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31P
Published in Guillaume Madelin, X-Nuclei Magnetic Resonance Imaging, 2022
Most of ATP (about 90%) in cells is produced by oxidative phosphorylation (OxPhos) in the mitochondria, and to a much smaller extent by glycolysis in the cytosol [5, 62]. In the brain, oxygen and glucose are supplied to cells by cerebral blood flow (CBF) through the capillaries. Glucose is transported by the glucose transporter into the cells and is then converted into 2 pyruvate molecules by glycolysis in the cytosol. Most of pyruvate molecules are metabolized in the mitochondria to form acetyl-CoA, which is oxidized via the tricarboxylic acid (TCA) cycle inside the mitochondria to generate NADH, the reduced form of nicotinamide adenine dinucleotide (NAD). NADH serves as an electron donor in the electron transport chain reactions and is converted to NAD+, the oxidized NAD, by oxygen metabolism. The electron transport chain generates an electrochemical potential gradient across the mitochondrial inner membrane via extrusion of H+ ions from the mitochondria. This transmembrane potential then enables the conversion of adenosine diphosphate (ADP) and inorganic phosphate (Pi) into ATP, catalyzed by the ATP synthase F1FO-ATPase (or H+-ATPase) enzyme, which can reversely transport the H+ ions back into the mitochondria.
Fiber-Optic Sensors in Bioprocess Control
Published in John V. Twork, Alexander M. Yacynych, Sensors in Bioprocess Control, 2020
NADH is present in all living cells of bacteria, fungi, plants, or animals. Unfortunately, the specific amount of NADH per cell varies within a vast range, but the following microorganisms have successfully have been studied with a fiber-optic flourosensor [13,21,22]:baker’s yeast, Bacillussubtilis, Candidatropicalis, Escherichiacoli, Sporotrichumthermophile, Penicilliumchrysogenum, Streptomycessp., andZymomonasmobilis. Many others have been investigated by conventional NADH fluorometry. The fluorescence data obtained with whole cells are said to be primarily relative data. They can be related to different metabolic states, to fluorescence data of a standardized process, or to biomass concentration, but a quantitation in terms of moles NADH per cell is difficult to achieve. A comparison of the NADH content of a batch cultivation of baker’s yeast as determined after cell rupture, with the NADH fluorescence signal obtained with a fiber inserted into the bioreactor is shown in Figure 6.
Application of Nonlinear Microscopy in Life Sciences
Published in Lingyan Shi, Robert R. Alfano, Deep Imaging in Tissue and Biomedical Materials, 2017
Zdenek Svindrych, Ammasi Periasamy
NADH, a reduced form of nicotinamide adenine dinucleotide (NAD) is a coenzyme important in cellular metabolism. Its fluorescence can be excited around 350 nm and the emission range is 450–550 nm. Because NADH takes part in oxidative phosphorylation, beta oxidation and the citric acid cycle, it is a vital part of the cellular metabolism and can be used to study metabolic state of native and cancerous tissues [122]. Free NADH experiences significant quenching [19] and displays short fluorescence lifetime (around 0.4 ns) and proportionally low quantum yield, when compared to protein-bound NADH, whose lifetime also depends on the particular protein, leading to wide range of lifetimes (1.5–4.5 ns). With these unique properties, the NADH fluorescence intensity (or lifetime, for more quantitative results) can be used to monitor cellular redox state [123].
Progress in microbiology for fermentative hydrogen production from organic wastes
Published in Critical Reviews in Environmental Science and Technology, 2019
Khanna et al. (2011) studied the redirection of biochemical pathways for the enhancement of H2 production by Enterobacter cloacae. Since NADH is usually generated by catabolism of glucose to pyruvate through glycolysis, and then hydrogen is produced through the oxidation of NADH. However, the conversion of pyruvate to ethanol and acids like lactic acid and butyric acid consumes NADH. Thus, they attempted to redirect the biochemical pathways to block alcohol and some of the organic acids formation in E. cloacae IIT-BT 08, increase the concentration of available NADH for hydrogen production, hydrogen yield and hydrogen production rate obtained were 2.26 mol H2/mol hexose and 1.25 L H2/L/h, which were 1.2 and 1.6 times higher than the wild type strain. Xiong et al. (2018) introduced xylA (encoding for xylose isomerase) and xylB from Thermoanaerobacter ethanolicus to cellulolytic bacteria Clostridium thermocellum DSM 1313, achieved simultaneous fermentation of xylose, glucose, cellobiose and cellulose. The results showed that both hydrogen and ethanol production were enhanced by twice when xylose and cellulose was consumed simultaneously, and hydrogen yield of 1.2 mol/mol hexose was obtained. Sekar et al. (2017) enhanced the co-production of hydrogen and ethanol from glucose in Escherichia coli by activating pentose-phosphate pathway through deletion of phosphoglucose isomerase and overexpression of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, hydrogen and ethanol yield obtained by the mutant strain was enhanced by 1.2 and 2.05 times over the wild strain, which were 1.74 mol H2/mol hexose and 1.62 mol ethanol/mol hexose, respectively.
Simultaneous separation and biocatalytic conversion of formaldehyde to methanol in enzymatic membrane reactor
Published in Chemical Engineering Communications, 2021
Farazatul Harnani Ismail, Fauziah Marpani, Nur Hidayati Othman, Nik Raikhan Nik Him
The concentration of enzyme immobilized was measured as protein concentration according to Bradford’s Assay. The NADH concentration was monitored at absorbance of 340 nm. Both absorbance for protein assay and NADH concentration were measured using UV/VIS spectrophotometer (Perkin Elmer, Germany).