Lactate-mediated mixotrophic co-cultivation of Clostridium drakei and recombinant Acetobacterium woodii for autotrophic production of volatile fatty acids.
IF 4.3 2区 生物学Q1 BIOTECHNOLOGY & APPLIED MICROBIOLOGY
Alexander Mook, Jan Herzog, Paul Walther, Peter Dürre, Frank R Bengelsdorf
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引用次数: 0
Abstract
Background: Acetogens, a diverse group of anaerobic autotrophic bacteria, are promising whole-cell biocatalysts that fix CO2 during their growth. However, because of energetic constraints, acetogens exhibit slow growth and the product spectrum is often limited to acetate. Enabling acetogens to form more valuable products such as volatile fatty acids during autotrophic growth is imperative for cementing their place in the future carbon neutral industry. Co-cultivation of strains with different capabilities has the potential to ease the limiting energetic constraints. The lactate-mediated co-culture of an Acetobacterium woodii mutant strain, capable of lactate production, with the Clostridium drakei SL1 type strain can produce butyrate and hexanoate. In this study, the preceding co-culture is characterized by comparison of monocultures and different co-culture approaches.
Results: C. drakei grew with H2 + CO2 as main carbon and energy source and thrived when further supplemented with D-lactate. Gas phase components and lactate were consumed in a mixotrophic manner with acetate and butyrate as main products and slight accumulation of hexanoate. Formate was periodically produced and eventually consumed by C. drakei. A lactate-mediated co-culture of the A. woodii [PbgaL_ldhD_NFP] strain, engineered for autotrophic lactate production, and C. drakei produced up to 4 ± 1.7 mM hexanoate and 18.5 ± 5.8 mM butyrate, quadrupling and doubling the respective titers compared to a non-lactate-mediated co-culture. Further co-cultivation experiments revealed the possible advantage of sequential co-culture over concurrent approaches, where both strains are inoculated simultaneously. Scanning electron microscopy of the strains revealed cell-to-cell contact between the co-culture partners. Finally, a combined pathway of A. woodii [PbgaL_ldhD_NFP] and C. drakei for chain-elongation with positive ATP yield is proposed.
Conclusion: Lactate was proven to be a well-suited intermediate to combine the high gas uptake capabilities of A. woodii with the chain-elongation potential of C. drakei. The cell-to-cell contact observed here remains to be further characterized in its nature but hints towards diffusive processes being involved in the co-culture. Furthermore, the metabolic pathways involved are still speculatory for C. drakei and do not fully explain the consumption of formate while H2 + CO2 is available. This study exemplifies the potential of combining metabolically engineered and native bacterial strains in a synthetic co-culture.
背景:乙酸菌是一类种类繁多的厌氧自养细菌,是一种很有前途的全细胞生物催化剂,可在生长过程中固定二氧化碳。然而,由于能量限制,乙酸菌生长缓慢,产品范围通常仅限于乙酸酯。让醋酸菌在自养生长过程中形成更有价值的产品(如挥发性脂肪酸),是巩固醋酸菌在未来碳中和工业中地位的当务之急。将具有不同能力的菌株进行联合培养有可能缓解能量限制。以乳酸为介质的木醋杆菌突变菌株(能产生乳酸)与德氏梭菌 SL1 型菌株的共培养可产生丁酸和己酸。本研究通过比较单培养基和不同的共培养方法,分析了前一种共培养的特点:结果:C. drakei 以 H2 + CO2 作为主要碳源和能量来源,并在进一步补充 D-乳酸盐后茁壮成长。气相成分和乳酸盐以混养方式消耗,主要产物是乙酸盐和丁酸盐,己酸盐略有积累。C. drakei周期性地产生甲酸并最终消耗甲酸。以乳酸为介质的木褶菌[PbgaL_ldhD_NFP]菌株与 C. drakei 的共培养产生了高达 4 ± 1.7 mM 的己酸盐和 18.5 ± 5.8 mM 的丁酸盐,与非以乳酸为介质的共培养相比,各自的滴度分别增加了四倍和一倍。进一步的共培养实验表明,与同时接种两种菌株的方法相比,顺序共培养可能更具优势。菌株的扫描电子显微镜显示,共培养菌株之间存在细胞间接触。最后,提出了木褶菌[PbgaL_ldhD_NFP]和C. drakei的联合途径,以实现具有正ATP产量的链延伸:结论:事实证明,乳酸是一种非常适合的中间体,可将木藻菌的高气体吸收能力与 C. drakei 的链延伸潜力结合起来。这里观察到的细胞间接触仍有待进一步确定其性质,但暗示共培养中涉及扩散过程。此外,对 C. drakei 而言,所涉及的代谢途径仍是推测性的,不能完全解释在有 H2 + CO2 的情况下甲酸盐的消耗。这项研究体现了在合成共培养中结合代谢工程菌株和本地细菌菌株的潜力。
期刊介绍:
Microbial Cell Factories is an open access peer-reviewed journal that covers any topic related to the development, use and investigation of microbial cells as producers of recombinant proteins and natural products, or as catalyzers of biological transformations of industrial interest. Microbial Cell Factories is the world leading, primary research journal fully focusing on Applied Microbiology.
The journal is divided into the following editorial sections:
-Metabolic engineering
-Synthetic biology
-Whole-cell biocatalysis
-Microbial regulations
-Recombinant protein production/bioprocessing
-Production of natural compounds
-Systems biology of cell factories
-Microbial production processes
-Cell-free systems