China
Africa
Explore chapters and articles related to this topic
Biofuels
Published in Robert Ehrlich, Harold A. Geller, John R. Cressman, Renewable Energy, 2023
Robert Ehrlich, Harold A. Geller, John R. Cressman
The process of photosynthesis is known to occur in two stages. In the first stage, light is captured primarily using the green pigment chlorophyll, and the energy is stored in energy-rich molecules such as adenosine triphosphate and nicotinamide adenine dinucleotide phosphate (Figure 5.3). In the second stage, light-independent reactions occur and CO2 is captured from the atmosphere. It is in this stage that the carbon is fixed or converted to plant matter such as sugar or starch in a series of reactions known as the Calvin cycle. Certain wavelengths of light are especially important in the first stage process, and while most photosynthetic organisms rely on visible light, there are some that use infrared or heat radiation—hence, the existence of those organisms capable of living deep underground or near undersea thermal vents. The details of the reactions in both stages of photosynthesis need not concern us here, as they involve some complex biochemistry.
Biosynthesis of Starch
Published in Jean-Luc Wertz, Bénédicte Goffin, Starch in the Bioeconomy, 2020
Jean-Luc Wertz, Bénédicte Goffin
The Calvin cycle10 includes three stages: (1) carbon fixation, where a carbon dioxide molecule combines with a five-carbon acceptor molecule to form a six-carbon molecule that splits into two molecules of 3-phosphoglycerate (3-PGA); (2) reduction, where the 3-PGA molecules are converted into molecules of glyceraldehyde-3-phosphate, also known as triose phosphate or 3-phosphoglyceraldehyde and abbreviated as G3P or PGAL; and (3) regeneration, where some G3P molecules go to make glucose, while others are recycled to generate the initial five-carbon acceptor. In photosynthetic tissues, starch and sucrose are synthesized from G3P in the chloroplast and cytosol respectively (Figure 3.4).4,11–14
Putting a Cell Together
Published in Thomas M. Nordlund, Peter M. Hoffmann, Quantitative Understanding of Biosystems, 2019
Thomas M. Nordlund, Peter M. Hoffmann
Figure 7.6a shows an optical micrograph of an example cyanobacterium, Anabaena scheremetievi, from the Cyanobacterial Image Gallery http://www-cyanosite.bio.purdue.edu/images/images.html. Notice that the “bacteria” form filamentous structures of many individual cells. Many such filaments are not simply linear arrays of cells, but of cells inside a protective, tubular sheath made of polysaccharides and other polymers. In most cyanobacteria the photosynthetic apparatus, the set of protein complexes that absorb light, transfer electrons, produce O2 and synthesize glucose, is embedded in disklike folds of the cell membrane, called thylakoids (Figure 7.7). Thylakoids usually form interconnected stacks called grana, but can also line the inner side of the cell membrane in certain cyanobacteria (Figure 7.7a). Photosynthesis in cyanobacteria generally uses electrons from H2O or H2S (hydrogen sulfide) and produces O2 as a by-product. Carbon dioxide is reduced to form carbohydrates via the Calvin cycle. The oxygen in the atmosphere is believed to have been originally generated by the activities of ancient cyanobacteria. Owing to their ability to fix nitrogen in aerobic conditions, they are often found as symbionts with a number of other groups of organisms such as fungi, lichens, and corals.
Changes of bacterial community in arable soil after short-term application of fresh manures and organic fertilizer
Published in Environmental Technology, 2022
Chunmei Ye, Shenfa Huang, Chenyan Sha, Jianqiang Wu, Changzheng Cui, Jinghua Su, Junjie Ruan, Juan Tan, Hao Tang, Jiajia Xue
The relative abundance of genes encoding enzymes was obtained by 16s functional prediction (Figure 6). The results showed that the relative abundance of genes encoding Ribulose-1,5-bisphosphate carboxylase/oxyg (RuBsiCO, EC4.1.1.39)(the enzymes in Calvin cycle), was significantly different in OF, CK, PM and CM (p < 0.05), and the relative abundance of those in OF was 20.51%, 31.12% and 39.06% higher than those in CK, CM and PM, respectively. RuBisCO catalyzes the first rate-limiting step of the Calvin cycle, the carbon dioxide (CO2) assimilation reaction [62]. The Calvin cycle are the predominant pathway for bacteria to assimilate CO2 and it is an important process of soil carbon cycle [16]. The relative abundance of genes encoding RuBisCO increased notably after the application of OF, indicating that the application of OF increased the CO2 assimilation potential of soil autotrophic bacteria.
Arthrospira sp. mediated bioremediation of gray water in ceramic membrane based photobioreactor: process optimization by response surface methodology
Published in International Journal of Phytoremediation, 2022
Shritama Mukhopadhyay, Animesh Jana, Sourja Ghosh, Swachchha Majumdar, Tapan Kumar Ghosh
High concentrations of DO hamper biomass productivity, thereby inhibiting photosynthesis. Marquez et al. (1995) observed a decrease in microalgal growth rate at higher DO concentration due to a decline in photosynthetic activity which, in turn, activated different enzymes involved in antioxidant defense mechanisms like superoxide dismutase and ascorbate peroxidase to combat the oxidative stress. Reduced growth and biomass yield due to elevated DO concentration in photobioreactor may also be linked to increased oxygenase activity of RuBisCo and the resulting process of photorespiration (Kliphuis et al.2011). RuBisCo, a bifunctional enzyme, catalyzes both the carboxylation (at high CO2 and low O2 concentration) and the oxygenation (at high O2 and low CO2 concentration) of RuBP (Ribulose 1,5-bisphosphate) during the Calvin cycle and Glycolate pathway, respectively. However, it cannot be utilized in the Calvin cycle during photorespiration as a result of which 3-phosphoglycerate and 2-phosphoglycolate are formed as by-products instead of only 3-phosphoglycerate (Cox and Nelson 2008). As recorded by Kazbar et al. (2019), DO concentration above 30 g/m3 in the photobioreactor reduced biomass production of Chlorella vulgaris by 30%. Hence, in the current study, DO concentration was properly maintained by supplying CO2 in the photobioreactor at regular intervals. Figure 2d represents the change in DO concentration with time, from which it can be clearly seen that the DO level increases each 24 h due to the increased photosynthetic activity of the microalgal biomass cultured in the photobioreactor and then decreases after CO2 purging. The removal of DO in the photobioreactor was also facilitated by the hydrophobic membranes having pores filled with gases that diminished the gas-liquid mass transfer resistance (Jana et al.2017). The maximum DO concentration was 10.1 mg/L on the 7th day which was finally reduced to 7.7 mg/L at the end of 10 days of culture. A relatively same pattern of DO profile, accompanied by an increase in every 24 h and decrease on the following day after CO2 saturation, was detected by Jana et al. (2017) during the growth of Spirulina sp. in membrane photobioreactor.