Department of Biological and Environmental Engineering, 214 Riley-Robb Hall, Cornell University, Ithaca, NY 14853, USA E-mail:
Water Sci Technol. 2014;69(1):62-8. doi: 10.2166/wst.2013.549.
High productivity and specificity in anaerobic digesters arise because complex microbiomes organize into a metabolic cascade to maximize energy recovery and to utilize the advantage that the gaseous end product methane freely bubbles out of the system. These lessons were applied to ascertain whether a reactor microbiome could be shaped to produce a different end product. The liquid product n-caproic acid was chosen, which is a 6-carbon-chain carboxylic acid that is valuable and that has a relatively low maximum solubility concentration for product recovery. Acetoclastic methanogenesis was inhibited by pH control and a route was provided for n-caproic acid extraction by implementing selective, in-line recovery. Next, ethanol was supplemented to promote chain elongation, which is a pathway in which short-chain carboxylic acids are elongated sequentially into medium-chain carboxylic acids with two-carbon units derived from ethanol. The reactor microbiome developed accordingly with the terminal process catalyzed by chain-elongating bacteria. As a result, n-caproic acid production rates increased to levels comparable to anaerobic digestion systems for solid waste treatment.
由于复杂的微生物群落组织成代谢级联，以最大限度地回收能量，并利用气态最终产物甲烷自由地从系统中逸出的优势，厌氧消化器具有高生产力和特异性。这些经验教训被应用于确定反应器微生物群落是否可以被塑造以产生不同的最终产物。选择了液体产物正己酸，这是一种有价值的 6 碳链羧酸，其产物回收的最大溶解度浓度相对较低。通过 pH 控制抑制乙酸型产甲烷作用，并通过实施选择性在线回收，为正己酸提取提供了途径。接下来，补充乙醇以促进链延长，这是一个将短链羧酸依次延长成具有两个碳单位的中链羧酸的途径，这些碳单位来自乙醇。反应器微生物群落随之发展，由链延长细菌催化末端过程。结果，正己酸的生产速率提高到与固体废弃物处理的厌氧消化系统相当的水平。
