Winkelhorst Marijn, Cabau-Peinado Oriol, Straathof Adrie J J, Jourdin Ludovic
Department of Biotechnology, Faculty of Applied Sciences, Delft University of Technology, Delft, Netherlands.
Front Bioeng Biotechnol. 2023 Jan 19;11:1096086. doi: 10.3389/fbioe.2023.1096086. eCollection 2023.
Microbial electrochemical technologies (METs) employ microorganisms utilizing solid-state electrodes as either electron sink or electron source, such as in microbial electrosynthesis (MES). METs reaction rate is traditionally normalized to the electrode dimensions or to the electrolyte volume, but should also be normalized to biomass amount present in the system at any given time. In biofilm-based systems, a major challenge is to determine the biomass amount in a non-destructive manner, especially in systems operated in continuous mode and using 3D electrodes. We developed a simple method using a nitrogen balance and optical density to determine the amount of microorganisms in biofilm and in suspension at any given time. For four MES reactors converting CO to carboxylates, >99% of the biomass was present as biofilm after 69 days of reactor operation. After a lag phase, the biomass-specific growth rate had increased to 0.12-0.16 days. After 100 days of operation, growth became insignificant. Biomass-specific production rates of carboxylates varied between 0.08-0.37 mol mol d. Using biomass-specific rates, one can more effectively assess the performance of MES, identify its limitations, and compare it to other fermentation technologies.
微生物电化学技术（METs）利用微生物将固态电极作为电子受体或电子供体，例如在微生物电合成（MES）中。传统上，METs的反应速率是根据电极尺寸或电解液体积进行归一化的，但也应该根据系统在任何给定时间存在的生物量进行归一化。在基于生物膜的系统中，一个主要挑战是以非破坏性方式确定生物量，特别是在以连续模式运行且使用三维电极的系统中。我们开发了一种简单的方法，利用氮平衡和光密度来确定在任何给定时间生物膜和悬浮液中的微生物数量。对于四个将CO转化为羧酸盐的MES反应器，在反应器运行69天后，>99%的生物量以生物膜形式存在。经过一个滞后期后，生物量特异性生长速率增加到0.12-0.16天。运行100天后，生长变得不明显。羧酸盐的生物量特异性生产率在0.08-0.37 mol mol d之间变化。使用生物量特异性速率，可以更有效地评估MES的性能，识别其局限性，并将其与其他发酵技术进行比较。
