自产乙醇梭菌可以转化废气(CO2,CO,H2)和木糖从水解生物质中转化为乙酸盐,乳酸,甲酸盐,乙醇和2,3-丁二醇,是木质纤维素生物精炼厂废物流转化的候选者。当使用梭菌菌株时,电发酵(EF)改变了传统发酵的模式,导致提高的产物产量。这项工作的目的是通过自产乙醇梭菌DSM10061评估pH对发酵过程中木糖和EF的微生物生长和产物分布的影响。发酵和EF在H型反应器中在三个受控pH:5.0、5.5和5.8下进行,EF中的固定电势为-600mV(相对于Ag/AgCl)。实验表明,最大生物量浓度随着发酵和EF的pH增加而增加。根据达到的最大生物量,对于两个系统,在pH5.8时观察到最高的底物转化率,发酵率为76.80%,EF率为96.18%。此外,在pH5.8的EF培养结束时,获得了最高浓度的乙酸(1.41±0.07gL-1)和乙醇(1.45±0.15gL-1)。不管pH值如何,通过施加外部电位,乳酸和甲酸的产量都会下降,在pH5.8时达到最低生产率。相比之下,在最低pH下,乙酸和乙醇的比生产率在发酵和EF中均较低。此外,仅在pH5.8的EF中检测到0.06gL-1的2,3-丁二醇的存在。结果表明,EF调节微生物代谢,这可以通过NADP+/NADPH辅因子的可能增加来解释,这将使代谢途径转向更多的还原产物。
Clostridium autoethanogenum can to convert waste gases (CO2, CO, H2) and xylose from hydrolyzed biomass into acetate, lactate, formate, ethanol and 2,3-butanediol, being a candidate for the transformation of waste streams of lignocellulosic biorefineries. Electro-fermentation (EF) modify the pattern of traditional fermentations resulting in improved product yields as has been shown when using Clostridium strains. The aim of this work was to evaluate the influence of pH on microbial growth and product distribution during fermentation and EF of xylose by C. autoethanogenum DSM10061. Fermentation and EF were carried out in a H-type reactor at three controlled pH: 5.0, 5.5 and 5.8, and at a fixed potential of -600 mV (versus Ag/AgCl) in the EF. The experiments showed that maximum biomass concentration increased as the pH increased in fermentation and EF. In accordance with maximum biomass reached, the highest substrate conversion was observed at pH 5.8 for both systems, with 76.80 % in fermentation and 96.18 % in EF. Moreover, the highest concentrations of acetic acid (1.41 ± 0.07 g L-1) and ethanol (1.45 ± 0.15 g L-1) were obtained at the end of cultures in the EF at pH 5.8. The production of lactic and formic acid decreased by the application of the external potential regardless of the pH value, reaching the lowest productivity at pH 5.8. In contrast, the specific productivity of acetic acid and ethanol was lower in both fermentation and EF at the lowest pH. Furthermore, the presence of 0.06 g L-1 of 2,3-butanediol was only detected in EF at pH 5.8. The results revealed that EF modulated microbial metabolism, which can be explained by a possible increased generation of NADP+/NADPH cofactors, which would redirect the metabolic pathway to more reduced products.