Applied Microbiology, Lund University, Getingevägen 60, SE-222 41 Lund, Sweden.
Microb Cell Fact. 2010 Nov 22;9:89. doi: 10.1186/1475-2859-9-89.
Global concerns about climate changes and their association with the use of fossil fuels have accelerated research on biological fuel production. Biological hydrogen production from hemicellulose-containing waste is considered one of the promising avenues. A major economical issue for such a process, however, is the low substrate conversion efficiency. Interestingly, the extreme thermophilic bacterium Caldicellulosiruptor saccharolyticus can produce hydrogen from carbohydrate-rich substrates at yields close to the theoretical maximum of the dark fermentation process (i.e., 4 mol H2/mol hexose). The organism is able to ferment an array of mono-, di- and polysaccharides, and is relatively tolerant to high partial hydrogen pressures, making it a promising candidate for exploitation in a biohydrogen process. The behaviour of this Gram-positive bacterium bears all hallmarks of being adapted to an environment sparse in free sugars, which is further reflected in its low volumetric hydrogen productivity and low osmotolerance. These two properties need to be improved by at least a factor of 10 and 5, respectively, for a cost-effective industrial process. In this review, the physiological characteristics of C. saccharolyticus are analyzed in view of the requirements for an efficient hydrogen cell factory. A special emphasis is put on the tight regulation of hydrogen production in C. saccharolyticus by both redox and energy metabolism. Suggestions for strategies to overcome the current challenges facing the potential use of the organism in hydrogen production are also discussed.
全球对气候变化及其与化石燃料使用的关联的担忧加速了生物燃料生产的研究。利用含半纤维素的废物生产生物氢被认为是一种很有前途的途径。然而，对于这样一个过程来说，一个主要的经济问题是低底物转化率。有趣的是，极端嗜热细菌Caldicellulosiruptor saccharolyticus 可以从富含碳水化合物的底物中产生氢气，其产率接近暗发酵过程的理论最大值（即 4 mol H2/mol 己糖）。该生物体能够发酵一系列单糖、二糖和多糖，并且对高分压氢气相对耐受，因此是在生物制氢过程中具有开发潜力的候选生物。这种革兰氏阳性菌的行为完全符合适应自由糖匮乏环境的特征，这进一步反映在其低体积产氢率和低渗透压耐受性上。要使这两个特性在成本效益高的工业过程中分别提高至少 10 倍和 5 倍。在这篇综述中，分析了 C. saccharolyticus 的生理特性，以了解其在高效氢细胞工厂中的要求。特别强调了 C. saccharolyticus 中通过氧化还原和能量代谢对氢气生产的严格调控。还讨论了克服该生物体在制氢中潜在应用所面临的当前挑战的策略建议。
