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Instrumentation and Test Methods
Published in Paul N. Cheremisinoff, Handbook of Water and Wastewater Treatment Technology, 2019
All living systems must obtain sources of carbon, other essential elements, and energy from their environments. For nonphotosynthetic organisms, this involves adsorption of organic compounds and the metabolism of these compounds to produce energy. In different organisms, the metabolic pathways may be significantly different. For an organism to be able to degrade, the following conditions must be met: The chemical substance must be able to reach the organism or the enzyme site.The compound must not be lethal.Enzymes necessary to transform the chemical must be present or be able to be induced.Environmental conditions must permit operation of the enzymes.
Transport of Nutrients and Carbon Catabolite Repression for the Selective Carbon Sources
Published in Kazuyuki Shimizu, Metabolic Regulation and Metabolic Engineering for Biofuel and Biochemical Production, 2017
In living organisms or cells, thousands of biochemical reactions as well as transport processes are linked together to break down various nutrients to generate energy and to synthesize cellular constituents, where the enzyme reactions are not static, but change dynamically in response to the change in the growth environment. Moreover, among possible topological networks, only a subset is active at any given point in time and growth condition. Complex signaling networks interconvert signals or stimuli for the efficient uptake of nutrients and their breakdown for energy generation and biomass synthesis. The living organism must maintain the cell system by the effective sensing of the external and/or internal state to survive in response to the variety of environmental changes (Janga et al. 2007). The enzymes which form the metabolic pathways are subject to multiple levels of regulation, where enzyme level and transcriptional regulations play important roles for metabolic regulation (Harbison et al. 2004, Luscombe et al. 2004, Balazsi et al. 2005, Moxley et al. 2009). It is thus important to understand the regulatory processes that govern the cellular metabolism.
Unsupervised Learning
Published in Mark Chang, Artificial Intelligence for Drug Development, Precision Medicine, and Healthcare, 2020
A metabolic pathway is a series of chemical reactions occurring within a cell, catalyzed by enzymes, resulting in either the formulation of a metabolic product to be used or stored by the cell, or the inhibition of another metabolic pathway. Pathways are important to the maintenance of homeostasis within an organism.
Effects of carbon source, C/N ratio, nitrate, temperature, and pH on N2O emission and functional denitrifying genes during heterotrophic denitrification
Published in Journal of Environmental Science and Health, Part A, 2018
Yun-Yeong Lee, Hyungjoo Choi, Kyung-Suk Cho
Simple carbons such as acetate, ethanol, methanol, and glucose have been traditionally used as organic carbon sources for heterotrophic denitrification.[6,16,32,33] These carbon sources have high efficiency for nitrate reduction because they are low molecular organic compounds that can be easily used and supply adequate amount of electrons for denitrification.[6,16,32,33] In general, acetate is more effective for denitrification than other carbon sources, such as glucose or methanol, because of its metabolic characteristics.[31] Two metabolic pathways (glycolytic pathway and TCA cycle) are required to utilize carbon sources in most organisms.[31] Acetate can be directly utilized for denitrification as it forms acetyl Co-A, which is a key compound of these two pathways.[31] However, in this study, methanol was the most effective carbon source for denitrification. Methanol is only used by a specific bacterial group called methylotrophs that utilizes single-carbon (C1) compounds such as methanol or methane.[31] A suitable methylotrophic denitrifying population might have already been present in the inoculum (humic soil), thus the higher denitrification performance found in methanol compared to other carbon sources in this study. Indeed, different microbial community structures for denitrification have been observed depending on the carbon source.[34]Hyphomicrobium and Paracoccus were dominant when methanol was utilized, while Halomonas was strongly dominant when acetate was used as the carbon source.[34] Therefore, for a better understanding, total microbial community structures for different carbon sources need to be investigated.