Production of caproic and caprylic acid through anaerobic fermentation of crops or residual and waste biomass has been regarded as an alternative to the conventional ways, where plant oils and animal fats are mostly used. The downstream processing of the fermentation broth is a particular challenge since the broth has a highly complex composition and low concentrations of the target products. In this study, the proof-of-principle for a separation cascade for caproic (C6) and caprylic acid (C8) produced in a maize silage-based fermentation process was demonstrated. For clarification of the fermentation broth, a filter press and a ceramic ultrafiltration membrane was used to remove coarse solids and to separate suspended particles and macromolecules from the fermentation broth, respectively. With both techniques, the dry matter content was reduced from 6.8 to 2.3% and a particle-free product solution was obtained. Subsequently, the carboxylic acids were extracted with oleyl alcohol by liquid-liquid extraction with an extraction efficiency of 85% for C6 and 97% for C8. Over the whole cascade, 58% of caproic acid and 66% of caprylic acid were recovered from the fermentation broth into the extract. Among all separation steps, solid-liquid separation with the filter press caused the major part of the product loss of 21% of each carboxylic acid. By using separation equipment with a better solid separation efficiency such as decanter centrifuges or belt filter presses this loss could be minimized.

中文翻译：

---

从玉米青贮发酵液中分离己酸和辛酸的下游加工级联。

通过作物或残余和废弃生物质的厌氧发酵生产己酸和辛酸已被认为是传统方法的替代方法，传统方法主要使用植物油和动物脂肪。发酵液的下游加工是一个特殊的挑战，因为发酵液的成分非常复杂，目标产物的浓度很低。在这项研究中，证明了在基于玉米青贮饲料的发酵过程中产生的己酸 (C6) 和辛酸 (C8) 的分离级联的原理验证。为了澄清发酵液，分别使用压滤机和陶瓷超滤膜去除粗固体并从发酵液中分离悬浮颗粒和大分子。使用这两种技术，干物质含量从 6.8% 降至 2.3%，并获得了无颗粒的产品溶液。随后，通过液-液萃取用油醇萃取羧酸，C6的萃取效率为85%，C8的萃取效率为97%。在整个级联过程中，58% 的己酸和 66% 的辛酸从发酵液中回收到提取物中。在所有分离步骤中，用压滤机进行的固液分离造成了大部分产物损失，每种羧酸损失了 21%。通过使用具有更好固体分离效率的分离设备，例如卧螺离心机或带式压滤机，可以将这种损失降至最低。羧酸用油醇通过液-液萃取法萃取，C6的萃取效率为85%，C8的萃取效率为97%。在整个级联过程中，58% 的己酸和 66% 的辛酸从发酵液中回收到提取物中。在所有分离步骤中，用压滤机进行的固液分离造成了大部分产物损失，每种羧酸损失了 21%。通过使用具有更好固体分离效率的分离设备，例如卧螺离心机或带式压滤机，可以将这种损失降至最低。羧酸用油醇通过液-液萃取法萃取，C6的萃取效率为85%，C8的萃取效率为97%。在整个级联过程中，58% 的己酸和 66% 的辛酸从发酵液中回收到提取物中。在所有分离步骤中，用压滤机进行的固液分离造成了大部分产物损失，每种羧酸损失了 21%。通过使用具有更好固体分离效率的分离设备，例如卧螺离心机或带式压滤机，可以将这种损失降至最低。使用压滤机进行固液分离导致产物中每种羧酸损失了 21% 的主要部分。通过使用具有更好固体分离效率的分离设备，例如卧螺离心机或带式压滤机，可以将这种损失降至最低。使用压滤机进行固液分离导致产物中每种羧酸损失了 21% 的主要部分。通过使用具有更好固体分离效率的分离设备，例如卧螺离心机或带式压滤机，可以将这种损失降至最低。