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AUTHOR(S): Ruki̇ye Özteki̇n, Deli̇a Teresa Sponza
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ABSTRACT This study explores the potential of biohydrogen production from some prokaryotic Algae (Synechocystis sp., Spirulina platensis, and Anabaena variabilis) under some environmental factors the influencing microalgal hydrogen (H2) production, determining the H2 production yields. The main environmental conditions affecting H2 production efficiency include the C/N ratio, pH, illumination intensity, incubation temperature, algae numbers and duration of H2 production. The effect of C/N ratio (0.1, 0.2, 0.4, 0.8 and 1.0), pH (6.5, 7.0, 7.5, 8.0, 8.5 and 9.0), illumination intensity (120, 168, 180, 216 and 250 μmol/m2.s), incubation temperature (20, 25, 30, 35 and 40oC), algae numbers and duration of H2 production (20, 40, 80, 100 and 120 hours), respectively, were examinec for the H2 production yields with prokaryotic Algae namely Synechocystis sp., Spirulina platensis, and Anabaena variabilis under direct photolysis and indirect biophotoylsis processes.Algae cultivation is crucial for biohydrogen production. Maximum 99.40% H2 production efficiency was measured at 0.1 C/N ratio, at pH=7.5, at 168 μmol/m2.s illumination intensity, at 30oC incubation temperature, at 35 EMS/100 ml Synechocystis sp., algae counts, after 100 h duration of H2 production, respectively, with Synechocystis sp., prokaryotic algae under direct photolysis process. Maximum 99.54% H2 production yield was obtained at 0.1 C/N ratio, at pH=9.0, at 180 mol/m2.s, at 35oC, at 88 EMS/100 ml Spirulina platensis algae counts, after 100 h, respectively, with Spirulina platensis prokaryotic algae under direct photolysis process. Maximum 99.44% H2 production efficiency was found at 0.1 C/N ratio, at pH=7.5, at 216 mol/m2.s, at 30oC, at 172 EMS/100 ml Anabaena variabilis algae counts, after 40 h, respectively, with Anabaena variabilis prokaryotic algae under direct photolysis process. H2 production yields in direct photolysis are higher than those in indirect biophotolysis. The responsible enzyme for H2 evolution is a reversible hydrogenase because it catalyzes the reaction in both directions. The reversible hydrogenase and nitrogenase, however, are sensitive to the O2 evolved in biophotolysis and promptly deactivated at quite low O2 partial pressures (< 2%v/v), which results in a transient H2 evolution. This intrinsic incompatibility of biophotolysis is a major barrier for sustained H2 evolution. This is because direct energy is converted into H2 energy in direct photolysis. Energy losses in direct photolysis are negligible compared to indirect biophotolysis. Therefore, H2 production yields in direct photolysis are much higher. Additionally, the study conducts a Technical Economic Analysis (TEA) to evaluate the economic feasibility. |
KEYWORDS Algae cultivation; Anabaena variabilis; Direct photolysis; H2 production; Illumination intensity; Indirect biophotolysis; Prokaryotic algae; Synechocystis sp.; Spirulina platensis, Technical economic analysis (TEA) |
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Cite this paper Ruki̇ye Özteki̇n, Deli̇a Teresa Sponza. (2025) H2 Production from Prokaryotic Algae Namely Synechocystis sp., Spirulina platensis, and Anabaena variabilis under Direct Photolysis and Indirect Biophotolysis. International Journal of Biochemistry Research, 9, 1-35 |
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