背景:微生物电合成(MES)和气体发酵是生物能源技术,其中微生物催化剂用来自生物电化学系统的阴极或来自诸如H2的气体的电子将CO2还原为有机碳分子。产乙酸原孢子菌具有通过气体发酵和MES将CO2还原为商品化学品的能力。乙酸盐通常是自养生长过程中由卵黄链球菌产生的唯一产物。
结果:在这项研究中,优化了S.ovata生长培养基中的微量元素,以提高MES和气体发酵生产率。在H2:CO2依赖性生长过程中,钨酸盐浓度的增加导致S.ovata的乙醇产量增加了2.9倍。与未改性的培养基相比,它还促进了乙醇在S.ovata驱动的MES反应器中的电合成,并使乙酸盐产量增加了4.4倍。此外,在气体发酵过程中,脂肪酸丙酸酯和丁酸酯成功地转化为相应的醇1-丙醇和1-丁醇。增加钨酸盐浓度可提高丙酸盐和丁酸盐的转化效率。基因表达分析表明,含钨醛铁氧还蛋白氧化还原酶(AORs)和含钨甲酸脱氢酶(FDH)参与了乙酸盐的生物合成。乙醇,1-丙醇,和1-丁醇。AOR和FDH有助于脂肪酸再同化途径和Wood-Ljungdahl途径,分别。
结论:此处提出的这项研究表明,优化微生物催化剂生长培养基可以提高生产率,并通过气体发酵和MES导致不同产物的生物合成。它还提供了有关产乙酸生物燃料生产代谢的见解,并表明S.ovata具有重要的未开发的代谢潜力,可通过包括MES在内的CO2转化生物过程生产除乙酸盐以外的其他化学物质。
BACKGROUND: Microbial electrosynthesis (MES) and gas fermentation are bioenergy technologies in which a microbial catalyst reduces CO2 into organic carbon molecules with electrons from the cathode of a bioelectrochemical system or from gases such as H2. The acetogen Sporomusa ovata has the capacity of reducing CO2 into commodity chemicals by both gas fermentation and MES. Acetate is often the only product generated by S. ovata during autotrophic growth.
RESULTS: In this study, trace elements in S. ovata growth medium were optimized to improve MES and gas fermentation productivity. Augmenting tungstate concentration resulted in a 2.9-fold increase in ethanol production by S. ovata during H2:CO2-dependent growth. It also promoted electrosynthesis of ethanol in a S. ovata-driven MES reactor and increased acetate production 4.4-fold compared to unmodified medium. Furthermore, fatty acids propionate and butyrate were successfully converted to their corresponding alcohols 1-propanol and 1-butanol by S. ovata during gas fermentation. Increasing tungstate concentration enhanced conversion efficiency for both propionate and butyrate. Gene expression analysis suggested that tungsten-containing aldehyde ferredoxin oxidoreductases (AORs) and a tungsten-containing formate dehydrogenase (FDH) were involved in the improved biosynthesis of acetate, ethanol, 1-propanol, and 1-butanol. AORs and FDH contribute to the fatty acids re-assimilation pathway and the Wood-Ljungdahl pathway, respectively.
CONCLUSIONS: This study presented here shows that optimization of microbial catalyst growth medium can improve productivity and lead to the biosynthesis of different products by gas fermentation and MES. It also provides insights on the metabolism of biofuels production in acetogens and demonstrates that S. ovata has an important untapped metabolic potential for the production of other chemicals than acetate via CO2-converting bioprocesses including MES.