China
Africa
Explore chapters and articles related to this topic
Bioprocessing of Microalgae for the Production of Value Compounds
Published in Gokare A. Ravishankar, Ranga Rao Ambati, Handbook of Algal Technologies and Phytochemicals, 2019
Giorgos Markou, Christina Ν. Economou, Imene Chentir
Microalgae in order to grow need several elements in bioavailable forms, such as carbon, nitrogen, phosphorus, iron, magnesium, etc. Under nutrient-limited/starvation conditions, the light-harvesting process, carbon fixation, and other cell metabolic processes are down-regulated resulting in lower growth rates as well as the alteration of biochemical composition of biomass (Geider et al. 1998; Markou et al. 2017). Typically, under nutrient limitation/starvation carbon fixation pathways are altered and cells synthesize and accumulate carbon-rich macromolecules such as carbohydrates or lipids. Moreover, because nutrient limitation/starvation impacts the photosynthetic machinery of microalgae, alteration of the composition of pigments occurs as well by accumulating pigments that act as protectors against photodamage (Panis and Carreon 2016). In general, it is observed that nutrient limitation/starvation is the most effective strategy for triggering microalgae to accumulate target molecules. Noticeable variation in the biochemical composition under nutrient limitation/starvation conditions can be observed depending upon the type of nutrient and degree of limitation. In response to nitrogen, phosphorus, and sulfur starvation, for example, accumulation of lipids (mainly TAG), β-carotene, and astaxanthin are observed in numerous microalgal strains (Yeh and Chang 2011; Praveenkumar et al. 2012; Chen et al. 2015; Panis and Carreon 2016).
Glutathione
Published in Ruth G. Alscher, John L. Hess, Antioxidants in Higher Plants, 2017
Alfred Hausladen, Ruth G. Alscher
A crucial aspect of the scavenging pathway, therefore, is the inducibility of its constituent enzymes and the increased synthesis of at least one of its components on exposure to oxidative stress. The operation of the scavenging pathway must be energy-requiring, and as such, should drain reductant and nucleotide triphosphates away from anabolic metabolism. Exposure of hybrid poplar to subacute levels of ozone was positively correlated with increases in SOD and in total glutathione.142 These increases did not involve an inhibition of electron transport, since the rate of production of NADPH in the light was unaffected by this exposure regime. Since carbon fixation was inhibited and electron transport remained constant, it may be that the resources of the photosynthetically active cell are being diverted from production to defense. The decreased biomass in ozone-exposed crop plants substantiate this competition at the whole plant level. Only when these defense systems have been overwhelmed should toxic molecular species persist long enough to damage essential processes and macromolecules there, which is supported by earlier studies using intact illuminated spinach chloroplasts.144,145 Concentrations of ascorbic acid and GSH remained constant in the absence of added CO2, when the Mehler reaction was expected to proceed at a maximal rate. However, if additional H2O2 was added, the ascorbate and glutathione pools became quickly oxidized.144,145
Anatomy, Biochemistry and Physiology
Published in Massimo Maffei, Vetiveria, 2002
Cinzia M. Bertea, Wanda Camusso
Higher plants can be divided into two groups, C3 and C4, based on the mechanism utilized for photosynthetic carbon assimilation and related to anatomical and ultrastructural features. Photosynthesis by C3 plants involves only one photosynthetic cell type, and in these plants atmospheric CO2 is fixed directly by the primary carbon fixation enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco). In contrast, C4 plants, such as the monocotyledonous maize, possess a Kranz-type anatomy consisting of two cell types, mesophyll and bundle sheath cells, that differ in their photosynthetic activities (Hatch, 1992; Maurino et al., 1997).
Metatranscriptomic analysis of an in vitro biofilm model reveals strain-specific interactions among multiple bacterial species
Published in Journal of Oral Microbiology, 2019
Yifei Zhang, Wenyu Shi, Yeqing Song, Jinfeng Wang
According to the results, we further identified some pathways that were specially modified in F. nucleatum (Figure 4(b,c)). Compared to P. nigrescens, the expression of the pathway relating to carbon fixation pathways in prokaryotes were down-regulated in F. nucleatum by P. gingivalis ATCC33277 (C2 vs. C6), and the down-regulation was more severe when co-cultured with P. gingivalis W83 (C3 vs. C2). Co-culture of P. intermedia and P. gingivalis W83 further aggravated the down-regulation (C5 vs. C3), while P. intermedia reversed the effect of P. gingivalis ATCC33277 (C4 vs. C2). Compared to P. nigrescens, both P. gingivalis ATCC33277 and W83 down-regulated the pathways related to the pentose phosphate pathway, valine, leucine and isoleucine degradation, glycerolipid metabolism, chloroalkane and chloroalkene degradation, and phosphotransferase system (PTS), while P. intermedia reversed the effect of both P. gingivalis ATCC33277 and W83. Accordingly, by affecting P. gingivalis (especially the W83 strain), P. intermedia may influence these metabolic pathways and further interfere with the proliferation of F. nucleatum.
Selection of fast and slow growing bacteria from fecal microbiota using continuous culture with changing dilution rate
Published in Microbial Ecology in Health and Disease, 2018
Higher carbon requirement was observed also in amino acid consumptions. Most of the amino acids were completely metabolized within the whole range of dilution rates studied, except for alanine, phenylalanine, and BCAA (Figure 3). The total consumption of free amino acids increased 16–18% at 0.06 1/h compared to that at μ 0.2 1/h (from 0.16–0.2 up to 0.22–0.26 mol/mol, respectively) (Figure 3). Partially amino acids derived from mucin (0.2 mol-AA/mol-carb in both media) and maximal total consumption of amino acids was 0.36–0.46 mol-AA/mol-carb at D = 0.06 1/h. This exceeded 3.6–4.6 times the requirement for biomass synthesis under anaerobic conditions (0.1 mol-AA/mol-carb) if protein content in dry biomass is 50%, biomass yield per ATP 10 g/mol-ATP and glycolytic ATP output 2 mol-ATP/mol-glucose. The extensive use of amino acids was observed earlier in pure cultures of B. thetaiotaomicron [40] and can be related to shortage of energy, ammonia, or NAD+ regeneration. Carbon fixation through reductive TCA cycle to reduce carbon loss via CO2 efflux is increased with the decrease of dilution rate and can also explain the elevated requirement of NADH. Reductive or bifurcated TCA cycle has been demonstrated for several anaerobic gut bacteria such as Clostridium butyricum [44], Prevotella ruminicola [45] or Bacteroides fragilis, and its relatives [46]. Degradation of alanine is among the simplest ways to provide NADH or transamination of BCAA, which are common pathways present in gut bacteria according to MetaCyc database.
Mono- and di-thiocarbamate inhibition studies of the δ-carbonic anhydrase TweCAδ from the marine diatom Thalassiosira weissflogii
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2018
Silvia Bua, Murat Bozdag, Sonia Del Prete, Fabrizio Carta, William A. Donald, Clemente Capasso, Claudiu T. Supuran
The first inhibition study of a δ-CA with mono- and di-thiocarbamates, classes of CAIs recently discovered, was reported. TweCAδ from the marine diatom T. weissflogii was not particularly sensitive to inhibition by these classes of compounds. Many of the mono- and di-thiocarbamates did not show inhibitory action up to 20 µM, whereas some aliphatic, heterocyclic, and aromatic inhibited this enzyme in the low micromolar range. Several MTCs/DTCs incorporating the piperazine ring effectively inhibited TweCAδ with KIs in the range of 129–791 nM. The most effective inhibitors identified were 3,4-dimethoxyphenyl-ethyl-mono-thiocarbamate (KI of 67.7 nM) and the R-enantiomer of the nipecotic acid DTC (KI of 93.6 nM). Such inhibitors can now be used as molecular probes to investigate the role of this enzyme in the carbon fixation processes in diatom marine organisms that are responsible for removing large amounts of CO2 from the atmosphere.