Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA.
Bioresour Technol. 2012 Jan;103(1):293-9. doi: 10.1016/j.biortech.2011.09.128. Epub 2011 Oct 8.
Our lab and most others have not been able to close a carbon balance for fermentation by the thermophilic, cellulolytic anaerobe, Clostridium thermocellum. We undertook a detailed accounting of product formation in C. thermocellum ATCC 27405. Elemental analysis revealed that for both cellulose (Avicel) and cellobiose, ≥92% of the substrate carbon utilized could be accounted for in the pellet, supernatant and off-gas when including sampling. However, 11.1% of the original substrate carbon was found in the liquid phase and not in the form of commonly-measured fermentation products--ethanol, acetate, lactate, and formate. Further detailed analysis revealed all the products to be <720 da and have not usually been associated with C. thermocellum fermentation, including malate, pyruvate, uracil, soluble glucans, and extracellular free amino acids. By accounting for these products, 92.9% and 93.2% of the final product carbon was identified during growth on cellobiose and Avicel, respectively.
我们实验室和大多数其他实验室都未能为嗜热、纤维分解厌氧微生物产甲烷菌（Clostridium thermocellum）的发酵过程建立碳平衡。我们对产甲烷菌（Clostridium thermocellum）ATCC 27405 的产物形成进行了详细的核算。元素分析表明，对于纤维素（微晶纤维素）和纤维二糖这两种底物，当包括采样时，在颗粒、上清液和废气中，可解释≥92%的利用底物碳。然而，11.1%的原始底物碳存在于液相中，而不是以通常测量的发酵产物——乙醇、乙酸盐、乳酸盐和甲酸盐的形式存在。进一步的详细分析表明，所有产物的分子量均<720 道尔顿，且通常与产甲烷菌（Clostridium thermocellum）发酵无关，包括苹果酸盐、丙酮酸、尿嘧啶、可溶性葡聚糖和细胞外游离氨基酸。通过核算这些产物，在以纤维二糖和微晶纤维素为生长基质时，分别有 92.9%和 93.2%的最终产物碳被鉴定出来。
