The efficient utilization of biomass fuels is a critical component of a sustainable energy economy. Via respiration, acetic acid bacteria can oxidize biomass ethanol into acetic acid using membrane-bound alcohol and aldehyde dehydrogenases (ADH and AlDH, respectively). Focusing on the ability of these enzymes to interact directly and electrically with electrode materials, we constructed a mediatorless bioanode for ethanol oxidation based on a direct electron transfer (DET)-type bienzymatic cascade by ADH and AlDH. The three-dimensional structural data of ADH and AlDH elucidated by cryo-electron microscopy were valuable for effectively designing electrode platforms with multi-walled carbon nanotubes (MWCNTs) and pyrene (Py) derivatives. DET-type bioelectrocatalysis by ADH and AlDH was improved by using 1-pyrene carboxylic acid-functionalized MWCNTs. The catalytic current densities for bienzymatic ethanol oxidation were recorded at the bioanodes modified by various ADH/AlDH ratios. The reaction model was constructed by focusing on the competitive adsorption of two enzymes on the electrode surface and the collection efficiency of the intermediately produced acetaldehyde. The power output of an ethanol/air biofuel cell using the bienzymatic bioanode reached 0.48 ± 0.01 mW cm^–2, which is the highest value reported for ethanol biofuel cells. In addition, the Faraday efficiency of acetate production by the cell reached 100 ± 4%. This study will lead to efficient conversion of biomass fuels based on a multi-catalytic cascade system.

中文翻译：

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用乙醇和醛脱氢酶进行无介体生物电化学乙醇氧化的双酶级联的实验和理论见解

生物质燃料的有效利用是可持续能源经济的重要组成部分。通过呼吸作用，乙酸细菌可以使用膜结合的醇和醛脱氢酶（分别为 ADH 和 AlDH）将生物质乙醇氧化成乙酸。着眼于这些酶与电极材料直接电相互作用的能力，我们构建了一种基于 ADH 和 AlDH 的直接电子转移 (DET) 型双酶级联的无介体生物阳极，用于乙醇氧化。通过冷冻电子显微镜阐明的ADH和AlDH的三维结构数据对于有效设计具有多壁碳纳米管（MWCNT）和芘（Py）衍生物的电极平台具有重要价值。通过使用 1-芘羧酸功能化的 MWCNT 改进了 ADH 和 AlDH 的 DET 型生物电催化作用。在由不同 ADH/AlDH 比例修饰的生物阳极处记录了双酶乙醇氧化的催化电流密度。通过关注两种酶在电极表面的竞争吸附以及中间产生的乙醛的收集效率来构建反应模型。使用双酶生物阳极的乙醇/空气生物燃料电池的功率输出达到0.48 ± 0.01 mW cm^–2，这是乙醇生物燃料电池报道的最高值。此外，该电池生产醋酸盐的法拉第效率达到100±4%。这项研究将基于多催化级联系统实现生物质燃料的高效转化。