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Current challenges for microbial electrosynthesis include the production of higher value chemicals than acetate, at high rates, using cheap electrode materials. We demonstrate here the continuous, biofilm-driven production of acetate (C2), n-butyrate (nC4), and n-caproate (nC6) from sole CO2 on unmodified carbon felt electrodes. No other organics were detected. This is the first quantified continuous demonstration of n-caproate production from CO2 using an electrode as sole electron donor. During continuous nutrients supply mode, a thick biofilm was developed covering the whole thickness of the felt (1.2-cm deep), which coincided with high current densities and organics production rates. Current density reached up to −14 kA m−3electrode (−175 A m−2). Maximum sustained production rates of 9.8 ± 0.65 g L−1 day−1 C2, 3.2 ± 0.1 g L−1 day−1 nC4, and 0.95 ± 0.05 g L−1 day−1 nC6 were achieved (averaged between duplicates), at electron recoveries of 60–100%. Scanning electron micrographs revealed a morphologically highly diverse biofilm with long filamentous microorganism assemblies (~400 μm). n-Caproate is a valuable chemical for various industrial application, e.g., it can be used as feed additives or serve as precursor for liquid biofuels production.

当前微生物电合成（microbial electrosynthesis）领域面临的核心挑战，在于采用廉价电极材料，以高生产速率合成乙酸盐之外的高附加值化学品。本文证实，可在未改性碳毡（carbon felt）电极上，以纯CO₂为唯一碳源，通过连续运行的生物膜驱动过程合成乙酸盐（acetate，C2）、正丁酸盐（n-butyrate，nC4）与正己酸盐（n-caproate，nC6），未检测到其他有机产物。这是首次以电极为唯一电子供体，从CO₂中连续合成正己酸盐的定量验证研究。
在连续供给营养物的运行模式下，形成的厚生物膜覆盖了碳毡的全部厚度（1.2 cm深），这与较高的电流密度和有机产物生成速率高度吻合。体系电流密度最高可达−14 kA·m⁻³（电极体积），即−175 A·m⁻²。在电子回收率60%~100%的条件下，平行样的平均最大持续生成速率分别为：乙酸盐9.8±0.65 g·L⁻¹·d⁻¹、正丁酸盐3.2±0.1 g·L⁻¹·d⁻¹、正己酸盐0.95±0.05 g·L⁻¹·d⁻¹。
扫描电子显微镜图像（scanning electron micrographs）显示，该生物膜形态多样性极高，存在长度约400 μm的长丝状微生物聚集体。正己酸盐是一类具有多种工业用途的高附加值化学品，例如可用作饲料添加剂，或作为液态生物燃料生产的前体物质。