	A	–	A	P	–	P	A	A	–	A	–	A
C. kronotskyensis 2002	–	P	–	A	A	A	A	A	–	A	P	–	P	A	A	–	A	–	A
C. saccharolyticus, DSM 8903	P	P	P	P	A	A	A	A	A	A	P	P	P	–	P	–	A	P	P
C. kristjanssonii 177R1B, DSM 12137	–	P	–	A	A	A	A	A	–	A	P	–	P	A	A	–	A	–	A
C. hydrothermalis 108	–	P	–	A	A	A	A	A	–	A	P	–	P	A	A	–	A	–	A
C. obsidiansis OB47	–	P	–	A	A	A	A	A	–	A	P	–	P	A	A	–	A	–	–
C. owensensis OL	–	P	–	A	A	A	A	A	–	A	P	–	P	A	A	–	A	–	A

A = auxotrophic, P = prototrophic, fifty-Lysine = Lys, fifty-glutamate = Glu, l-alanine = Ala, l-aspartate = Asp, 50-phenylalanine = Phe, l-tyrosine = Tyr, l-tryptophan = Trp, fifty-histidine = His, Glycine = Gly, 50-arginine = Arg, 50-asparagine = Asn, 50-cysteine = Cys, l-glutamine = Gln, l-isoleucine = Ile, 50-leucine = Leu, 50-proline = Pro, l-serine = Ser, l-threonine = Thr, fifty-valine = Val.

By culturing on defined minimal media, it was confirmed that C. thermocellum, the fastest known cellulose degrader, is impaired of biosynthesizing four vitamins: biotin, pyridoxamine, vitamin B₁₂, and p-aminobenzoic acid. ⁶⁹ Cocultures of C. thermocellum with noncellulolytic Thermoanaerobacter strains (X514 or 39E) resulted in 194–440% comeback in ethanol product in comparison to C. thermocellum monocultures. The presence of a complete vitamin B12 biosynthesis pathway in strain X514, in contrast to T. pseudethanolicus 39E, immune the C. thermocellum X514 coculture to produce 62% more ethanol compared with the C. thermocellum 39E coculture. ⁶² The significance of de novo B12 synthesis was further supported past the realization that the exogenous addition of B12 to culture medium of C. thermocellum 39E cocultures showed improved ethanol production comparable to that of C. thermocellum X514 cocultures. ^seventy Exchange of substrate and growth factors was as well observed betwixt Clostridium strain C7, a mesophilic cellulose degrader, and Klebsiella strain W1, a noncellulolytic bacterium. On defined medium, Klebsiella utilized soluble sugars released by Clostridium and excreted biotin and p-aminobenzoic acrid that were required for the growth of Clostridium. ⁷¹

Two farthermost thermophiles, C. saccharolyticus DSM 8903 and C. kristjanssonii DSM 12137, exhibited a stable coculture on glucose and xylose for 70 days in a chemostat at different dilutions. The H₂ yield of 3.7 mol/mol glucose obtained from the combined culture was higher than those from monocultures past either organism. When C. kristjanssonii was grown on glucose with and without the addition of cell-free culture broth of C. saccharolyticus, the lag stage of C. kristjanssonii was shortened with eighteen% higher biomass yield. On the ground of this observation, it was concluded that a growth enhancement compound for C. kristjanssonii was supplied by C. saccharolyticus growth supernatant. ⁶⁵ This chemical compound is possibly related to the biosynthesis of 1 or more of the 4 amino acids l-Aspartate, l-leucine, fifty-valine, and 50-threonine because C. saccharolyticus is a prototroph and C. kristjanssonii is an auxotroph every bit revealed past the amino acid metabolism data presented in Tabular array 4. However, detailed genomic- and proteomic-level investigation involving the amino acid biosynthesis pathways of these organisms is required to ostend such assumptions.

Mutually benign interactions have been reported between aerobe-anaerobe and chemo-photoheterotroph organisms. ^63,72 During an investigation on a stable consortium of 5 bacterial strains, synergistic relationships were detected amid an anaerobic cellulolytic bacterium (C. straminisolvens CSK1) and 2 strains of aerobic bacteria (Pseudoxanthomonas sp. strain M1-3 and Brevibacillus sp. strain M1-v). The aerobes introduced an anaerobic status whereas the anaerobe supplied metabolites (acetate and glucose), and cellulose degradation was more efficient in the presence of these aerobes, resembling perfect weather condition for symbiosis. ⁷² The cellulosic hydrogen production rate by C. cellulolyticum H10 doubled with 1.6-times more total aggregating when cocultured with Rhodopseudomonas palustris CGA676, a photoheterotrophic facultative aerobe, as a result of the higher (2-fold) growth charge per unit and cell density (two.half-dozen fold) of C. cellulolyticum compared with its monoculture. Removal of acetate and pyruvate, two major metabolites of C. cellulolyticum, by R. palustris, was identified as the benign effect of the co-culture that reduced terminate product inhibition and pH drops. ⁶³

A sequential culture of Zymomonas anaerobia and C. thermocellum was attempted by growing each culture separately for 3 days and and then inoculating C. thermocellum cultures with Z. anaerobia followed by incubation of the co-culture at 37 °C. Ethanol yield with the co-civilisation on i% cellulose was almost 9 times greater (ii.7 g/L) than the value obtained from C. thermocellum lone. ⁷³ Ethanol produced by the co-culture from the steam-exploded wood fraction was similar to that from equivalent amounts of solka floc. ⁷⁴ Under a loftier pH environment (pH = nine), synergistic effects of a coculture consisting of C. themocellum and Clostridium thermolacticum were studied through fermentation of lignocellulose derivatives (xylose, cellobiose, and cellulose) into ethanol. The lag period of fermentation was always shorter in this co-culture compared with monocultures and consistently yielded several fold more ethanol than monocultures. ⁷⁵ Enhanced product was witnessed by these studies, and only cross-feeding of growth substrate could not sufficiently explain the underlying cause. Because none of these studies explored the possible sharing of metabolites released by co-culturing species, in-depth analyses applying omics tools such as metabolomics is warranted. Indeed, a recent analysis of secreted metabolites in C. thermocellum ATCC 27405 has demonstrated meaning secretion of a wide range of amino acids into medium when cells are grown on Avicel. ⁷⁶ This excretion may facilitate the growth of other organisms in their environment, permitting growth of both in a minimal medium.

Interdependence of participants in cellulose-degrading cocultures, as discussed above, mimics the syntrophy of anaerobic microflora in a natural environment where the conversion is wearisome only efficient. In addition to enhanced rates of cellulose degradation and biofuels production, cross-feeding between co-culturing organisms may allow (i) elimination of vitamins, reducing agents and/or pH control chemicals from growth medium and (2) utilization of undesired metabolites and leftover substrates. In turn, these would result in medium toll-savings and waste minimization, which translates to a more economically competitive bioprocess.

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White Biotechnology for Amino Acids

Murali Anusree , G. Madhavan Nampoothiri , in Industrial Biorefineries & White Biotechnology, 2015

5.ane Glutamic Acrid

Dr Kikunae Ikeda isolated the crystals of MSG from sea weeds in 1908. ^fourteen Ajinomoto began the commercial production of MSG from acid hydrolysate of wheat gluten and defatted soybean in 1909. The era of microbial amino acid fermentation started with the discovery of the glutamate producer in the 1950s by Kinoshita and coworkers from the avian fecal contaminated samples of Ueno zoo in Nippon. Soon the strains were fine-tuned for amino acrid overproduction by process optimization, random and point mutations.

The factors affecting glutamic acid fermentation are ammonium concentration, dissolved oxygen concentration, and pH. Likewise, high glutamate dehydrogenase action, reduction in two-oxoglutarate dehydrogenase circuitous (ODHC), and glutamate efflux attribute to overproduction. Under the high ammonium concentrations favoring glutamic acid synthesis, glutamate dehydrogenase (GDH) catalyzes ammonia absorption of 2-oxoglutarate to form glutamic acid. ^15,16 The ODHC catalyzes the oxidative decarboxylation of two-oxoglutarate to succinyl coenzyme A (succinyl-CoA). ODHC and GDH compete for 2-oxoglutarate at the branch point for glutamate synthesis in the TCA cycle. A loftier glutamate dehydrogenase activity will better glutamate aggregating and a high α-ketoglutarate dehydrogenase activity will shift the flux toward succinic acid. Under atmospheric condition of bereft oxygen, lactic acid and succinic acid accumulate and in the excess oxygen concentrations α-ketoglutarate accumulates in the fermentation broth.

Glutamate overproduction may be directly linked to higher rate of glutamate efflux from the cell. Glutamate excretion is reported to improve under conditions of biotin limitation. ¹⁷ In the excess of biotin, the improver of surfactants or beta lactam antibiotics like penicillin tin improve the efflux. ^18,19 Biotin is the cofactor of acetyl CoA and during biotin depletion, the fatty acid biosynthesis does not take identify properly and hence the fat acid composition of the cell wall changes resulting in glutamate efflux. During biotin limitation, penicillin or surfactant improver, the ODHC activity reduces to almost 10%, resulting in increased activity of GDH and the metabolic flux is directed to glutamate germination. Penicillin is a β lactam antibiotic that binds to the penicillin-bounden proteins on the cell surface and inhibits peptidoglycan synthesis resulting in glutamate efflux out of the prison cell. Glutamate efflux is also triggered with ethambutol consecration. ²⁰ Since, all these consecration methods (Figure 12.ane) cause some cell surface changes, glutamate efflux were ascribed to a leaky prison cell membrane. ²¹

Figure 12.1. Consecration of glutamate production in Corynebacterium glutamicum.

Mutations in the ODHA gene have shown to affect the glutamate product in C. glutamicum without changes in the cell wall or in the fatty acid composition. Increased ODHC activeness was shown to subtract glutamate production even in the presence of surfactants or β lactam antibiotics. An odh A mutant without ODHC activity showed higher 2-oxoglutarate and glutamate accumulation. Fine-tuning of the GDH activity further increased the glutamate accumulation. ²² A mutant strain with lesser ODHC activeness was also constructed by in vitro mutagenesis. ²³ odhA-disrupted mutants were further analyzed and found that they carried additional mutations in the NCgl1221 gene, which encodes a mechanosensitive channel homolog. These NCgl1221 gene mutations lead to constitutive l-glutamic acid secretion even in the absence of odhA disruption and also render cells resistant to an fifty-glutamic acid analogue, 4-fluoroglutamic acrid. ²⁴

The genes involved in lipid biosynthesis were also altered for glutamate overproduction. The change in phospholipid composition was achieved by the overexpression of plsC (acylglycerolacyl transferase) gene which resulted in a detergent-triggered increment of l-glutamate accumulation from 92 to 108   mM. ²⁵ dtsR1 is a gene whose product shows homology to the β subunit of the biotin enzyme acetyl-CoA carboxylase circuitous that is involved in fatty acrid synthesis ^26–28 and it decreased in presence of Tween 40 or biotin limitation.

A dtsR1 deletion mutant, auxotrophic to oleic acrid, Tween 80 (oleate ester) or Tween 20 (laurate ester) overproduced glutamate. ²⁹ Glutamate overproduction was observed in biotin limitation and Tween 40 equally information technology might lead to inactivation of the biotin enzyme complex that includes DtsR. The dtsR1 gene disruption completely suppressed glutamate overproduction in presence of Tween 40 and partially suppressed glutamate overproduction by penicillin addition and biotin limitation. dtsR1 gene production makes a complex with AccBc, the biotin carboxyl carrier protein—a sub unit of acyl Co A carboxylase required for fatty acrid biosynthesis. The homologs of dtsR1 viz dtsR2, accD3, and accD4 and their products form complexes with AccBc and are involved in fatty acrid biosynthesis. ³⁰ ODHC activity decreased with dtsR1 gene disruption and suppressed past overexpression. Niebisch et al. ³¹ found that ODHC was regulated by a protein kinase, PknG via phosphorylation of odh1 protein.

The preferred sugars for glutamic acid fermentation were refined sugars including glucose, fructose, and sucrose. Later, glutamic acid production was reported from starch hydrolysates, molasses, wheat and rice brans, alkenes, ethanol, acetic acid, etc. Glutamic acid product has already been demonstrated with palm waste hydrolysate, cassava starch hydrolysate, date waste product hydrolysate, and rice hydrolysate and dissimilar agricultural residues by different bacterial strains. ^32–34 Dissimilar methods of fermentation were too employed for glutamic acrid. Solid state fermentation using sugar cane bagasse every bit inert support has been reported for glutamic acid fermentation. ³⁵ Utilization of waste glycerol streams from the biodiesel industry for glutamate production is realized with engineering science the glycerol utilization pathway in C. glutamicum. ³⁶ Direct conversion of starchy substrates has been realized with the cloning and cell surface expression of amylase genes in C. glutamicum cells. In attempts to utilize lignocelluloses derived sugars, araBAD operon and xylose metabolizing genes from Eastward. coli were cloned in C. glutamicum and glutamate production was accomplished.

The industrial product of glutamate started developing with the extraction, isolation, and purification of glutamic acid from wheat gluten by Dr Kikunae Ikeda. Wheat gluten was preferred as it contained high quantities of gluten among the industrially available raw materials. In 1909, began the industrial production of monosodium l-glutamate (MSG) with an entrepreneur Saburosuke Suzuki (founder of Ajinomoto Co) and Ikeda. The yields were very low in the process due to the technical drawbacks. No new methods of production were developed till the 1950s.And so a chemical synthesis method was developed with acrylonitrile equally the starting fabric and the subsequent resolution of the racemic mixture of glutamic acid. The entire procedure was adult by Ajinomoto over 10   years of R&D and airplane pilot plant operations and was started on industrial scale by 1963. The initial product was 300   tons/month which afterward increased to 1000   tons/month. The procedure was overridden by fermentation procedure by 1973 in view of optically pure, loftier quantity glutamate with much bottom ecology burden. Thus was the humble beginning of the multibillion dollar manufacture.

The bodily industrial product processes remain proprietary for each visitor and the general enquiry community is enlightened of but the standard bioprocess. The amino acid product process is usually fed-batch as it lowers the sugar needs, plant downtime, power consumption and increases process efficiency. The production strain used is Corynebacterium or its variants. For instance, C. glutamicum S9114 is widely used for industrial glutamate production in Communist china. ³⁷ The processing in the fermentation facility starts with the cleaning up, calibration, and sterilization of the equipment. The microbial civilisation is revived from its lyophilized form into fine media in shake flasks. Then the seed train proceeds in tanks of varying capacities of 0.2–i   g³, then 10–twenty   one thousand³, and finally the production tank of most 50–500   m^three. The procedure undergoes vigorous quality checks at each step and then that cell density, nutrient composition, temperature, pH, aeration, agitation rates, and sugar flow rates are as consistent as possible. Saturated fatty acids, antibiotics, or surfactants are added to increase cell permeability to increase glutamate excretion. Ammonia is purged to maintain the pH betwixt 7 and 8. Feed during the process is almost 160   g glucose per liter, or its equivalent. Glutamate concentrations are monitored at intervals and the broth is fed into recovery tanks. The cells are removed; the broth is concentrated under reduced force per unit area; pH is adjusted to the isoelectric pH of glutamic acrid i.eastward., three.two. Crystallization is oftentimes tricky; varying crystal sizes are used for varied food applications like sprinkling on foods or mixed in liquid soups or dissolved in water for spraying fowl. MSG is commonly crystallized equally long crystals with the longest centrality 10 or more times longer than the curt centrality. This possesses uneven mixing in soup mixtures as the long crystals tend to separate out from the mix during shipping and resulting in uneven proportions when the packet used in portions. This necessitates the formation of varying crystal sizes needed for varying applications and the crystallization methods thus depend on the last use in the market. In that location are several patents on the crystallization of MSG. ^38–forty

The major product of glutamic acid in market is MSG every bit a season enhancer in Japanese and Chinese cuisine and an indispensable ingredient of most packaged foods. MSG is condign increasingly popular in spite of its proclaimed wellness risks. The production of MSG has increased at to the lowest degree thrice (∼iii   meg tons) since beginning of the century. China has been the major producer and supplier of the amino acid in the Asia Pacific with 90% of the consumption inside the region. There was a depletion in the prices of MSG due to oversupply in 2013, simply has regained momentum and the market place is now tightened with stable prices. At that place is always tight competition between the companies for market authorization and lower prices and are governed past the economic system of calibration of product and a abiding loftier product quality.

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Advanced nutrient removal from surface water past a consortium of attached microalgae and bacteria: A review

Junzhuo Liu , ... Bruce Rittmann , in Bioresource Technology, 2017

4.1 Nitrogen removal pathways

During photoautotrophic and heterotrophic microbial growth, absorption is the major inorganic nitrogen removal mechanisms (Gonçalves et al., 2017). Assimilation of oxidized nitrogen forms such as NO₃ ^- or NO_ii ^- starts with their reduction into ammonium and further incorporation into amino acids, while the reduced nitrogen (NH_iv ⁺) can exist direct assimilated by microalgae. Specifically, nitrate reductase uses the reduced grade of nicotinamide adenine dinucleotide (NADH) to transfer ii electrons, resulting in the conversion of nitrate into nitrite. Nitrite will then be converted into ammonium by the enzyme nitrite reductase using ferredoxin (Fd) as electron donor (Fig. 3 reactions 1A&B). Thus, all forms of inorganic nitrogen are ultimately converted into ammonium and thereafter, ammonium is incorporated into amino acids by using glutamate and ATP (Fig. iii reactions 1C) (Cai et al., 2013; Gonçalves et al., 2017).

Fig. 3. Nitrogen removal mechanisms by the fastened microalgae-bacteria consortium: (ane) absorption of inorganic nitrogen by microalgae: 1A nitrate reductase, 1B nitrite reductase, 1C glutamine synthetase; (2) ammonia volatilization caused by pH increment; (three) nitrification of ammonia: 3A, oxidation of ammonia to nitrite; 3B, oxidation of nitrite to nitrate; (four) consummate nitrification by a single microorganism; (v) denitrification: 5A, reduction of nitrate to nitrite; 5B, reduction of nitrite to North₂; (vi) anaerobic ammonium oxidation; (7) shortcut denitrification in the nitrite way: 7A, oxidation of ammonia to nitrite; 7B, reduction of nitrite to Northward₂; (viii) mineralization of organic nitrogen.

Besides assimilation, ammonia volatilization, nitrification and denitrification are also key mechanisms during inorganic nitrogen removal (Peng and Zhu, 2006; Strohm et al., 2007; Daims et al., 2015; Basílico et al., 2016). At high pH (e.g., >8), ammonia tin volatilize from water every bit ammonia gas (NH_iii) (Fig. 3, reaction two) (Basílico et al., 2016). Nitrification is the oxidation of ammonia to nitrite (Fig. 3, reaction 3A) and then to nitrate (Fig. 3, reaction 3B) by ammonia oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA) and nitrite oxidizing bacteria (NOB) or complete ammonia oxidation leaner (Comammox, Fig. 3, reaction four). On the other mitt, denitrification is the reduction of nitrate into nitrite (Fig. 3, reaction 5A) and then to Northward₂ or North_twoO (Fig. iii, reaction 5B) by denitrifying leaner in the absence of O₂ in the aquatic environment (Fitzgerald et al., 2015; Courtens et al., 2016). Traditionally, information technology was assumed that ammonium is oxidized into nitrite and so nitrate under aerobic weather condition, and nitrate is transformed into N₂ or N₂O through denitrification anaerobically (Strohm et al., 2007). However, in the last few decades, more and more anaerobic ammonium oxidizing bacteria (Anammox, Fig. 3, reaction 6) and aerobic denitrifying leaner (ADB) have been found, which enabled a straightforward nitrogen removal under consummate aerobic or anaerobic conditions (Yao et al., 2013). For instance, Candidatus brocadia anammoxidans is capable of anaerobically oxidizing ammonium into N₂ with the anammox enzyme hydroxylamine oxidoreductase (Jetten et al., 2001). Pseudomonas sp. and Alcaligenes faecalis can perform aerobic denitrification (Guo et al., 2013), while the combination of heterotrophic nitrifying-aerobic denitrifying bacteria (e.1000., Acinetobacter sp. and Bacillus methylotrophicus strain L7) is capable of performing nitrification and denitrification simultaneously under aerobic weather (Zhang et al., 2012; Yao et al., 2013). Additionally, shortcut nitrification and denitrification via nitrite can occur in surface h2o (Fig. iii, reactions 7A&B) (Peng and Zhu, 2006).

Organic nitrogen (e.g., amino acids and proteins) can exist decomposed into ammonia with the participation of enzymes such every bit Gln Synthetase, Glu 2-oxoglutarate aminotransferase and Glu Dehydrogenase secreted by a variety of leaner (Fig. iii, reaction 8) in the so called ammonification or mineralization reactions (Simsek et al., 2016). Thereafter, the NH₄ ⁺ generated can be removed from surface water every bit in a higher place described.

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