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Cyanobacteria: A Biocatalyst in Microbial Fuel Cell for Sustainable Electricity Generation
Published in Lakhveer Singh, Durga Madhab Mahapatra, Waste to Sustainable Energy, 2019
Thingujam Indrama, O.N. Tiwari, Tarun Kanti Bandyopadhyay, Abhijit Mondal, Biswanath Bhunia
Chlorophyll-b shows the absorption maximum at 680 nm. It is already established that both centers are boosted to higher energy levels during adsorption of light energy. However, it is further emitted and passed to electron carriers. It is obviously true that passed energy is reduced due to splitting of water, and electron is passed towards potential gradient through redox active species (Kruse et al. 2005). Therefore, the energy is released in the form of ATP, and release of protons takes place from the stroma into the thylakoid lumen due to pH gradient (Kruse et al. 2005). As the protons are diffused against the concentration gradient, they flow with ATP synthetase (Kruse et al. 2005). Cyclic phosphorylation can take place if large amounts of NADPH exist and subsequently, electrons drive from the electron transport chain to PSI. The above electron from PSI is further passed to PSII. However, during formation of ATP, the electrons return to PSI and make PSII redundant. Depending on conditions, electrons can reduce protons to molecular hydrogen or reduce oxygen to water (Maly et al. 2005). The stroma of chloroplasts is the place where light independent reactions occur; however, previously generated ATP for energy is required. In the Calvin cycle, rubisco catalysed the combination process between carbon dioxide and sugar ribulose-1,5-bisphosphate RuBP (Kruse et al. 2005).
Microalgae as a Source of Sustainability
Published in Pau Loke Show, Wai Siong Chai, Tau Chuan Ling, Microalgae for Environmental Biotechnology, 2023
Pik Han Chong, Jian Hong Tan, Joshua Troop
Photosynthesis is a common process utilized by all organisms with chloroplast organelles, mainly composed of light dependent and light-independent reactions (refer to Figure 1.5). Photosynthesis, simply put, is a process required to convert solar energy produced by the sun into chemical-based energy that plants use for food and nutrition (Blankenship 2008). The light-dependent reaction uses energy from the sun to photodissociate water to synthesize hydrogen ions (H+), energy in form of adenosine 5′-triphosphate (ATP), and oxygen. The light-independent reaction or Calvin cycle is the next crucial element for the process of photosynthesis, which fixes the carbon from carbon dioxide using the energy from ATP into sugars. To explain the Calvin cycle in a simple manner, it is the process of turning carbon dioxide in the atmosphere into sugars, which plants then utilize to grow (Raines 2003). The Calvin cycle is split into three different procedures. The first is the carbon fixation stage, which is where carbon dioxide is absorbed from the atmosphere to produce carboxylate ribulose 1,5-bisphosphate (RuBP) with the help of enzyme ribulose-1,5- bisphosphate carboxylase/oxygenase (RuBisCO) thus kick-starting the action of photosynthesis (Heureux et al. 2017). The second phase also known as the reduction phase prompts energy reaction with chemicals to create the essential sugar glyceraldehyde 3-phosphate (G-3-P). Finally, with the regenerative phase, utilizing the stored energy and sugar, the two can interrelate with each other, creating RuBisCO, ready to begin photosynthesis and repeat the cycle (Tamoi et al. 2005). The discovery of photosynthesis in algae was made in the nineteenth century, where microalgae cultures of Chlorella vulgaris went under trials for further research and grew by applying 14C-labeled CO2 in short bursts of photoassimilation (Bassham and Calvin 1960; Birmingham, Coleman, and Colman 1982).
Mathematical model validation of floating PV parks impact on the growth of green algae using experimental chamber
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
ATP and NADPH generated by the light reaction are necessary for the photosynthetic dark reaction. In this reaction, a high-energy sugar is formed using ATP and NADPH. Ribulose-1,5-bisphosphate, a five-carbon acceptor molecule, bonds to a carbon dioxide molecule (RuBP). The 6-carbon complex results in dividing into two PGA molecules. The photoreaction’s ATP and NADPH energy is employed to change the PGA molecule into a tri-carbonate glyceraldehyde-3-phosphate molecule (G3P). The differential equation for the dark reaction can be stated as if C is the concentration of CO2 (Shevtsov et al. 2016):
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.