Suenaga Toshikazu, Aoyagi Ryo, Sakamoto Nozomi, Riya Shohei, Ohashi Hidenori, Hosomi Masaaki, Tokuyama Hideaki, Terada Akihiko
Department of Chemical Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan.
Department of Chemical Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan.
J Biosci Bioeng. 2018 Aug;126(2):213-219. doi: 10.1016/j.jbiosc.2018.02.014. Epub 2018 Apr 19.
Development of a strategy to mitigate nitrous oxide (NO) emitted from biological sources is important in the nexus of wastewater treatment and greenhouse gas emission. To this end, immobilization of NO-reducing bacteria as a biofilm has the potential to ameliorate oxygen (O) inhibition of the metabolic activity of the bacteria. We demonstrated the effectiveness of calcium alginate gel entrapment of the nosZ clade II type NO-reducing bacterium, Azospira sp. strain I13, in reducing levels of NO, irrespective of the presence of O. Azospira sp. strain I13 cells in the gel exhibited NO reduction up to a maximum dissolved oxygen concentration of 100 μM in the bulk liquid. The maximum apparent NO uptake rate, [Formula: see text] , by gel immobilization did not appreciably decrease, retaining 72% of the NO reduction rate of the cell suspension of Azospira sp. strain I13. Whereas gel immobilization increased the apparent half-saturation constant for NO, [Formula: see text] , and the apparent O inhibition constant, [Formula: see text] , representing the degree of O resistance, correspondingly increased. A mechanistic model introducing diffusion and the reactions of NO consumption was used to describe the experimental observations. Incorporating Thieles modulus into the model determined an appropriate gel size to achieve NO reduction even under aerobic conditions.
制定一项减轻生物源一氧化二氮（N₂O）排放的策略，对于污水处理与温室气体排放的关联而言至关重要。为此，将还原N₂O的细菌固定为生物膜，有可能改善氧气（O₂）对细菌代谢活性的抑制作用。我们证明了海藻酸钙凝胶包埋Ⅱ型nosZ类还原N₂O细菌Azospira sp.菌株I13在降低N₂O水平方面的有效性，无论是否存在O₂。凝胶中的Azospira sp.菌株I13细胞在本体液体中，在高达100μM的最大溶解氧浓度下都表现出N₂O还原能力。通过凝胶固定化得到的最大表观N₂O摄取速率，[公式：见原文]，并未明显降低，保留了Azospira sp.菌株I13细胞悬液N₂O还原速率的72%。虽然凝胶固定化增加了N₂O的表观半饱和常数，[公式：见原文]，但代表O₂抗性程度的表观O₂抑制常数，[公式：见原文]，相应增加。引入扩散和N₂O消耗反应的机理模型用于描述实验观察结果。将蒂勒斯模量纳入模型确定了一个合适的凝胶尺寸，即使在有氧条件下也能实现N₂O还原。
