Department of Civil and Environmental Engineering, Graduate School of Engineering, Nagoya University, Tokai National Higher Education and Research System, Chikusa, Nagoya 464-8603, Japan; Institute of Materials and Systems for Sustainability, Nagoya University, Tokai National Higher Education and Research System, Chikusa, Nagoya 464-8603, Japan.
Department of Civil and Environmental Engineering, Graduate School of Engineering, Nagoya University, Tokai National Higher Education and Research System, Chikusa, Nagoya 464-8603, Japan; Institute of Materials and Systems for Sustainability, Nagoya University, Tokai National Higher Education and Research System, Chikusa, Nagoya 464-8603, Japan.
J Biosci Bioeng. 2022 Aug;134(2):144-152. doi: 10.1016/j.jbiosc.2022.04.011. Epub 2022 May 26.
Dark fermentative biological hydrogen (Bio-H) production is expected to be a clean and sustainable H production technology, and the technologies have been studied to increase in the product yield as index. This study achieved high product yields of Bio-H using nitrogen-fixing consortia under nitrogen-deficient conditions with glucose or mannitol as substrate and humin as the extracellular electron mediator: 4.12 mol-H/mol-glucose and 3.12 mol-H/mol-mannitol. The high Bio-H production was observed under the conditions where both nitrogenase and hydrogenase were active in the presence of humin. Nitrogenase activity was confirmed by acetylene reduction activity and hydrogenase activity by Bio-H production under nitrogenase-inhibiting conditions with NHNO. [Fe-Fe] hydrogenase detected by a specific PCR and acetate, butyrate, formate, lactate, and pyruvate produced as by-products suggested the involvement of both pyruvate-ferredoxin-oxidoreductase and pyruvate formate lyase pathways in Bio-H production. Humin promoted the Bio-H production beyond the capacity of the consortium, which had reached saturation with the optimum concentrations of glucose and mannitol. Carbon balance suggested the concurrent H consumption by hydrogenotrophic methanogenesis and acetogenesis. Bio-H production of the washed and starved consortium with reduced humin under conditions with or without NHNO suggests that humin promoted hydrogenase and nitrogenase activity by donating extracellular electrons. Clostridium and Ruminococcus in the consortia were considered major hydrogen producers. Thus, this study demonstrated the outstanding potential of nitrogen-fixing consortia under nitrogen-deficient conditions with humin as an extracellular electron mediator for dark fermentative Bio-H production with high yields.
暗发酵生物制氢（Bio-H）有望成为一种清洁可持续的制氢技术，为提高产氢量这一指标，相关技术已被广泛研究。本研究在氮饥饿条件下，以葡萄糖或甘露醇为底物、腐殖质为细胞外电子介体，利用固氮菌共生体实现了高产量的 Bio-H 生产：以葡萄糖为底物时，产氢量为 4.12 mol-H/mol-葡萄糖；以甘露醇为底物时，产氢量为 3.12 mol-H/mol-甘露醇。在腐殖质存在的条件下，氮酶和氢酶均具有活性，观察到 Bio-H 产量较高。氮酶活性通过乙炔还原活性来证实，氢酶活性通过在有 NHNO 的条件下抑制氮酶生成 Bio-H 来证实。通过特定的 PCR 检测到 [Fe-Fe] 氢化酶，并且作为副产物产生了乙酸盐、丁酸盐、甲酸盐、乳酸盐和丙酮酸，表明在 Bio-H 生产中涉及丙酮酸-铁氧还蛋白氧化还原酶和丙酮酸甲酸裂解酶途径。腐殖质促进了 Bio-H 生产，超出了共生体的能力，而葡萄糖和甘露醇的最佳浓度已经使共生体达到饱和。碳平衡表明，同时存在由氢营养型产甲烷菌和乙酰营养型产甲烷菌进行的 H 消耗。在有或没有 NHNO 的条件下，用减少的腐殖质对经洗涤和饥饿处理的共生体进行 Bio-H 生产的实验表明，腐殖质通过提供细胞外电子来促进氢化酶和氮酶的活性。该共生体中的梭菌属和瘤胃球菌属被认为是主要的产氢菌。因此，本研究表明，在氮饥饿条件下，固氮菌共生体与腐殖质作为细胞外电子介体具有很高的产氢潜力，可用于暗发酵生物制氢，产量较高。
