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    Photobiohydrogen Production and Strategies for H2 Yield Improvements in Cyanobacteria
    (2023-01-01)
    Khetkorn, Wanthanee
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    Raksajit, Wuttinun
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    Lindblad, Peter
    Hydrogen gas (H<inf>2</inf>) is one of the potential future sustainable and clean energy carriers that may substitute the use of fossil resources including fuels since it has a high energy content (heating value of 141.65 MJ/kg) when compared to traditional hydrocarbon fuels [1]. Water is a primary product of combustion being a most significant advantage of H<inf>2</inf> being environmentally friendly with the capacity to reduce global greenhouse gas emissions. H<inf>2</inf> is used in various applications. It generates electricity in fuel cells, including applications in transportation, and can be applied as fuel in rocket engines [2]. Moreover, H<inf>2</inf> is an important gas and raw material in many industrial applications. However, the high cost of the H<inf>2</inf> production processes requiring the use of other energy sources is a significant disadvantage. At present, H<inf>2</inf> can be prepared in many conventional ways, such as steam reforming, electrolysis, and biohydrogen production processes. Steam reforming uses high-temperature steam to produce hydrogen gas from fossil resources including natural gas. Electrolysis is an electrolytic process to decompose water molecules into O<inf>2</inf> and H<inf>2</inf>. However, both these two methods are energy-intensive and producing hydrogen from natural gas, which is mostly methane (CH<inf>4</inf>) and in steam reforming generates CO<inf>2</inf> and pollutants as by-products. On the other hand, biological hydrogen production is more environmentally sustainable and less energy intensive than thermochemical and electrochemical processes [3], but most concepts are not yet developed to production scale.
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    Item type:Publication,
    Highly effective reduction of phosphate and harmful bacterial community in shrimp wastewater using short-term biological treatment with immobilized engineering microalgae
    (2023-01-01)
    Krasaesueb, Nattawut
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    Boonnorat, Jarungwit
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    Khetkorn, Wanthanee
    Shrimp farming wastewater includes high amounts of phosphate and microbiological contaminants, necessitating further treatment before release into receiving water bodies. After 24 h of shrimp wastewater treatment, alginate beads containing the blue-green algal Synechocystis strain lacking the phosphate regulator gene (mutant strain ΔSphU) at 150 mg L<sup>−1</sup> reduced phosphate content from 17.5 mg L<sup>−1</sup> to 5.0 mg L<sup>−1</sup>, representing 71.5% removal efficiency, with phosphate removal rate reaching 6.9 mg gDW<sup>−1</sup> h<sup>−1</sup> during photobioreactor operation. For short-term treatment, removal rates of nitrate, ammonium and nitrite were 42.7, 48.5 and 92.9%, respectively. Microalgal encapsulated beads also impacted the bacterial community composition dynamics in shrimp wastewater. Next-generation sequencing targeting the V3–V4 region of the 16S rDNA gene showed significant differences in bacterial community composition after 24 h of treatment. Proteobacteria are the most abundant phylum in shrimp wastewater. After 24 h of bioremediation, reductions of harmful bacteria in the Cellvibrionaceae and Pseudomonadaceae families were recorded at 5.85 and 3.18%, respectively. Engineered microalgal immobilization under optimal conditions can be applied as an alternative short-term bioremediation strategy to remove phosphate and other harmful microbial contamination from shrimp farming wastewater.