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Production of Clean Energy from Cyanobacterial Biochemical Products
Published in Stephen A. Roosa, International Solutions to Sustainable Energy, Policies and Applications, 2020
Figure 4-1 shows the oxygenic “light reactions” of photosynthesis driven by the solar energy captured by the light-harvesting complexes of PSI and PSII. Electrons extracted from H2O by the oxygen-evolving complex of PSII are passed along to the photosynthetic electron transport chain via plastoquinone (PQ), the cytochrome b6f complex (Cyt b6f), plastocyanin (PC), photosystem I (PSI), and ferredoxin (Fd), then by ferredox- in-NADP+ oxidoreductase to NADP+ ultimately producing NADPH. H+ are released into the thylakoid lumen by the PSII and PQ/PQH2 cycles and used for adenosine triphosphate (ATP) production via ATP synthase.
Influence of key operating parameters and bio-fouling on simultaneous desalination of seawater & reduction of organic wastes from petroleum industrial wastewater
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
V. R. V Ashwaniy, M. Perumalsamy
Microbial Desalination Cell (MDC) is considered to be the most appropriate emerging promising technology that integrates wastewater treatment, desalination and bioelectricity production in a single reactor which is evolved from the architecture of microbial fuel cell (MFC) (Cao et al. 2009). The process maintains electroneutrality by simultaneous oxidation of organic matter and electron transfer thus leading to the desalination process. (Sevda et al. 2015) (Lovley 2008) Substantial research over the past decade significantly improved MDC reactor’s architecture, performance and its application in various fields. Among different configurations, bio-cathode MDC is gaining importance as it utilizes autotrophic and phototrophic microorganisms (e.g. algal species) in cathode instead of air cathode with an expensive catalyst (e.g. platinum catalyst). Algae conduct oxygenic photosynthesis to produce oxygen in the cathode chamber through membrane-bound proteins such as cytochrome b6F complex, PSI and PSII along with plastoquinone (an isoprenoid quinine molecule) and plastocyanin (water-soluble electron carrier) (Taiz and Zeiger 2010). El Nadi reported the direct elimination of 95% of the salt content with the Scenedesmus species (El Nadi, El Sergany, and El Hosseiny 2014). The current study utilizes Scenedesmus abundans as catholyte along with petroleum wastewater as anolyte, and it is already studied by our research group with the above species and obtained 55% salt removal efficiency with 35 g L−1 salt concentration (Ashwaniy and Perumalsamy 2017).
Response of microcystin biosynthesis and its biosynthesis gene cluster transcription in Microcystis aeruginosa on electrochemical oxidation
Published in Environmental Technology, 2019
Yu Gao, Kazuya Shimizu, Chie Amano, Xin Wang, Thanh Luu Pham, Norio Sugiura, Motoo Utsumi
The transcription levels of mcyB and mcyD under different conditions in cDNA and DNA were measured by RT-qPCR, and the results were expressed as relative gene expression level (Figure 6). mcyB transcription in all conditions showed sharp decrease from days 0 to 2. Afterwards, the transcription in oxygenated, air aerated and unaerated conditions stabilised in the subsequent experimental period but continuously decreased from day 2 to undetectable level on day 6 under electrolysis condition. The transcription of mcyD in electrolysis condition could not be detected from day 2. Cyanobacteria have a simple photosynthetic apparatus than the higher plant. The chlorophyll-protein complex and phycobiliproteins are two major antenna complexes in cyanobacteria, in which chlorophyll a and phycocyanin are important. The protein complexes, namely, photosystemI (PSI), photosystemII (PSII) and cytochrome b6f complex, which perform light-driven reactions of photosynthesis, are embedded in the membranes. Transcription of MC synthesis genes requires an active photosynthetic electron transfer chain. However, the reactive oxygen species (ROS) produced in photosynthetic reactions in both PSI and PSII cause oxidative damage to membrane lipids, proteins and nuclear acids in cyanobacteria. Experiments on the transcriptional inhibition of MC synthesis genes in Microcystis by ROS have been conducted. Kaebernick et al. [15] and Sevilla et al. [21] found that a decrease in mcyB and mcyD transcription was observed in Microcystis cells when they were exposed in methylviologen, an agent causing oxidative stress, by inhibiting the electron transfer between PSII and PSI using RPAs in RT-qPCR. Moreover, Sevilla et al. [21] tested the response of MC synthesis and mcyD transcription in Microcystis cell on hydrogen peroxide. The results showed a reduction in MC-LR concentration and mcyD transcription compared with the control. Thus, aside from ROS, other oxidative agents could also cause the decrease of MC content and MC synthesis gene. In the present study, the down-regulation in both the mcyB and mcyD transcription levels indicated that the active photosynthetic electron transfer chain was probably destroyed when cells were exposed to oxidative conditions formed by high oxidising substances, such as hydroxyl radicals and chloride.