Chemical Engineering Laboratory, Faculty of Sciences and Center for Advanced Scientific Research (CICA), BIOENGIN Group, University of La Coruña, E-15008, La Coruña, Spain.
Chemical Engineering Laboratory, Faculty of Sciences and Center for Advanced Scientific Research (CICA), BIOENGIN Group, University of La Coruña, E-15008, La Coruña, Spain.
J Environ Manage. 2022 Jan 15;302(Pt A):113992. doi: 10.1016/j.jenvman.2021.113992. Epub 2021 Oct 25.
In recent years, the possibility of merging technologies for waste recovery such as those based on syngas fermentation and chain elongation has been studied for the production of medium chain fatty acids (MCFAs) and bioalcohols, in an attempt to integrate the concept of circular economy in the industry. Nevertheless, one of the main issues of this approach is the pH mismatch between acetogens and chain elongating microorganisms. This work reports, for the first time, the suitability of a co-culture of C. aceticum and C. kluyveri metabolizing syngas at near neutral pH in stirred tank bioreactors. For this purpose, bioreactor studies were carried out with continuous syngas supply. In the first experiment, maximum concentrations of n-butyrate and n-caproate of 7.0 and 8.2 g/L, respectively, were obtained. In the second experiment, considerable amounts of n-butanol were produced as a result of the reduction, by C. aceticum, of the carboxylates already formed in the broth. In both experiments, ethanol was used as an exogenous electron agent at some point. Finally, batch bottle assays were performed with a pure culture of C. aceticum grown on CO in presence of n-butyrate to assess and confirm its ability to produce n-butanol, reaching concentrations up to 951 mg/L, with a n-butyrate conversion efficiency of 96%, which had never been reported before in this species. Therefore, this work contributes to the state of the art, presenting a novel system for the bioproduction of MCFAs by combining syngas fermentation and chain elongation at near neutral pH, as opposed to the acidic pH range used in all previously reported literature.
近年来，人们研究了将基于合成气发酵和链延长等技术融合的可能性，以生产中链脂肪酸（MCFAs）和生物醇，试图将循环经济的概念纳入工业。然而，这种方法的主要问题之一是乙酰生成菌和链延长微生物之间的 pH 值不匹配。本工作首次报道了 C. aceticum 和 C. kluyveri 共培养物在近中性 pH 值下在搅拌罐生物反应器中代谢合成气的适宜性。为此，进行了带有连续合成气供应的生物反应器研究。在第一个实验中，分别获得了 7.0 和 8.2 g/L 的正丁酸和正己酸的最大浓度。在第二个实验中，由于 C. aceticum 将已经在发酵液中形成的羧酸盐还原，产生了相当数量的正丁醇。在这两个实验中，在某个时间点都使用了乙醇作为外源电子供体。最后，使用在 CO 存在下以正丁酸为唯一碳源生长的 C. aceticum 纯培养物进行分批瓶实验，以评估并确认其生产正丁醇的能力，达到高达 951 mg/L 的浓度，正丁酸转化率为 96%，这在该物种之前从未有过报道。因此，这项工作为在近中性 pH 值下将合成气发酵和链延长相结合生产 MCFAs 的生物生产提供了一种新的系统，与所有之前报道的文献中使用的酸性 pH 值范围相反，这是该领域的一项重要贡献。
