de Leeuw Kasper D, van Willigen Marius J W, Vrauwdeunt Ton, Strik David P P T B
Environmental Technology, Wageningen University and Research, Wageningen, Netherlands.
ChainCraft B.V., Amsterdam, Netherlands.
Front Bioeng Biotechnol. 2024 Apr 24;12:1329288. doi: 10.3389/fbioe.2024.1329288. eCollection 2024.
Anaerobic fermentation technology enables the production of medium chain carboxylates and alcohols through microbial chain elongation. This involves steering reactor microbiomes to yield desired products, with CO supply playing a crucial role in controlling ethanol-based chain elongation and facilitating various bioprocesses simultaneously. In the absence of CO supply (Phase I), chain elongation predominantly led to n-caproate with a high selectivity of 96 Cmol%, albeit leaving approximately 80% of ethanol unconverted. During this phase, and -related species dominated the reactors. In Phase II, with low CO input (2.0 NmL L min), formation of n-butyrate, butanol, and hexanol was stimulated. Increasing CO doses in Phase III (6 NmL L min) led to CO utilization via homoacetogenesis, coinciding with the enrichment of , a bacterium that can use CO as an electron acceptor. Lowering CO dose to 0.5 NmL L min led to a shift in microbiome composition, diminishing the dominance of while increasing abundance. Additionally, other , , and -related species became prevalent. This decrease in CO load from 6 to 0.5 NmL L min minimized excessive ethanol oxidation from 30%-50% to 0%-3%, restoring a microbiome favoring net n-butyrate consumption and n-caproate production. The decreased ethanol oxidation coincided with the resurgence of hydrogen formation at partial pressures above 1%. High concentrations of butyrate, caproate, and ethanol in the reactor, along with low acetate concentration, promoted the formation of butanol and hexanol. It is evident that CO supply is indispensable for controlling chain elongation in an open culture and it can be harnessed to stimulate higher alcohol formation or induce CO utilization as an electron acceptor.
厌氧发酵技术能够通过微生物链延长来生产中链羧酸盐和醇类。这涉及引导反应器微生物群落产生所需产品，其中CO供应在控制基于乙醇的链延长和同时促进各种生物过程中起着关键作用。在没有CO供应的情况下（第一阶段），链延长主要产生己酸盐，选择性高达96 Cmol%，尽管约80%的乙醇未转化。在此阶段， 和 相关物种在反应器中占主导地位。在第二阶段，低CO输入（2.0 NmL L min）刺激了丁酸盐、丁醇和己醇的形成。在第三阶段增加CO剂量（6 NmL L min）导致通过同型产乙酸作用利用CO，同时富集了 ，一种可以将CO用作电子受体的细菌。将CO剂量降低到0.5 NmL L min导致微生物群落组成发生变化，减少了 的优势，同时增加了 丰度。此外，其他 、 和 相关物种变得普遍。将CO负荷从6降低到0.5 NmL L min，使过量乙醇氧化从30%-50%降至0%-3%，恢复了有利于净丁酸盐消耗和己酸盐生产的微生物群落。乙醇氧化的减少与分压高于1%时氢气形成的复苏同时发生。反应器中高浓度的丁酸盐、己酸盐和乙醇，以及低浓度的乙酸盐，促进了丁醇和己醇的形成。显然，CO供应对于控制开放培养中的链延长是不可或缺的，并且可以利用它来刺激高级醇的形成或诱导将CO用作电子受体。
